Radiation Exposure of the U. S. Population from Consumer Products and Miscellaneous Sources (N C R P Report)

NCRP REPORT No. 95

Radiation Exposure of the U.S. ~opulation from Consumer Products and Miscellaneous Sources Recommendations of the NATIONAL COUNCIL O N RADIATION PROTECTION AND MEASUREMENTS

Issued December 30, 1987 First Reprinting June 30, 2995 National Council on Radiation Protection and Measurements 7910 W O O D M O N T AVENUE / BETHESDA, MD 20814

LEGAL NOTICE This report was prepared by the National Council on Radiation Protection and Measurements (NCRP). The Council strives to provide accurate, complete and useful information in its reports. However, neither the NCRP, the members of NCRP, other persons contributing to or assisting in the preparation of this report, nor any person acting on the behalf of any of these parties (a) makes any warranty or representation, express or implied, with respect to the accuracy, oompleteness or usefulness of the information contained in this report, or that the use of any information, method or p m x s d i s c 1 4 in this report may not infringe on privately owned rights; or (b) assumes any liability with respect to the use of, or for damages resulting from the use of, any information, method or process disclosed in this report, under the Civil Rights Act of 1964, Section 701 et seg. as amended 42 U.S.C. Section 2000e et se9. (TitleVZZ) or any other statutory or common hw theory governing liabiluy.

Library of Congress Catal-g-in-Public~tion

Data

National Council on Radiation Protection and Measurements. Radiation exposure of the U.S. population from consumer products and miscellaneoue

sources.

(NCRPreport ;no. 95) Bibliography: p. Includes index. 1. Radiation-Dosage. 2. Ionizing radiation-Measurement. 3. Radioactive substances-United States. 4. Commercial products-United States. 5. Product safetyUnited States. I. Title. 11. Series. 363.1'79 87-24720 RA569.N353 1987b ISBN 0-913392-94-4

Copyright Q National Council on Radiation Protection and Measurements 1987 AU rights reserved Thispublication is protected by copyright. No part of this publicetion may be reproduced in any form or by any means, including photocopying, or utilized by any information storage and retrieval system without written permission from the copyright owner, except for brief quotation in critical articles or reviews. Library of Congms Catalog Card Number International Standard Book Number

Preface The NCRP has long recognized the need for a clear assessment of the magnitude of doses from various sources of radiation to which the population of the U.S. is exposed. In anticipation of the need to gather data for input into this process five assessment committees, each addressing a different source category, were established in 1971. NCRP reports assessing exposures from natural background and from consumer products were produced (NCRP, 1975,1977). In 1985, the NCRP reconsidered its overall effort in this area and, with the further support and stimulation of the Committee on Interagency Radiation Research and Policy Coordination (Office of Science and Technology Policy, Executive Office of the President of the United States), undertook to evaluate the exposure of the U.S. population from all sources. This resulted in the reconstitution of an NCRP committee to re-assess the radiation exposure of the population from consumer products and miscellaneous sources. This report updates and supersedes NCRP Report No. 56 (1977) and includes television receivers, airport x-ray baggage inspection systems, smoke detectors, high voltage rectifiers and control circuits, static eliminators, radioactive luminous devices, dental prostheses, fertilizer and phosphate products, natural gas, and combustible fossil fuels. Notable additional sources to the previous report are domestic water supplies, video display terminals, plutonium-powered cardiac pacemakers, and a greater emphasis on tobacco products. Some products, such as shoefitting fluoroscopes, that are no longer available or whose use has essentially been discontinued, have been deleted. This report represents one source of information for the overall summary effort, NCRP Report No. 93, Ionizing Radiation Exposure of the Populution of the United States. The International System of Units (SI) is used in this report followed by conventional units in parentheses in accordance with the procedure set forth in NCRP Report No. 82, SI Units in Radiation Protection and Measurements. This report was prepared by the Council's Scientific Committee 28 on Radiation Exposure from Consumer Products. Serving on the

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PREFACE

Committee during the preparation of this report were: Dade W. Moeller, Chairmon Harvard School of Public Health Boston, MA 02115 Richard J. Guimond Office of Radiation Programs US.Environmental Protection Agency Washington. DC

Edwin A. Miller Center for Devices and Radiological Health U.S. Department of Health and Human Services Silver Spring, MD

John W. N. Hickey Office of Nuclear Material Safety and Safeguards U. S. Nuclear Regulatory Commission Washington, DC

Gail D. Schmidt Center for Devices and Radiological Health U.S. Department of Health and Human Services Rockville, MD

NCRP Secretariat-Thomas M. Koval

The Council wishes t o express its appreciation to the members of the Committee and reviewers for the time and effort they devoted to the preparation of this report. Bethesda, Maryland 9 September 1987

Warren K. Sinclair President, NCRP

Contents . .

1 2

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3

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electronic Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Unwanted By-product X Rays . . . . . . . . . . . . . . . . . . . . 2.1.1 Television Receivers . . . . . . . . . . . . . . . . . . . . . . 2.1.2 Video Display Terminals (VDTs) . . . . . . . . . . . 2.2 Intentional X Rays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.1 Airport Luggage Inspection Systems . . . . . . . . 2.2.2 Personnel Scanning Systems . . . . . . . . . . . . . . . 2.2.3 Shoe-Fitting Fluoroscopes . . . . . . . . . . . . . . . . . Radioactive Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Processed Radioactive Materials . . . . . . . . . . . . . . . . . . 3.1.1 Radioluminous Products . . . . . . . . . . . . . . . . . . . 3.1.1.1 Miscellaneous Radioluminous Items 3.1.2 Static Eliminators . . . . . . . . . . . . . . . . . . . . . . . . 3.1.3 Spark Gap Irradiators and Electron Tubes . . . 3.1.3.1 Spark Gap Irradiators . . . . . . . . . . . . 3.1.3.2 Electron Tubes . . . . . . . . . . . . . . . . . . 3.1.4 Gasand AerosolDetectors ("Smoke Detectors") . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.5 Check Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.6 Plutonium-Powered Cardiac Pacemakers . . . . 3.1.7 Lightning Rods . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Natural Radioactive Materials . . . . . . . . . . . . . . . . . . . . 3.2.1 Tobacco Products . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2 Building Materials . . . . . . . . . . . . . . . . . . . . . . . . 3.2.3 Domestic Water Supplies . . . . . . . . . . . . . . . . . . 3.2.4 Highway and Road Construction Materials . . . 3.2.5 Mining and Agricultural Products . . . . . . . . . . . 3.2.5.1 Fertilizer Products . . . . . . . . . . . . . . . 3.2.5.2 Phosphate Products. By-products and Wastes . . . . . . . . 3.2.6 Combustible Fuels . . . . . . . . . . . . . . . . . . . . . . . . 3.2.6.1 Combustion of Coal . . . . . . . . . . . . . . 3.2.6.2 Combustion of Oil . . . . . . . . . . . . . . . . 3.2.6.3 Combustion of Natural Gas . . . . . . . . 3.2.7 Glass and Ceramics . . . . . . . . . . . . . . . . . . . . . . .

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vi

CONTENTS

Uranium in Glassware . . . . . . . . . . . . Uranium in Glazes . . . . . . . . . . . . . . . Uranium in Glass Enamel . . . . . . . . . Dental Products . . . . . . . . . . . . . . . . . Uranium and Thorium Impurities in Ophthalmic Glass . . . . . . . . . . . . . . 3.2.8 Thorium Products . . . . . . . . . . . . . . . . . . . . . . . . 3.2.8.1 Thoriated Optical Glass . . . . . . . . . . . 3.2.8.2 Gas Mantles . . . . . . . . . . . . . . . . . . . . 3.2.8.3 Camera Lenses . . . . . . . . . . . . . . . . . . 3.2.8.4 Thoriated Tungsten Welding Rods . 3.2.8.5 Fluorescent Lamp Starters . . . . . . . . 4 Miscellaneous Exposure Sources. . . . . . . . . . . . . . . . . . . . 4.1 High Voltage Vacuum Electronic Units . . . . . . . . . . . . 4.2 Contaminated or Irradiated Materials . . . . . . . . . . . . . . 4.3 Disposal of Radioactive Surplus Items . . . . . . . . . . . . . 4.4 Aircraft Transport of Radioactive Materials . . . . . . . . 5 Snmmary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 Sources and Estimates of Associated Population Dose Equivalents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Special Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Recommendations for Dose Reduction and Research . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The NCRP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NCRP Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.7.1 3.2.7.2 3.2.7.3 3.2.7.4 3.2.7.5

. .

1. Introduction During the last several decades, there has been a tremendous increase in the types and quantities of consumer products commercially available to the general public within the United States. Many of these involve novel materials that have properties and behaviors with which the average citizen is unfamiliar (Abelson, 1973). One such property is the emission of ionizing radiation. In many cases, such emission is essential to the proper performance of the device. Examples in this category include airport luggage inspection systems, radioluminous products, gas and aerosol (smoke) detectors, and static eliminators. In other cases, such emissions are incidental or extraneous to the purpose for which the consumer product was designed. Examples in this category include television receivers, video display terminals, tobacco products, combustible fuels, building materials, gas mantles, camera lenses and welding rods. The primary goal of the effort that resulted in this report was to update the earlier report issued by the NCRP on this subject (NCRP, 1977). In so doing, the Council has identified additional consumer products that can be sources of ionizing radiation, and has deleted coverage of some products that are either no longer available or whose use has essentially been discontinued. For each source category, a major effort has been made to provide data on the number of products currently in use, the rate a t which such usage is changing, and the range of typical dose equivalents being received from that source by the general public. To the extent possible, an attempt has been made to provide information to assist in making decisions on whether a given application might better be replaced by some other method of accomplishing the same task without involving radiation exposure to the population. Although it is recognized that there is considerable uncertainty in many of the dose equivalent estimates given in this report, no variance or error estimates are available. If the dose equivalent estimates were near the upper limits recommended by the NCRP or the International Commission on Radiological Protection (ICRP), these potential uncertainties would be considered a problem and more detailed monitoring and data evaluation would be required. At the moment, however, except for the case of tobacco products and domestic water supplies 1

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1. INTRODUCTION

(see data presented subsequently), the quoted dose equivalents are low and may be considered sufficiently accurate to permit an overall evaluation of the contribution from consumer products to the population dose in the United States. Because of the relatively high dose contributions from tobacco products and domestic water supplies, more detailed monitoring and evaluation of these two sources appears to be warranted. This report was developed as part of the efforts of the Council to update information on the sources and amounts of ionizing radiation exposure being received by the U.S.public. The main source of information for the study was the published scientific literature. In those instances where published data were insufficient, unpublished data were utilized when the quality of the data was judged to be acceptable. Because of the range in the quality of these sources, however, it must be recognized that there is a corresponding range in the quality of the data included in this report.

2. Electronic Products 2.1 UnwantedByproductX Rays 2.1.1

Tekvision Receivers

Voluntary guidelines for the control of x-ray emissions from television receivers have existed since 1955, when the International Commission on Radiological Protection recommended that the emission of x rays should not exceed 1.55 x lo-'' C/(kg s) (0.6 pR/s (-2 mR/h)) at any accessible surface on home television receivers (ICRP, 1955). In 1960, both the International Commission on Radiological Protection (ICRP, 1960) and the National Council on Radiation Protection and Measurements (NCRP, 1960) recommended that the guideline be reduced to 1.3 X loA7C/(kg h) (0.5 mR/h) averaged over 10 cm2 at any readily accessible point 5 cm from the surface, under normal operating conditions. This change was based largely on the work of Braestrup and Mooney (1959). By 1967, it became a matter of public concern, and of Congressional hearings, that the voluntary efforts of manufacturers of color television receivers were insufficient to maintain accessible x-ray exposure rates below recommended levels. Monochrome (black and white) receivers were not implicated because of their lower cathode ray tube (CRT) accelerating potentials and currents. Color television receivers, however, required greater CRT anode voltages, with tube currents perhaps five times greater. In addition, many circuits included a voltage regulator tube for stability. Such receivers included as many as three separate sources of x rays-the picture tube, the shunt regulator tube, and the vacuum tube rectifier. In May 1967, a major manufacturer of color television receivers announced that 90,000 large screen receivers would be recalled and modified in order to comply with the NCRP recommended limit of 1.3 X C/(kg h) (0.5 mR/h). This action prompted a field survey in Florida of color receivers (NCRH, 1968a). Twenty-three of 149 sets that were checked exceeded the recommended 1.3 x lo-' C/(kg h) (0.5 mR/h) limit, with two of the sets producing exposure rates in excess 3

4

1

2. ELECTRONIC PRODUCTS

of 2.58 X loe5 C/(kg h) (100 mR/h). In all cases where the limit was exceeded, the manufacturer took action t o correct the problem. A home survey of 1,124 color receivers in the Washington, D.C.area during 1967-68 showed that while 76 percent did not emit a measurable amount of x rays, 6 percent exhibited exposure rates that were above the NCRP recommended values (NCRH, 1968b). Similar findings were obtained in subsequent s w e y s by Becker (1970, 1971) in New York, Das Gupta and Fujimoto (1970) in Canada, and the Department of Health (CPRDH, 1971) in the Commonwealth of Puerto Rico. It was found, generally, that excessive x-ray emissions from television receivers could be reduced to less than 2.58 X lo-' C/(kg h) (0.1 mR/h) by reducing the high voltage from 26 to 34 kV (a range exceeding specifications) to 18 to 25 kV (the normal range). Although the receivers were usually adjusted to acceptable levels at the factory, the operating voltages were often later increased by service personnel to improve picture quality. In the United States, Congress passed the "Radiation Control for Health and Safety Act of 1968" (PL 90-602, 1968), with enforcement principally delegated to the Food and Drug Administration. Performance standards for television receivers were adopted in 1970 (CFR, 1970) and are enforceable through the Act. The exposure rate limit was set a t 1.3 x C/(kg h) (0.5 mR/h), measured in accordance with the recommendations of the NCRP (1960). New measurement conditions, as detailed in the performance standard, are designed to ensure that the exposure rate limit will not be exceeded even under the most adverse operating conditions. If these conditions are met, the exposure rates under normal operating conditions are ordinarily a small fraction of the 1.3 x C/(kg h) (0.5 mR/h) a t 5 cm, as specified in the standard. Population exposure to television x rays probably reached a maximum in 1968 or 1969, having been virtually zero in 1956, when color television receivers first became popular (EIA, 1971). Braestrup and Mooney (1959) had originally estimated that a permissible level of 1.3 X C/(kg h) (0.5 mR/h) a t 5 cm would result, under normal viewing conditions, in an average gonadal absorbed dose rate of 43 to 172 pGyl y (4.3to 17.2 madly). Both Neill et d (1971) and an X-Ray Ad Hoc Committee of the Electronic Industries Association (EIA, 1971), analyzed the data from the Washington, D.C. 1967-68 survey (NCRH, 1968b). Neill et nl. estimated that for an assumed average viewer situation and an exposure rate of 1.1 x lo-' C/(kg h) (0.043 mR/h) a t 5 cm, the average male gonadal absorbed dose rates were 7 to 15 pGy/ y (0.7 to 1.5 mrad/y) and the average female gonadal absorbed dose rates were 2 to 4 pGy/y (0.2 to 0.4 mradly), ranges that roughly

2.1

UNWANTED BYPRODUCT X RAYS

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5

confirmed earlier estimates by Braestrup and Mooney (1959). The EIA Committee (EIA, 1971), using a more detailed analysis of the same data, derived an average annual genetically significant dose equivalent to the U.S.population from television usage in early 1968 of 5 pSv (0.5 mrem). NeiU et al. further estimated that one percent of the exposed viewers from the Washington study might receive gonadal absorbed doses 60 times higher than the average (Neil1 et d,1971). However, it must be recognized that all of the significant exposures (ie., those that were 60 times the average) occurred in relatively few households, and only where color television receivers were used. Since 1968-69, x-ray emissions from color television sets have decreased markedly. This trend was indicated in the surveys cited above, such as the second survey made by Becker (1971), where a definite downward trend was noted in the number of older color television receivers exceeding voluntary guidelines. In that study, none of the older color receivers serviced by factory-trained service personnel, and none of the color receivers manufactured after the effective date of the performance standard, exhibited x-ray exposure rates greater than 2.58 x lo-' C/(kg h) (0.1 mR/h). Solid-state technology has eliminated shunt regulator and high voltage rectifier tubes. Design of television receivers has been extensively improved with high voltage "hold downn circuits now being a standard design feature. Hold down circuits prevent excessive high voltage even if a critical component were to fail. Service controls have been permanently locked or eliminated to ensure that design limits cannot be exceeded. The manufacture of thin walled picture tubes has also been discontinued. Modem picture tubes use glasses of improved x-radiation attenuation characteristics. Continued laboratory testing by the Center for Devices and Radiological Health confirms that x-radiation exposure rates are below the minimum detectable limits of standard instruments (CDRH, 1986a). Estimates of the average annual total population gonadal dose equivalent made in 1977 attributed 5 pSv (0.5 mrem) to this source (NCRP, 1977). The major source of population exposure to x rays from television receivers were those manufactured before 1970. These had an expected useful life of five to eight years. This source has now virtually disappeared. Although essentially the entire U. S. population is exposed to radiation from television sets, current estimates are that the average dose equivalent rate is much less than 10 pSv/y (1 mrem/y). Although insufficient data are available to calculate the annual collective population dose equivalent in a precise manner, it is estimated to be much less than 2,300 person-Sv (<<230,000 person-rem).

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2.1.2

2. ELECTRONIC PRODUCTS

Video Display Terminals (VDTs)

Video display terminals, such as those used in office and home computers and word processors, share the same technology as television receivers. The discussion of technical characteristics in Section 2.1.1 is also applicable to VDTs. The Center for Devices and Radiological Health includes VDTs in its television product testing program. An analysis of radiation emission characteristics from VDTs was first published in 1981 (BRH, 1981). Results of testing to date indicate no differences between the x-ray emissions characteristics of VDTs and television receivers. The most likely emission a t 5 cm from the surface of the VDT under both normal and failure operating modes is below the detectable limits of the standard monitoring instruments. Reports of cataract formation and "clusters" of birth defects among VDT operators have led to evaluation of health risks by groups in the U.S.,Canada, and Western Europe. Radiation surveys in the workplace conducted by the National Institute for Occupational Safety and Health could find no health hazard associated with any radiation emitted by VDTs (NIOSH, 1981;Millar, 1984). The National Research Council likewise concluded that levels of radiation emitted by VDTs are unlikely to represent a health hazard (NRC, 1983). The American College of Obstetricians and Gynecologists has adopted the position that birth defects and spontaneous abortions are not attributable to radiation emissions from VDTs (ACOG, 1984). The average dose equivalent rate to the approximately 50 million members of the U. S. population who operate video display terminals is estimated to be much less than 10 r S ~ / y(1 mrem/y) and the annual collective dose is estimated t o be well below 500 person-Sv (50,000 person-rem).

2.2

2.2.1

Intentional X Rays

Airport Luggage Inspection Systems

Concern over aircraft hijacking, terrorist activities, and bomb threats resulted in the issuance of Federal regulations for aircraft security (CFR, 1973). An Executive Order of January 5, i973, required that airline companies inspect all passengers and their hand carried baggage for concealed guns, dangerous weapons, explosives and incendiary devices before permitting them to board commercial aircraft.

2.2 INTENTIONAL X RAYS

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To assist in this task, airline companies began to use x-ray fluoroscopic scanning systems for the inspection of hand-carried luggage. By 1985, about 1,000 x-ray inspection systems had been installed at 40 or more major airports. Carry-on luggage for about 400 million passenger trips was inspected in 1985 (Tscoumis, 1986). The x-ray inspection is generally conducted at the entrance to the secured area in the presence of the traveler. Therefore, the inspection equipment could provide a potential source of radiation exposure to the public if not properly controlled. The Federal performance standard for cabinet x-ray systems published in 1974 covers x-ray inspection systems used in public access areas (CFR, 1974). The standard limits x-ray emissions at a point 5 cm from the external surface of the system to 1.3 X lo-' C/kg (0.5 mR) in any one hour. The Federal Aviation Administration requires that radiation surveys of x-ray scanning equipment be performed a t the time of its installation, upon relocation, and annually thereafter (CFR, 1981). Additional surveys are conducted by state and local radiation control programs and Food and Drug Administration investigators. Results of surveys indicate the average exposure at the external surface of the system is less than 2.1 x lo-'' C/kg (0.08 pR) per inspection. In 1985, luggage was inspected for approximately 400 million passenger trips. Assuming that about 30 million people made those trips and each one was immediately adjacent to the inspection system while 2 bags were examined, the average gonadal dose to those 30 million people would be about 0.021 pSv (2.1 prem). On the basis of this estimate, this source would contribute an average of about 0.003 pSv (0.3 prem) as an annual dose equivalent to the U. S. population, resulting in an annual collective effective dose equivalent of about 0.6 person-Sv (60 person-rem).

2.2.2

Personnel Scanning Systems

Personnel inspection x-ray units were used frequently in shipyards and other defense-related plants during World War I1 for security purposes. They were also commonly located in penitentiaries where they were used to search prisoners and visitors. Studies by Nivert (1972) provided ranges of exposures between 6.5 x lo-' C/kg (0.25 mR) and 2.1 x C/kg (800 mR) for different types of inspection systems.

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2. ELECTRONIC PRODUCTS

State and local radiation control laws have curtailed use of x-ray personnel inspection systems. The suggested State Regulations for Control of Radiation on which state agencies pattern their control programs specifically prohibit deliberate exposure for non-healing arts purposes (CRCPD, 1982a). Under current Food and Drug Administration policy, personnel scanning systems are considered medical diagnostic x-ray systems and must comply with the Federal performance standard applicable to that class of equipment. There is no known use of x-ray personnel screening systems a t this time. With the development of alternative screening technology, it is suggested that x-ray systems not be used for routine personnel screening. Most personnel screening devices in use today are magnetic metal detectors.

2.2.3

Shoe-Fitting Fluoroscopes

In 1953, it was estimated that there were approximately 10,000shoefitting fluoroscopes in use in the United States (Moeller et d, 1953). Reported exposures (Dillingham and Stalker, 1951; AMA, 1949) to the feet ranged from 18.1 to 36.1 x Cjkg (7 to 14 roentgens) per 20second exposure (an average setting). Concurrent exposures to the pelvis were reported in the range of 7.7 to 43.9 x lo* C/kg (30 to 170 mR) (AMA, 1949). Like the personnel scanning systems, health authorities consider such exposures unnecessary and the application of x-ray fluoroscopes in shoe-fitting is prohibited by the states (CRCPD,1982a). The last reported discovery of a shoe-fitting fluoroscope in use was in 1978. It is unlikely that any units remain in operation in the U.S. today.

3. Radioactive Materials 3.1 hocessed Radioactive Materials

3.1.1 Radioluminous Products The use and distribution of radioluminous products have changed dramatically since World War 11. During the War, 226Rawas incorporated into numerous timepieces, compasses, and other products such as gauges, markers, and instrument dials, used by the military forces. Following the end of the War, many of these products became available to the public as government surplus items and some remain in use today. With the development of the nuclear industry, by-produd materials rapidly began to replace radium in luminous compounds. One of the fust such radioactive materials was '"Sr, which was used in timepieces. Its use, however, was curtailed shortly after its introduction due to the associated radiation levels. Subsequently, two other artificially produced radionuclides, 3H(tritium) and 147Pm,were found to be acceptable for use in radioluminous compounds and today their use has almost totally replaced the use of 226Ra. Reports from industry and regulatory agencies indicate that the last wristwatches incorporating 226Rain luminous compounds were produced in about 1968, the last radium clocks using 226Rawere produced in about 1978. Data shown in Table 3.1 indicate that about nine million radioluminous timepieces were sold annually in the U.S. during the time period from 1974 to 1977 (Buckley et d , 1980). Data on the sales of timepieces containing tritium and 14'Pm are from licensee reports submitted to the U.S.Nuclear Regulatory Commission; data on timepieces containing =Ra are those supplied by a U.S. manufacturer. The data on radium clock sales are contradicted by Simpson et al. (1983), who have reported the sale of 2.5 million ='R.a clocks manufactured in Florida over the three-year period from 1976 to 1978. Data reported by industry sources indicate that tritium gas tube light sources (GTLS) were produced for only a few years. Such sources were used to backlight liquid crystal display (LCD) watches. Problems with the leakage of small amounts of tritium from GTLS, which typically contained about 7.4 GBq (200 mCi) of this radionuclide, 9

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3.

