Limit for Exposure to ''Hot Particles'' on the Skin: Recommendations of the National Council on Radiation Protection and Measurements (Ncrp Report, No 106) (N C R P Report)

NCRP REPORT No. 106

LIMIT FOR EXPOSURE TO "HOT PARTICLES" ON TH.E SKIN Recommendations of the NATIONAL COUNCIL O N RADIATION PROTECTION AND MEASUREMENTS

Issued December 31, 1989 National Council on Radiation Protection and Measurements 7910 WOODMONT 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 reporta. 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, completeness or usefulnees of the information contained in this report, or that the use of any information, method or procees disclosed 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 seq. as amended 42 U.S.C. Section 2000e et seq. (Title VII) or any other statutory or common law theory governing liability.

Library of Congress Cataloging-in-PublicationData National Council on Radiation Protection and Measurements. Limits for exposure to "hot particles" on the skin: recommendations of the National Council on Radiation Protection and Measurements. p. cm.-(NCRP report ; no. 106) "Issued January 15, 1990." Includes bibliographical references. ISBN 0-929600-11-8 : $12.00 (est.) 1. Ionizing radiation-Safety measures. 2. Ionizing radiationDosageStandards. 3. Beta rays-Health aspects. 4. Skin-Effect of radiation on. I. Title. 11. Series. [DNLM: 1. Environmental Exposure. 2. Radiation Injuries. 3. Skin-radiation effects. WR 100 N277Ll RA569.N353 1990 612'.01448-dc20 DNLMDLC for Library of Congress

89-71259 CIP

Copyright 8 National Council on Radiation Protection and Measurements 1989 All rights resewed. This publication is protected by copyright. No part of this publication 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.

Preface This report has been prepared as a result of a request to the National Council on Radiation Protedion and Measurements (NCRP) from the Nuclear Regulatory Commission (NRC). In recent years, nuclear utilities have identified the potential for a limited number of employees to come in contact with microscopic particles that are radioactive. These particles have been given the generic name, independent of their source and particular chemical and radioactive content, of "hot particles." This report addresses the potential biological effects of hot particles on the skin and reviews the presently available information on the subject. This information is presently less complete than one would wish, and more information is to be expected in the near future. In the meantime, the report makes recommendations on limits of exposure from hot particles in the work place based on avoidance of severe deterministic effects. The support of the NRC for this particular facet of the NCRP program on radiation effects on the skin is gratefully acknowledged. Serving on Scientific Committee 80-1, that prepared this report were: Thomas F. Gesell, Chairman U.S. Department of Energy Idaho Falls, Idaho Members

P. Donald Forbes Temple University Philadelphia, Pennsylvania

William C.Roesch Richland, Washington

Charles B. Meinhold Brookhaven National Laboratory Upton, New York

H. Rodney Withers University of California at Los Angeles Los Angeles, California Consultants

R. J. Michael Fry Oak Ridge National Laboratory Oak Ridge, Tennessee

Roy E. Shore New York University Medical Center New York, New York

NCRP Secretariat- William M. Beckner

The Council wishes to express its gratitude to the members and consultants of the Committee for the time and effort devoted to the preparation of this report. Bethesda, Maryland October 25, 1989

Warren K.Sinclair President, NCRP

Contents Preface ............................................................. 1. Introduction ................................................... 2. Scope of the Report ........................................... 3. Biological Effects of Irradiation of the Skin ............. 3.1 Introduction ................................................ 3.2 Nonstochastic Effects (Deterministic Effects) ........... 3.2.1 Acute Nonstochastic Effects ....................... 3.2.2 Late Nonstochastic Effects ......................... 3.2.3 Nonstochastic Effects Versus Dose for Large Area Irradiation ..................................... 3.2.4 Nonstochastic Effects From Hot Particles ........ 3.2.5 Review of Biological Effects of Hot Particle Irradiations .......................................... 3.2.5.1 Monkey Experiments ...................... 3.2.5.2 Human Experiment ........................ 3.2.5.3 Swine Experiments ........................ 3.2.5.4 Comparison of Studies ..................... 3.3 Stochastic Risk of Irradiation ............................. 3.4 Comparison of Nonstochastic Effects (Deterministic effects) and Stochastic Risk of Hot Particle Irradiation 4 Approach to Establishing a Practical Limit ............. 5. Interpretation of Experiments With Hot Particles Using the Approach of the Total Number of Beta Particles Emitted ............................................. 5.1 Monkey Studies ............................................ 5.2 Human Study ............................................... 5.3 Swine Studies with Microspheres ........................ 5.4 Swine Studies with Other Sources ....................... 5.5 Estimation of a Threshold ................................. 6 Observations on Humans Exposed Inadvertently in the Work Place ................................................ 7 Derivation of an Exposure Limit for a Hot Particle on the Skin ......................................................... 8. Recommendations on Radiation Exposure Limits for the Special Case of a Hot Particle on the Skin .......... Appendix A: Comparison of Point Dose with Dose Measured with an Extrapolation Chamber

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CONTENTS

Appendix B: Number of Beta Particles from Irradiated a96UC.Microspheres ............................. References ......................................................... The NCRP .......................................................... NCRP Publications ............................................. Index ................................................................

29 32 36 43 53

1. Introduction Small alpha-emitting radioactive particles in the lung have been previously recognized as a radiation protection issue (NCRP, 19751.' Recently, irradiation of the skin by small beta or beta-gamma emitting particles has become of concern in the nuclear reactor industry. This concern has occurred, a t least in part, as a result of the employment of more sensitive personnel monitoring equipment than was previously available. This increased sensitivity has resulted in an increase in the number of incidents involving identification of radioactive particles on the skin. These particles are known as "hot particles," 'Yeas," or "specks." The term "hot particles" will be used in this report. They most commonly contain T o or fission products. The likely source of the particles containing *Co is particles of wear-resistant alloy from valve seats, etc., containing a high percentage of stable cobalt, that enter the primary coolant and become activated in the core via the reaction 6 9 C(n, ~ Y) '%o. The source of the particles which contain fission products is fuel elements which have defects in their cladding. Hot particles usually cannot be detected by the unaided eye because they range in size from approximately one pm to several hundreds of pm. Hot particles apparently become electrically charged as a result of radioactive decay and, therefore, tend to be fairly mobile, "hopping" from one surface to another. The radioactivity of particles containing fission products ranges from 40 Bq to 400 kBq (1nCi to 10 pCi) with most particles being in the range of 400 Bq to 40 kBq (10 nCi to 1 pCi). The radioactivity of the O ' Co particles ranges from 40 Bq to 20 MBq (1nCi to 500 pCi), with most in the range from 400 Bq to 200 kBq (10 nCi to 5 pCi) (Warnock, et al., 1987). The particles are not water soluble and if embedded in clothing are difficult to remove, even by laundering. "Clean" laundry has

NCRP,1975 concluded that particulate plutonium in the lung causes no greater risk of lung cancer than the same amount of plutonium more uniformly distributed throughout the lung. However, for hot particles on the skin the effect to be protected against is the nonstochastic risk of acute ulceration of the skin (see Section 3.41, for which the concept used in NCRP, 1975 may not be applicable and therefore it is not considered further in this report.

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1. INTRODUCTION

been implicated a s the source of hot particles involved in some skin contamination events (INPO, 1987). A unique aspect of hot particles in contact with the skin is that very small amounts of tissue can be exposed to very large, highly non-uniform doses. Average doses can be calculated if the particle can be characterized by nuclide and by activity, but the result will depend strongly upon the amount of tissue included in the averaging process and the depth or depths a t which the averaging is performed. The interpretation of the resultant dose, when various forms of averaging are used, is not straightforward. Existing methods for assessing exposure of the skin are appropriate when large areas of skin, greater than a few tens of square centimeters, are irradiated. For skin irradiation of a few square centimeters, the existing limits provide more than adequate protection, and for very small areas of skin irradiation, such a s occurs with hot particles, the existing limits (NCRP, 1987) are overly restrictive. Minimizing the production and release of hot particles and prevention of skin contamination are clearly the preferable control methods, but the possibility of contamination events cannot be ignored. A consistent method for assessing the biological effect of these events is required so that reasonable radiation protection criteria can be applied to this unique situation.

2. Scope of the Report This report reviews the radiobiological effects of hot particles on the skin and recommends a limit on the product of their beta-particle emission rate and duration of e ~ p o s u r eFor . ~ the end points addressed by this report, beta particles are the radiation of concern. Relative to the beta particle dose, the gamma radiation associated with a beta-emitting hot particle on the skin does not contribute significantly to the tissue dose in the vicinity of the particle. This report does not deal with general skin contamination, skin exposure from distant sources, or inhalation or ingestion of hotparticles, and it does not deal with the special cases that might arise, for example, as a result of hot particles in the eyes or on the eardrums. For the purpose of this report, a hot particle is arbitrarily considered to be a discrete radioactive fragment that is insoluble in water and is no larger than approximately 1mm in any dimension. In addition, only hot particles directly on the skin are considered in this report.

Beta emission rate is the rate of beta particles emitted from the radionuclide(s1 making up the hot particle and not the rate of beta particles emitted from the surface of the hot particle.

3. Biological Effects of Irradiation of the Skin 3.1 Introduction The fimdamental philosophy of radiation protection includes: (1) prevention, to the extent practicable, of the occurrence of severe nonstochastic diseases (deterministic effects), (2) limitation of stochastic risks, fatal cancer and genetic effeds, to a reasonable level in comparison with non-radiation risks, and (3)maintenance of radiation exposure a t levels as low as reasonably achievable (ALARA) economic and social factors being taken into account (NCRP, 1987). The biological effects of irradiation of the skin that are of interest are acute and chronic nonstochastic effects and the stochastic risk of non-melanoma skin cancer.

3.2 3.2.1

Nonstochastic Effects ( D e t e r m h b t i c Effects)

Acute Nonstocbtic Effects

Acute, nonstochastic effects on the skin (those occurring in a few hours to a few weeks) after irradiation of 1cm2 or greater are, with increasing dose, transient erythema, more prolonged erythema, dry and then moist desquamation (after a latency of three to six weeks) and finally secondary ulceration. The latency period of these effects is not strongly dependent on dose. Dry and moist desquamation are related to the reduced reproductive capacity of target cells in the basal layer of the epithelium a t a depth of about 20 to 120 pm. If moist desquamation persists, secondary ulceration may develop with loss of dermal tissue; such ulceration heals by invasive fibrosis. 3.2.2

Late Nonstochclstic Effects

Late or chronic nonstochastic effects developing after protracted irradiation of large areas of skin, with increasing dose, and possibly

3.2 NONSTOCHASTICEFFECTS

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without acute effects, include changes in pigmentation; atrophy of the dermis, sweat glands, sebaceous glands, and hair follicles;fibrosis of the dermis: and increased susceptibility to trauma with the development of late necrosis. 3.2.3 Nonstochastic Effects Versus Dose for Large Area Irmdiation Based on experience with radiotherapy with orthovoltage x rays, Ellis (1942) and Paterson (1948) proposed safe ''tolerance" doses for irradiation of human skin. The dose of x rays or gamma rays required to produce a certain level of clinical damage (clinical tolerance level) increases as the area of irradiation decreases (Cohen, 1966; Eads, 1972; ICRP, 1984). However, the biological basis of clinical tolerance was not defined and tolerance should not be confused with isoeffect doses. The threshold d m for a visible reaction for beta particle irradiation also increases with decreasing field size (Wells et al., 1982; ICRP,1984). The slope of the curve of the mean skin reaction versus acute xray dose, for large field irradiations, required to produce the various acute nonstochastic effects for single exposures is very steep (see Figure 9 of ICRP, 1984). The acute dose required to produce faint erythema is approximately 8 to 10 Gy while the acute dose required to produce ulceration is 20 to 25 Gy. 3.2.4 Nonstochtic Effects From Hot Particles

Irradiation of the skin by hot particles does not produce acute nonstochastic effects that are comparable to those seen with large field irradiations. For example, with small areas of irradiation, migration of basal cells of the epithelium from the edge of the damaged area prevents moist desquamation. The detrimental reaction, seen after very high exposures of hot particle irradiation, is acute ulceration or necrosis. The underlying mechanism responsible for the effect is the killing of endothelial and fibroblast cells in interphase (the interval between two successive cell divisions) at a depth of about 150-300 p.m in the superficial dermis. The effect develops over a much shorter period of time (about 1to 2 weeks) than do dry and moist desquamation following large field irradiation. The rapidity of the appearance of the effect is due to the characteristics of cell death during interphase (Hopewell, 1986h3 Charles, M., Forbes, P. D., Fry, R. J. M., and Hopewell, J. W. (1989).Personal communication on the nonstochastic decta of hot particles.