RADIOACTIVE MATERIALS TABLE 3.1-Productwn

of luminescent timepieces' Number in thousands

Item

Tritium paint Watches Clocks Tritium gas Watches

1974

1975

1976

1977

1978

4860 429

6,740 75.5

6,740 8.4

6,170 944

N/Db N/Db

12.3

81.9

1,470 694

1,280 587

1,oQc'

Negl.' 500

Negl.'

Negl.'

230 -8,900

230 -9,500

2,020

147h

Watches Clocks =Ra Watches Clocks Roundedtotals

958

856 Negl.' 1,500 -8,400

-9.500

947

N/Db N/Db Negl.' 60

>2,000

'Buckley et d , 1980. N/D-No data.

'Neg1.-Negligible.

apparently made these sources unable to compete on an economic basis with battery operated units. At this time, industry reports indicate that the Japanese are using 14'Pm paint in timepieces and that tritium is being incorporated into timepieces being shipped into the U.S. from the Federal Republic of Germany and Switzerland. Estimated current sales in the United States for timepieces containing tritium and ld7Pmare about one million per year. A review of estimates of the gonadal dose-equivalent rate to wearers of 226Rawatches was made by Robinson (1968). These estimates, all of which were reported in 1959 to 1961, were made for the populations of several European countries and ranged from 5 to 33 @V/Y (0.5 to 3.3 mrem/y) for the annual genetic dose to the population, with individual gonadal dose-equivalent rates as high as 3.10 mSv/y (310 mrem/y) for a wearer of a wristwatch containing 160 kBq (4.5 &i) of 226Ra. Overall, i t is estimated that the average gonadal dose-equivalent rate is 30 pSv/y (3 mrem/y) for any person in the U.S.who may still be wearing one of these watches. Although there are no federal regulations limiting the radium content in timepieces, the Model State Regulations for Control of Radiation (CRCPD, 1982b) provide an exemption from licensure only for timepieces containing less than 3.7 kBq (0.1 &i) 226Raand acquired before the effective date of the regulations. U.S. Nuclear Regulatory Commission regulations (CFR, 1986a) limit the quantities of I4'Pm and 3Hwhich can be used in these items. For 147Pm,the limit is 3,700 kBq (100 pCi) per watch and 7,400 kBq (200 &i) for any other

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3.1 PROCESSED RADIOACTIVE MATERIALS

11

timepiece; for 3H, it is 925 MBq (25 mCi) per watch. As may be seen from the data in Table 3.2, the quantities of 147Pmand 3Hcontained in timepieces sold in the U.S. from 1974 to 1978 averaged only a fraction of these limits (Buckley et aL, 1980). In addition, for 147Pm there is a limit on the permissible dose rate (CFR, 1986a). Specifically, the absorbed dose rate in air from the radioactive hands and dial of a '47Pm-activated timepiece, measured through a 50 mg/cm2 absorber, may not exceed: (a) 1 pGy/h (0.1 mrad/h) at 10 cm for wristwatches; (b) 1pGy/h (0.1 mrad/h) a t 1cm for pocket watches1; (c) 2 pGy/h (0.2 mrad/h) a t 10 cm for any other timepiece. Fifty mg/cm2 is normally the minimum thickness of a watch case and assures that the low-energy beta particles from 3H and '"Pm are stopped within the absorber. In the case of 3H, therefore, the principal radiation exposure arises from the inhalation or absorption through the skin of 3H-containing gases. In the case of 147Pm,the exposure arises fiom bremsstrahlung and from gamma-emitting isotopic impurities. TABLE 3.2-Assumptiom for luminescent timepiece dose estimates' Tritium paint

Timepieces in use Watches-Number (lo6) -Average activity Clocks-Number (lo6) -Average activity Exposed population Delivery drivers Terminal workers Marketing/storage Workers Customers'

use

Watch wearers Non-wearers Clocks

Users

Tritium gas

53.6 68.5 MBqb 3.7 18.5 MBqb 390 25,000

0.85 316

53.6 160.8 14.8

16 7,400 MBqb NIA N/A

"Tm

3.7 1.7 MBqb 4.4 1.7 MBqb

2,200

96 18,500 (Number in Millions) 55.0'33

0.85 316

0.85 316

16 48

3.7

N/A

-

17.6

'Buckley et aL, 1980. 1 MBq = 27 pCi. 'Some people are exposed as a customer several times a year.

'

The maximum absorbed dose rates for pocket watches are set lower than for other timepieces due to the fact that pocket watches are normally carried closer to the gonads.

12

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3.

RADIOACTIVE MATERIALS

Fitzsimmons et al. (1972) estimated the average annual whole-body dose equivalent to wearers of 3H-activated luminous wristwatches using an equation developed by Moghissi and Porter (1968). They calculated the average whole-body dose-equivalent rate to be 6 pSv/y (0.6 mrem/y), with a range of 2 to 18 pSv/y (0.2 to 1.8 mrem/y). It is important to note that this dose-equivalent rate arises from the intake of 3H; it is not due to external exposure. Measured 3H release rates from the watches ranged up to 3.1 kBq/d (83 nCi/d). Other data have been reported by Moghissi and Carter (1975) based on measurements of human subjects exposed to tritium from radioluminous watches. Based on tritium concentrations observed in urine, the average dose to the users of 3H-activated luminous timepieces was estimated to be 0.008 pSv (0.8 prem) per MBq (27 pCi) (range: 0.003 to 0.12 pSv/MBq (0.3 to 12 prem/27 pCi)) of tritium paint incorporated into the watches. In subsequent analyses, Buckley et al. (1980) have estimated an annual dose to the user of 0.6 pSv (0.06 mrem) (assuming about 74 MBq (2 mCi) of tritium per watch). Based on the total number of users of such watches within the U.S. (as of the late 1970's), these authors estimated an annual collective dose of about 32.75 person-Sv (3,275 person-rem). Using the CONDOS computer program, a group at the Oak Ridge National Laboratory has further estimated the doses to people involved in the distribution, storage, installation, use and disposal of various consumer products. Its results have been incorporated into the data published by Buckley et al. (1980), which give a collective dose estimate for such people of 24 person-Sv (2,400 personrem). This value is the result obtained when the estimate of McDowellBoyer and O'Donnell (1978a) is adjusted for the exposed population groups indicated in Table 3.2. McDowell-Boyer and O'Domell (1978a) have also estimated the population collective dose resulting from the use of clocks in which tritium is used as a luminous compound. These authors assumed that 75 percent of these clocks were used in the bedroom, 20 percent elsewhere within the home, and 5 percent in offices. Assuming also that the major exposure occurs through the release of tritium, that clocks used in bedrooms expose an average of 4 people for 2,920 hours per year, that other clocks used in the home expose 4 people for an average of 8,760 hours per year, and that clocks used in oftices expose 4 persons for an average of 2,000 hours per year, the collective dose estimate is 1.75 person-Sv (175 person-rem) per year. The collective population dose equivalent to users and non-users of tritium watches and clocks is 58.5-person-~v(5,850 person-rem) per year (see Table 3.3).

/

3.1 PROCESSED RADIOACTIVE MATERIALS

13

TABLE3.3-Collective dose estimates for luminescent timepieces' Population dose ( p e m n - S V / ~ ) ~

Manufacture Distribution and marketing Use Waste collection Landfill disposal Incineration Total 'Buckley et d , 1980. 1 person-Sv = 100 person-rem.

1.10 0.54 58.5

-

-

0.25 6039

0.20 0.09 3.6

-

0.016 3.2

10

0.005

77.19

3.22

63.3

0.064 0.007 96 0.24

-

0.59 95.9

Using similar assumptions, McDowell-Boyer and O'Donnell (1978a and 1978b) have estimated the dose to wearers and others who handle gaseous tritium light source watches, watches and clocks containing ld7Prnand clocks containing '=Ra. The results of their estimates, when adjusted for the distribution of timepieces as indicated in Table 3.2, is summarized in Table 3.3 (Buckley et d,1980).Table 3.3 also includes the estimates of the collective dose that occurs during the manufacture, distribution, and disposal for those cases in which such doses were found to be significant. The International Atomic Energy Agency (IAEA, 1967) has recommended that the use of in pocket watches be discontinued because of the associated high exposure to people. Klein et al. (1970) measured the absorbed doses in a phantom from 226Rain pocket watches. On the basis of these studies, they calculated a gonadal doseequivalent rate of 16.2 &3v/y (1.62 mrem/y) per kBq (27 nCi) of 226Ra. The annual absorbed dose to the skin directly under the face of the watch was estimated to be 1.65 Gy (165 rad). All reports indicate that pocket watches containing *%a have not been produced or sold in the U.S. for several decades. Additional data collected since the information in Table 3.3 was assembled indicate substantial changes in the distribution and use of luminescent timepieces that incorporate tritium paint, tritium gas, and In fact, recent estimates (CDRH, 1986b) are that collective population dose equivalents from the use of timepieces incorporating tritium paint are about 20 percent of those listed in Table 3.3. For timepieces incorporating tritium gas, current estimates are that the resulting population doses are insignificant; the same is true for timepieces incorporating *6Ra. Collective population dose equivalents arising through the use of timepieces incorporating "7Pm are estimated to be equal to the values presented in Table 3.3. Using these

14

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3. RADIOACTIVE MATERIALS

latest estimates, the collective population dose equivalent due to the use of luminous timepieces in the U.S. is about 15 person-Sv (1,500 person-rem) per year. 3.1.l.1 Miscellaneous Radioluminous Items. There is a large variety of radioluminous items (other than timepieces) that are in the exempt or general license categories of the federal and state regulations and that can potentially cause exposure to consumers. These include portable and marine compasses, thermostats, light switches, automobile shift quadrants and lock illuminators, gun sights and aircraft and building safety devices (exit signs). As a practical matter, however, the only items that have been distributed in significant numbers are aircraft and building exit markers. Based on industry production figures through October 1970, it was estimated that about 80,000 aircraft and commercial exit markers containing 3Hgas in a sealed glass tube were in use in 1977. The total quantity of 3Hin these markers was approximately 9,250,000 GBq (250,000 curies). While no data are available on the number currently in use, it is estimated that the annual production of aircraft and commercial exit markers exceeds 20,000 (Bradley, 1986). Since the weak beta particles emitted by tritium are easily absorbed by the containment materials of construction, the genetic dose to the population is essentially zero. An exception would be the case of release of 3H gas by leakage or rupture of one or more exit markers in a crash. Since these sources would only result in exposures in aircraft crashes, which fortunately are very infrequent, the resulting population dose is small. In the past, l4'Prn was used in very few aircraft devices so the population exposure from these sources would also be insignificant. It is understood that exit markers and other safety devices utilizing tritium in sealed glass tubes are being sold for commercial uses. No estimates of the number distributed are available. Such devices are "generally licensed" by the U.S. Nuclear Regulatory Commission and may contain up to 925 GBq (25 Ci) of tritium. Based on the assessment of timepieces, it is probable that the most significant doses resulting from this type of application will occur when such devices, after their use has been terminated, are .sent for disposal with ordinary trash rather than being returned to the manufacturer for disposal as provided by the general license. No estimates of the accompanying doses are currently available.

3.1.2

Static Eliminators

Static eliminators containing radioactive sources are widely used in industry to reduce the electrical charge buildup on certain materials.

3.1 PROCESSED RADIOACTIVE MATERIALS

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15

The radiation ionizes the air around a charged object and thereby allows the charge to be neutralized. Static eliminators containing radioactive. materials are used as consumer products to reduce the static charge on phonograph records and photographic film. Polonium-210 (half-life of 138 days) used as the ionizing source is primarily an alpha emitter with an 803 keV gamma ray being emitted in 0.001 percent of the disintegrations. According to the manufacturer, the 2'0Poused in consumer goods is interspersed in "microspheres" of ceramic material. This is in contrast to most commercial static eliminators which are available with both microsphere sources and metal foil sources similar to those used in gas and aerosol detectors, but with a thicker window. The ceramic microspheres currently in use are claimed to be insoluble in body fluids, if ingested. Also, the physical size of the microspheres is large enough so that the inhalation of the material is unlikely. Static eliminators nominally contain 18.5 to 37 MBq (500 to 1,000 pCi) of 210Po.Because of the relatively short half-life of this radionuclide (138 days), these devices have an effective life of little more than one year. Wipe tests of such devices, conducted by personnel in the U.S.at the Oak Ridge National Laboratory (Niemeyer et al., 1978) and in the U.K. (Webb et al., 1975), indicated the presence of removable activity that ranged from 0.000024 to 0.02 percent of their total radionuclide content. Associated population dose estimates, assuming the sale of 37,000 units annually, each initially containing 18.5 MBq (500 rCi) of 'loPo, are presented in Table 3.4. As may be noted, the total annual collective effective population dose equivalent from these sources is estimated to be about 0.13 person-Sv (13 person-rem). The most significant dose associated with the use of static eliminators is that based on inadvertent burning of such devices stored, for example, in a warehouse. Assuming that 1,000 such devices might be stored in a single warehouse, that they each contained 46.25 MBq (1,250 pCi) of 210Po,and that 10 percent of this activity becomes airborne in a fire, estimates of the lung dose to a fireman who breathes the resulting concentrations over an &hour period can range as hlgh as 2.5 Sv (250 rem). The respiratory protection normally worn by firefighting personnel, however, should provide adequate protection. Estimates of the actual doses resulting from such exposures are, however, not available. 3.1.3

Spark Gap Irradiators and Electron Tubes

3.1.3.1 Spark Gap Irradiators. The use of spark gap irradiators containing up to 1 rCi of 6 0 Cin ~ plated or alloy form was proposed in

16

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3. RADIOACTIVE MATERIALS

3.4-he estimates for static eliminators' TAEILE Collective doseb

MY

c

r

Lungs

0.008 0.003 0.011 0.011

0.007 0.026 0.033 0.002

0.003 0.012 0.015 0.002

0.003 0.95 0.953 0.114

(Total collective effective dose equivalent = 0.13 person Individual Dose (mSv)* Warehouse f m Effective dose equivalent

G1

Kidney

0.0005 0.0013 0.0018 0.0001

0.023

(person or organ - Sv)'

Source of Exposure Use Incineration Total Effective dose equivalent

Bone

7.6 7.6

68. 4.1

32. 3.8

-

0.023 0.001

- Sv)

2,500 300

3.4 0.2

(Total individual effective dose equivalent = 316 mSv) 'Buckley et al., 1980. Assumes annual and equilibrium distribution of 37,600 units containing an initial activity of 18.5 MBq (500 &i). 1 person-Sv = 100 person-rem. 1 mSv = 0.1 rem.

1975 (FR, 1975) and is now permitted by the U.S.Nuclear Regulatory Commission (CFR, 1986a). Such irradiators would be attached near the spark gap used as an electric ignitor in an industrial fuel oil burner to enhance the reliability of ignition and safety during the ignition sequence. This would be accomplished through use of the emitted radiation to maintain an ionized atmosphere between the electrodes of the spark gap. Other methods of preventing spark delay are available, but they are disruptive and less efficient in the hot oil burner environment. The estimated potential market for spark gap irradiators containing 60 Co is approximately 6,000 units per year. Generally about 37 kBq (1 pCi) of 60Co has been proposed as the source for such irradiators since estimates show that this amount will provide adequate ionization over the 15-year useful lifetime of a typical oil burner. Other applications could include industrial boilers, power plants, and other heavy duty equipment. Use of 60Co spark gap irradiators in private home furnaces or internal combustion engines is not proposed. The latest information for the U.S. indicates that few, if any, spark gap irradiators have been produced and/or distributed. The associated collective population dose is essentially zero. 3.1.3.2 Electron Tubes.Radioactive materials are currently in widespread application in many electronic products used for voltage regu-

3.1 PROCESSED RADIOACTIVE MATERIALS

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17

lation, current surge protection, and as indicator lights. A widespread use involves indicator lights used in appliances such as clothes washers and dryers, stereos, coffeemakers, and pinball machines. Such lights typically contain about 740 kBq (20 FtCi)of tritium, or about 7.4 kBq (0.2 pCi) of "Kr, and typically have dimensions of 2.5 cm (1inch) in length and 0.5 cm (0.2 inch) in diameter. Several hundred million of these tubes, which have a service life of 25,000 hours, were utilized in appliances during the 1970's (Buckley et ah, 1980). Voltage regulators and cunent surge protectors are used in many types of electronic devices that incorporate integrated circuit devices and digital systems. These devices are of a size similar to indicator lights and usually contain 13'Cs, 63Ni,=Kr, or 'lOPbwith activities of less than 37 kBq (1 &i) per unit (Buckley et d,1980). Spark gap tubes or glow Lamps are used as starters for fluorescent lamps (see Section 3.2.7) and in electric blanket thermostats and other specialty devices. Several million of these devices are manufactured annually. They generally contain from 37 to 333 kBq (1 to 9 pCi) of 'j3Ni,=Kr, or 14'Pm (Buckley et al, 1980). Data on the annual distribution and sales of electron tubes have been published by Buckley et al. (1980). These data are summarized in Table 3.5. It is estimated that about 10,000 surge arrestors, each containing about 0.6 pBq (22 kCi) of *lOPb,are produced annually a t present (Keating, 1986). Collective doses resulting from the use and disposal of electron tubes have been estimated by Buckley et al. (1980). These are presented in Table 3.6. Despite the large number of tubes distributed, the collective dose is estimated to be no more than about 10 person-Sv (1,000 person-rem), largely due to the small quantity of radioactive material used per unit, particularly for those containing 85Kr. The highest individual doses (4 pSv/y) (0.4 mremly) are estimated to result from the use of units containing 13'Cs. TABLE 3.5-Assum~tiom for electron tube dose estimates' Radionuclide

31 a&

=Ni =Kr '"Cs "'Pm

Units/y (~109~

15 0.078 0.081 98 0.017 2.4

W/unit

800 5 30

5 40

300

'Buckley et d , 1980.

Equilibrium number is equal to 10 times annual distribution. '1 kBq = 27 nCi.

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3. RADIOACTIVE MATERIALS

TABLE3.6-Cdlechire d0.w equivalent estimates for electron tubes' Collective dose equivalent (personor organ-SvIb Use condition

Tritium tubes Other radionuclides Landfill Incineration Total

Effectivt dose equivalent

Liver

Bone

Lungs

GI

Gonads

0.0076

0.011

0.01

0.0075

0.0074

3 5.8 1.2 0.0074 10.01

'Buckley et d , 1980.

3.1.4

Gas and Aerosol Detectors ('Smoke Detectors")

Gas and aerosol detectors use alpha radiation to ionize the air between two electrodes, thereby allowing an electric current to flow across the air gap under the influence of a small potential. Combustion products entering the air gap change the current flow by increasing or decreasing the resistance. This change in current is then amplied to trigger an alarm. The first units developed contained 226Raas the alpha source. However, manufacturers presently make only models containing 241Am (half-life = -430 y). The amount of 241Amin gas and aerosol detectors manufactured for installation in public and commercial buildings ranges up to 3.7 MBq (100 &i). Normally, however, the amount of 241Amincorporated in the units intended for use in homes is 185 kBq (5 pCi) or less. Household smoke detectors incorporating "'Ra commonly contain 1.85 kBq (0.05 pCi), with the maximum amount being about 3.7 kBq (0.1 pCi). Smoke detectors containing americium are subject to regulations of the U.S. Nuclear Regulatory Commission (CFR,1986b),while smoke detectors containing radium are subject to similar radiological safety criteria prescribed through the regulations of the individual states (CRCPD, 1982~). In 1973, approximately 250,000 gas and aerosol detectors were sold in this country, most of the units going into public or commercial buildings. These units contained a total of approximately 480 GBq (13 Ci) of 241Am,an average of about 1.85 MBq (50 pCi) per unit. Calculated dose-equivalent rates to the whole body range from 6.3 to 15 rSv/y (0.63 to 1.5 mrem/y). It is estimated that by 1978, 26 million gas and aerosol detectors had been distributed and projections for 1986 show that the number in use will reach an equilibrium a t about 90 to 100 million (Belanger

3.1 PROCESSED RADIOACTIVE MATERIALS

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19

et al., 1979). Belanger et al. estimate that the manufacture, distribution and disposal of 14 million smoke detectors (1978 sales), each containing 110 kBq (3pCi) of 241Am,may result in a collective total body dose of about 11person-Sv (1,100 person-rem) over their estimated 10-year useful life. For an equilibrium distribution of 100 million, with annual sales and disposal of 10 million each, the annual collective dose would be about 7.85 person-Sv (785person-rem). This dose is divided as follows: manufacture/distribution of 10 million units -0.71 person-Sv (71 person-rem); use and maintenance of 100 million units -7.07 personSv (707 person-rem); and disposal of 10 million units -0.05 personSv (5 person-rem). Some annual individual doses of interest include: maximum occupational dose of 10 mSv (1 rem); average dose to retail clerks of 5 pSv (0.5 mrem); dose during transport of 2 units -0.02 pSv (2.0 prem); average user -0.093 pSv (9.3 prem); and average user test and maintenance -0.0018 pSv (0.18 prem). A more recent assessment by personnel at the Oak Ridge National Laboratory (O'Donnell et d,1981) shows an annual collective population dose due to the handling and use of the 10 million additional smoke detectors containing 241Am to be 0.38 person-Sv (38 personrem) for the total body and 1.3 Sv (130 rem) to the bone. Individual doses to residential users were estimated to range from 0.009 to 0.05 gSv (0.9 to 5 prem), which is in reasonable agreement with the estimates provided by Belanger et al. (1979). For purposes of this report, it will be assumed that 100 million gas and aerosol detectors are in w e in the U.S.and that they result in an annual average dose equivalent of about 0.08 pSv (8 prem) to 100 million people. On this basis, the annual collective dose equivalent would be about 8 person-Sv (800 person-rem) which, again, is in agreement with the estimates provided by Belanger et al. (1979). While current sources indicate that smoke detectors incorporating '16Ra have not been sold in the U.S. for several years, data provided by manufacturers indicate that 2.1 million units were sold through 1978 (Belanger et d,1979). These units typically contained about 2 kBq (0.05 pCi) of Assessments by Belanger et d provide an external radiation dose estimate for 226Raunits that would be 90 times that for units containing the same amount of 241Am,taking into account the relative energies of the radionuclide emissions. Adjusting for the relative activities in the units, 2 kBq (0.05 pCi) for 226Raand 110 kBq (3 pCi) for "'Am, the external dose from the 22sRa units would be about 1.5 times that for the 241Amunits. For doses due to the inadvertent burning of these units, Belanger et al. provide the following relative (*%a to 241Am)dose ratios: total body = 10; bone

20

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3. RADIOACTIVE MATERIALS

= 1.0; and lung = 0.24. Based on the relatively small number of units produced and the small differences in relative doses, the contribution to population dose from smoke detector units containing '26Ra and still in use is probably very small. A recent survey reports that 52 million households in the U.S. currently have smoke detectors with half of these having a single unit (CPSC, 1985). Assuming two detectors in the other households and that 85 percent are the ionization type, it can be estimated that there are about 66 million detectors containing radioactive materials in use in U.S. households. While there are residential type units in some hotel rooms and other locations, the estimate of 90 to 100 million units assumed here should be adequately conservative for purposes of estimating the associated population dose.