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3. BIOLOGICAL EFFECTS OF IRRADIATION OF THE SKIN

3.2.5 Review of Biological Effects of Hot Particle Irradiations

Experiments, applicable to hot particles, have been performed on animals, and in one case on a human. These studies are reviewed below. 3.2.5.1 Monkey Experiments. The skin on the backs of monkeys (Macaca speciosa) was exposed to hot particles in a series of three experiments conducted a t the Los Alamos Scientific Laboratory (Biological and Medical Research Group, 1965 and Dean et d.,1970). The authors reported that histological examination of the unexposed monkey skin showed similarity to the thickness and structure of human skin, especially that on the dorsal forearm.The hot particles were 236UC2 "microspheres" which had been irradiated in a reactor. They were covered with a 25 pm layer of graphite and ranged in total diameter from 150 to 250 pm. The particles were placed directly on the skin, and exposures were "acute", taking less than 6 hours. Radiation dose was expressed by the authors as a point dose 100 pm directly beneath the particles. In the first monkey experiment, a total of 13 areas were exposed with point doses ranging from 12.7 to 96 Gy (1.27'to 9.6 krad) and, hence, only a few areas were exposed a t similar doses. The only reaction observed was a slight erythema, 1to 2 mm in diameter, a t the highest dose site. The maximum erythema occurred 48 hours post exposure suggesting that cell death during interphase was i n ~ o l v e dThere .~ was no evidence of the exposure after 26 days. The second monkey experiment involved nine areas exposed with point doses ranging from 158 to 521 Gy (15.8 to 52.1 krad). Erythema was visible a t all exposure sites a t 48 hours. There was an elevation of the stratum corneum a t the two highest dose sites. Based on current knowledge, the observed change was probably blistering due to the separation of the epidermis from the underlying damaged dennis, and therefore the initiation of a shallow ulcer.3 It was reported that a t 28 days, a shallow, dry desquamation was observed only a t the site irradiated to 521 Gy (52.1 krad). The dry desquamation had disappeared by 36 days. There was no observable ulceration or dermal necrosis reported in this series. However, from the description and current knowledge, the dry desquamation was probably a superficial ulcer covered by dry serum exudate3 By 90 days no lesions were visible or palpable. In the third monkey experiment, a total of 11sites were exposed to doses ranging from 1,570 to 6,640 Gy (157 to 664 krad). There was erythema a t all sites with a maximum diameter of 8 mm a t the highest dose, elevation of the stratum corneum, and palpable nodules

5 to 8 mm in diameter. The maximum gross observable reaction occurred a t 15 days. Ulceration was observed a t sites with point doses of 2,610 Gy (261 krad) or higher. This lesion is presumed to represent deep ~ l c e r a t i o nAll . ~ sites a t lower doses showed what was termed dry desquamation of 3 to 4 mm diameter. As suggested above, the term dry desquamation appears to have been used to describe what is now considered to be a superficial ulcer covered by dry serum e ~ u d a t eThe . ~ ulcers remained as open sores for about two weeks. By 71 days, all ulcerated sites had healed. The ulcerated sites showed a dimple about 3 mm in diameter. After 300 days the residual clinical lesions a t the higher dose sites consisted of a crater-form depression some 2.5 mm in diameter surrounded by a flattened crater lip 1.5 mm in width. The floor of the crater and the flattened lip were devoid of hair. Welldeveloped hair was present along the outer margin of the lip. Human Experiment. The inner surface of the forearm of a human volunteer was exposed to three different dose levels using 2S6UCz microspheres like those described above (Dean and Langham, 1969 and Dean et al., 1970). The point dose values were 142,400 and 540 Gy (14.2, 40 and 54 krad). The lowest dose produced a slight erythema, the intermediate dose produced an erythema and the highest dose produced a possible small dry desquamation following the erythema reaction. No ulceration was reported. However, as indicated previously, the small area of dry desquamation was probably a superficial ulcer covered with dry serum exudate3 Following the erythema response, a small freckle was visible. Two years after the experiment, the exposure sites could not be found on the skin. 3.2.56

3.2.5.3 Swine Experiments. Forbes and Mikhail (196914 exposed microspheres similar to the skin of swine to radiation from 236UCz those used for the monkey and human studies by Dean and coworkers described earlier. A total of 19 exposures were made with point doses which ranged from 2,400 to 74,000 Gy (240 to 7,400 krad). Exposures were acute with exposure times typically in the range of two to three hours. All the exposures were large enough to produce lesions described by the authors as ulcers. The diameter of the ulcers Circumstances outside the control of the authorsforced terminationof their studies before exposures sufficiently low to defme a threshold could be made. Although a report was prepared (Forbes and Mikhail, 1969) it was never published, except as an abstract,due to termination of the study. However, the basic data have been published and discussed (Wells and Charles, 1979; Charles and Wells, 1980; Wells, 1986; and Charles, 1986) and the original report was made available to the committee that drafted this report by one of the authors (Forbes).

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3. BIOLOGICAL EFFECTS OF IRRADIATION OF THE SKIN

ranged from 0.5 mm a t the lower doses to 8 mm a t the highest dose. Ulcer diameter was defined by the authors as the diameter of the denuded, oozing sore and, in turn, the diameter of the eschar (scab) which subsequently filled the denuded space. The clinical sequence of events is summarized as follows. The site of each exposure exhibited erythema by the time the particles were removed from the skin. Reddening peaked a t 24 hours and reappeared irregularly thereafter, possibly because of infection. Hair growth ceased in the erythematous area but began again after 30 days except in the central scarred area. Beginning on the third day, darkening of normally pigmented skin formed a halo around the center of the exposed spot. A narrow ring of hyperpigmentation remained permanently around the edge of the scar.The skin nearest the particle was permanently depigmented. The disappearance of early erythema coincided with the appearance of one or more very small vesicles (blisters). These gave way to a single bulla or larger blister which was always transient, usually granular in appearance and variable in contour. With the loss of this surface material, each lesion developed into a n oozing sore. The authors interpreted this sore as indicating loss of functional epidermis. The larger lesions, associated with the higher doses, developed cavitation which the authors interpreted as evidence for loss of some dermis. The authors applied the designation of ulcer to all of the lesions but suggested that the smaller lesions may not have been ulcers in the strict sense. These observations are consistent with the description given in the human and monkey studies. In those studies,the change was described as elevation of the stratum corneum, although after lower doses than those used in these studies on swine. All ofthe observations of Forbes and Mikhail on swine are consistent with interphase cell death and deep ulceration that involved damage to the dermis (Hope~e11,1986).~ The development of the lesion was more rapid a t the sites of higher dose; healing events occurred more rapidly after lower doses. An effect described as moist desquamation appeared at the sites as early as the second day after exposure. Today, such a finding would be considered to be blistering, as described earlier, since moist desquamation can not occur a t such an early time as two days after irradiat i ~ nThe . ~ area of involvement gradually spread outward to its maximum size; full development of the lesion took two to four weeks. Dry eschar (scab) formation commenced within three days after the appearance of an ulcer; six weeks after exposure all lesions were dry. Scarification was completed in most cases by 12 weeks. Residual evidence of damage included scars, flaking, hair loss, and pigment