3.1.5 Check Sources Federal regulations allow small radioactive sources for checking radiation detection instruments to be possessed without a license (CFR, 1986a). The check sources can be individual external sources, or up to ten internal check sources can be installed in a single instrument. The limits for the radioactive material which can be contained in exempt check sources are listed in the regulations. For example, a source can contain up to 37 kBq (1&i), so a single instrument could contain up to 370 kl3q (10 pCi). The dose rate from an unshielded 370 kBq (10 pCi) 60Cosource is approximately 2.58 X lo-' C/kg/h (10 f l / h) at 1m. Data are not available on the number of unlicensed check sources in use. Population dose estimates are not possible because of a lack of information on the numbers of sources, shielding, occupancy factors, and distance factors. However, the nature of the sources is such that prolonged contact with the sources and instruments is unlikely, so individual doses would be small. Most of the dose is probably received by radiation workers. Over the years, Civil Defense authorities have purchased nearly one half-million survey meters containing check sources. Of these, it is estimated that approximately 400,000 are still in use, and that a like number are also in use by the military, schools, etc. Some of the early survey meter models were provided with 0.037 kBq (0.001 j&i) of 226Ra as a check source, but these are no longer in the Civil Defense system. A small percentage of the survey meters in current use are provided with 210Pb(Radium D) check sources, but the

3.1 PROCESSED RADIOACTIVE MATERIALS

/

21

vast majority are provided with 0.55 kBq (0.015 pCi) of 238Uin the form of a depleted uranium metal foil. wSr and "Kr sources are also used in quantities ranging up to 37 and 185 kBq (1 and 5 pCi), respectively. The absorbed dose rate in air near the surface of such a source is less than 10 pGy/h (1mrad/h), so the whole body dose equivalent rate to a user would be less than 10 pSvjh (1 mremjh). The annual dose equivalent to the exposed population is probably less than 10 pSv (1 mrem). Considering an exposed population of 800,000 people, the average annual collective whole body dose equivalent would thus be less than 8 person-Sv (800 person-rem).

3.1.6

Plutonium-Powered Cardiac Pacemakers

Some cardiac pacemakers are powered by thermoelectric batteries 'Pu is 87.8 years, so a battery can containing =Pu. The half-life of " last for the lifetime of a patient. Nuclear pacemakers are designed to maintain their integrity when subjected to impact, crushing force, or fire in credible accidents which might involve a patient. The pacemakers are marked as radioactive with fire-resistant labels (USNRC, 1976a). Medical institutions which implant pacemakers must be licensed by the U.S. Nuclear Regulatory Commission (USNRC) or a State regulatory agency. The licensed institutions are required to track patients and recover pacemakers for proper disposal at the time of their removal or the death of the patient. Nuclear pacemakers have been in use since 1973. The USNRC projected in 1976 that 10,000 nuclear pacemakers would be in use within a few years, out of a total of 100,000 pacemakers. However, by 1986 only 1,560 pacemakers from four manufacturers had been implanted, with 900 of these still being in use. Only three new nuclear pacemakers were implanted in 1985 (USNRC, 1986a). The decline in use is probably due to improved non-nuclear batteries, and the regulatory requirements applicable to nuclear devices. Nuclear pacemakers usually contain 250 mg (150 GBq (4 Ci)) or ~ with small amounts of other Pu isotopes. Although less of 2 3 s Palong normally implanted in the upper chest muscles, nuclear pacemakers sometimes are implanted in the abdomen. Dose equivalent rates at the surface of a pacemaker are about 50 to 150 pSv/h (5 to 15 mrem/h) due to gammajneutron radiation, including a significant contribution of gamma radiation from the 236Pu contaminant and its decay products (USNRC, 1976a). For the tissue within 7 cm of the pacemaker, the

22

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3. RADIOACTIVE MATERIALS

neutron contribution to the dose equivalent predominates. Therefore, the dose equivalent to tissue in immediate contact with an implanted pacemaker is significant [up to 0.9 Sv/y (90 rem/y)]. The dose equivalent for a pacemaker implanted in the chest is estimated to be about 1 mSv/y (0.1 rem/y) for the whole body, 0.3 mSv/y (0.03 rem/y) for the gonads, and 7 mSv/y (0.7 rem/y) for organs near the pacemaker. Estimates for pacemakers implanted in the abdomen are about 1.6 mSv/y (0.16 remjy) for the whole body and 1 to 3 mSv/y (0.1 to 0.3 rem/y) for the gonads and other organs near the pacemaker (USNRC, 1976a). For 1,000 implanted pacemakers, the patient population collective whole body dose rate would be about 1 person-Sv/y (100 person-rem/y). The estimated whole body dose equivalent for spouses of pacemaker recipients is about 75 &3v/y (7.5 mrem/y), and for other household members and medical personnel it is 1to 15 pSv/y (0.1 to 1.5 mrem/ y). Therefore, the population dose equivalent for persons other than recipients, or those involved with them, is small and would be negligible in comparison to the dose from other consumer products evaluated in this report.

3.1.7

Lightning Rods

It was proposed by Szilard in 1914 that "'Ra be used on lightning rods to enhance ionization and, in 1932, Capart patented a radioactive rod in France and the U.S. (Delhove, 1970). Belli et al. (1978) report that 226Raand 241Am have been used in lightning rods in amounts of 3.7 to 220 MBq (0.1 to 6 mCi) and that 12,000 lightning rods had been installed in Italy by 1973. World-wide installations were estimated a t 200,000 by Fornes and Ortiz (1978). Fornes and Ortiz have also estimated the total collective dose that would result from the annual installation of 1,500 radionuclide containing lightning rods, coupled with the use of a cumulative total of 12,000 such units. The annual dose to each of 12 installers of *"Am equipped lightning rods was estimated to be 8.75 mSv (875 mrem), yielding an annual collective dose of 0.1 person-Sv (10 person-rem). To estimate the associated dose to the general population, these authors assumed that 10 people were exposed 8 hours/day to each unit, resulting in an annual individual dose of 0.5 pSv (0.05 mrem) and an annual collective dose equivalent of 0.06 person-Sv (6 personrem). In addition, the population was estimated t o receive small doses due to the inhalation of air and the ingestion of water contaminated

3.2 NATURAL RADIOACTIVE MA'IXRIALS

/

23

by these sources. On this basis, the total annual collective dose from these courses would be about 0.2 person-Sv (20 person-rem). In the U.S.,the only known use of radioactive lightning rods is in New York State where the State Department of Labor has licensed the distribution of rods containing 2P6Ra. The license requires that the title to the units be retained by the licensed distributor/installer and that the units be leak tested every six months. Distribution is estimated to total about 100 units, each containing about 260 MBq (7 mCi) (Bradley, 1986). Their use a t this time has been limited to commercial and industrial applications. Because of the remote locations of these units, the only significant doses are probably those resulting from installation and leak testing, and associated exposures of building maintenance personnel. Although no collective dose estimates are available a t the present time, presumably they are small.

3.2 Natural Radioactive Materials

3.2.1

Tobacco Products

'lOPb and 'loPo have been detected in tobacco and in cigarette smoke. and data indicate possibly increased concentrations in the lungs of smokers (Radford and Hunt, 1964; Little et al., 1965).210Pohas further been reported to concentrate in "hot spots" a t bifurcations of segmental bronchi (Little et d., 1965; Cohen et d.,1980; Cross, 1984). Although it is likely that the inhaled volatile compounds of 'loPo are widely dispersed and rapidly cleared from the lung, localized accumulations of insoluble particles of 'lOPb may, due to subsequent ingrodh of 'loPo, give rise to a relatively high localized dose (Martell, 1974). The presence of " T b and 'lTo in tobacco appears to result primarily from the deposition of airborne radon decay products on the leaves of the tobacco plant during its growth. Tobacco leaves are large and have characteristics that appear to retain the radon decay products once they deposit on the leaves. The concentrations of naturally occurring radionuclides in the soil, and uptake of these radionuclides into the plant via its root system, do not appear to be a significant contributor to the presence of 'lOPb and 210Poin tobacco. In 1985, about 33 percent of the adult males and 2 8 percent of the adult females in the U.S. smoked cigarettes, with the average daily consumption being about 30 cigarettes (HHS, 1986).Assuming localization of deposition, the maximum average dose-equivalent rate to

24

1

3. RADIOACTIVE

MATERIALS

small areas of the bronchial epithelium at segmental bifurcations of each of the approximately 50 to 55 million adult smokers in the United States would be 8 to 10 mGy/y (0.8 to 1.0 rad/y) (Little et aL, 1965; Cohen et al., 1980). Applying a quality factor of 20 (ICRP, 1977), this would yield an annual dose equivalent of about 160 mSv (16 rem). Although there is general agreement on this estimate, the NCRP currently does not have the data necessary to convert this number to an effective dose equivalent. If an attempt were made to derive a suitable tissue weighting factor by weighting the dose to the bronchial epithelium and the pulmonary region, a value of 0.08 can be derived (based on data published in ICRP Publication 32).2 This would yield an estimated effective dose equivalent of about 13 mSv (1,300 mrem). Whether such a weighting factor and the associated effective dose equivalent are applicable is open to question since only a small percent of the bronchial epithelium is actually exposed and receives the indicated dose. Furthermore, any value of the effective dose equivalent that would be calculated would be based on numerous assumptions and would be of uncertain validity. For this reason, the NCRP prefers, at the present time, not to attempt to estimate an effective dose equivalent for the exposures associated with the use of tobacco products.

3.2.2 Buiiding Materials A summary of information on the concentrations of naturally occurring radionuclides in basic building materials (Table 3.7) has been prepared from data reported by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR, 1972). The major radionuclides of importance are isotopes of uranium, thorium, and potassium. The dose rate to a person within a building is influenced by a variety of factors. These include, for example, the nature and specific radionuclide content of the building material, the geometry of exposure, the ventilation rate, and the nature and type of inner wall surfaces. For this reason, computation of the dose rate to occupants within a building is a complicated and difficult task. *This derivation is based on calculations given in ICRP Publication 32 (ICRP, 1981). The ICRP cites a W.I. of 0.12 for whole lung and 0.06 each for bronchial epithelium and pulmonary tissue. Radon and its decay products irradiate the tracheobronchial region mainly. In Publication 32, the ICRP uses the James-Birchall model to establish dose equivalents to the bronchial basal cell layer in the range of 0.06 to 0.18 Sv per WLM for an average of 0.12 SvjWLM. This,combined with the ICRP conversion factor of 0.01 Sv/WLM, yields a weighting factor of 0.08.

3.2 NATURAL

TABLE 3.7-Estimates Material

Granite Shndstone Cement Limestone concrete Sandstone concrete Dry w a l b o a d c Manufacturedanhydride (by-productgypsum)

1

RADIOACTIVE MATERIALS

25

of concentmtions of uranium, thoriwn, and potassium in building materialr' Uranium Thorium Potassium ( P P ~ ) mBg/t?

( P P ~ ) mBdg

4.7 0.45 3.4 2.3 0.8 1.0 13.7

2.0 1.7 5.1 2.1 2.1 3.0 16.1

63 6 46 31 11 14 186

8 7 21

8.5 8.5 12 66

( P P ~ ) mBg/g

4.0 1.4 0.8 0.3 1.3 0.3 0.02

0.118 0.041 0.024 0.009 0.038 0.009 0.0006

NOTE: mBq/g calculations based on the following assumed specific activities: Uranium: 1.36 X lo7mBQ/g, thorium: 4.11 X lo6 ml3q/& potassium: 29.600 mBa/n. 'Adepted from UNSCEAR (1972). 1 mBa = 27 fCi. The estimated concentrations of urenium, thorium, and potassium in dry wallboard are those measured by Wollenberg and Smith (1962) for five samples of gypsum which were probably typical of that found in wallboard.

There have been many measurements of dose rates inside and outside buildings of various types. On the basis of a review of published data, Oakley (1972)concluded that dose rates inside frame buildings were approximately 70 percent, and those inside masonry buildings were approximately 100 percent of outdoor terrestrial dose rates in the same general area. Using this approach, one can estimate that naturally occurring radionuclides in materials such as masonry contribute a dose rate to building occupants approximately equal to 50 percent of the corresponding terrestrial dose rate due to natural background radiation. This would correspond to approximately 130 pSv/y (13mrem/y) to the whole body (NCRP, 1975). By use of the above information and the data given below from Oakley (1972), it is possible to estimate the contribution of radionuclides in building materials to the dose-equivalent rate for various segments of the U.S. population. For example, if = Total U.S. population = 230 x lo6 = Annual dose equivalent from building materials to occupants of masonry buildings = (0.3) (Average annual terrestrial whole-body dose-equivalent) = (0.3) (440 @/y) = 130 pSv/ Y (13mrem/y) Ph. = Proportion of population living in masonry buildings = 0.27 P w = Proportion of population working or attending school = 0.68

/

26

3. RADIOACTIVE MATERIALS

PWM = Proportion of workers or students in masonry buildings

=

0.50 PWW = Proportion of time spent by workers and students at work = 0.24 PWH = Proportion of time spent by workers and students at home = 0.76 PI = Proportion of time population is indoors = 0.90, then the average annual whole-body dose equivalent from this source, calculated using the relationship shown in Table 3.8, for the approximately 120 million people receiving a significant radiation exposure from building materials, either at home, work, or school is 0.07 mSv (7 mrem). It should be noted that this value is for "whole-bodyn external penetrating radiation. In contrast, the United Nations Scientific Committee on the Effects of Atomic Radiation, in its report on the "Sources and Effects of Ionizing Radiationn (UNSCEAR, 1977), estimated that the increased annual whole-bodydose equivalent, above ambient outdoor values, to occupants in an average masonry building containing "representativen quantities of naturally occurring radioactive materials would be 0.11 mSv (11 mrem). Considering the many assumptions made in such assessments, this difference is probably not significant. Assuming an average annual increased dose rate of 0.07 mSv (7 mrem) per year to the occupants of concrete and brick houses in the United States, the contribution to the average annual population dose equivalent from this source would be 0.035 mSv (3.5 rnrem). The associated collective effective dose equivalent for the U.S. population would be 8,400 person-Sv (840,000 person-rem). While certain building materials, such as brick and concrete, can increase the dose equivalent t o occupants of a building, it also needs to be recognized that buildings constructed of wood can actually result in a reduction in the dose equivalent to the occupants. Although subject to further refinement, estimates show that the reductions in dose equivalent brought about by the use of wood in the construction TABLE 3.8-Annual whole-body dose equivalent to o c c u p ~ t sof masonry buddings works Liws in Or Group masonry house masonry building

:kztn Does

I I1 111

IV

Yes Yes No Yes

not work or go to school

Yes

Yes Yes No

Population (millions)

-

P M ( l Pw)PT = 20 PwP-PMPT = 21 PwPwm(l - PM)PT= 57 P,Pw(l P-)P, 21

-

Annual whole-body dose equivalent (mSv)

P,H 0.12 PIH = 0.12 P I P w H = 0.03 PI(Pw)H 0.09

3.2

NATURAL RADIOACTIVE MATERIALS

/

27

of buildings just about compensates for the increase in dose equivalent to the U.S.population due to the use of brick and concrete. One other aspect to consider relative to the influence of building materials on the population dose equivalent is that the decay of naturally occurring radionuclides in such materials, in the soil beneath a building, and in well waters used in a building, can lead to the production of radon. This gas can, in turn, diffuse into the air within a building and, in combination with its radioactive decay products, cause significant exposures to the lungs of the occupants. This is particularly true in closed or poorly ventilated indoor areas where radon and its decay products can reach concentrations many times those in the ambient outdoor air. Because, in most cases, the soil beneath a home or radon dissolved in domestic water supplies are the major sources of airborne radon and its decay products inside buildings, the contribution from building materials will not be considered in this report. Data on the dose equivalents to the public due to releases of radon from the soil beneath buildings are presented in another report issued by the NCRP (NCRP, 1984). Estimates of the dose equivalents to the public arising through the release of radon from domestic water supplies are given in the Section that follows.

3.2.3

Domestic Water Supplies

Radon in domestic water supplies can be released into the air within a home during the course of various water usage activities. Although water supplies obtained from surface sources (rivers and lakes) are seldom a source of radon, waters obtained from wells and other groundwater sources can contain relatively high radon concentrations. In fact, radon concentrations up to values of 3.7 x 10' Bq/m3 (1 pCi/ 1) have been reported in some drinking water supplies (Hess et al., 1985). The rate at which radon is released from domestic water supplies into a building, the concentrations of radon that result, and the collective dose equivalents to the building occupants, depend on a host of factors. These include the concentration of dissolved radon in the water, the degree to which the water is aerated and heated, the total quantities of water used, the total air volume within the building, and the amount of time the people spend there. A major factor that influences the amount of the dissolved radon in water that will be released into the air within a house is the manner in which the water is used. Quoted radon release fractions range from 30 percent to 50 percent for bathing and toilet flushing to 90 percent

28

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3.

RADIOACTIVE MATERIALS

to 98 percent for dishwashing and laundering (Hess et al., 1985). Based on the number of households using domestic waters from surface, well and groundwater sources, estimates can be made of the number of people exposed, the resulting concentrations of airborne radon in their homes, and the resulting average individual and collective population doses. On a nationwide basis, Cothern et d (1986) estimate that the population weighted average radon concentration in drinking water is between 2 and 11 Bq/l (50 and 300 pCi/l). The estimated range of airborne radon concentrations in homes using these waters, assuming for release of radon from the water a transfer coefficient of 1 x into the air (Hess et aL, 1985), would be from 0.2 to 1Bq/m3 (5 X to 3 x pCi/l). This, in turn would yield an average annual dose equivalent to the bronchial epithelium of the U.S. population of 0.15 to 0.9 mSv (15 to 90 mrem). If the weighting factor for converting these doses to an effective dose equivalent is assumed to be 0.083,then this would yield an average annual effective dose equivalent in the range of 10 to 60 @v (1to 6 mrem). On this basis, it can be estimated that, of the airborne radon currently in homes in the US.,approximately 0.5 to 3 percent originates from domestic water supplies. This is in close agreement with data published by Nazaroff et al. (1987)who estimated that, for homes served by public ground water supplies, an average of two percent of the mean indoor radon concentration is contributed through this source. The contribution from domestic water supplies to the annual collective effective population dose equivalent would be in the range of 2,300 to 14,000 person-Sv (230,000 to 1,400,000 person-rem). Although ingestion of waters containing elevated radon concentrations can also result in internal radiation exposures to organs of the body other than the lungs, the radiation doses incurred through this avenue of exposure are far less than those associated with inhalation of the airborne radon and its decay products (Cross et aL, 1985; Nazaroff et d, 1987). 3.2.4

Highway and Road Construction Materiuls

Aggregates made from some granites and phosphates have higher than average concentrations of naturally occurring radioactive elements, especially uranium and thorium. In a limited study near Stone 'This value is bared on data reported in Publication 32 of the International Commission on Radiological Protection (ICRP, 1981).It was derived by weighting the dose to the bronchial epithelium and the pulmonary region. See also footnote 2, Section 3.2.1.

3.2 NATURAL

RADIOACTIVE MATERIALS

/

29

Mountain, Georgia, and Bartow, Florida (Auxier, 1973),the absorbed dose rate to the gonads of motor vehicle passengers was estimated to be approximately 0.2 pGy/h (20 prad/h) higher than off-highway rates. The off-highway rates were also high near the sources of the raw materials. No accurate or complete surveys have been attempted to determine average passenger miles per year in the area or the total miles of roadway of high radionuclide content. As a minimum, there are several hundred miles of roadway in each of the two areas cited. For an average driving speed of 50 miles per hour and an average annual traveling distance of 10,000 miles, people living in the area would spend approximately 200 hours/y on the road and might receive an average increased gonadal dose-equivalent rate of 40 pSv/y (4 mrem/y). For the U.S. as a whole, it is estimated that five million people are similarly exposed in these and other high granitic areas. Based on these estimates, this source would contribute about 1 pSv (0.1 mrem) to the average annual population gonadal dose equivalent, and the average annual collection effective dose equivalent to the U.S. population would be about 200 person-Sv (20,000 person-rem).

3.2.5 Mining and Agricultural Products

3.2.5.1 Fertilizer Products. Agricultural fertilizer products contain various trace elements including several radionuclides. The principal radionuclides contained in fertilizers are members of the uranium and thorium decay series and 'OK. The concentration of each radionuclide in commercial and consumer fertilizer products depends on the origin of the phosphate ore in the fertilizer and the specific blend of materials in the fertilizer products. Fertilizers are primarily composed of materials containing biologically available nitrogen, phosphorus, and potassium. The guaranteed analysis of a fertilizer lists the respective available percent of each of these elements (%N-%P-%K). Generally the nitrogen is derived from an ammonia-related product, the phosphorus is obtained from phosphate rock, and the potassium comes from potash. The nitrogen portion has little associated radioactivity. However, the phosphorus portion may have substantial concentrations of uranium and thorium, and their decay products. The potassium part has a small concentration of potassium-40 in accordance with its general concentration in nature. In general, however, in commercial and consumer fertilizer products, the radionuclides of the uranium decay series are the most significant contributors to the radiation dose of people.

30

/

3. RADIOACTIVE MATERIALS

In the United States, concentrations of natural uranium and thorium in phosphate ores vary from about 100 to 900 mBq (3 to 24 pCi) per gram and 15 to 150 mBq (0.4 to 4 pCi) per gram, respectively (Menzel, 1965; Guimond and Windham, 1975). The highest concentrations have been reported in phosphate rocks from South Carolina and the lowest in phosphate rocks from Tennessee. Mining and processing phosphate ores redistributes the uranium, thorium, and their decay products among the various products, by-products, and wastes (Guimond and Windham, 1975). Fertilizers available to consumers in garden shops, hardware stores, and home centers are generally produced by mining and blending various primary commercial and industrial fertilizer products to achieve the desired concentration of nitrogen, phosphorus, and potassium. The concentrations of uranium, thorium, and their decay products in principal fertilizer products in the U.S. have been extensively studied by the U.S. Environmental Protection Agency (Guimond and Windham, 1975; EPA, 1977a, 1978). Some of the primary commercial fertilizer products are normal superphosphate, diammonium phosphate (DAP), monammonium phosphate (MAP), triple superphosphate (TSP),and phosphoric acid. The concentrations of uranium, thorium, and their decay products produced by facilities using Florida and Idaho phosphate ores are listed in Tables 3.9 and 3.10, respectively. The concentrations of natural radionuclides in consumer fertilizer products are variable. They will depend on which primary fertilizer products were blended into the consumer products. However, typical concentrations in various lawn or garden fertilizers are expected to be about 10 percent to 50 percent of the concentrations listed in Tables 3.9 and 3.10. Boxed and bagged consumer fertilizer products sold in garden or home centers are not expected to present much direct radiation exposure to consumers because of the reduction in.concentrations that occurs during the blending or mixing process. However, large stocks of concentrated fertilizer products may result in significant exposures. TABLE 3.9-Natural mdionuclide concentratianv in fertiliter

rmrterials made from

Fbrida phosphates frnBq/gla Material

Normal superphosphate Diammonium phosphate (18-46-0) Concentmted nuperphosphate Monoammonium phosphate (11-54-0) Phos~horicacidb 'lrnBq=27fCi. 28 per cent PnOe

=Ra

=U

fOlrb

800 200

750 2,300 2,100

700 2.400

20 15

1,800

50

2,000 900

1,850

60 115

800 200 40

1.000

31

3.2 NATURAL RADIOACTIVE MATERIALS

TABLE 3.10-Natural radionuclide concentrations in fertilizer m a t e d made from Idaho phos~hata(mBqld* Material

Triple superphosphate (Ts) (0-45-0) Ammonium sulphate (21-0-0) Ammonium phosphate (11-54-0) Diammonium phosphate (18-64-0) Phosphoric acid ( m w )(10-34-0)

%a

500 5 30 25

1,600

900

5,200

150

1,000 800

"Th

T h

2,000 5 2,300 200 16,000

170 5 70

5 140

" 1 mBq = 27 fCi.