alterations. Reappearance of inflammatory changes was noted a t irregular intervals but healing proceeded satisfactorily. A team of British researchers has performed an extensive series of measurements of the effects of beta sources of different sizes and different energies on swine skin. The results are summarized by Hopewell et al., (1986). Some of their measurements were conducted with sources too large to approximate hot particle geometry. For the larger sources, they obtained about the same threshold doses observed by others for such sources (Moritz and Henrique, 1952; George and Bustad, 1966). Hopewell et al, (1986), however, did conduct extensive studies with a range of beta-particle energies and exposures of a large number of areas of pig skin, which included experiments with 1and 2 mm "Sr sources, with 0.1,0.5 and 1mm 17Tmsources and with a 2 mm 147Pmsource. They performed multiple exposures a t numerous dose levels and constructed plots of the probability of an effect as a function of dose. This approach allowed the determination of the dose required to produce the effect 50 percent of the time and allowed estimates of the threshold and the dose required to produce the effect 100 percent of the time. (This type of analysis was possible because the number of irradiated areas was larger than was used in the other studies.) The doses reported in the British studies were not precisely the point doses reported by the studies described above but were doses measured with an extrapolation chamber with a window thickness of 16 pm and an effective collecting area of 1.1mm2. Their sources were attached to source holders making the irradiation geometries different from that involved with the 236UC2 microspheres. The endpoint used in the British studies was designated by the authors as acute necrosis which is biologically consistent with acute ulceration. The authors also explicitly stated that moist desquamation could not occur with source sizes less than 2 rnm in diameter because the mechanism of the lesion is different with small area irradiation. The time course of acute necrosis varied with the dose level. For doses which induced the effect more than 50 percent of the time, the acute necrosis was visible in about two weeks and persisted for four to five weeks. For doses that induced the effect less than 50 percent of the time, the effect was very transient, so much so that scoring the animals twice a week resulted in more positive observations than scoring them once a week. Comparison of Studies. The data h m the studies described above are plotted in Figure 3.1 using end-points and doses as reported by the authors. It can be seen that the data for monkeys, the human and the swine study of Forbes and Mikhail(1969) show a consistent 3.2.5.4

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3. BIOLOGICAL EFFECTS OF IRRADIATION OF THE SKIN - KEY TO EFFECTS A

WEPPECT

B

WLDERNEY*

C D

ERrmEYl DRYDEBOUIYITK)(I ACUTENECROBLS ULCERATON

E F

Fig. 3.1 Biological effects of small radioactive particles on the skin as a function of dose.

pattern. These studies were all conducted with irradiated 236U62 fuel particles in the 100 to 200 micrometer size range. All of these studies related effects to a point dose a t 100 pm beneath the particle. Where observed, the authors reported mild erythema, erythema, dry desquarnation and u l c e r a t i ~ n . ~ The points plotted in Figure 3.1 for the swine studies summarized by Hopewell, et al. (1986) differ in several respects from the others shown. The doses were delivered by 1mm diameter and by 0.1, 0.5 and 1mm 170Tmsources. All three sizes of the 17% sources gave essentially the same dose response and are plotted as a single point in Figure 3.1. The reported doses were measurements made with an extrapolation chamber with a window thickness of 16 pm and an effective collection area of 1.1mm2.Other measurements were made a t different depths and over different areas. The points plotted represent the dose required to produce acute necrosis 50 percent of the time. The authors did not publish data for other endpoints such as erythema. Estimated thresholds (zero percent probability of effect) could have been plotted. These thresholds are two to three times less than the dose required to produce an effect 50 percent of the time. The term dry desquamation when used to describe an effect aseociated with hot particle irradiation is assumed to be synonomous with superficial ulceration that was covered with dried serum exudate, Charles, M., Forbes. D., Fry, R. J. M. and Hopewell, J. W. (1989)personal communication.

3.3 STOCHASTIC RISKS OF IRRADLATION

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-KEY TO EFFECTS A NOERECT 0 UnDrnEYA C CRYrnaU D D R I ~ A ~ O N E *CUILtlEcROSP) F ULcEnAmc

Fig. 3.2 Biological effects of small radioactive particles on the skin. Doses have been adjusted to a common basis.

In a further comparison of the results of the various studies, the doses for the 236UCzmicrospheres were reevaluated by calculating the dose they would have produced had they been measured using the extrapolation chamber used in the British studies (see Appendix A). This calculation resulted in a reduction of the point doses for the microspheres by a factor of three (see Figure 3.2). With the doses on a common basis and current interpretation of the description of the lesions, there is reasonable agreement among the results of the studies.

3.3 Stochastic Risk of Irradiation

The principal stochastic risk associated with irradiation of the skin is non-melanoma skin cancer, i.e. basal cell and squamous cell skin cancers (NASINRC, 1980). The risk of skin cancer following irradiation of the skin by hot particles is less than when extended areas of the skin are irradiated due to the very small number of cells involved and the greater potential for cell killing from the possibly high local beta particle dose. In the past decade, a number of radiation epidemiology studies have obtained data on skin cancer incidence. Most have found an association between radiation and non-melanoma skin cancer. (The

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3. BIOLOGICAL EFFECTS OF IRRADIATION OF THE SKIN

association of radiation with malignant melanomas is equivocal.) The irradiated skin areas in the studies have ranged from about 100 cm2up to whole body exposures. Ten studies have the requisite information for deriving risk estimates: a defined irradiated study group with reasonably complete follow-up for skin cancer incidence and estimates of skin dose. Six of them provide data on skin cancer induction following irradiation of skin areas which have appreciable ultraviolet radiation (UVR)exposure (primarily head and neck) (Schneider et al., 1986; Van Daal et al., 1983 and Van Vloten et al., 1987; Hildreth et al., 1985; Ron et al., 1988; Shore et al., 1984; Sevcova et al., 1978, Sevcova et al., 1984 and Sevc 1988). Five of the studies provide data on irradiation of relatively UVR-shielded skin areas (trunk irradiation or irradiation of blacks who are UVR-shielded by melanin) (Davis et al., 1987, Hrubec et al., 1989 and Boice, 1988; Shore et al., 1986 and Hildreth and Shore, 1988; Boice et al., 1985; Hay et al., 1984; Shore et al., 1984). These studies show that radiation induction of skin cancer is greater in UVR-exposed skin than in WR-shielded skin, suggesting that UVR is a promoter of skin cancer in cells initiated by ionizing radiation. This interpretation is supported by experimental results as well (Fry et al., 1986). Composite estimates of excess skin cancer incidence have been calculated based on the studies of UVR-exposed and WR-shielded skin. The estimates were projected out to lifetime risks using lifetable methods, under the assumption that exposures were received over a working lifetime of ages 20 to 60 (Shore 1989). Although the available data tend to favor a relative risk (RR) projection model over an absolute risk (AR) model (Shore 1989), the data are too limited to be definitive, so both models were examined. Separate estimates were calculated for males and females (who differ somewhat in baseline skin cancer rates and in life-spans), but the results are similar enough that averages across sexes can be used. If the irradiation of an area of 2 mm2 per hot particle a t 100 pm depth (Dean and Langham, 1969) is assumed, then the risk of skin cancer per hot particle exposure would reflect this small irradiated area. The estimates of skin cancer induction, therefore, were scaled down in proportion to skin surface area from the approximate area of UVR-exposed (3,000 cm2)or UVR-shielded (15,000 cm2)skin to an area of 2 mm2. The risks of skin cancer induction for a 2 mm2 irradiated area are shown in Table 3.1. For UVR-exposed skin the risk estimates are <7 x lo-' Gy-I (<7 x rad-I). For WR-shielded Gy-' (<8 x lo-" rad-I). skin they are <8 x The mortality associated with radiation-induced skin cancer also