Warehouse persons and people in blending and mixing facilities could thus receive increased doses. Windham et al. (1976) estimated that direct gamma dose equivalents to workers a t phosphate plants could range between 0.3 to 3 mSv/y (30 to 300 mrem/y). The maximum potential dose equivalent rate to the lungs from dust producing operations could be 50 mSv/y (5 rem/ Y).

Millions of tons of fertilizer are used in the U.S. every year. Guimond (1978) estimated that this could annually redistribute over 37 TBq (1,000 Ci) each of '%, =U, and '30Th from the phosphate ores in the ground to the surface plow layer. Erosion losses of sediment to U.S. waters have been estimated a t about four billion tons annually with about half of this being due to agricultural practices. It is not known exactly how much of the radioactive material in commercial and consumer fertilizers is soluble. Consequently, the impact that runoff has on the quantities of radioactive materials in streams and rivers is not known. However, Spalding and Sachett (1972) have suggested that increasing concentrations of uranium have been found in recent years in rivers that flow into the Gulf of Mexico as compared to 20 years earlier. They attributed these increases to the widespread . application of phosphate fertilizers in agriculture. There are few data available for estimating the relationship between concentrations of natural radionuclides in various food crops and the specific fertilizers used to produce them. Potassium-40 is homeostatically controlled by the body and consequently is of less concern than the uranium and its decay products associated with the phosphate in fertilizers. Some crops, such as potatoes and tomatoes, require greater than 200 Ibs P205/acre each year. Guimond (1978), who studied the potential accumulation of '"Ra and 25BU over time, estimated that over a 50-year period the buildup of 226Raand 238U due to fertilizer use may range up to 37 and 59 mBq/g (1 and 1.6 pCi/g) of soil, respectively. Since typical 228Raand 238Uconcentrations in soil in the United States are about 3.7 to 74 mBq/g (0.1 to 2 pCi/g), he concluded that long-term application of phosphate fertilizers may lead to con-

32

/

3. RADIOACTIVE MATERIALS

centrations of series radionuclides in the plow layer that are several times greater than are normally present. Although definitive calculations are difficult, estimates are that some 200 million people in the U.S. receive exposures as a result of the ingestion of foods grown on lands in which radionuclide concentrations have been increased due to the use of phosphate fertilizers. It is estimated that the resulting dose rates are in the range of 5 to 50 pSv/y (0.5 to 5 mremly) (whole body). For the U.S.as a whole, the average annual effective dose equivalent rate would be less than 10 to 20 pSv/y (1to 2 mrem/y). This would result in a collective effective dose equivalent of less than 2,000 person-Sv (200,000 person-rem). 3.2.5.2 Phosphate Products, By-products, and Wastes. In addition to fertilizer products, radionuclides from the uranium and thorium decay series are present in a wide variety of other phosphate products, by-products, and wastes. These include elemental phosphorus, animal feed supplements, by-product gypsum, soil conditioners, slag, and ferrophosphorus. These are produced a t wet-process phosphoric acid plants or electric furnaces. The radioactivity associated with each material varies considerably depending on the origin of the ore and the process stream a t the facilities. The radioactivity concentrations in various materials are listed in Table 3.11 as reported by various investigators (Guimond and Windham, 1975; EPA, 1977a, 197%; CRCPD, 1978). Estimates of the population dose equivalents resulting from the use of these materials are not available. They are not anticipated, however, to be significant at this time.

3.2.6 Combustible Fuels There are three fuels-coal, oil, and natural gas-used by industry and the general public that hold potential for causing radiation exposure as an unwanted by-product. 3.2.6.1 Combustion of Coat. For illustrative purposes, it is reasonable to assume that 100 percent of the radon, 10 percent of the lead and polonium, and 1 percent of the other radionuclides in coal are released into the atmosphere from a modem coal-fired electric generating station, having air cleaning equipment that provides 99.5 percent total ash retention (Corbett, 1983). Typical emission rates for such a plant, burning coal a t a rate of 4 x lo6 tons per 1,000 MWe per year, would be as shown in Table 3.12, although emissions of non-volatile species may be substantially higher from older plants with less efficient ash retention.

3.2

NATURAL RADIOACTIVE MATERIALS

1

33

T ~ L3.11-Radionuclide E concentrations in various phosphute products, by-products and wastes ImBoIe)' Material

"To

"eU

T

h

*Th

Elementary phosphorusb Ferrophosphorusb Fenophosphoms' Fluid bed prillsb Slag" Gypsumb Gypsum' Sodium fluorosilicate' Animal fee# 'lmBq=27fCi Made from Idaho phosphate rock.

'Made from Florida phosphate rock.

TABLE 3.12-Possale release of radioactive material from a modem coal-fired electric nenemhire olant* Radionuclide

'"K

100

?I% series

=U-=Ra % Z'Opb-Z'T~

=u

Release rate/Year mCi/1,000 GBq/l.m MWe MWe

series

10 20 2,000 200

1

4 0.4

0.8 80 8 0.04

'Corbett, 1983.

As a result of the distribution of this radioactive material within the environment, the public will receive exposure through inhalation, through external radiation exposure from radioactive materials deposited on the ground, through resuspension of this material into the air, and through the movement of the deposited radioactive material within the terrestrial, aquatic, and marine food chains. A summary of the maximum annual effective dose equivalents from each of these sources to any individual member of the public, and estimates of the annual collective effective population dose equivalent due to the operation of a 1,000 MWe coal-fued electric generating station are given in Table 3.13. These estimates are based entirely on the work of Corbett (1983),who cautions that significantly different release rates are possible and that the environmental conditions assumed have a strong bias toward the situation in the U.K. and Europe.

34

/

3. RADIOACTIVE MATERIALS

TABLE 3.13-Summary of individwl and population effective dose equwalents due to the operation of a 1.000 MWe cod-fired electricpower p h P Route of e m u r e

Annual effective dose equivalent to marimally

individualb

Inhalation From plume Of resuspended material External exposure from deposited radionuclides Ingestion Via terrestrial food chain . Via marine food chain

Total 'Corbett. 1983.

AMual co,,eetiw effective population dose equivalent'

0.3 pSv 0.7 #Sv

2 person-Sv

1 pSv

0.3 person-Sv

50 pSv

2 person-Sv 0.5 person-Sv 4.9 person-Sv

20 &I

0.1 person-Sv

1 PSV= 0.1 mrem. 1 person-Sv = 100 person-rem.

Within these limitations, no single person within the general population is predicted to receive a dose equivalent from this source as high as that received from natural background and the total collective effective dose equivalent to the population served is estimated to be about 0.2 percent of that from natural background (Corbett, 1983). More recentIy, the U.S.Environmental Protection Agency has, in support of their final rules on the emission of radionuclides pursuant to the Clean Air Act, conducted an assessment of the release of radioactive materials from coal-fired boilers (EPA, 1984). Personnel conducting this assessment took into consideration large coal-fired boilers used to generate steam at electric generating stations, as well as those operated to provide industrial process steam, process hot water and space heat. Based on more than 5,000 coal samples from all major coal producing regions in the U.S.,they estimated that the typical concentration of 238U in such samples is 1.3 ppm and that the concentration of 232Thaverages about 3.2 ppm. A value of 330 mBq/g in fly ash was obtained from measurements on (9 pCi/g) of 23BU samples collected at coal-fired plants considered to be representative. The calculated estimates for 23BU and =Yrh in fly ash were 410 mBq/ g (11 pCi/g) and 150 rnBq/g (4 pCi/g), respectively. Values for other naturally occurring radionuclides in the uranium and thorium series can be obtained by assuming enrichment factors compared to uranium of 1.5 for radium, 5 for lead and polonium, and 1 for all other radionuclides. Based on a fly ash concentration of 330 mBq/g (9 pCi/g) and an estimated total U.S. atmospheric release of fly ash from electric

3.2

NATURAL RADIOACTIVE MATERIALS

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35

utilities of 0.9 million metric tons per year, the annual release of can be estimated at about 300 GBq (8 curies). Summarized in Table 3.14 are estimates of the collective doses due to inhalation, direct radiation, and ingestion to the population living within 80 kilometers of a reference electric generating station assumed to be discharging 3,700 MBq/y (100 mCi/y) of to the environment (EPA, 1984). Since a typical plant is located in a suburban or rural area, the dose equivalent estimates are calculated for an average rural and suburban site. Application of the ICRP weighting factors to the organ dose estimates results in an annual collective effective dose equivalent of 38.3 person-Sv (3,830 person-rem) and an average individual effective dose equivalent of 0.3 r S ~(0.03 mrem) for the 124 million people living within 80 kilometers of the coal-fired electric utility plants operating within the U.S. The maximum individual annual doses, estimated to occur a t m a l sites, were as follows: lung-17pSv (1.7 mrem); red marrow-21 pSv (2.1 mrem); kidney-24 pSv (2.4 mrem); bone surface-47 pSv (4.7 mrem); and liver-19 pSv (1.9 mrem). Similar estimates for a reference industrial boiler with a '38U discharge rate of 370 MBq/y (10 mCi/y) are presented in Table 3.15. The total 238U discharge for all industrial boilers in the U.S. was estimated to be 111GBq/y (3 Ci/y), and the resulting annual collective effective dose equivalent was estimated to be about 45 person-Sv (4,500 personrem). The maximum individual annual doses were estimated as follows: lung-3.4 pSv (0.34 mrem); red marrow-0.4 pSv (0.04 mrem); kidney-0.4 pSv (0.04 mrem); bone surface-4.3 1Sv (0.43 mrem); and TABLE 3.14-Collective dose equiualent estimates for reference d - f i r e d electric genemting plant dischmging 3.7 GBg/y (100 mCi/y) of CoUective dose equivalent (organ-Sv).

Loation of Plant

u h (17.2)'

Liver

Lung

0.71

42

&$ 3.3

Kidney

1.3

Endosteum

46

Suburban (2.5)' 0.27 3.9 0.43 0.8 5 Rural (0.59)' 0.14 1.1 0.19 0.3 1.4 Remote (0.012)' 0.001 0.01 0.0015 0.0003 0.02 Total collective organ dose equivalent in U.S. (124)d 16 200 24.8 44 256 Total collective effective dose equivalent 0.96 24 29.8 26.4 76.8 '1 organ-Sv = 100 organ-rem. Population within 80 km in millions 'EPA, 1984. Estimate using an average of the suburban and rural sites for a total discharge of 300 GBq/y (8 Ci/y) of W.

36

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3. RADIOACTIW MATERIALS

TABLE 3.15-Collective dose estimates for reference indusbial boiler discharging 370 MBq (10 mCi) of -U per year CoUectiw dose (organ-Svr

Liver

Reference plant Total collective organ dose equivalent in U.S. Total collective effective dose equivalentb

0.03

Lung

0.8

manow

0.07

Kidney

0.1

Bone

1

100

230

20

30

270

6

30

2

2

8

(Total collective effective dose equivalent -45 person-Sv/y (4,500person-rem/y))

' 1 organ-Sv = 100 organ-rem. For total discharge of 111 GBq (3 Ci) of 'TJper year.

liver-0.2 ctSv (0.02 mrem). For the combined coal usage in electric utilities and industrial boilers, the collective effective dose equivalent in the U.S. would be 83.5 person-Sv (8,350 person-rem). The data reported by Corbett (1983) for Europe and the U.K. and those reported by EPA (1984) may be roughly compared as follows. The current coal consumption in the U.S.for the operation of industrial boilers and electricity generating stations is 600 million tons per year. This is equivalent to that required for the operation of about one hundred and fifty 1,000 MW electric generating stations. Based on the estimates provided by Corbett, the resulting annual collective effective population dose equivalent due to inhalation would be about (150 x 2.10) person-Sv or 315 person-Sv (31,500 person-rem), and the total collective effective population dose equivalent from all routes of exposure would be about (150 x 4.90) or 735 person-Sv (73,500 personrem). The figure of 735 person-Sv (73,500 person-rem) by Corbett is about nine times the EPA estimate of 83.5 person-Sv (8,350 personrem). The reason for this difference (a factor of about nine) is not entirely clear. Possible explanations are the greater population densities in the U.K. and Europe and differences in the estimates for new plants vs. old plant.. Another possible factor is that the EPA estimate was based on more refined or detailed dose data. Another possible source of population exposures arising through the combustion of coal is the use of fly ash in building materials. According to a recent report (EPRI, 1987), 28 percent of the fly ash generated through the combustion of coal in the U.S. in 1985 was used commercially, with cement and concrete products accounting for almost 40 percent of the total. Any products containing fly ash, and used in building materials, could potentially serve as a source of external

3.2

NATURAL RADIOACTlVE MATERIALS

/

37

radiation exposure to the occupants. Data on the resulting doses to the population from such uses, however, are not available. As a final comment, it might be noted that Martin (1974) and Corbett (1983) have cited an interesting dose-reduction effect resulting from the combustion of coal. This is due to the fact that carbon discharged as C02 in the combustion of coal is free of the radioactive isotope, 14C. This, in turn, results in a reduction in the specific activity of carbon-14 being utilized in the carbon cycle and in the dose to biological species which interact with it (NCRP, 1985). Corbett estimates the maximum dose reduction. to a person due to the operation of a 1,000 MWe coal-fired electric generating station to be 0.02 j~Sv (0.002 mrem) per year, and a local population collective effective dose equivalent reduction of 0.15 person-Sv (15 person-rem) per year for each power station. 3.2.6.2 Combustion of Oil. Although the combustion of oil for the generation of electricity is also a source of release of natural radionuclides into the environment, the amount of fly ash from an oil-frred plant is only about one-fourth that from a coal-fired station. In addition, studies have shown that the concentrations of radioactive materials in fly ash from such a plant are much lower than those from a coal-fired plant. In fact, a study of an oil-fired plant conducted by Gordon (1968) indicated that normal environmental radioactive material concentrations around the plant were sufficiently high to preclude accurate determinations of the additional quantities discharged as a result of the combustion of oil within the plant. Similarly, Martin et al. (1969) have estimated that a typical 1,000 MW coal-fired electric generating plant with 70 percent fly ash removal may be expected to release 885 times more radioactive material than a typical 1,000 MW oil-fired plant. Further confvmation of the low level of radionuclide releases from an oil-fired plant is given in a report of the U.S. Atomic Energy Commission (USAEC, 1973) that lists total airborne releases from an oil-fued plant as being about one-hundredth of those from a coal-fired plant. In the latter case, the comparison was made on the assumption that the coal-fired plant was equipped with modem (80 percent to 97.5 percent removal efficiency) fly ash controls. In 1975, about 500 million barrels of petroleum were consumed annually in the United States for the generation of electricity (Dupree and Corsentino, 1975). This corresponds to the operation of the equivalent of thirty 1,000 M W electric generating stations. Assuming the population distribution around these plants is similar to that for coal-fired stations, it can be estimated that the total population within 16 km (10 miles) of these plants would be about 18,000,000 and that

these people would receive lung dose-equivalent rates in the range of 0.02 to 0.4 pSv/y (2 to 40 prem/y). Again, if the assumption is made that the electric power needs are met through the operation of a larger number of plants of smaller capacity, the number of people exposed would probably be larger, but their lung dose-equivalent rates would probably be correspondingly reduced. In either case, however, the dose-equivalent rates are so low as to make the contribution from this source of little significance in the assessment of the total population dose from consumer products. 3.2.6.3 Combustion of Natural Gas. Natural gas contains on the order of 370 to 740 mBd1 (10 to 20 pCi/l) of radon. This amount contributes less than 370 TBq/y (lo4Ci/y) to the worldwide inventory, estimated to be 1.5 EBq (40 MCi) (NCRP, 1975). The dose equivalent to the lungs of people using natural gas in cooking ranges in the home has been calculated by Barton et al. (1973) and appears to be about two percent of the normal natural background dose equivalent from radon and its decay products. On that basis, the resulting effective dose equivalent rates to people in homes using natural gas for cooking would be about 20 aSv/y (2 mremly) to the alveolar region and 90 pSv/y (9 mrem/y) to the segmental bronchial region of the lung. This latter estimate agrees well with the 60 pSv/y (6 mremly) value reported by Johnson et d.(1973). According to the American Gas Association (AGA, 1974). the number of residential households using natural gas is about 41 million. If there are, on an average, 3.1 persons per household, the total number of people exposed to radon from the combustion of natural gas in ranges within homes in the United States is estimated to be about 125 million. The average annual bronchial epithelial dose equivalent to those people who are exposed would be about 50 pSv (5 mrem). Using a weighting factor of 0.08,4 the annual average effective dose equivalent to these people would be about 4 pSv (0.4 mrem) and the associated collective effective annual dose equivalent would be about 500 person-Sv (50,000 person-rem). In addition, i t is estimated that about 16 million people are exposed to radon as a result of the combustion of natural gas in unvented heaters in homes. The dose-equivalent rate to the bronchial epithelium for tbcse people is estimated to be about 0.22 mSv/y (22 mremly) (Johnson et aL, 1973; Gesell, 1974). Again, using a weighting factor of 0.08, the annual average effective dose equivalent to these people would be about 18 pSv (1.8 mrem) and the associated collective effective annual dose equivalent to the U.S.population would be about 290 person-Sv (29,000 person-rem). 'See Section 3.2.1.

3.2 NATURAL RADIOACTIVE MATERIALS

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39

Moghissi et al. (1978) have summarized data on collective doses resulting from the use of natural gas. These estimates were based on state-by-state data provided by Johnson et al. (1973). Estim'ates of the annual doses to the tracheobronchial section of the lung were 8,500 organ-Sv (850,000 organ-rem) due to the operation of unvented space heaters and 18,000 organ-Sv (1,800,000 organ-rem) due to the operation of gas ranges. The estimated associated annual effective dose equivalent for people exposed to space heaters was about 50 pSv (5 mrem); the estimate for people exposed ta gas ranges was about 10 pSv (1 mrem). The %n concentrations assumed in the natural gas were 5,550 mBq11 (150 pCi/l) for California, 3,700 mBq/l (100 pCi/l) for Texas, 1,850 mBq/l (50 pCi/l) for another 5 states, and 370 mBq/ 1 (10 pCi/l) for all other states. A similar analysis of the use of liquefied petroleum gas (LPG) yields annual collective doses to the tracheobronchial section of the lung of 105 organ-Sv (10,500 organ-rem) from unvented heaters, and 185 organ-Sv (18,500 organ-rem) from ranges (Gesell et d, 1977). These estimates are based on an assumed 713,000 dwellings with unvented LPG heaters and 5.3 million dwellings with LPG ranges.

3.2.7

Glass and Ceramics

Naturally occurring radioactive materials have been used in the glass and ceramic industry for over 150 years (Jensen, 1952). Uranium compounds have been employed to produce fluorescent glassware, a variety of colored glazes, and wall tiles. More recently uranium has been incorporated into artificial teeth both for coloring and fluorescent properties. Thorium compounds have been used in wall tiles and electrical materials. 3.2.7.1 Uranium in Glassware. Sodium uranyl carbonate has been commonly employed in the production of fluorescent and iridescent glass. In particular, it was popular until the 1940's to use this material to produce dichroic properties in glass. As the concentration of uranium is increased, the glass becomes more opaque. In 1972 two manufacturers were identified as using uranium as a colorant in nonfood glass products such as candlesticks and flower containers. Federal regulations allow glassware to contain up to ten percent by weight uranium or thorium, except in commercially manufactured glass brick, pane glass, ceramic tile, or other glass or ceramic used in construction. Uranium or thorium concentrations in these latter items are limited to 0.05 percent (CFR,1986~).

40

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3.

RADIOACTIVE MATERIALS

Uranium in Glazes. Uranium in the form of oxides and as sodium uranite has been used to produce glazes of black, brown, green, and the spectrum from yellow to red. The glazes were frequently used to decorate tableware and pottery at concentrations ranging from one to twenty percent by weight. As with glassware, the restrictions on the availability of uranium during the 1940's forced manufacturers to find other coloring agents. Since the substitutes were frequently more economical, uranium has not often been used in glazes in recent years. At present no manufacturer is known to use uranium as a glaze for dinnerware. U.S.Nuclear Regulatory Commission (USNRC) exemption limits are set at a maximum of 20 percent by weight (of the glaze) for uranium compounds in glazed ceramic tableware (CFR, 1986~). The acceptability of ceramic glazes for use in food containers is subject to the food additive provisions of the Food and Drug Administration and the use of such glazes is prohibited unless specifically approved. No approvals for such applications of uranium ceramic glazes have been granted to date. Measurements using film badges have shown that surface dose rates due to gross beta and gamma radiation from various tableware items glazed with uranium range from 5 to 200 pGy/h (0.5 to 20 mrad/h) (Menczer, 1965). Measured uranium enamel surface dose rates of 37 pGy/h (3.7 mrad/h) have been reported (USNRC, 1983). In addition to the external exposures, uranium and lead have been found on occasion to be leachable from glazed ceramics at levels of 10to 55 ppm (concentration in the leach solution) (Kendig and Schmidt, 1972).The latter is equivalent to 630 mBq/ml (17 pCi/ml) which is in excess of the Maximum Permissible Concentration in drinking water for occupational exposures, 220 mBq/ml (6 pCi/ml) (NCRP, 1959). At the measured concentrations, the chemical toxicity of uranium is considered to be a greater hazard than its associated radiation. As a result of these measurements, the only known producer of uranium glazes for use in foodware in the U.S. has ceased operations. 3.2.7.3 Uranium in G h s Enamel. Uranium has also been used as a coloring agent in various enamel objects, including tableware and jewelry. Problems associated with the use of such items were highlighted by reports in the early 1980's of relatively high exposures associated with the use of cloisonne jewelry. A surface dose rate of 37 pGy/h (3.7 mrad/h) from similar sources has been reported by staff members of the U.S. Nuclear Regulatory Commission (USNRC, 1983). Such jewelry, most of which was being imported, has proven very popular in the U.S. and could be worn in direct contact with the body. Stimulated by these problems, the U.S. Nuclear Regulatory Commission in 1983 banned the use of uranium in enamel products to be sold

3.2.7.2

3.2

NATURAL RADIOACTIVE M A T E W

41

in the U.S. (USNRC, 1983, 1984). Produds already distributed to retail outlets and consumers were not recalled because of logistical problems and the relatively low estimates of the associated radiological hazard. 3.2.7.4 Dental Products. Porcelain teeth and crowns are composed principally of feldspar minerals that contain small quantities (0.001 percent) of naturally occurring aK.The practice of adding uranium salts was initiated at least half a century ago when it was discovered that small amounts of the element contributed a natural color and fluorescence to dentures. Restoration of natural appearance is one of the major reasons for using prostheses. Other substances have been found to imitate these characteristics over a broad range of daylight and artificial lighting conditions. The concentrations of uranium required were considered trivial and easily qualified for a licence exempt status when controls were imposed in the 1960's on the use of source material in ceramics. Under regulations of the U.S. Nuclear Regulatory Commission, neither domestic nor imported teeth and powders may contain in excess of 0.05 percent by weight of uranium (CFR, 1986a). Dental products also contain naturally occurring radioactive potassium but there are no controls over the potassium content in these products. A study by O'Riordan and Hunt (1974) in Great Britain indicated that porcelain teeth containing 0.10 percent uranium could deliver an annual dose equivalent to the oral mucosa of almost 6 Sv (600 rem) by alpha particles and 0.028 Sv (2.8 rem) by beta particles. This estimate is in close agreement yith a more recent study by Papastefanou et ul. (1987) in Greece in which it was reported that uranium concentrations of 500 ppm could yield a surface dose equivalent of about 4 Sv (400 rem) per year. In a study of dental products in the U.S. (Thompson, 1976), the highest concentration observed, 0.044 percent, was calculated to deliver an annual mucosal dose equivalent of 1.3 Sv (130 rem) from alpha emissions. However, the maximum range of alpha particles in tissue is 30 pm so that most of their energy is expended in the superficial cells overlying the sensitive basal layer. Saliva, dental pellicle, calculus, food, and tobacco residues in the mouth further reduce the intensity of the alpha flux to a level where it does not appear to present a significant hazard. Beta particles can penetrate in tissue to a depth of 200 pm. The combined beta emissions of uranium and potassium-40 for the highest concentration sample observed in a study by the Bureau of Radiological Health, were calculated to deliver an annual dose equivalent of 9 mSv (0.9 rem) to the basal layer. The average concentration of uranium in U.S. dental porcelain was estimated to be 0.02 percent. This