3.3 STOCHASTIC RISKS OF IRFWDLATION

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TABLE 3.1-Lifdime

risk of mdicrtion-induced skin cancer incidence and mortality (per 2 mmz exposure field per Cy), resulting from irradiation at me1 20-60. Skin Skin Cancer Cancer R* Rink (Incidence) Mortality)

WR-exposed skinb Absolute risk model Relative risk model

1 . 2 lo-1 ~ 6.6 X

2.4~ 1.3~

WRghielded &inc 7.4 x 10-@ 1 . 5 10-la ~ Abeolute risk model Relative risk model 2.2 x lo-'0 4 . 4 10-l3 ~ "~stimateaof excess incidence of non-melanoma akin cancer cumulated for the remaininglifetime. Skin cancer mortality was calculated by applying a 0.2% lethality rate (see text). bFor UVRexpOBed skin (3,000 cm2),the absolute risk estimate was 6.5 x lo-' y-' Gy-I and the relative risk estimate was 57.9% Gy-I (Shore, 1989). T o r UVR-shielded skin (15,000 cm2), the absolute risk estimate was 2.0 x lD-'y-l Gy-I and the relative risk estimate was 0.5% Gy-I (Shore, 1989).

needs to be estimated. The amount of mortality associated with squamous cell skin cancer is not well characterized. The several studies which appear to be reasonably representative of squamous cell carcinoma mortality in the general population suggest that the mortality rate is about one percent (Epstein et al., 1968, Dunn et al., 1965, Giles et al., 1988). Basal cell carcinomas, on the other hand, are almost never metastatic or fatal (estimated fatality rate < 0.01%) Weedon and Wall, 1975; Kopf, 1979; and, Paver et al., 1973. There is no evidence that mortality following radiation-induced skin cancer is any different than for UVR-induced skin cancer unless there is overt chronic skin damage (radiodermatitis or radiation burn), so these estimates should be applicable to radiogenic skin cancer. The available data indicate that basal cell cancers are induced by radiation a t least five times-as frequently as squamous cell cancers (Shore, 1989), so a weighted average of the squamous cell and basal cell rates yields an average case-fatality rate of about 0.2 percent. This factor is applied to the estimates of skin cancer yield to calculate excess skin cancer deaths. The results are shown in Table 3.1. The highest mortality risk shown there is about 1 x lo-' Gy-' (1 x lo-'' rad-I). In summary, a conservative estimate of the risk of skin cancer following a liot particle exposure is 7 x lo-' Gy-' (7 x lo-' rad-'1, and the risk of skin cancer mortality is about 1 x lo-' Gy-' (1 x lo-" rad-'), assuming an irradiated skin area of 2 rnrn2.

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3. BIOLOGICAL EFFECTS OF IRRADIATION OF THE SKIN

3.4 Comparison of Nonstochastic Effecta (Deterministic Effects) and Stochastic Risk of Hot Particle Irradiation The stochastic lifetime risk estimate for incidence of non-melanoma skin cancer from hot particle'irradiation is estimated to be very small, being on the order of 7 x Gy-I (7 x rad-I). The stochastic lifetime risk estimate for fatal non-melanoma skin Gy-I (1 x lo-" cancers is even smaller, on the order of 1 x rad-I). Acute deep ulceration occurs a t a threshold dose of approximately 2,300 Gy (230 krad), when the dose is evaluated a t a depth of 100 p,m directly under a hot particle (see Figure 3.116At this dose, if the dose is given a t high dose rate, the probability of inducing a non-melanoma skin cancer mortality would be approximately 2,300 Gy x 1 x 10-9Gy-' = 2.3 x This result is probably an overestimate of the stochastic risk of mortality a t the high dose required for acute ulceration, because cell killing will result in a reduced cancer risk. This value is several orders of magnitude below the observed lifetime occupational stochastic risk of mortality from accidents in "safe industry" of approximately one-half percent (NCRP,1987). When the small areas involved in hot particle irradiation are irradiated sufficiently to cause erythema and lesions which give the visual appearance of dry desquamation, such effeds are temporary, are confined to an area of a few square millimeters and are not considered to be severe nonstochastic effects (see Section 3.2). Dermal thinning and pigment changes in such small areas are essentially cosmetic and are also not considered to be severe nonatochastic effeds. Many dimples or freckles might be considered undesirable, but the occurrence of many hot particle exposures per individual is unlikely. As pointed out previously in Section 3.1, radiation protection phi-

s The approximate dose for 100 percent probability of acute ulceration, measured a t a depth of 16 bm over a s extrapolation chamber window area of l.lmmz was 700 Gy (70 h a d ) [i.e. 2,100 Gy (210 krad) point dose a t a depth of 100 ~ m for l a circular lrnrn diameter 90Sreource when scoring was done twice weekly. (see Appendix A and Hopewell et al., 1986). When the scoring was done once weekly the 100 percent probability dose for this eource was approximately 1,000 Gy (100 krad) [i.e. 3,000 Gy (300 krad) point dose a t a depth of 100 pm] [see Appendix A and Hopewell et al., (1986)l. As indicated in Section 3.2.5.4, the results of the various studies appear to be consistent. However, since the source used by Forbes and Mikhail(1969) and by Dean and coworkers (Biological and Medical Research Group, 1965; Dean and Langham, 1969; and Dean et al., 1970) are more comparable to hot particles than the sources used by Hopewell et al, (1986). the threshold dose for acute deep ulceration for hot particles of 2,300 Gy (230 krad) as estimated from these studies is utilized here.

3.4

COMPARISON OFRISKS

1

15

losophy includes prevention, to the extent practicable, of the occurrence of severe, radiation induced, nonstochastic diseases (NCRP, 1987). For this reason, acute deep ulceration (rather than some lesser effect such as superficial ulceration), as identified by Forbes and Mikhail(1969) and by Dean and coworkers (Biological and Medical Research Group, 1965; Dean and Langham, 1969; and Dean et al., 1970) is selected as the biological endpoint of concern for radiation exposure of the skin by a hot particle. Ulceration of a minute area of skin, such as that which may occur near the threshold for acute deep ulceration, is not considered to be a severe nonstochastic effect. Prevention of acute deep ulcers will keep the concomitant stochastic risks to several orders of magnitude below observed risks of mortality from accidents in safe industries. Implicit in this argument is that multiple hot particle exposures to the same spot on the skin and/or large numbers of hot particle exposures to the same individual are extremely unlikely. The foregoing arguments are estimates based on incomplete data that are used to examine the relative risks from stochastic and nonstochastic effects from hot particles. As more definitive information becomes available on these risks, it may be possible to produce better estimates.

4. Approach to Establishing a Practical Limit Several approaches to establishing a limit for radiation exposure of the skin by hot particles have been considered: (1) Limit the dose .toa point directly under the particle, (2) Limit the average dose over some small (about 1cmZ)area at the depth of the basal cells of the epidermis, (3) Limit the average dose over some larger area of the epidermis or (10 to 100 cm2), (4) Limit exposure on the basis of the total number of beta particles emitted from a hot particle.

In any case, it is necessary to relate a recommended limit to biological effects and preferably to be able to measure it readily. Most calculations of dose start from equations for the dose near point sources. One or the other of two such equations are usually used: an empirically based expression due to Loevinger (1956)or an expression calculated by the moments methods, most recently by Berger (1971). At distances from a point that are small compared with the range of the beta particles, the two expressions give doses that are comparable (differing by a maximum of approximately 40 percent). Figure 4.1 gives calculations of the number of beta particles per Gy for several depths utilizing the,moments method of Berger. At distances beyond one-half the range, the differences between the Loevinger method and the moments method of Berger become even larger, finally becoming more than a factor of ten. Furthermore, neither of these point-source equations takes into account the difference in density between the source material (uranium for example) and tissue. Also, the two expressions incorporate the effects of betaparticle scattering as they exist in an infinite mass of tissue, and, therefore, do not reflect the much different scattering that occurs when a dense particle is sitting in air on the surface of a mass of tissue. The differences between the Loevinger and Berger equations a t small and a t large distances are related as a result of how the expressions were normalized. Both were normalized so that they give the total energy absorbed in the surrounding medium to be equal to the

4. APPROACH TO ESTABLISHING A PRACTICAL LIMIT

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17

Em,, (MeV)

Fig. 4.1 The number of beta particles that must be emitted fmm a point source to produce a dose of one gray, at several depths in tissue, for beta particle spectra of E , ) . Calculated by the moments method of Berger different maximum energiea ( (Berger, 1971).

energy emitted by the point source. Consequently, if one equation gives higher doses than the other close to the source, it must give smaller doses at large distances. This compensation results in quantities resulting from calculations that average the doses over a sufficient range of distances from the source being numerically close. Therefore, a limit based on d m has not been recommended because of the error inherent in determining dose from small beta-particleemitting sources and because of the lack of a clear biological basis for selecting an area and depth or volume over which to evaluate dose. Approach 4, the use of the total number of beta-particles emitted, avoids the difficulties of the dosimetric approaches. Independent of which equation is employed, the differences in the doses calculated are not extreme for simple arrangements of beta-particle emitters of different maximum energy. Thus, the number of beta particles emitted can serve as an index for the risk of hot particles containing different energy beta-particle emitters.

5. Interpretation of Experiments With Hot Particles Using the Approach of the Total Number of Beta Particles Emitted 5.1 Monkey Studies As described in Section 3.2.5.1 above, Dean and Langham (1969) and Dean et al. (1970) used neutron-irradiated 236UC2 spheres (producing beta particle emitting fission products) to irradiate the skin of monkeys. Their work included doses that caused effects spanning the entire range of effects from transient erythema to ulceration. These data were originally reported as a function of point dose a t a depth of 100 pm directly below the particle. These doses have been converted to total beta particle emission by the method described in Appendix B. The largest beta particle emission that did not produce ulceration in monkeys was 3.2 x 10lO;all beta particle emissions of 3.4 x 101° or more produced ulceration. Thus a threshold for acute ulceration of 3.2 x 101° beta particles can be estimated from this experiment.

5.2 Human Study The results of the experiment in which Dean et al. (1970) exposed the inner forearm skin of a human to beta particles from a fission product hot particle (Section 3.2.5.2) can also be expressed in terms of total beta particle emission. Although originally reported in terms of point dose, the maximum exposure of 540 Gy corresponds to 7 x loe beta particles (see Appendix B). The strongest reaction they saw was a small dry desquamation (superficial ulceration). A few years

5.4 S

m STUDlES WITH OTHER SOURCES

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19

later the exposure site could not be found on the skin. Because no deep ulcer was found, the result is consistent with the threshold of 3.2 x 101°beta particles found in monkeys.

5.3 Swine Studies With Microspheres

Forbes and Mikhail(1969) exposed the skin of swine to beta parmicrospheres that had been irradiated in a ticles from small 236UC2 reactor (Section 3.2.5.3). A11 of the doses from the beta particle emitting fission products were large enough to produce ulcers so it is not possible to determine a threshold in the conventional manner. Fortunately, a precise value of the threshold is not necessary for setting limits because the effects near or even somewhat in excess of the threshold are small. In order to estimate an approximate threshold from these data, the diameters of the ulcers produced were plotted against the total number of beta particles produced in the spheres during the irradiation (see Figure 5.1). As with the monkey and human studies described above, these data were originally reported as a function of point dose (100 pm directly below the particle). These doses have been converted to beta particles emitted (see Appendix B). In Figure 5.1, the data of Forbes and Mikhail(1969) form an approximately straight line on a semi-logarithmic plot. Although not strictly rigorous from a statistical standpoint, the intercept, i.e., zero diameter ulcer, was estimated by fitting the data to a straight line by the least squares method. The intercept on the abscissa was found to be 3 x 101° beta particles. A straight line that was obtained by a least squares fit to the eight points with smallest emission gave an intercept of 1.5 x 10''. The value of 3 x 101° beta particles was selected as the best estimate of the threshold because it was believed to give the best fit to the Forbes-Mikhail data and because it agreed with the data on monkeys (Dean Langham, 1969 and Dean et al., 1970). It should be noted that the ulcer produced by an emission of 3.14 x 101° beta particles was only 0.5 mm in diameter.

5.4 Swine Studies With Other Sources

Hopewell et al. (1986) used three radionuclides and source sizes ranging from several centimeters down to 0.1 mm in diameter for 'I%. The small sources were not like the hot particles used in the experiments described earlier but were of various geometries and

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20

2

-

5. INTERPRETATIONOF EXPERIMENTS

THRESHOLDS FORBES-MIKHAIL

'"1 .

E 8

I

I

LARGE PARTICULATES SMALL PARTICULATES

.