42

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3. RADIOACTIVE MATERIALS

corresponds to a uranium beta dose equivalent rate of about 5 mSv (0.5 rem) per year. The potassium-40 contribution generally ranged from 1.4 to 1.9 mSv (0.14 to 0.19 rem) per year. As of 1971, over 19 million persons in the United States were estimated to wear full dentures and 60 million to wear crowns (DHEW, 1962, 1971). Some 90 million persons were missing at least one tooth although it is not known how many wore bridges or partial dentures. More recent published estimates are not available; however, knowledgeable sources in the dental industry indicate that 40 percent of new dental prostheses contain porcelain, and that uranium is no longer used in porcelain by domestic manufacturers (ADA, 1986). The balance of dental products are acrylics and do not contain uranium. If it is assumed that 45 million people are wearing dental prostheses with an average concentration of 0.02 percent uranium, and that only beta dose need be considered, they will receive a dose equivalent to 7 mSv (0.7 rem) to the basal mucosa. The contribution from this source to the average annual population dose equivalent to the basal mucosa of the mouth would be estimated to be about 1.3 mSv (0.13 rem). On the basis of a weighting factor of 0.01 for the human skin, and assuming that irradiation of the basal mucosa is equivalent to irradiation of 1 percent of the skin, the weighting factor for irradiation of the basal mucosa could be estimated to be 0.01 x 1percent or The resulting annual collective effective dose equivalent to the U.S. population from this source would be 31.5 person-Sv (3,150 person-rem). This dose is expected to decrease over time as porcelain without uranium displaces the old porcelain containing uranium for use in dental prostheses. 3.2.7.5 Uranium and Thorium Impurities in Ophthalmic Glass. Ophthalmic glass is used to manufacture lenses for eyeglasses and eyepieces. At present, up to 0.05 percent by weight of source material (uranium or thorium or any combination of these materials) may be contained in any chemical mixture, compound, solution, or alloy without NRC regulation or license requirements. There is a further maximum allowable limit of 0.25 percent by weight of source material in rare earth mixtures and products (CFR, 1986~). Pecora and Munton (1974) have reported that ophthalmic lenses, tinted by adding thorium salts, can be a source of radiation. They tested rose-tinted lenses from several manufacturers and concluded that the dose-equivalent rate to the corneal epithelium from alpha radiation was 0.1 to 0.3 mSvjb (10 to 30 mrem/h). At a depth of 0.2 cm, the beta dose-equivalent rate was calculated to range from 0.7 to 2 pSv/h (0.07 to 0.20 mrem/h) with a gamma dose-equivalent rate to the entire eye of 0.06 to 0.3 &/h (0.006 to 0.030 mremb). Another study (Yaniv, 1974) reported thorium concentrations of up to 0.14

3 2 NATURAL RADIOACTIVE MATERIALS

/

43

percent by weight in some samples of ophthalmic glass, with large variations in natural thorium and uranium content for different batches of glass. Thorium has been shown (McMillan et al., 1975) to exist as an impurity in the rare earth oxides that are used in the manufacture of certain ophthalmic glasses. The thorium content was found to exceed the limit specified in federal regulations (CFR, 1986a) by as much as a factor of ten. These oxides, and their impurities, are generally thought to be the primary source of radioactivity in certain ophthalmic glasses. Dose calculations by Tobias and Chatterjee (1974) indicate that the annual alpha-particle dose to the critical tissues of the germinal cell layer of the cornea (50 pm), from eyeglasses containing 0.05 percent by weight of T h in equilibrium with its decay products and worn for 16 hours a day, is 2 mGy (0.2 rad) (estimated to be accurate within a factor of two), with an approximately equal absorbed dose from beta particles. Using these data, and applying a quality factor of 20 for alpha radiation, Casarett et al. (1974) estimated that the dose-equivd e n t rate to the germinal cells of the cornea (50 pm depth) would be approximately 40 mSv/y (4 remjy). The dose-equivalent rate a t 60 pm tissue depth was estimated to be 10 mSv/y (1remjy). The beta doseequivalent rate would be a small fraction of this, however, because of the much smaller quality factor of this radiation. The Yaniv (1974) study concluded that the radiation dose rates from the ophthalmic glass could be reduced significantly with better quality control of the rare earth and zirconium oxides. Another problem revealed by this study was that the observed radiation is not directly related to the source material content of the glass, due to widely varying daughter-parent equilibrium conditions. The radiation emissions are, in fact, mainly due to the short-lived decay products of T h and 9, which can be present in glass even after the parent radionuclides are removed. Thus, control of source material content is not sufficient to eliminate radioactive material from glass. Yaniv recommended that new regulations for ophthalmic glass be established on the basis of emission rates rather than on the abundance by percent of weight of the parent nuclide. The Optical Manufacturers Association, with the assistance of the U.S. Nuclear Regulatory Commission and other governmental agencies, has established a voluntary radiological standard for ophthalmic glass (OMA, 1975). In 1977, about 96,000,000 persons in the U.S.wore eyeglasses (BOC, 1979). Currently, it is estimated that about half of the eyeglasses in use in the U.S. contain plastic lenses which do not contain radioactive material. The same is true for plastic contact lenses (Buckley et al.,

44

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3. RADIOACTNE MATERIALS

1980). As a result, the current estimate of the number of people who are wearing eyeglasses with glass lenses in the U.S. totaIs about 50,000,000. Assuming an annual dose equivalent of 40 mSv (4 rem) to the comea at 50 micrometers depth, and assuming a tissue weighting factor of the annual collective effective dose equivalent to the U.S. population would be about 1200 person-Sv (120,000 personrem).5

3.2.8

Thorium Products

Thorium is used in optical glass, gas mantles, tungsten welding electrodes, and in various metal alloys. Approximately 250,000 pounds of thorium were used for these purposes within the United States during 1972. 3.2.8.1 Thoriated Optical Glass. Thorium is added to optical instrument glass in concentrations up to 30 percent by weight to provide certain optical properties. Specifically, glasses having an index of refraction greater than 1.65 or with a product of Abbe number and index of refraction greater than 70 are often made with glasses of high thorium content. The most abundant isotope of natural thorium, 232Th,is the very longlived parent of the "thorium series." The presence of the decay products in equilibrium with the parent produces alpha-emission rates six times the parent emission rate. Along with the alpha emissions, a very significant beta- and gamma-emission rate also exists. The use of thorium in optical glass raises few problems unless the glass is used for an eyepiece in an optical instrument. The alpha and beta radiations are easily stopped by almost any lens enclosure. However, the direct exposure of the eye to a lens a t a close distance for long periods of time can deliver a significant dose to the outer tissues of the eye. The use of these special optical glasses near the eye is not authorized under the exemptions issued by the U.S. Nuclear Regulatory Commission (CFR, 1986~).However, cases have been reported of eyepieces containing large quantities of thorium (McMillan and Home, 1973). These thoriated eyepieces were without labels or specifications indicating that thoriated glass was used The extent to which these lenses are used (deliberately or inadvertently) for eyepieces in optical instruments is not known. 'There are no reported radiation induced cancers of the comea Based on this obscmtion, a weighting factorof s104 has been considered appropriate for estimating the effective dose equivalent due to exposures of this organ.

3 2 NATURAL RADIOACTIVE MATERLALS

1

45

Casarett et al. (1974) have calculated the dose-equivalentrate delivered to the critical tissue (50 to 60 pm depth) of the eye. They assumed that the eyepiece of an instrument that was used for 20 hours per week by a professional user was made from glass with 16 percent 232Thin equilibrium with its daughters. By also assuming an air gap distance of 0.1 cm between the lens and the outer surface of the lacrimal layer of the eye, they calculated the annual absorbed dose to the critical tissue of the eye at 50 and 60 pm depth to be 0.44 and 0.18 Gy (44 and 18.rad), respectively. With the assumption that the quality factor for alpha particles is 20, the corresponding dose-equivalent rates to the eye are 8.8 and 3.0 Sv/y (880 and 360 rem/y), respectively. Eyepieces made from glass having 0.05 percent thorium may be expected to yield a dose-equivalent rate of approximately 30 mSv/y (3 rem/y) at 50 pm depth. McMillan and Home (1973), after having discovered that these lenses were being used as eyepieces, made similar calculations. Their calculated results agree with those of Casarett et al. to within 20 to 40 percent. They also confvmed by laboratory measurement the accuracy of their calculated fluence rates at the surface of the glass. One measurement of a lens containing 18percent thorium by weight yielded a dose rate a t the surface of 10 p G / h (1mrad/h). The number of such lenses in use is unknown although it is probably small. An estimate of the average annual population dose equivalent is not possible. 3-2.8.2 Gas Mantles. The mantles in gas-lanterns and gas yard lights consist almost entirely of the oxides of thorium (95 percent), magnesium, aluminum, cerium, beryllium, and silicon. These mantles are the major incandescent element in such lanterns. During their initial curing, they release about 50 percent of their stable beryllium oxide and many of the decay products of thorium into the atmosphere (Griggs, 1973). Although beryllium probably represents the greater health hazard, because of its chemical toxicity to the lungs, alpha and gamma radiation associated with the thorium oxide can also result in radiation exposure to the user. Recent reports indicate that about 25 million thorium gas mantles are distributed annually in the U.S. (O'Donnell and Etnier, 1981 and Buckley et al., 1980). Approximately 85 percent are used in portable lanterns (e.g., camping), 8 percent in residential and commercial outdoor lights, 5 percent in residential indoor lights and 2 percent in recreational vehicles. The collective dose rate estimates for transportation, distribution, and use of these devices are about 9 person-Sv/y (900 person-rem/y) (Buckley et al., 1980) and 40 person-Sv/y (4,000 person-rem/y) (O'Donnell and Etnier, 1981). The major differences are due to an estimate by O'Donnell and Etnier of a dose of 10 person-

46

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3. RADIOACTIVE MATERIALS

Sv/y (1,000 person-rem/y) due to indoor residential use and 7 personSv/y (700 person-rem/y) due to use in recreational vehicles. The more comprehensive estimates of O'Donnell and Etnier are summarized in Table 3.16 and are considered the best estimate of current doses due to thorium gas mantles. O'Donnell and Etnier caution that "The dose calculations were complicated by uncertainties regarding the radionuclide composition in new mantles, the behavior of the nuclides during mantle operation, the rate of "% diffusion from the mantles and the behavior of mantle changers." These uncertainties result in a range of dose estimates (as noted in Table 3.16). It was the conclusion of O'Donnell and Etnier that while % and its progeny would certainly volatilize during burning of the mantle, the radium/actinium may not. The radon and progeny account for about 60 percent of the external radiation and will reach equilibrium rather rapidly. Radionuclides in the radiumjactinium group account for about 40 percent of the external radiation and a major portion of the doses due to ingestion. They grow back into equilibrium very slowly. If these radionuclides are removed either during manufacture or initial burning, the doses, except those due to inhalation, would be much reduced. O'Donnell and Etnier (1981) also estimated doses from miscellaneous events such as campground contamination I0.006 pSv (0.0006 mrem) during a 2-day camping trip] and from ingestion of a mantle [2 mSv (200 rem) to the total body, 9 mSv (900 mrem) to the bone and 0.8 pSv (0.08 mrem) to the lungs]. These and other internal doses are 50-year dose commitments. TABLE 3.16-Dose

estimates for Mlural distribution of 25 millwn thorium gas mantlesm

Individual almual doses

total boay (mSvP

Marimurn

Transport Distribution and instal-

lation campers Indoor residential Outdoor

Recreational vehicles Disposal Total best estimate)

'O'Domell and Etnier, 1981. 1 mSv = 100 mrem. '1 personSv = 100 person-rein.

Average

Annual co11eaive population doses (penon or organ-9~)' Lungs

3.2 NATURAL RADIOACTIVE MATERIALS

1

47

Using the data presented in Table 3.16, the annual collective population dose due to the annual distribution and use of 25 million thorium gas mantles would be about 86 personSv (8,600 person-rem). This is based on an assumed weighting factor of 0.03 for estimates of the effective dose equivalent due to exposures to the bone, and of 0.08 for estimates of the effective dose equivalent due to exposures to the lung. 3.2.8.3 Camera Lemes. The presence of elevated concentrations of radioactive material in camera lenses has been discussed in three recent reports (Taylor et al., 1983; Lewinsky, 1985; and Waligorski et al., 1985).All three reports identify U2Thand its progeny as the source of the radioactive material. Lewinsky (1985) reported on a lens system in a television camera that contained five lenses. Three of the five contained elevated concentrations of 232Th with the contact dose rate of the front lens measuring 30 pGy/h (3 mrad/h) gamma and 100 pGy/h (10 mrad/h) beta. A dose of 10 crSv (1mrem) in 24 hours was estimated at a distance of 0.5 meter from the lens. Waligorski et aL (1985) reported the observation of elevated levels in 13 of 80 photographic lenses while Taylor et al. (1983) o b s e ~ e delevated concentrations in 12 of 32 lenses involving 11different brands. Al! 11 samples of 1 brand, and 1 lens of a different brand, were observed to have elevated levels. Waligorski et J.reported both survey meter (GM)and TLD measurements. The TLD measured dose rates were 24.0 x 10" C/(kgh) (9.3 d / h ) contact with the lens surface and 0.4 x C/ (kgh) (0.15 mR/h) at the film plane in the camera for the maximum activity lens. Survey meter measurements by Taylor et d.,(1983) gave a value of 4.8 pGy/h (0.48 mrad/h) at contact and 0.8 pGy/h (0.08 mrad/h) at the back of the camera. In this case, Taylor et d.estimate an abdominal dose of 5 pGy (0.5 mrad) during 6 hours of daily use. If these samples are representative of p2Th concentrations in popular 35 mm camera lenses, this source might constitute a significant exposure of the population. In the absence of more definitive data, no population dose estimates can be made. 3.2.8.4 Thoriuted Tungsten Welding Rods. One of the electrodes utilized in electric arc welding contains thoriated tungsten. Such electrodes have the reported advantage of easier starting, greater arc stability and less weld metal contamination. Such electrodes are commonly used in the construction industry, and in the aircraft, petrochemical, and food processing equipment industries. It is estimated that 1,350 to 1,500 kilograms of thorium dioxide are used annually in the manufacture of thoriated tungsten electrodes in the United States, and the annual distribution of rods is estimated at 5.2 million (Buckley et al., 1980). Assuming a 2 percent content of

thorium dioxide (the most common value), the average rod will contain 0.275 gram or 1,130 kBq (30.6 pCi) of thorium. Estimates were made at the Oak Ridge National Laboratory of the doses resulting from the distribution, use, and disposal of such rods (McDowell-Boyer, 1979). Exposures result from external whole body radiation and from the inhalation of 220Rn and its decay products as well as radioactive materials volatilized during the welding process and during the disposal (incineration) of the discarded rods. Of the two, the doses resulting from inhalation dominate. A summary of these doses, as reported by Buckley et al. (1980) is presented in Table 3.17. The primary exposures occur during the use of the rods. Per year of exposure, typical 50-year whole body dose commitments due to internal exposures are estimated to range from 4 to 140 pSv (0.4 to 14 mrem) for welders who are classified as heavy users, to 1 to 30 pSv (0.1 to 3 mrem) for occasional welders, to 6 to 40 pSv (0.6 to 4 mrem) for people working with the welders. Estimates of the 50-year dose commitment to the bone for welders range from 550 pSv to 0.02 Sv (55 to 2,000 mrem) for a one-year exposure. Welders using such rods on an occasional basis were estimated to have a 50year dose commitment to the bone ranging from 0.01 to 1.0 mSv (10 to 100 mrem) for a one-year exposure. The maximum individual bone dose commitment for nonwelders was estimated to range from 0.03 to 0.23 mSv (30 to 230 mrem). External dose rates for these people were all estimated to be less than 10 pSv/y (1 mrem/y).

TABLE 3.17-Annual dose equivalent estimates for thorioted tungsten welding rods' Liver

Collective dose Dibution

Usec Incineration Total

0.04 8 0.5 8.5

Bone

Log

GI

(person or organ-SV)~

-

-

-

8

200

0.5 8.5

10 210

120 5 125

0.05 0.001 0.05

-

C o d

8 0.5 8.5

(Total annual collective effective dose equivalent - -50 person-SV) Individual dose 54 Warehow fire' 0.05 0.05 1.3 0.7 0.2 0.05 (Effective dose eauivalent

-

0.3 w-n-SV)

1 l n - S v = 100 person-rem. For purposes of these estimates,the geometric mean values were used This provides what is believed to be reasonable estimates of the associated population dose equivalents. 1 Sv = 100 rern. 'A &man was assumed to be exposed for 8 hours to a fire in a warehouse that contained 50,000 welding rods.

3.2

NATURAL RADIOACTIVE MATERIALS

1

49

On a nationwide basis, it is estimated that some 300,000 people are exposed annually in the direct or indirect use of thoriated tungsten welding rods in the U.S. and that the total annual collective effective dose equivalent is about 50 person-Sv (5,000 person-rem). 3.2.8.5 Fluorescent Lamp Starters. A fluorescent lamp starter typically contains thorium to produce ionization within the starter. The starter is basically a switch which applies the voltage to the fluorescent tube after sufficient preheating to allow the tube to conduct an electric current. The starters used typically on 40-watt consumer lamps significantly extend the functional life of the tube. According to Buckley et al. (1980),about 6 million starters are sold annually with a total of 50 million being in use. The average starter contains 185 mBq (5 pCi) of thorium. The collective dose during use is estimated at about 0.005 person-Sv (0.5 person-rem) per year. For a "worst casen accident, a warehouse fire of 500,000 starters, the dose to the bone of an individual was estimated at 4.7 mSv (0.47 rem).

4.

Miscellaneous Exposure Sources 4.1

High Voltage Vacuum Electronic Units

There is a variety of high voltage vacuum equipment which appears to be capable of emitting x rays during use. This includes high voltage vacuum switches, capacitors, voltage dividers, and relays. In general, potentials of more than 15 kV across a gap in a vacuum chamber cause emission of x rays only when there is a source of electrons to be accelerated. X rays may be expected in these high voltage devices therefore only in the event that the electrons are ejected from the negative electrode or from residual gas within the device. The intensity of these x rays would be expected to vary over a wide range and would depend on the condition of the device as well as the applied voltage. By far the largest application for these devices is high voltage vacuum interrupters incorporated into circuit breakers used for electrical power switching. About one half of the circuit breakers are used by utilities and the remainder among industry and other heavy power users. Vacuum interrupters for these applications have a design operating voltage of 15.5 kV. A voluntary standard published by the American National Standsrds Institute (ANSI, 1972), ANSI-C37.85, "Safety Requirements for X-Radiation Limits for AC High-Voltage Power Vacuum Interrupters Used in Power Switchgear," sets design limits for these devices. Two segments of the population are most likely to be exposed to these sources: (a) persons at the factories who test these products before packaging; and (b) persons who work around or perform maintenance on circuit breakers containing interrupters. Under current conditions, neither group of people would be classified as radiation workers and monitored for the associated exposures. Approximately 55,000 interrupters are manufactured annually in the United States. No detectable x-ray emission has been observed at the 15.5 kV operating range. Dielectric withstand test voltages between 37.5 and 50 kV are applied for 1minute during the manufacturing and 50

'

4.1 HIGH VOLTAGE VACUMN ELECTRONIC UNITS

I

51

test process. Test results indicate that the probable exposure rate during testing is less than 3.9 x loe7 C/(kgh) (1.5 mR/h) at 1 meter. If it is assumed that 20 people conduct all of the testing and are located at a minimum distance of 2 meters during application of high voltage and each person shares the exposure equally, then each would receive an annual dose equivalent of about 0.2 mSv (0.02 rem) to the gonads. Data are not available to estimate the exposure to personnel from the circuit breakers in normal use. There are no data to suggest that emission increases with age for interrupters operating in these kV ranges. The time the interrupters are in the open position is small and highly variable and electrical safety dictates access denial. In addition, the circuit breaker hardware provides some degree of shielding. It is unlikely that personnel would be exposed to x-ray emissions from vacuum interrupters incorporated into power distribution circuit breakers. Studies (ORNL,1968; BRH, 1970, 1972; Haywood, et al., 1970; Greenhouse and Peterson, 1972) have shown that some high voltage vacuum equipment, particularly that intended for use at potentials greater than 50 kV, will emit x rays when operated at or above design levels with the contacts open. These studies were made on high voltage vacuum devices similar to those shown in Fig. 4.1, which, though not necessarily representative of widely used devices, serve to demonstrate the problems involved. Measurements with the contacts open and applied potentials greater than 30 kV revealed that x-ray emissions were greater in used devices than in new devices (see Fig. 4.2). This result is due to increases in electric field strength from pitting and erosion of the electrodes. No x-ray emission would be expected when the switch is closed, and none has been reported. Other radiation exposure characteristics of high voltage vacuum devices of importance in population dose assessment include the angular distribution of the radiation, the decrease in radiation as a function of time after the potential is applied, and the effective photon energy. X-ray exposure rates for several different switches for AC and DC high voltage are presented in Table 4.1. The Table indicates that the exposure rate at 1m from a switch can be very high [greaterthan 2.58 x C/(kgh) (100 mR/h)] and could present a significant problem. It has been observed that improperly operating devices often produce extremely high exposure rates. Greenhouse and Peterson (1972) report that an improperly operating relay produced an estimated exposure rate of 51.6 x C/(kgh) (20 R/h) at 1m.

52

/

4.

MISCELLANEOUS EXPOSURE SOURCES

Fig. 4.1. Diagram of a typical high voltage switching tube (from ORNL, 1968).

Estimates have been made indicating that about 5,000 switches with ratings 250 kV are manufactured each year and tested at 75 kV for 5 minutes each. For these tests, the potential exposure rate may be as high as 10.3 X 10" C/(kgh) (400 mR/h) at 2 m. If a person annually tests 500 units for 5 minutes each, the potential average annual gonadal dose equivalent would be expected to be slightly less than 0.17 Sv (17 rem). Even though indications are that the number of workers potentially exposed at these dose rates is extremely small, good radiation protection practices would mandate that such workers be identified and actions taken to reduce their exposures. Because, however,

4.2.

CONTAMINATED OR IRRGDIATED MATERLGLS

/

53

-

Applied voltage kV

Fig. 4.2. Representative exposure rates for high voltage vacuum earitches (see Table 4.1) (from Greenhouse and Peterson. 1972).

the number of workers involved is small, the contribution of these products to the population dose equivalent is only 0.01 to 0.02 pSv (1 to 2 prem). 4.2

Contaminated or Irradiated Materials

Radioactive materials can occur naturally in the ores of some metals or by contamination; they can also be introduced by activation. The precious metals (silver, gold, platinum, etc.) and gems that are used in consumer or other public applications are of particular interest.

54

/

4. MISCELLANEoUS EXPOSURE SOURCES

TABLE 4.1-X-ray exposure rates for several different switches ouer a mnge of AC and AC

(kv)

High voltage contectoP (New)

45

mR/b' (at 2 m)

o

0

0

56 62

1 2

0 0

o

-

-

-

45 50 45 50 56

3 22

1 6 5 18 56

62

High voltage switch-2' (Used)

mR/W (at 1 m)

50

High voltage switch' (New) High voltage swim-1' (used)

DC high voltages' E e rate

-

20 76 237

-

-

-

45 50 56

0 1 2

0 0

0

62

7

2

D~

Exposurenteb

vm mR/W (kV)

45 50 56

(at 2 rn)

3 5 8

1

62

12

70 80 45 60

16 35

45

50 56 62 45 50

56 62

mRm'

(at 1 ml

4

6 8 16 48 98 3

4 4 8

1 2 3 4 8

0 2 2 4

25 0 1 2 2

'From O W L ,1968. Mean value of 5-minute measurement.

'Presented in units given by the authors; 1mR/h = 2.58 X lo-' C/(kg h). dUsed for RF and DC transfer switching, DC switching under load, capacitor discharging, and 60 Hz power switching -85 kV rating. Used for DC switching under load and capacitor discharging -20 kV rating. 'Used for DC switching under load, capacitor discharging and 60 Hz power switching -60 kV rating.

Radioactive materials, when used carelessly or unknowingly, can contaminate metals used for these purposes and can cause significant health hazards. Radioactive contamination in precious metals such as gold and platinum became known during the 1960's. Contaminated gold apparently came from recycled spent radon-222 seeds which had been used in cancer therapy. Lead-210 and bimuth-210, decay products of radon222, are known to deposit on the interior surfaces of gold seeds and this was undoubtedly the origin of the contamination. Concern about the problem prompted the Bureau of Radiological Health (now the Center for Devices and Radiological Health) to form a committee and meet with representatives of government, industry and medicine to promote compliance with state radiation regulations on the proper disposal of spent radon seeds (Boggs et d.,1969). About 200 gold jewelry items contaminated with radon decay prod-

4.2.

CONTAMINATED OR IRRADIATED MATE3UALS

I

55

ucts have been identified (Baptiste et al., 1984, and Stutzman and Schmidt, 1984). Most of the contaminated items are gold rings purchased prior to 1950, and they have been traced to New York State. About 155 exposed persons have been identified. Of the 135 who were identified as wearing contaminated rings,41 have developed dermatitis and 9 have developed skin cancers attributable to having worn the rings. Although most rings are old and from one geographical region, New York, there are reports of the purchase as late as 1981 of contaminated gold for use in jewelry. Since, in the past, the operation of radon plants and the use of radon seeds were common practice throughout the U.S., the problem could be more widespread. The U.S. Food and Drug Administration (FDA) recommends that suspicious cases of cancer of the fingers or dermatitis should be reported to the FDA. Exposure rates and dose rates are difficult to estimate because of widely varying conditions. Jones et al. (1968) measured dose rates for three rings using a phantom and determined maximum rates of 219 Gy (21,900 rad) per year to the basal skin layer and 44 mGy (4.4 rad) per year to the finger bone marrow. The U.S. Atomic Energy Commission (USAEC, 1960) has reported the observation of samples of platinum contaminated by '06Ru. The source of the contamination was weapons testing fallout (Kruger, 1962). It occurred as a result of the large amounts of air and water used in processing and refining this metal. Because of the relatively short half-life of lMRu(369d), and the discontinuation of major weapons testing in the atmosphere, this should no longer be a significant problem. There are still other chemical compounds (NASWRC, 1961) that have become contaminated by fission products. These products have been introduced into the environment through fallout from nuclear weapons testing and through gaseous effluents from the nuclear fuel cycle. At this time, the low radiation doses resulting from the use of such materials are not considered to be a health problem. Radioactive contamination in chemicals, however, often restricts their use for certain purposes. For example, at the present time krypton gas is contaminated with 86Krto the extent that it is no longer satisfactory as a counter gas in low-background radiation detectors. Minute quantities of radionuclides are sometimes introduced into a process for control purposes. For example, steel companies commonly incorporate 60Coin the linings of blast furnaces (NAS/NRC, 1961 and Bee et al., 1985) in order to assess the degree of erosion of the lining. As the lining becomes thinner, the measured activity in the lining

56

1

4. MISCELLANEOUS EXPOSURE SOURCES

decreases, a change signaling that the lining needs to be replaced. Erosion of the lining causes '"Co to be introduced into the steel. Although the degree of radioactive contamination is small, new steel usually cannot be used for shielding in low-level counting facilities. Other incidents have occurred where lost or misplaced radioactive sources were melted down by scrap metal foundries (Bee et al., 1985). In one case, a teletherapy source from a Mexican hospital was melted down and the contaminated steel was imported into the U.S. (USNRC, 1985; Lubenau and Nussbaurner, 1986). Radiation levels for table bases containing the steel ranged up to 1 mGy/h (100 mrad/h) on contact. The steel was recalled except for cases where it was already encased in concrete as reinforcing bar. Other cases involving contaminated products resulted in radiation exposure rates below 2 pGy/h (0.2 mrad/h), probably due to substantial dilution of the melted sources. Since 1983, however, there have been three reported incidents a t U.S. steel mills where radioactive materials have accidently been processed with steel scrap (USNCR, 1986~).Similar incidents have occurred a t foreign steel mills. The costs associated with the ~decontamination of the contaminated mills have, in some cases, exceeded $2,000,000. Fortunately, associated doses to the public have been estimated t o be small. Another potential source of radioactive products reaching the public sector is through the irradiation of various materials in research reactors. It has been reported that, in recent years, operators of several such reactors have apparently been irradiating gems, silicon chips, and other materials which, in turn, have been released to unlicensed receivers. Since such distribution is prohibited under existing regulations without specific authorization, the U.S. Nuclear Regulatory Commission has alerted licensees to this fact (USNRC, 1986d, 1987). Since the number of people exposed and the dose rates associated with each of these practices is not known, it is not possible to estimate the resulting collective population doses. With the exception of personal items such as jewelry, individual doses would be expected to be low. However, it seems likely that the introduction of contaminated materials, both accidently and intentionally, into the public domain will increase. The Department of Energy in 1974 requested authorization from the U.S. Nuclear Regulatory Commission to release to the public scrap metal with low levels of uranium and T c contamination (USNRC, 1980, 1986b). This application was subsequently denied. Many foundries and waste disposal facilities have installed radiation equipment to detect unexpected contamination or lost radioactive sources.

4.3.

4.3

DISPOSAL OF RADIOACTIVE SURPLUS lT!3MS

/

57

Disposal of Radioactive Surplus Items

Materials which contain radium have been used by the military services for more than 60 years, principally as luminous compounds in gunsights, watch dials, compass cards, and a variety of aircraft instruments. An early reference to the use of radium in aircraft reports that instruments with self-luminous dials were used in the Navy flying boat NC-4 which flew the Atlantic Ocean in 1919 (Halperin and Heslep, 1966). M a n y surplus military items that contain radioactive materials have been made available for purchase by the public in retail stores. For example, large numbers of aerial cameras, produced in the 1940's and equipped with lenses containing thorium, were later sold without restriction as war surplus. It has been estimated that 10 grams of radium were used by the military services in luminous compounds during World War I. The quantity used in World War I1 is estimated to be several hundred grams and additional amounts were used during the intervening years. Other examples of military items containing radioactive materials that have found their way into the commercial market, largely through retail war surplus stores, are listed in Table 4.2. Typical amounts of 226Rapresent in individual self-luminous pieces as reported by Halperin and Heslep (1966) range from 2 x lo3 to 55 x 105Bq (0.06 to 14.6 pCi) (see Table 4.3). Another source of exposure to be considered with respect to military surplus items is the dose to customers standing for periods of time near storage bins displaying such items within stores. In 1964 the Bureau of Radiological Health of the California Department of Public Health (Halperin and Heslep, 1966) observed readings of 12.9 x 10"

TABLE 4.2-Examples

of commodities eonmining nufiooctioe materials tfwt huve been

observed on sale in military s w p h stow' Aircraft turn and bank indicators Aircraft tuning metem Manifold pressure gauges Altimeters Oxygen flow indicatm Electric engine speed indicators Field telephone components Pocket compass components Electron tubes

'Based on Halperin and Heslep, 1966.

O i l pressure gauges Lewyt black light meters Toggle switches C i t breakers Switch knobs Remote control indicator units Ship clocks Surface lookout alidade8

TABLE 4.3-Radium-226 content of

typicaf swplus lcrmimus items' Activity

Itam (uCi)

Luminous diaLs Toggle switch Switch knob Speedometer

Luminous markers

0.06 to 4.4 0.3 0.3 to 1.3 0.37 0.4 1 lto5 1 to 10

Japanese meter

14.6

Alarm clock Pocket watch Aircraft circuit breakers

(kJ3a)

From Halperin and Heslep, 1966.

C/(kgh) (5 mR/h) at the face of a storage bin and 5.2 x lo-' C/(kgh) (2 mR/h) in the center of the aisles inside one war surplus store. Beginning in 1968, the U.S. Army prohibited the procurement of self-luminous items containing radium (Taras, 1978). During recent years, U.S. Department of Defense agencies have been actively disposing of radioactive products as radioactive waste rather than allowing such products to enter surplus channels. Discussions with state radiation program personnel confirm that few radioactive products are entering the consumer market from government surplus at the present time. In those few cases that have been observed, the U.S. Department of Defense has removed the product for disposal as radioactive waste. Because of the better control and absence of identified distributions of such materials, accompanying population exposures are believed to be minimal and no dose estimates have been made for this source.

4.4 Aircraft Transport of Radioactive Materials Most of the radiopharmaceuticals used in the United States have short half-lives, and, therefore, are shipped by the fastest means possible to the hospitals or clinics where they are to be used. This usually means transport by passenger aircraft at some point in the journey. Such shipments can cause radiation exposures to passengers, attendants, and pilots, as well as ground personnel. Data published by Barker et ad. (1974) indicate that the total number of passengers traveling by aircraft each year in the United States was about 175 million, making approximately 5 million departures from over 300 airports. It is estimated that in 1975 about 800,000 packages

4.4.

AIRCRAFT TRANSPORT OF RADIOACTIVE MATERIALS

/

59

of radioactive material (USNRC, 1976b), most of which contained radiopharmaceuticals, were transported by such aircraft. Radiation surveys on board aircraft have shown that approximately 6 million passengers and crew members are exposed annually to radiation from such shipments. The distribution of doses to these people, as estimated by Barker et al. (1974) is shown in Table 4.4. Other estimates indicate that the annual dose equivalents for selected groups of passengers may range up to 1.6 to 1.7 mSv (160 to 170 millirem) (USAEC, 1974). Projections in 1977 indicated that the number of radiopharmaceutical packages transported by passenger aircraft would increase at an annual rate of 15 to 20 percent, and that the average annual radiation dose to passengers and crew members would increase proportionately. In 1980, however, the Department of Transportation regulations applicable to such shipments were amended (DOT, 1980), and additional restrictions were placed on the radiation exposure rates, number of packages, and the required separation distances for packages handled in such shipments. As a result, the number of shipments and the corresponding doses to aircraft passengers have not increased as rapidly as projected in 1977. Based on the data shown in Table 4.4, the total collective dose to the U.S. population in 1974 due to the transport of radioactive materials on passenger aircraft was about 15person-Sv (1,500 person-rem). The total collective dose today would be about 30 person-Sv (3,000 person-rem). TABLE 4.4-Dose equivalent from aircroft bumport of radimtiue materials' Erposed group

Passengers Pilots Attendants

Number of exposed

Average annual dce-quivalent ( ~ S V ) ~

Collective dose equivaknt [person-Sv)'

6 X lo6 1.5 x lo' 2x10'

0.0023 0.0007 0.035

13.8 0.01 0.7

Persons

Tatal

'From Barker et aL, 1974.

" 1 mSv = 100 mrem. ' 1 person-Sv = 100 person-rem.

14 51

5. Summary This examination of the available information indicates that there continues to be a variety of consumer products and miscellaneous sources of ionizing radiation that result in low levels of exposure to the U.S. population. Comparison of the data summarized here with those presented in NCRP Report No. 56 (NCRP, 1977) shows three significant differences. First is the estimate of the dose equivalent to the bronchial epithelium of cigarette smokers due to the presence of '?Po in tobacco. In the earlier NCRP Report, the dose equivalent rate from this source was given as 80 mSv/y (8 rem/y); in this report, this value has been doubled due to an intervening change in the quality factor assigned to alpha radiation (ICRP, 1977). The second change is the addition of domestic water supplies as a source of airborne radon inside the home. This source was not included in the earlier NCRP report. The third change relates to the collective population dose equivalent due to the use of luminous timepieces. Evaluation by the Center for Devices and Radiological Health (CDRH, 1986b)has shown are no longer being used by that older timepieces, containing 226Ra, the U.S. public. These same evaluations have shown that timepieces incorporating 3H gas have decreased significantly, and that many members of the public own multiple timepieces incorporating 3Hpaint so that only a fraction of the t o w numbers sold are being worn at any one time. Thus, exposures resulting from this source are now estimated to be lower than those presented in an earlier NCRP report (NCRP, 1977). A summary of the number of people exposed to each source evaluated in this report, an estimate of the resulting dose equivalents to the exposed population, and an estimate of the average annual collective effective population dose equivalent (based upon an assumed U.S. population of 230 million) are presented in Table 5.1.

5.1 Sources and Estimates of Associated Population Dose Equivalents

Based on the data resulting from this overall review, it appears that consumer products can be categorized into three groups (Table 5.2), 60

5.1 ASSOClATED POPULATION DOSE EQUIVALENTS

/

61

depending on the number of people being exposed and the associated dose equivalents: Group I-involves large numbers of people and the individual dose equivalent is relatively large (a)-Tobacco products (b)-Domestic water supplies (c)-Building materials (d)-Mining and agricultural products (e)-Combustible fuels-Natural gas heaters and cooking ranges (0-Glass and ceramics-Dental prostheses (g)-Ophthalmic glass As was noted from the data presented in Table 5.1, the dominant contributor to the dose to individual body organs is tobacco products. It is also important to note that the dose given is that for cigarette smokers, only. It does not include doses that may be experienced by other members of the population who are subjected to so-called "passive" smoke. Second in importance to tobacco products are building materials and domestic water supplies. Both the tobacco products and the radon in domestic water supplies, it might be noted, contribute a major portion of their dose to a single body organ, the lung. These three sources are followed by the contributions to the population dose equivalent from the use of phosphate fertilizers containing naturally occurring radioactive materials (Table 5.2). All other sources in this group are relatively small in comparison to the first three.

Group 11-involves many people but the dose equivalent is relatively small or is limited to a small portion of the body (a)-Television receivers (b)-Radioluminous products (c)-Auport inspection systems (d)-Gas and aerosol (smoke) detectors (e)-Highway and road construction materials (0-Aircraft transport of radioactive materials (g)-Spark gap irradiators and electron tubes (h)-Thorium Products-Fluorescent lamp starters and gas mantles None of the sources in this Group compares, in terms of their population dose contribution, to those in Group I. Group 111-involves relatively few people and the collective dose equivalent is small

TABLE 5.1-Radiation

source

Electronic producta Unwanted byproduet x rays Television reeeivem Video diaplay terminala I n t e n t i o ~ xl rays Airport luggage inspection systems Radioactive materials Processed radioactive materials Radioluminous products Luminous watches and clocks 'H activated watches clocks "'Pm activated watches clocke Ststic eliminators Electron tuben Gas and aerosol detectors Check source8 Natural radioactive mnteriela Tobacco products Building materials Domestic anrter supplies Highway and road construction materiels Mining and agricultural products Fertilizer producte

Combustible fuels Coal

Number of people exposed in the United States

exposure from consumer products and miscelhneous sources Average annual dose equivalent to the exposed population'

Remarks

Average annual effective dose equivalent to the exposed population'

Whole body exposure Whole body exposure 0.021 usv

Whole body exposure

Whole body exposure Whole body exposure Whole body exposure Whole body exposure Whole body exposure Whole body exposure Bronchial epithelial dose equivalent Whole body exposure Bronchial epithelial doae equivalent Whole body exposure and gonadal dose equivalent Whole body exposure and ingestion dose from food Exposure is to ssveral organs

0.021 usv

Average annual effective dose equivalent to the U.S. population'

Annual collective effective population doae equivalent (person-SvIb

Natural gaa Heaters Cooking ranges Liquified petroleum gaa

]

Glass and ceramics Dental proathesea

Basal mucosa doae equivalent Corneal germinal dose equivalent

Ophthalmic glass Thorium producta Gas mantles

Whole body exposure plus mleeted organ dose equivalent Whole body exposure plus selected organ dose equivalent Whole body expoaure plua selected organ doae equivalent

Tungaten welding rode Fluorescent lamp starbra Miwellaneoua sourcea Aircraft transport of radioactive material Passengers Pilote Attendante

Bronchial epithelial doee equivalent Bronchial epithelial dose equivalent

14,000,000 15,000 20.000

2.3pSv 0.7 pSv 35 uSv

Whole body exposure

2.4 pSv

0.13 pSv

30

' 1 mSv = 100 mrem. 1 person-Sv = 100 peraon-rem. Data neeeasary to convert the organ dose to an effective dose equivalent are not currently available (See Section 3.2.1). dAlthough mme radon is present in all domestic water supplies, (how members of the population using groundwater sourma would be expected to receive the largest doses fmm thin source. * Fatimates ofthe population dose equivalent vary so widely that only e range can be given at the present time. 'Baaed on a weighting factor of 0.08 (See Section 3.2.3). 'Based on a weighting factor of lo-' (See Section 3.2.7.4). Qaaed on a weighting factor of lo-' (See Section 3.27.6).

TABLE 5.2-Radiation

exposure from consumer products arranged in groups in actordance with their significance

Number of people exposed -

Averege annual effective dose equivalent to the U.9. population

(IISv)'

Annual wllective effective population done equivalent (person-SV)~

Croup I-involvea many people and the dose equivalent is relatively large Tobacco products Domestic water suppliea Building materials Mining and agricultural p d u c t 8 Combustible fuels Coal Natural gae hentern Natural gas cooking ranges Dental prosthews Ophthelmic glans Group 11-involves many people but the done equivalent is relatively small or is limited to a very small portion of the body Television receivers Video diiplay terminals Radioluminous products Watches and clocke Airport luggage inspection systems Gas and aerosol detectors Highway and road constmction materials Aircraft transport of radioactive materials Spark gap irradiatore and electron t u h Thorium products Fluorescent lamp starters Gas mantles G m p Ill-involves relatively Taw people and the dose equivalent is amall Thorium Products 300,000 0.2 50 Tungsten welding rodc 800,000 <0.04 <8 Check murcea Rounded Total 60-130d l2,O00-29,00~ 1 pSv = 0.1 mrem. '1 person-Sv = 100 person-rem; values have been rounded. ' Data necegaary tn convert the done to the segmental bifurcations of the bronchial epithelium (estimated e t 16 rem/y for the everage cigarette smoker) to an effective dose equivalent are not available (aee Section8 3.2.1 and 6.2). 'The tabulations do not include the contribution to the affectim d m equivalent lmm tobecco products.

5.2 SPECLAL CONSIDERATIONS

/

65

(a)-Thorium products-Tungsten welding rods (b)-Check sources Again, as may be noted from the data in Table 5.2, neither of these sources represents a significant contributor to the overall collective effective population dose.

5.2

Special Considerations

It may be noted from the data presented that the annual average effective dose equivalent from consumer products, exclusive of the dose equivalent from tobacco products, is in the range of 0.05 to 0.13 mSv (5 to 13 rnrem). This compares to a value of less than 50 gSv (5 mrem) published in NCRP Report No. 56 (NCRP, 1977). The major reason for this difference is the inclusion in this report of the contribution of exposures due to airborne radon decay products associated with the use of domestic water supplies-a source not considered in the previous evaluation-plus the intervening development of the effective dose equivalent concept which now permits estimates to be made of the whole body dose equivalents arising through partial body exposures resulting from the use of consumer products. Although it is recognized that there is considerable uncertainty in some of the dose equivalent estimates associated with the use of consumer products, it is not anticipated that the estimates presented in Tables 5.1 and 5.2 are in error by a factor of more than ten. Because of the associated uncertainties, however, the collective dose equivalents resulting from certain consumer products have had to be expressed as a range or as a "less thann value, rather than as a specific number. As a result, it has been necessary to express the overall collective dose equivalent due to the use of radiation emitting consumer products in the U.S. as a range, rather than as a single quantitative estimate. As mentioned in Section 3.2.1, also to be considered in this assessment are the doses being received by cigarette smokers due to the deposition of *loPo in their lungs. As noted in Table 5.1, this results in an annual dose of 0.16 Sv (16 rem) to the segmental bifurcations of the bronchial epithelium of the average cigarette smoker. Although the data necessary for converting this to an effective dose equivalent are not available, based on information given in Publication 32 of the International Commission on Radiological Protection (ICRP, 1981) a weighting factor of 0.08 appears to be a reasonable estimate (see Section 3.2.1, footnote 2). This would yield an annual effective dose

equivalent to the average smoker of about 13 mSv (1,300 mrem); the corresponding average population effective dose equivalent would be 2.8 mSv/y (280 rnremly). Had this approach been utilized, it would have resulted in tobacco products King the greatest contributor to the effective population dose equivalent of all consumer products. In fact, tobacco products probably would have been the greatest single contributor to the effective population dose equivalent of all radiation sources, including natural background sources and medical radiation [see the NCRP report summarking exposures from all sources (NCRP, 1987a)l. Because of the widespread recognition that a high risk of lung cancer is associated with smoking, and because the effective dose equivalent from this source is likely to be so far in excess of that from any other consumer product, it would appear mandatory to call for more detailed monitoring and evaluation of the dose equivalent from this source. Studies indicate that smokers face a risk of fatal lung cancer of about 3 to 9 percent while for non-smokers the same risk is only about 0.5 percent (Boice and Blot, 1986): The risk associated with an effective dose equivalent of 13 mSv/y (1.3 rem/y) would, in 50 years, amount to about 1 percent. This is evidently only a portion of the risk for smokers. Whether *loPois a contributing factor in the development of lung cancer (such as an initiator or promoter) can only be conjectured a t this time. The average effective dose equivalent estimates for the remaining consumer products, with the possible exception of domestic water supplies, appear to be so far below the recommended limits for the general population that additional refinements in the data are not considered necessary at this time. If the higher range of the values for the estimates of the dose equivalent arising through domestic water supplies were to prove to be the case, then this source alone could contribute as much as 60 pSv (6 mrem) annual effective dose equivalent, on the average, to the U.S. population. For certain groups using water supplies with the higher concentrations of radon, the dose equivalents could be much higher. For this reason, it would appear that further analyses of these dose estimates would be justified, coupled with additional evaluations of effective methods for mitigating these doses for those people most affected by this source. 5.3

Discussion

In evaluating the risks and benefits of the application of the various types of consumer products reviewed, a variety of matters must be

5.3 DISCUSSION

/

67

considered. Based on existing information, it appears that the following comments are appropriate. Certain sources or applications serve little or no useful purpose and should be eliminated. Egamples are the past use of radium-226 instead of, for example, the less hazardous tritium, in luminous compounds and the past use of radioactive materials as a glaze in ceramicproducts. Certain sources or applicationsserve a useful purpose but experience has shown that the same goal can be accomplished by other techniques without accompanying radiation exposure. Examples include personnel x-ray scanning systems and certain applications of static e h i n a tors. Certain sources involve significant exposure but represent practices to which the public has become accustomed through years of use. Although changes may be warranted, they will require alterations in basic human behavioral patterns and may be difficult to accomplish. Sources in this category include tobacco produds, domestic water supplies, building materials, and combustible fuels. In certain cases the use of radiation, although not mandatory, enables a task to be performed more rapidly and/or economically. In a few cases, there may be no technologically better way of conducting the given operation. As long as the associated individual and collective radiation doses are small, such applications appear to be acceptable. Examples include airport luggage inspection systems and gas and aerosol (smoke) detectors. In other cases, radiation is sometimes an unwanted by-product of the use or application of a given device. If possible, the goal should be to reduce the associated exposure to zero. Since, in some instances, this may not be practical, the goal should be to reduce and maintain the associated dose equivalent to a level that is as low as reasonably achievable (ALARA) and to continue use of the devices only as long as they represent a positive benefit to society. Examples of such sources include television receivers and video display terminals. In the latter case, it should be noted that there is essentially no radiation exposure associated with the use of such deirices. Thus, the initial goal has been achieved. Video display terminals were evaluated primarily because of the mistaken assumption on the part of many people that they are a source of ionizing radiation exposure. Lastly, there are instances of exposure to the general public that occur as a result of the transport, handling, and disposal of radioactive consumer products. Included in this category is by-product contamination of consumer products. In these cases, there is no direct benefit associated with the exposure and public health measures should be

applied to reduce and maintain associated exposures at minimum values.