NUMBER OF BETA PARTICLES EMITTED Fig. 5.1 The diameters of the ulcers produced in pig skin by activated =UC2 microspheres in the experiment of Forbes and Mikhail (1969) as a function of the number of beta particles emitted in the spheres during the irradiation. The number of beta particles emitted are calculated a t 10a seconds following irradiation of the rnicrospheres. Extrapolating this data, a zero diameter lesion occurs a t 3 x 101°beta particles emitted.

were attached to source holders. For the large sources, they obtained about the same threshold dose as observed by others for such sources (Moritz and Henrique, 1952; George and Bustad, 1966). For the smaller sources, however, the dose required to produce acute necrosis on 50percent of the irradiated fields increased with decreasing source size, becoming as much as 275 Gy (27.5 krad) a t a source diameter less than or equal to 1 mm. Because of the source geometry, it was not possible to confidently convert these doses to beta particle emission as was done for the hot particle studies described; but a comparison of the studies on a dose basis was made in Section 3.2.5.4 above.

5.5

Estimation of a Threshold

Based on the above analyses, a threshold for the induction of acute deep ulceration by hot particles of 3 x 101°beta particles emitted in

5.5 ESTIhiATION OF A

THRESHOLD

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21

the hot particle has been estimated. This value has been determined from the monkey experiments of Dean et al., 1970 and Dean and Langham, 1969 as supported by the swine experiment of Forbes and Mikhail (1969)and the human experiment of Dean et al., 1970. Hopewell et al., (1986)reported effects at somewhat lower doses. Their effect, particularly for doses less than that required to produce the effect 50 percent of the time, was transient and frequently disappeared in less than a week. In addition, the source geometries used did not match the hot particle geometry under consideration here as well as that of the sources used by Dean et al., 1970;Dean and Langham, 1969;and by Forbes and Mikhail, 1969.

6. Observations on Humans Exposed Inadvertently in the Work Place INPO (1987)summarized 19 human exposure events for which the activity and duration of the exposures were known. The exposures ranged from 1.1 x lo7 to 6.4 x lo8 beta particles. No effects were observed from any of these exposures. This lack of observed effects is consistent with the animal and human experiments described above since they were below the threshold for acute deep ulceration.

7. Derivation of an Exposure Limit for a Hot particle on the Skin A recommended limit should be for point sources to allow for the potential of encountering hot particles of very small size and essentially no self absorption. A recommendation for point sources is a conservative one because self absorption in larger particles, such as those actually used in the experiments, would always result in a lower beta particle emission rate from the surface of the particle. Figure 7.1 gives the calculated point source dose rates for 236UCz spheres of various diameters a t a depth of 100 pm (Ulberg and Kochendorfer, 1966). A point source would have to emit about one third the number of beta particles to produce the same dose a t 100 pm depth as the 100 pm particles used by Forbes and Mikhail. Hence, the acute deep ulceration threshold estimated for point sources of irradiated nuclear fuel particles on human skin is estimated to be: 3 x 101° x 1/9 = 1010beta particles.

If each disintegration is assumed to emit one beta particle, this limit can be expressed as 10 GBq s, or in traditional units as 75 pCi h. It is not unusual in setting radiation protection limits to provide a specific safety factor or element of conservatism. This approach is warranted when the endpoint to be avoided or minimized is a serious health consequence. In the present case, however, the selected endpoint to be prevented, acute deep ulceration of minute areas of the skin, is not a serious health consequence. The cost both in additional whole body radiation exposure due to frequent surveillance of workers and in money that would be required to comply with a limit employing a safety factor is not justified in this case. Therefore, an explicit safety factor has not been incorporated into these recommendations.

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1

7. DERIVATION OF AN EXPOSURE LIMIT

DIAMETER OF p6UC, MICROSPHERES ( p m )

Fig. 7.1 The points are the dose rates calculated by Ulberg and Kochendorfer (1966) at 100 pm distance from activated T J C 2 microspheres of different diameters for time (T)equal to lo3 and 10' seconds after removal from the reactor. The lines represent the dose rates that would have been produced by point sources (no self absorption) with the same activities.

8. Recommendations on Radiation Exposure Limits for the Special Case of A Hot Particle on the Skin It is recommended that:

(1) A limit for exposure to hot particles be based on ensuring that acute deep ulceration of the skin be prevented and that this be accomplished by a limit based on the time integral of the beta particles emitted due to the activity of the particle in contact with the skin, (2) Exposure to the skin from a "pint" particle or a particle of unknown size but less than 1 m m i n diameter be limited to 101° beta particles emitted from the radionuclides contained in the particle. For the case where 1 beta particle is emitted per disintegration, this limit may be expressed as 10 GBq s or 75 pCi h. For a particle for which the self absorption can be measured or calculated, the limit can be increased by the ratio of the beta particles emitted by the radionuclides divided by the beta particles emitted from the surface of the particle. Alternatively, the limit can be.expressed as 101° beta particles emitted from the surface of the particle, (3) Exposure in excess of the limit should require periodic medical evaluation of the exposed site for a period of approximately four weeks in order to determine what effect, i f any, occurs. If an ulcer occurs, the decision on allowing the exposed individual to work should be based on the same criteria one would apply to any open wound. The affected individual should be aware that the risk of skin cancer from such events is extremely small. The basis for this recommendation is data obtained primarily from beta particle emissions fmm irradiated fuel particles. The probability for serious tissue damage from particles containing60Cois no greater than that for particles containing irradiated fuel and is likely to be much less due to the shorter range of the 60Cobeta particle.

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1

8. RECOMMENDATIONSON RADIATJQN EXPOSURE LIMITS

The recommendations in this report are intended for application to hot particles in contact with the skin. When a given hot particle is not in contact, it produces lower doses in the skin; also the radiation field changes less rapidly with distance, both laterally and with depth. Under these circumstances, a given hot particle is expected to produce less harm. When hot particles are found on a person, they are not always in contact with the skin. They may, for example, be on clothing or in the hair. Regardless of where they are found, due to their considerable mobility, their past positions and movements are not known and cannot be determined. In general, therefore, to be conservative, it is recommended that a hot particle be assumed to have been in contact with the skin throughout the possible irradiation period. In cases where it can be determined that the hot particle was never in contact with the skin (for example, if it were between two layers of clothing) dose limits for exposure of large areas of the skin should be applied. The circumstance in which skin is irradiated by hot particles not directly on the skin requires further study. There are wide variations in the data on which recommendations for limits of exposure of the skin to hot particles must be based. Additional research is occurring presently and should be continued on both the biological effects of hot particles and the dosimetry of hot particles. Results from this ongoing work may well eventually provide sufficient new information to further support these recommendations or to require their review a t a later time.