5.4 Recommendations for Dose Reduction and Research With regard to dose reduction, the NCRP considers the primary factor to be the levels of exposure resulting from these sources. In related reports, the Council has defined an individual risk level that can be considered negligible (NCRP, 198%). This level corresponds to a source producing no more than 0.01 mSv/y (1 mrem/y) to the exposed individual. Sources delivering lower doses can generally be dismissed from consideration. Among the sources listed above, tobacco products, domestic water supplies, building materials, mining and a g r i c h a l products, natural gas heaters, and tungsten welding rods might be considered for possible mitigative action. Reduction in the use of tobacco products would, of course, produce a significant reduction in dose to the exposed individual. As a result, the NCRP encourages and supports the many societal efforts already underway to limit and to reduce the use of cigarettes by the general population. Although domestic water supplies are not a major contributor to the total exposure of the US. population to indoor radon, they can be a signscant source of exposure if their concentrations of radon are unusually high. In those cases, this source would appear to be worthy of dose reduction techniques. Recommendations on the implementation of a variety of radon mitigation techniques are being developed in a report being prepared. Since building materials are a significant contributor of dose from consumer products, some thought might be given to actions that would reduce the contribution from this source. However, while it might seem that the use of construction materials containing low concentrations of naturally occurring radionuclides should be encouraged, the associated economic and logistic problems would probably prove to be over-riding. Much the same consideration would apply to the application of mitigative measures to mining and agricultural products. Much of the population dose equivalent due to the use of natural gas in heaters and cooking ranges is due to the associated radon gas. Techniques are available for properly venting such units and these techniques are generally effective in controlling the associated radon releases.

6.4 DOSE REDUCTION AND RESEARCH

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For tungsten welding products, the exposures are primarily from external radiation and are limited to a small group of people not usually classified as radiation workers. The usual principles of radiation protection and ALAFW should be applied to reduce the dose to the individuals involved. For the other sources cited in Table 5.1, no efforts a t dose reduction appear to be warranted at the present time.

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1075. TARAS,D. N. (1978). "Controls exercised by the Army over radioactive consumer-type items," page 479 in Radioactivity in Consumer Products, NRC Report NUREG/CP-0001 (U.S. Nuclear Regulatory Commission, Washington, DC). H. W., GIBBINS,W. A. AND SVOBODA, J. (1983). "Gamma Radiation TAYLOR, from Camera Lenses," Radiat. Prot. Dosimetry 5, 187. THOMPSON, D. L. (1976). Umnium in Dental Porcelain, HEW Publication (FDA) 76-8061 (Center for Devices and Radiological Health, Rockville, Maryland). E , (1974). Penetration of the H m n Eye by TOBIAS,C. A. AND C H A ~ E R J EA. Alpha Particles from Glasses Containing Isotopes (Directorate of Regulatory Standards, U.S. Atomic Energy Commission, Washington, DC). T s c o u ~ r sT. , (1986). Private communication (Office of Civil Aviation Security, Federal Aviation Administration, Washington, DC). UNSCEAR (1972). United Nations Scientific Committee on the Effects of Atomic Radiation. Ionizing Radiution: Levels and Effects (United Nations, New York). UNSCEAR (1977). United Nations Scientific Committee on the Effects of Atomic Radiation. Sources and Effects of Ionizing Radiation (United Nations, New York). USAEC (1960). U.S. Atomic Energy Commission. AEC Concludes Investigation of Ruthenium Use by Jewelry Industry, Public Release No. C-169 (U.S. Atomic Energy Commission, Washington, DC). USAEC (1973). U.S. Atomic Energy Commission. Comparative Risk-Cost Benefit Study of Alternate Sources of Electrical Energy, Preliminary Draft of Report WASH-1224 (U.S. Atomic Energy Commission, Washington,

DC). USAEC (1974). U.S. Atomic Energy Commission. Recommendations for Revising Regulutions Governing the Transportation of Radioactive Materials in Passenger Aircraft, Recommendations submitted to the Federal Aviation Administration by the U.S. Atomic Energy Commission (US. Nuclear Regulatory Commission, Washington, DC). USNRC (1976a). U.S. Nuclear Regulatory Commission. Final Generic Environmental Statement on Routine Use of Plutonium-Powered Cardioc P a makers, NRC Report NUR;EG-0060 (Nuclear Regulatory Commission, Washington, DC). USNRC (1976b). U.S. Nuclear Regulatory Commission. Transportation of Radioactiue Material in the NRC Report NUREG-0073 (U.S. Nuclear Regulatory Commission, Washington, DC). USNRC (1980). U.S. Nuclear Regulatory Commission. Federal Register, 45 FR 70874, October 27, 1980 (Government Printing Office, Washington, DC). USNRC (1983). U.S. Nuclear Regulatory Commission. "Suspension of exemption permitting use of glass enamel and glass enamel frit containing small amounts o f uranium," in Federal Register, 48 FR 93697, July 25, 1983

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REFERENCES

(Government Printing Office, Washington, DC). USNRC (1984). U.S. Nuclear Regulatory Commission. "Glass enamel and glass enamel frit containing small amounts of uranium," in Federal Register, 49 FFi 35611, September 11, 1984 (Government Printing Office, Washington, DC). USNRC (1985). U.S. Nuclear Regulatory Commission. Contaminated Mexican Steel Incident, NRC Report NUREG-1103 (Nuclear Regulatory Commission, Washington, DC). USNRC (1986a). U.S. Nuclear Regulatory Commission. Internal documents based on pacemaker's manufacturers' reports (U.S. Nuclear Regulatory Commission, Washington, DC). USNRC (1986b). U.S. Nuclear Regulatory Commission. Federal Register. 51 FR 8842, March 14, 1986 (Government Printing Office, Washington, DC). USNRC (1986~).U.S. Nuclear Regulatory Commission. Memorandum from Assistant Director for State Agreement Program, Office of State hograms, to Ferrous Metal Scrap Dealers, Mills and Foundries, August 18,1986, (U.S. Nuclear Regulatory Commission, Washington, DC). USNRC (1986d). U.S. Nuclear Regulatory Commission. "Distribution of products irradiated in research reactors (Generic Letter 86-11)." June 25, 1986 (U.S. Nuclear Regulatory Commission, Washington, DC). USNRC (1987). U.S. Nuclear Regulatory Commission. Distribution of Radioactive Gems Irradiated in Reactors to U d i e ~ e Persons, d Internal Document SECY-87-186, July 28, 1987 (U.S. Nuclear Regulatory Commission, Washington, DC). WALIGORSKI, M. P. R., JASINSKA,M. AND SCHWABENTHAN, J. (1985). "Enhanced Nuclear Radiation from Camera Lenses," Health Phys. 49,491. WEBB,G. A. M., WILKENS,B. T. AND WRIXON,A. D. (1975). Assessment of the Hazard to the Public From Anti-stntic Brushes Containing Polomium210 in the Form of Ceramic Microspheres," NRPB Report R-36 (National Radiological Protection Board, Hamell, United Kingdom). J. AND HORMN,T. (1976). Radiation Dose WINDHAM, S. T., PARTRIDGE, Estimates to Ptwsphote Industry Personnel, EPA Report EPA-520/5-76-014 (United States Environmental Protection Agency, Montgomery, Alabama). WOLLENBERG, H. A. AND SMITH,A. R. (1962). Portland Cement for a LowBackground Counting Facility, AEC Report UCRL-10475 (Lawrence Radiation Laboratory, Berkeley, California). YANIV,S. S. (1974). Thorium and Other Naturally Occurring Alpha Emitters in Ophthalmic Glass, Summary of Radiation Survey (U.S. Atomic Energy Commission, Washington, DC).

The NCRP The National Council on Radiation Protection and Measurements is a nonprofit corporation chartered by Congress in 1964 to: 1. Collect, analyze, develop, and disseminate in the public interest information and recommendations about (a) protection against radiation and (b) radiation measurements, quantities, and units, particularly those concerned with radiation protection; 2. Provide a means by which organizations concerned with the scientific and related aspects of radiation protection and of radiation quantities, units, and measurements may cooperate for effective utilization of their combined resources, and to stimulate the work of such organizations. 3. Develop basic concepts about radiation quantities, units, and measurements, about the application of these concepts, and about radiation protection; 4. Cooperate with the International Commission on Radiological Protection, the International Commission on Radiation Units and Measurements, and other national and international organizations, governmental and private, concerned with radiation quantities, units, and measurements and with radiation protection. The Council is the successor to the unincorporated association of scientists known as the National Committee on Radiation Protection and Measurements and was formed to carry on the work begun by the Committee. The Council is made up of the members and the participants who serve on the eighty-two scientific committees of the Council. The scientific committees, composed of experts having detailed knowledge and competence in the particular area of the committee's interest, draft proposed recommendations. These are then submitted to the full membership of the Council for careful review and approval before being published. The following comprise the current officers and membership of the Council: ofFern

President Vice President Secretary and Treasurer Assistant Secretmy Assistant Treasuwr

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SEYMOUR ABWHAMSON S. JAMES ADELSTEIN PETERR. ALMOND EDWARD L. ALPEN JOHN A. AUXIER WILLUMJ. BAlR MICHAEL A. BENDER BRUCEB. BOECKER JOHND. BOICE,JR. ROBERTL BRENT ANTONEBROOKS THOMAS F. BWINGER MELVIN W. CARTER RANDALL S. CASWELL FREDT. CROSS STANLEY B. CURTIS GERALDD. DODD PATRICIA W. DURF~IN JOEA. ELDER THOMASS. ELY EDWARD R. EPP JACOBI. FABRIKANT R. J. MICHAELFRY ETHELS. GILBERT ROBERT A. GOEPP J o n E. GRAY ARTHURW. GUY ERICJ. HALL NAOMIH. HARLEY WILLIAMR. HENDEE DONALD G. JACOBS A. l3vmmm JAMES,JR. BERNDKAHN KENNETHR KASE CHARLESE. LAND GEORGER. LEOPOLD RAY D. LLOYD

ARTHURC. LUCAS CHARLESW. MAYS ROGER0. MCCLELLAN JAMES E. MCLAUGHLIN BARBARA J. MCNEIL THOMASF. MEANEY CHARLESB. MEINHOLD L. MENDELSOHN MORTIMER FREDA. M ~ E R WILLIAMA. MILLS DADEW. MOELLER A. ALANMOGHISSI WESLEYNYBORG MARYELLENO'CONNOR K. POZNANSW ANDREW NORMAN C. ~ S M U S S E N WILW C. REINIG CHESTERR. RICHMOND JAMES S. ROBERTSON LAWRENCE N. ROTHENBERG LEONARD A. SAGAN WILLIAMJ. SCHULL GLENNE. SHELINE ROYE. SHORE WARRENK. SINCLAIR PAULSLOWC LEWISV. SPENCER WILLIAML. TEMPLETON J. W. THIESSEN ROYC. THOMPSON JOHN E. TILL ARTHURC. UPTON GEORGEL. VOELZ EDWARD W. WEBSTER GEORGEM. WILKENINC H. RODNEY WITHERS MARVIN ZISKIN

Hommry Members LAURISTONS.TAYLOR, H o ~ r n r yPresident WILPRIDB. -N RICHARDF. FOSTER EDGARC. BARNES VICTORP. BOND HYMERL. F'RIEDELL KARL Z.MORGAN REYNOLD F. BROWN R o e m 0. GORSON ROBERTD. MOSELEYJR: AUSTINM.BRUES JOHNH. HARLEY ROBERTJ. NELSEN GEORGEW. CASARFIT JOHNW. HEUY HARALD H. ROSSI F'DERICK P. COWAN LOUISH. WILLUML- RUSSELL JOHN H. RUST HEMPELMANN, JR. JAMES F. CROW MERRILLEISENBUD PAULC. HODGES EUGENEL-SAENGER ROBLEYD. EVANS GEORGEV. LEROY J. NEWELLSTANNARD HAROLD0. WYCKOPF

*Electedposthumously

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Currently, the following subgroups are actively engaged in formulating recommendations:

sc-1: SC-3:

Basic Radiation Protection Criteria Medical X-Ray, Electron Beam and Gamma-Ray Protection for Energies Up to 60 MeV (Equipment Performance and Use) X-Ray Protection in Dental Offices Standards and Measurements of Radioactivity for Radiological Use Biological Aspects of Radiation Protection Criteria Task Group on Atomic Bomb Survivor Dosimetry Subgroup on Biological Aspects of Dosimetry of Atomic Bomb SUIViVOrS Radiation Associated with Medical Examination Radiation Received by Radiation Employees Operational Radiation Safety Task Group 2 on Uranium Mining and Milling-F&diation Safety Programs Task Group 3 on A L A . for Occupationally Exposed Individuals in Clinical Radiology Task Group 4 on Calibration of Instrumentation Task Group 5 on Maintaining Radiation Protection Records Task Group 6 on Radiation Protection for Allied Health Personnel Task Group 7 on Emergency Planning Task Group 8 on Radiation Protection Design Guidelines for Particle Accelerators Task Group 9 on ALARA at Nuclear Power Plants Instrumentation for the Determination of Dose Equivalent Conceptual Basis of Calculations of Dose Distributions Internal Emitter Standards Task Group 2 on Respiratory Tract Model Task Group 5 on Gastrointeetinal Models Task Group 6 on Bone Problems Task Group 8 on Leukemia Risk Task Group 9 on Lung Cancer Risk Task Group 10 on Liver Cancer Risk Task Group 12 on Strontium Task Group 14 on Placental Transfer Task Group 15 on Uranium Human Radiation Exposure Experience Radon Measurements Radiation Exposure Control in a Nuclear Emergency Task Group on Public Knowledge About Radiation Criteria for Radiation Instruments for the Public Task Group on Exposure Criteria for SpecializedCategories of the Public Environmental Radioactivity and Waste Management Task Group 6 on Screening Models Task Group 7 on Contaminated Soil as a Source of Radiation Expoawe Task Group 8 on Ocean Disposal of Radioactive Waste Task Group 9 on Biological Effects on Aquatic Organism Task Croup 10 on Low Level Waste Task Group 11 on Xenon Quality Assurance and Accuracy in Radiation Protection Measurements Biological Effects and Exposure Criteria for Ultrasound

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THE NCRP Biological Effects of Magnetic Fields Microprocessors in Dosimetry Efficacy of Radiographic Procedures Quality Assurance and Measurement in Diagnostic RBdi010gy Radiation Exposure and Potentially Related Injury Radiation Received in the Decontamination of Nuclear Facilities Guidance on Radiation Received in Space Activities Effects of Radiation on the Embryo-Fetus Guidance on Occupational and Public Exposure Resulting from Diegnostic Nuclear Medicine Procedures Practical Guidance on the Evaluation of Human Exp08ures in Radiofrequency Radiation Extremely Low-Frequency Electric and Magnetic Fields Radiation Biology of the Skin (Beta-Ray Dosimetry) Assessment of Exposure from Therapy Control of Indoor Radon

Study Group on Comparative Risk Task Group on Comparative Carcinogenicity of Pollutant ChemicaIs Ad Hoc Group on Medical Evaluation of Radiation Workers Ad Hoc Group on Video Display Terminals Task Force on Occupational Exposure Lwels

In recognition of its responsibility to facilitate and stimulate cooperation among organizations concerned with the scientific and related aspects of radiation protection and measurement, the Council has created a category of NCRP Collaborating Organizations. Organizations or groups of organizations that are national or international in scope and are concerned with scientific problems involving radiation quantities, units, measurements, and effects, or radiation protection may be admitted to collaborating status by the Council. The present Collaborating Organizations with which the NCRP maintains liaison are as follows: American Academy of Dermatology American Association of Physicists in Medicine American College of Medical Physics American College of Nuclear Physicians American College of Radiology American Dental Association Americnn Industrial Hygiene Association American Institute of Ultrasound in Medicine American Insurance Association American Medical Aemciation American Nuclear Society American Occupational Medical A8socintion

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American Pediatric Medical Association American Public Health Association American Radium Society American Roentgen Ray Society American Society of Radiologic Technologists American Society for Therapeutic Radiology and Oncology Association of University Radiologists Atomic Industrial Forum Bioelectromagnetics Society College of American Pathologists Conference of Radiation Control Program Directors Federal Communications Commission Federal Emergency Management Agency Genetics Society of America Health Physics Society National Bureau of Standardn National Electrical Manufacturers Association Radiation Research Society Radiological Society of North America Society of Nuclear Medicine United States Air Force United States Army United States Department of Energy United States Department of Housing and Urban Development United States Department of Labor United States Environmental Protection Agency United States Navy United States Nuclear Regulatory Commission United States Public Health Service

The NCRP has found its relationships with these organizations to be extremely valuable to continued progress in its program. Another aspect of the cooperative efforts of the NCRP relates to the special liaison relationships established with various governmental organizations that have an interest in radiation protection and measurements. This liaison relationship provides: (1),anopportunity for participating organizations to designate an individual to provide liaison between the organization and the NCRP; (2) that the individual designated will receive copies of draft NCRP reports (at the time that these are submitted to the members of the Council) with an invitation to comment, but not vote; and (3) that new NCRP efforts might be discussed with liaison individuals as appropriate, so that they might have an opportunity to make suggestions on new studies and related matters. The following organizations participate in the special liaison program: Commission of the European Communities Cornmisariat a I'Energie Atomique (Ftan~e)

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THE NCRP

Defense Nuclear Agency Federal Emergency Management Agency Japan Radiation Council National Bureau of Standards National Radiological Protection Board (United Kingdom) National Research Council (Canada) Office of Science and Technology Policy Office of Technology Aaseesment United States Air Force United States Army United States Coast Guard United States Department of Energy United States Department of Health and Human Services United States Department of Labor United States Department of Transportation United States Environmental Protection Agency United States Navy United States Nuclear Regulatory Commission

The NCRP values highly the participation of these organizations in the liaison program. The Council's activities are made possible by the voluntary contribution of time and effort by its members and participants and the generous support of the following organizations: Alfred P. Sloan Foundation Alliance of American Insurers American Academy of Dental Radiology American ~ c a d e m yof Dermatology American Association of Physicists in Medicine American College of ~ u c l e &Physicians American College of Radiology American College of Radiology Foundation American Dental Association American Hospital Radiology Administrators American Industrial Hygiene Association American Insurance Association American Medical Association American Nuclear Society American Occuwtional Medical Associition American 0ste&thic College of Radiology Americau Pediatric Medical Association American Public Health Association American Radium Society American Roentgen Ray Society American Society of Radiologic Technologkts American Society for Therapeutic Radiology and On~010gy American Veterinary Medical Association American Veterinary Radiology Society Association of University Radiologists -~

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Atomic Industrial Forum Battelle Memorial Institute Center for Devices and Radiological Health College of American Pathologists Commonwealth of Penn~lvania Defense Nuclear Agency Edison Electric Institute Edward Mallinckrodt, Jr. Foundation Electric Power Research hdihte Federal Emergency Management Agency Florida Institute of Phosphate Research Genetics Society of America Health Physics Society Institute of Nuclear Power Operations James Picker Foundation National Aeronautics and Space Administration National Association of Photographic Manufacturers National Bureau of Standards National Cancer Institute National Electrical Manufacturers Association Radiation Research Society Radiological Sociiety of North America Society of Nuclear Medicine United States Department of Energy United States Department of Labor United States Environmental Protection Agency United States Navy United States Nuclear Regulatory Commission

T o all of these organizations the Council expresses its profound appreciation for their support. Initial funds for publication of NCRP reports were provided by a grant from the James Picker Foundation and for this the Council wishes to express its deep appreciation. The NCRP seeks t o promulgate information and recommendations based on leading scientific judgment on matters of radiation protection and measurement and to foster cooperation among organizations concerned with these matters. These efforts are intended to serve the public interest and the Council welcomes comments and suggestions on its reports or activities from those interested in its work.

NCRP Publications NCRP publications are distributed by the NCRP Publications Office. Information on prices and how to order may be obtained by

directing an inquiry to:

NCRP Publications 7910 Woodmont Avenue

Suite 800 Bethesda, MD 208143095 The currently available publications are listed below. NCRP Reports No. Title Control and Removal of Radioactive Contamination i n Labomtories (1951) Maxirnwn Permissible Body Butdens and Mcrtimum Permissible Col10en.tmti~ns of Radionuclides in Air and in Waterfor Occupatiod Exposure (1959)llncludes Addendum 1 issued in August 19631 Meusurwnent of N e W n F h and Spectm for Physical and B wbgiad Applications (1960) Measutellcent of A b s o r b e d k ofNeutmns, and of Mixturn of Neuimns and Gammu Rays (1961) Stopping Powers for Use with Cavity Chambers (1961) Safe Handling of Radimdie Mahzriak (1964) Radiation Protection in Educational Institutions (1966) D e d X-RayProtection (1970) Radiation Protection in Veterintuy Medicine (1970) Precautions i n the Management of Patients Who Have Receiued Themputac Amounts of Radionwtides (1970) h t e c t i o n Against Neutron Radiation (1971) Pn,tection Against Radi&on b r n Bmchytherupy S o u m s (1972) Spenpenjkabkn of G u m - R a y Bmhythenqg So(1974) Radiological Factors Affecting Decision-Making in a Nwlecrr Attack (1974) Krypton45 in the Atmosphere-Aocwnhn, Biological Signi&ame, and Condm1 TechnorogV (1975)

NCRP PUBLICATIONS

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89

Alpha-Emitting Particles in Lungs (1975) Tritium Mecrsumment Techniques (1976) StructuralShieldingDesign a d Evaluationfor Me& Use of X Rays and Gamma Rays of Energies Up to 10 MeV (1976) Envimnmlltal Radiation Measurements (1976) Radiation Protection Design Guidelines for 0.1-100 MeV PEvticle Accelerator Facilities (1977) Cesium-137ftvm the Environment to M m Metabolism and Dose (1977) Mediccrl R a d W n Exposum of Ptegnunt and PotenticrUy Pregnunt Women (1977) Protection of the Thyroid GZand i n the Event of R h e s of Radioiodine (1977) Instrunentcrtion and Monitoring M e t f i t for Radiation Pmikction (1978) A Handbook of Radioactivity Measurements Procedures, 2nd ed. (1985) Opemtional Raclirrtion Safety Pmgmm (1978) Physiccrl, Chemical, and Biological Properties of Radiocerium Rekvant to R a d i d o n Protection Guidelines (1978) Radiation Safety Training CTiteria for Industrial Radiogmphy (1978) Tritium in the Environment (1979) Tritium and Other Radionuclide L-abekd Organic Compounds Incorporated in Genetic Material (1979) Influence of Dose and Its Distribution in Time on D m Response Relationships for Low-LETRcrdiations (1980) Management of Persons Accidentally Contaminated with Radionuclides (1980) Radiofrequency Electromagnetic Fields-Prqoerties, Quantities and Units, Biophysical Interaction, and Measurements (1981) Radiation Protection in Pedirrtric R&gy (1981) Dosimetry of X-Ray and Gamma-Ray Beams for Radiation Thempy in the Energy Range 10 k V to 50 MeV (1981) Nuclear Medicine-Factors ln@zming the Choice and Use of Radionuclides in Diagnosis and T h e m (1982) Operational Ra&iation Safdy--Tmining (1983) Radiation Protection and Measurement fir Low-Voltage Neutron Generators (1983) Protection in Nuclear Medicine and UltTasowrd Diagnostic Pmedwes in C h W v n (1983)

NCRP PUBLICATIONS

Biologzcal Effects of Ultrasound: Mechanism and Clinical Implications (1983) Iodine-129: Evaluution of Releases from Nuclear Power Genercrtion (1983) Radwlo& Assessment: Predicting the Tmnsport,Bioaccumulation, and Uptake by Man of Radionuclides Released to the Environment (1984) Exposures from the Uranium Series with Emphasis on Radon and Its D a u g h (1984) Eualuution of 0ccup.tiorualand Envhnrnetal Eqwsum toRadon and R a d o n D a t l g h in the United Stcrtes (1984) Neutron Contaminationfrom Medical Eiktmn Acceletators (1984) Induction of Thymid Cancer by Ionizing Radiation (1985) Carbon-24 in the Environment (1985) SI Units in Radiation Protection and Measurements (1985) TheExperimentcrl Basis for Absorbed-Dose Calculations in Medzccrl Uses of Radionuclides (1985) General Concepts for the Dosimetry of X n t e d y Deposited Radionzlclides (1985) Mammogmphy-A Usefs Guide (1986) Bwlogid Effects and Eqwrsw Criteria for Radi~frequency Electromagmtic FieIds (1986) Use of Bioassay Procedures for Assessment of Internal Radionuclide Deposition (1987) Radiation Aiarms and Access Control Systems (1986) Genetic Effects fiom Internally Deposited Radionuclides (1987) Neptunium: Radiahn Protection Guidelines (1988) Public Radktion Exposure from Nuclew Power Genemtion in the United Stcrtes (1987) Ionizing Radiation Erposure of thePopulation of the United States (1987) Exposure of the Populahn in the United Sbatesand Cwuada from N a t m d Baekgmwrd R-n (1987) Radiution Exposure of the U S . Populcrtion h r n Consumer Products and Miscellaneous Sources (1987) Comparative Carcinogenicity of Ionizing Radiation and Chemimls (1989) Measurement of Radon and Radon Daughters in Air (1988) Guidcrnce on Raaktion Received in Space Activities (1989) Qclality Assurance fir Diugnostic Imuging (1988) Eqmwe of the U S . Populdon ftvm Diugmstic Medial Radicrtian (1989)

NCRP PUBLICATIONS

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Exposure of the U.S. Population from Occupational Radiation (1989) Medical X-Ray, Ekctmn Beam a d Gamma-RayProtection for Energies Up to 50 MeV G%quipmentDesign, Performance and Usel (1989) Control of Rcrdon in Houses (1989) TheRekrtiveBwlo& Effectiveness ofRadiaiions ofDifferent Quahty (1990) Radiation Protection for Medical and Allied Health Personnel (1989) Limit for Exposum to 'Wot P " on the Skin (1989) Implementation of the Principle of As Low As Reasonubly Achievable (ALARA) for Medial and Dentd Personnel (1990) Conceptual Basis for Calculations of Absorbed-Dose Distributions (1991) Effects of Ionizing Radiation on Aquatic 0eanisrn.s (1991) Some Aspects of Strontium Radiobiology (1991) DevelopingRaahtion EmergencyPlans fordcademic, Medical or Industrial Facilities (1991) Calibmtionof Swvey Instruments Used inRadiationProtection for the Assessment of lonizing R4d-n Fields and Radioactive S u r f m Coniaminniion (1991) Exposure Criteria for Mediwl Diaghostic Ultrasou'd:I. Cn'teria Based on T h e m 1 Mec?tanisms (1992) Maintaining Radidon Protection Records (1992) Risk Estimates for Radiaabn Protection (1993) Limitcttion of Exposure to Ionizing Radiutwn (1993) Research Needs for Rcrdiation Protection (1993) Radiation Protection in the Mineral Eztraction Industry (1993) A Prcrctical Guide to the Determirrcrtion ofHumanE*-goswe to Radiofrequency Fields (1993) Binders for NCRP reportsare available. Two sizesmake it possible to collect into small binders the "old series" ofreports (NCRF' Reports Nos.8-30) and intolarge bindersthe more recentpublications (NCRP Reports Nos. 32-119).Each binder will accommodate h r n five to seven reports. The binders carry the identificationWCRP Reportsn and come with label holders which permit the user to attach labels showing the reports contained in each binder. The following bound sets of NCRP reports are also available: Volume I. Volume II.

NCRP Reports Nos. 8,22 NCRP Reports Nos. 23,25,27,30

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NCRP PUBLICATIONS

Volume Ill. Volume IV. Volume V. Volume VI. Volume VII. Volume VIII. Volume M. Volume X. Volume XI. Volume XU. Volume XJII. Volume XTV. Volume XV. Volume XVI. Volume XVII. Volume XVIII. Volume XIX Volume XX. Volume XXI. Volume XXII. Volume XXIII.

NCRP Reports Nos. 32,35,36,37 NCRP Reports Nos. 38,40,41 NCRP Reports Nos. 42,44,46 NCRP Reports Nos. 47,49,50,51 NCRP Reports Nos. 52,53,54,55,57 NCRP Report No. 58 NCRP Reports Nos. 59,60,61,62,63 NCRP Reports Nos. 64,65,66,67 NCRP Reports Nos. 68, 69,70,71,72 NCRP Reports Nos. 73,74,75,76 NCRP Reports Nos. 77,78,79,80 NCRP Reports Nos. 81,82,83,84,85 NCRP Reports Nos. 86,87,88,89 NCRP Reports Nos. 90,91,92,93 NCRP Reports Nos. 94, 95,96,97 NCRP Reports Nos. 98,99,100 NCRP Reports Nos. 101,102,103,104 NCRP Reports Nos. 105,106,107,108 NCRP Reports Nos. 109,110,111 NCRP Reports Nos. 112,113,114 NCRP Reports Nos. 115,116,117,118

(Titles of the individual reports contained in each volume are given above.)

NCRP Commentaries No.

1 2 3 4

5 6

Title

Krypton# in the Atmosph-With Specific Reference to the Public Heulth Signifioanceof the Proposed ContmUed Release at Three Mile I S M (1980) hliminary Evalwtion ofcriteria fir theDispwd ofTnznsuranic Contaminated Waste (1982) Screening Techniques for Determining Compliance with Envimnmental S-Rebes of Radwnzcclides to the Atmosphere (19861,Revised (1989) Guidelines for the Release o f Waste Water from Nuclear Facilities with SpecialReference to the Public H d h Signifioance of the Proposed Release of Tmated Waste Waters at Three Mile Island (1987) Review of the Publication, Living Withoui Landfills (1989) Radon Exposure of the U.S. Population-Status of the Pmblem (1991)

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Misadministration of Radioactive Material in MedicineScientijie Background (1991) Uncertuinty in NCRP Screening Models Relating to Atmospheric Transport, Deposition and Uptake by Humans (1993) Procgedings of the A n n d Meeting

No. 1

Title

Perceptions of Risk, Proceedings of the Fifteenth Annual Meeting held on March 1415, 1979 (including Taylor Lecture No. 3) (1980) Critical Issues in Setting Radiation Dose Limits, Proceedings of the Seventeenth Annual Meeting held on April & 9, 1981 (includmg Taylor Lecture No. 5) (1982) Radiation Protection and New Medical Diagnostic Approaches, Proceedings of the Eighteenth Annual Meeting held on April 6 7 , 1982 (including Taylor Lecture No. 6) (1983) Environmental Radioactivity, Proceedings of the Nineteenth Annual Meeting held on April 67,1983 (including Taylor Lecture No. 7) (1983) Some Issues Important in Developing Basic Radiation Protection R e c o m m e ~ n sProceedings , of the Twentieth Annual Meeting held on April 45,1984 (includingTaylor Lecture No. 8) (1985) Radimctive Waste,Rocdings of the Wenty-first Annual Meeting held on April 34,1985 (includingTaylor Lecture No. 9) (1986) Nonionizing Ekctromagwtic Radiutions and Wtmsound, Proceedings of the Twenty-second Annual Meeting held on April 2-3,1986 (including Taylor Lecture No. 10) (1988) New Dosimetry at Himshima andNagasaki and ltsImp2icatiom for Risk Estimates, F k c d i q p of the Twenty-third Annual Meeting held on April 89,1987 (including Taylor Lecture No. 11)(1988) Rcrdon, Rocdings of the Twenty-fourth Annual Meeting held on March 30-31, 1988 (including Taylor Lecture No. 12) (1989) Radiation Protection Today-TTreNCRP at Siziy Years,Proceedings of the Twenty-fiFth Annual Meeting held on April 5-6, 1989 (including Taylor Lecture No. 13)(1990)

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Health and Ecobgzd Imptkations of Radioactively Contaminated Environments, Proceedings of the Twentysixth A n n d Meeting held on April 4-5,1990 (including Taylor Lecture No. 14) (1991) Genes, Cancer and Radiation Protection, Proceedings of the Twenty-seventh Annual Meetmg held on April 3-4,1991 (including Taylor Lecture No. 15) (1992) of the 'henRadiation Protection in Medicine, tyeighth Annual Meeting held on April 1-2,1992(including Taylor Lecture No.16) (1993)

No. 1

Lauriston S. Taylor Lectures Title The Squares of theNcr~rralNumbersin Radiation Protection by Herbert M. Parker (1977) Why be Quuntitative abolrt Radiation Risk Estimates? by Sir Edward Pochin (1978) Radiabbn Prvtdor+Concqts and Tmde O ~ by S Hymer L Friedell (1979) [Available also in Perceptions ofRisk, see above] From "Qtcantity of Radiution" and r)ose" to "Exposure" and "Absorbed Dosen-An Historical Review by Harold 0. wyckoff (1980) How WeU Can We Asses Genefic Risk? Not Very by James F. Crow (1981) [Available also in criticcrlIssues in Setting Radiation Dose Limits, see above] Ethics, Trade-offs and Medical Radiation by Eugene L. Saenger (1982) [Available also in Radiation Protection and New Medical Diagnostic Approaches, see above] The Human Environment-Past, Present and Future b y Merril Eisenbud (1983)[Available also in Environmental Radiocrdivity, see above1 Limitation and Assessment i n Radiation Protection b y Harald H. Rossi (1984) [Available also in Some Issues Important in Developing Basic Radiation Protection Recornrnendaabns, see abovel Tmth (and Beauty) in Radiation M e a s u m n t by John H. Harley (1985) [Available also in Radiaudve Waste, see above] Biological Effects of Non-ionizing Radiations: Cellular Pmpertk and Intenrctions b y Herman P. Schwan (1987) [Available also in Nonionizing Ekchmagmtic Radiations and Ulaasound,see above1

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How to be Qwntitutive about Radiution Risk Estimates by Seymour Jablon (1988)[Availablealso in New Dosimetry at H i m s h i m and Nagasaki and its Impliccrtions for Risk Estimates, see above] How Safe is Safe Enough? by Bo Lindell(1988) [Available also in Radon, see above] Radiobiology and Radiation Pmtectiorr The P a t Century and Prospects for the F&m by Arthur C. Upton (1989) [Availablealso in Rad&ionhtection Today,see above] Radiation Protection and the Internal Emitter Saga by J. Newel1 Stannard (1990)[Availablealso in He& a d Ecological Implications of Radioactively Contaminated Enuitonments, see above] When is a Dose Not a Dose? by Victor P. Bond (1992)[Available also in Genes,Cancer and Radiation Protection, see above] Dose and Risk in Diagnostic Radiology: How Big? How Little? by Edward W. Webster (1992)[Availablealso in Radiuiion Protection in Medicine, see above] Science, Radi&on Pmtection and the NCRP by Warren K. Sinclair (1993)

The Control ofhkpsum of the Public toIonizing Radiadon in the Event ofAccidkntorAttack, l h c d b g s ofa Symposium held April 27-29, 1981 (1982)

NCRP Statements No. 1

Title "Blood Counts, Statement of the National Committee on Radiation Protection," Radiology 63,428 (1954) "Statements on Maximum Permissible Dose from Television Receivers and Maximum Permissible Dose to the Skin of the Whole Body," Am. J. Roentgenol., Radium Ther. and Nucl. Med 84, 152 (1960)and Radiology 75, 122 (1960) X-Ray P r o e n Standards fir Home TelevisionR e c e k , Interim Stcrtement of t k National Council on Radiatian Protection and Merrswme& (1968) S p e c r p e c r ~UILitsofNatwalUmniurnandNcrtumlTlronof rium, S m m e n t of th4 N&nd Council on Radiatian Protection and Measmmem, (1973)

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NCRP PUBLICATIONS

NCRP Stdement on Dose Limit far Neutrons (1980) Control of Air Emissions of Radionuclides (1984) The ProMi& That a Particular Malignancy May Haw Been Caused by a Specified Irradiation (1992)

Other Documents The following documents of the NCRP were published outside of the NCRP Report, Commentary and Statement series: Somatic Radiation Dose for the Geneml Population, Report of the Ad Hoc Committee of the National Council on Radiation Protection and Measurements, 6 May 1959, Science, February 19,1960, Vol. 131, No. 3399, pages 482486 Dose Effect Modifjing Factors In Radiation Protection, Repart of Subcommittee M-4(Relative Biological Effectiveness) of the National Council on Radiation Protection and Measurements, Report BNL 50073 0 4 7 1)(1967) Brookhaven National Laboratory (National Technical Information Service Springfield, Virginia) The following documents are now superseded andlor out of print:

NCRP Reports No.

Title X-Ray Pmktion (1931) [Supemded by N O Report No. 31 Radium Pmktzon (1934) [.s"upersededby NCRP Report No. 41 X-Ray Prdection (1936) [Superseded by NCRP Report NO.61 RadiunzProtecabn(l!XN)[SupersededbyNCRPReportNo. 131 Safe Handling of Raclioactive Luminous Compound (1941) [Out of Print] Medical X-Ray P m W n Up tQ Two Million Volts (1949) [Superseded by NCW Report No. 181 Safe Handling of Rodiocrctive Isotopes (1949) [Superseded by NCRP Report No. 301 Recommendations fir Was& Disposal of P h o s p h ~ t l ~ and 32 Iodine-131 for Medical Users (1951) [Out of Print] Radiobghl Monitoring Methods and Instruments (1952) [Superseded by NCRP Report No. 571 Maximum Permissible Amounts of Radioisotopes in the Human Body and Maximum Permissible Concentmtbns in Air and Water (1953) [Superseded by NCRP Report No. 221 Recommendations for the Disposal of Carbon-14 Wastes (1953) [Superseded by NCRP Report No. 811

Protection Against Rad&iom f b m Radium, Cobcrlt-60 and Cesium-137 (1954)[Supersededby NCRP Report No. 241 Pmtection Against BetatmnSymhtron Radicrtions Up to 100 MiUwn Electron Volts (1954)[Superseded by NCRP Report No. 51] Safe Handling of Codwers Containing Radioactive Isotopes (1953)[Supersededby NCRP Report No. 211 Radioactiue-Waste Disposal in the Ocean (1954)[Out of Print] Permissible Dose fin External Soof Ionizing R&tion (1954)including Maximum Permissible Exposures to Man, Addendum to N&nul Bwvau of Standards Handbook 59 (1958)[Supersededby NCRP Report No. 391 X-Ray Pmte&on (1955)[sqxmdedby NCRP Report No. 261 Regulation of Radiation Exposure by Legislative Means (1955)[Outof Print1 Pmhxtbn AgainstNeutron R-n Up to30 Million Electron VoZts (1957)[Supersededby NCRP Report No. 381 Safe Handling of Bodies Contuining Radbmtiw Isotopes (1958)[Supersededby NCRP Report No. 371 Pro&dionAgainst Radiations from Sealed Gamma S o m s (1960)[Superseded by NCRP Reports No. 33,34 and 401 Medical X-Ray Pmtection Up to Three MiUwn Volt%(1961) [Supersededby NCRP Reports No. 33,34,35and 361 A Man& of Radioactivity Prooedwes (1961)[Superseded by NCRP Report No. 581 Exposure to Radiation in an Emergency (1962)[Superseded by NCRP Report No. 421 Shielding for High-Energy Electmn Accelemtor Imtalkrtiom (1964)[Supersededby NCRP Report No. 511 Medical X-Ray and Gamma-Ray Protection for Energies up to 10 MeV-Equipment Design and Use (1968)[Superseded by NCRP Report No. 1021 Medical X-Ray and Gamma-RayPtotsction for Energies Up to 10 MeV--Structural Shielding Design, and Evaluadon Handbook (1970)[Supersededby NCRP Report No. 491 Basic Radiation PTotection C M (1971)[Supersededby NCRP Report No. 911 Review of the C M State of Radiution Protection Philosophy (1975)[Supersededby NCRP Report No. 911 Natural Background Radiation in the United States (1975) [Supersededby NCRP Report No. 941 Radiution Protection for Medical curd Allied He4Ur Personnel (1976)[Supersededby NCRP Report No. 1051

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NCRP PUBLICATIONS

Review ofNCRP RodiationDose Limit firEmbryo andFetus in Occupatwdy-Exposed Women (1977) [Out of Print] R a d i a t i o n ~ j i v m C o ~ ~ c u r d M ~ u s ~(19Ti?[SupersededbyNCRPReportN0.953 A Handbook of Radioactivity Measurements Procedures, 1st ed. (1978) [Superseded by NCRP Report No. 58, 2nd d l Mammgmphy (1980) [Outof Print] Recommedatbns on L i d firlhpswv to Ionizing Radiuiim (1987) [Superseded by NCRP Report No. 1161

NCRP F'roceedings No. 2

Title Quantitative Risk in Standurds Setting,Proceedingsof the Sixteenth Annual Meeting held on April 2-3,1980 [Out of Print1

INDEX Aerosol detectors, 18.61.63 Aircraft and building exit markers, 14 Aircraft passengers and crew,d m to. 59 Aircraft transport of radioactive materials, 58,62,63 Airport inspection systems. 1.6,61,63 American College of Obstetricians and Gynecologists, 6 "'Am, 18.22 American National Standards Institute, 50

Atomic Energy Commission, 55 Background radiation. 25 B a d mucosa, 41 n'JBi. 54 Biological effecta of radiation skin disease, 55 squamous cell carcinoma, 55 Bone. 16, 18,35,36,46,48 Bremsstrahlung radiation. 11 Bronchial epithelium, 24. 27, 28. 38. 60, 61, 62, 65 Building materials, 1,24,61,63,68 Bureau of Radiological Health, 41,54 Camera lenses, 1.47 'F,37 Cardiac pacemakers @lutonium-powered), 21 Center for Devices and Radiological Health, 5,6,54,60

Ceramia, 39.62 Check sources, 20.63 C i s , 23,60,61,63 Civil defense, 20 Clocks, 12,61,63 %, 16.20.55 Coal, 32.62.63 Combustible fuels. 1.32.62.63 combustion of coal, 32.62.63 Combustion of natural gas, 38,62,63

Combustion of oil, 37 CONDOS Computer Program.12 Contmninated raw materials, 53 Corneal epithelium, 42,45,62 13'Cs, 17 Dental p r o s k s , 41,62,63 Department of Defense. 58 Department of Transportation, 59 Disposal of surplus products, 57 Domestic water supplies, 2, 27. 60. 61, 63 Dose quivalent from specific sources (see Effective dose equivalent) Dose reduction. 68 Effective dose equivalent aerosol detectors, 18,61.63 aircraft transport of radioactive mate-

rials. 58.62.63 airport inspection systems, 7,61,63 building materials, 24,61,63 camera lenses. 47 cardiac pacemakers (plutonium-powered), 21 ceramics, 39,62 check sources,20,61,63 cigarettes, 23.61.63 clocks, 12,61,63 coal, 33,62,63

combustible &Is, 33.62.63 contaminated materials, 55 dental prostheses, 41.62.63 disposal of radioactive surplus products, 57

domestic water supplies, 2861.63 electron tubes, 17,61,63 fertilizer products, 32,62,63 fluorescent lamp sterters, 49.62.63 gas and aerosol detectors, 18.61,63 gas mantles,45,62,63 glass enamel. 40 glassware, 39

100

I

INDEX

glazes, 40 high voltage vacuum electronic prod-

ucts, 50 highway and road construction materials, 29,62,63 lightning rods. 22 liquefied petroleum gas, 39 natural gas, 38,62,63 02.37

ophthalmic glass, 43, 62,63 optical glass (thoriated), 45 personnel scanning systems. 7 phosphate products, 32,62,63 plutonium-powered cardiac pacemakers, 21 pocket watches, 11,61,63 road construction material,29,62,63 shoe-fitting fluoroscopes,8 smoke d e m r s , 18.61.63 spark gap irradiators, 1 6 6 3 static eliminators, 15,61 television receivers. 5.61.63 thoriated optical glass, 45 tobacco products, 23,61,63 video display terminals, 6,61,63 welding rods (thoriated tungsten), 48, 62,63

wristwatches, 12,61,63 Electron tubes,16,61,63 Environmental Protection Agency, 30, 34 Exit markers (aircraft and building). 14 Exposure of hands, 55

Eye.42,45,47 Eyeglasses, 43

Federal Aviation Administration, 7 Fertilizer Products, 29,62,63 Fluorescent lamp starters,49,62,63 Food and Drug Adminhtration, 7,8,55 Gas and aerosol detectors, 1, 18.61.63 Gas mantles, 1, 45, 62, 63 Glass and ceramics, 39,62,63 Gonadal dose equivalent. 10.29.52 =H, 10, 14,60 High voltage vacuum electronic units, 50 Highway and road construction materials. 28, 62,63

Intentional x rays, 6 International Commission on Radiological Protection, 1,3,65

Lightning rods, 22 Luminous wmpounds, 9 Luminous timepieces. 9.60.61.63 Lung,24,27,28,35,38,48, 65

Mitary surplus items. 9.57 Mining and agricultural products, 29, 62, 63,68

National Council on Rediation Protection and Measurements. 1 Natural background, 25 Natural gas, 38,62,63,68 Natural radioactive materials, 23 "Ni. 17 Nuclear Regulatory Commission, 9, 10, 14,16,18,21,40,43,44,56

Oak Ridge National Laboratory. 12.48 Oil, 37 Ophthalmic glass. 42.62.63 optical glass, 43 Optical Manufacturers Association, 43 Personnel scanning systems.7 Phosphate products, 32.62.63 2"JPb, 17,20, 23,32,60 14%.

10.14

ZlOPo, 15,23, 32,65 Pocket watches, 11,61,63 Population effective dose equivalent Effective dose equivalent) Potassium, 24,29,41 Processed radioactive materials, 9 ==Tu.21

=Ra.

(~ee

9,1% 20,22,31,57,60

Radiation exposure (see Effective dose equivalent) Radioactive luminous device%9,61,63 Radioactive surplus items. 57

INDEX Radioluminous products, 1,9,61,63 Radiopharmaceuticals. 59 Radium.9,18,20,22.31,34.57 Ra,&n, 27,38,46,54,60

mRn, 46,48 mRn, 27 Road construction materials, 28,62,63 '08Ru. 55

Shoe-fittingfluoroscopes. 8 Skin disease,55 Smoke detectors, 18 Spark gap irradiators, 16,63 BOSr,9, 21 Static eliminators, 1.14.61 Switching tubes, 50.52 Television receivers, 1,3,61, 63 q. 31 PSTb, 34,44,47 Thoriated optical glass. 44 Thoriated tungsten welding rods, 1. 47. 62.63.68

/

101

Tobacco products, 1,23,61,63,68

Tritium. 9

United Nations Scientific Committee on the Effects of Atomic Radiation, 24, 26 Unwanted byproduct x rays, 3

-u.

21.31.34

Uranium. 24.29,31,39,41,42 Video display terminals,1,6, 61,63,67 Welding rods (thoriated tungsten). 1, 47, 62.63.68 Wristwatches, 9,61,63 X-ray baggage inspection systems, 6, 61, 63 X rays airport inepeetion systems.7.61.63 high voltage vacuum electmnic units, 50

pemnnel ecanning systems, 7 shoe-fittingfluoros~opes,8