APPENDIX A

Comparison of Point Dose with Dose Measured with an Extrapolation Chamber In swine, monkey and human experiments conducted in the United States (Forbes and Mikhail, 1969; Dean and Langham, 1969; Dean et al., 1970)a quantity "point dose" was used to describe the delivered radiation dose. This point dose is defined as the dose 100 pm directly below the center of the particle. In swine studies conducted in Britain and reviewed by Hopewell, et al. (1986),the reported dose was most often the average dose at a depth of 16 pm (thickness of the window of the extrapolation chamber) averaged over a 600 Frn radius disk (1.1 mm2 collecting area) centered beneath the source as measured directly by an extrapolation chamber. To compare the results of the studies properly, it is necessary to use the same doses for all studies. One way to obtain equivalent doses is to compute the average dose that would be delivered by the particles used in the United States studies to the extrapolation chamber used in the British studies. Assuming the activity in the source particles to be concentrated in the center, the average dose [D(ave)lto the extrapolation chamber's effective collecting area would be: D(ave)

= I T - ~ O - ~D(r) ~ ~dr I T Z

where x is the radius of a circular element of the disk of radius a and D(r) is the dose at a distance r from the source. To an accuracy of about 10 percent and for distances up to about 1rnm, the doses around the particle can be approximated by the inverse square law (derived from Ulberg and Kochendorfer, 19661, i.e.,

28

1

APPENDIXA

D(r) = (175)20 0 7 5 ) r-2 where 175 pm is the distance from the center of a hot particle with a diameter of 100 pm plus a coating 25 p,m thick to a point 100 p.m deep in tissue and D(175) is the dose a t that point. Because

~ s s u m i unit n ~ dose at 175 pm and the case a t hand where a = 600 pm and y = 91 pm, [one half the radius of the particle (50 pm) plus the thickness of the coating (25 pm) plus the window thickness of the British extrapolation chamber (16 pm)l, D(ave) is 0.3. This means that the point doses reported by the American investigators can be multiplied by approximately 0.3 to compare the results with the British studies.

APPENDIX B

Number of Beta Particles from Irradiated 235UC2 Microspheres The activities of the sources used in the Forbes-Mikhail experiment (1976) were determined, but the records were lost. This appendix describes how the number of beta particles emitted from the sources were redetermined using the dose calculation model employed in the experiment. Forbes and Mikhail gave calculations made by the TDD (transmission, degradation and cjissipation computer code) model of determining the doses, a t 100 Fm in tissue, D(100), from the =UC2 microspheres they used. The TDD model (Ulberg and Kochendorfer, 1966) was a combination of Monte Carlo calculations of the number of beta particles emerging from the sphere and Berger (1971) calculations of their transport in tissue. The number (N) of beta particles emitted was determined from

where D,(100) is the dose a t 100 Fm due to a single beta particle. Ulberg and Kochendorfer (1966) gave extensive tables of doses calculated by the TDD model a t different distances h m 236UC2 spheres of different sizes irradiated in an aerospace reactor (1,000 MW for 10 minutes) at different times after removal from the reactor; they did not, however, list the number ~f beta particles emitted. The number were determined from the results for two other models, EXP (exponential model) and EMP (empirical model), given in the same table. The EXP model assumed no attenuation of the beta particles in emerging from the source and exponential attenuation in tissue; the EMF' model was similar but corrected for attenuation in the source by factors determined by comparing calculations with measured doses. Computer programs were written to duplicate the EXP

30

/

APPENDIXB

TABLE B.l-Number of beta particks emitted from the =UC2 spheres wed by Forbes and Mikhai1(1969), assuming they were used lo3seconds a@r removal from the reactor Particle Identification

Large Particles 1 3 4 5 6 7 8 9 10

Number of beta particlee! (N)

7.99 1.01 7.43 2.41 1.75 1.19 5.32 3.51 5.42

x loL1 x loL2 x loL1 x loL2

x loL2 x loLZ x loLL x loL1 x

loL1

Small Particles 11 2.24 x loL1 12 1.82 x loLL 13 3.14 x loL0 14 3.54 X loL0 15 8.65 x loL0 16 7.44 x loL0 17 6.97 x loL0 18 6.25 x loL0 19 9.80 x loL0 20 7.16 x loL0 Ulberg and Kochedorfer's tables were given to only two significant figures. The numbers in this column are, therefore, of no greater significance than the orginal data. Three figures are given to permit easier comparisons.

and EMP models and used to obtain D,(100) for the tabulated data. Equation B.l was then used to compute N. The values of N obtained from the two models agreed quite well, usually to within 13 percent (17 percent a t worst). Finally, D,(100) was obtained from these values of N and the TDD doses with equation B.1. The Ulberg and Kochendorfer spheres did not have the 25 pm graphite coating used by Forbes and Mikhail. The absorption in the graphite was only a few percent and was neglected. An inversesquare correction was made to their D,(100) for the thickness of the coat. Graphs were then prepared of the corrected D,(100) divided by the cubes of the diameters of the spheres to provide a quantity less dependent on the sizes of the sources. Interpolations on these graphs were used to obtain the D,(100) used in equation B.l to convert the Forbes-Mikhail D,(lOO)'s into the N's given in Table B.1. The results in Table B.l are for a time of lo3seconds after removal from the reactor, the shortest time used by Ulberg and Kochendorfer. It is approximately the time that Dr. Forbes indicated had elapsed

APPENDIXB

1

31

between removal of the particles from the reactor and their attachment to the swine. Slight variations in this time have negligible effect. Repetition of the calculations for lo4seconds after removal, the next time calculated by Ulberg and Kochendorfer and already well beyond the time used by Forbes and Mikhail, gave beta particle emissions only about 10 percent larger than those in Table B.1. The slow change with time after removal from the reactor is due to different decay rates of different radionuclides changing the beta particle spectrum.

References ARCHAMBEAU, J.0. AND MATHEIU, G.R. (1969). "Comparison of the observed results of irradiation on the skin with those expected from an idealized model," Radiat. Res. 40 (2),285. BERGER, M.J. (1971). "Distribution of absorbed dose around point sources of electrons and beta particles in water and other media, MJRD Pamphlet No. 7, J. Nucl. Med., Suppl. 5,3. BIOLOGICAL AND MEDICAL RESEARCH GROUP(1965). "Some biological aspects of radioactive microspheres," page 58 in Los Alamos Scientific Laboratory Report LA-3365-MS, (National Technical Information Service, Springfield, Virginia). BOICE,J., JR(1988). Personal communication. (National Cancer Institute, Bethesda, Maryland). BOICE,J., JR., DAY,N.E., ANDERSEN, A., BRINTON,L.A., BROWN,R., CHOI, N.W., CLARKE, E.A., COLEMAN, N.P., CURTIS,R.E., FLANNERY,J.T., ETU. (1985). "Second cancers following radiation treatment for cervical cancer. An international collaboration among cancer registries," J. Natl. Cancer Inst., 7461, 955. CHARLES, M. W. (1986). "The biological bases of radiological protection criteria for superficial, low penetrating radiation exposure," Radiat. Protect. Dosim. 14,79. CHARLES, M. W. AND WELLS,J. (1980). "The development of criteria for limiting the non-stochastic effects of non-uniform skin exposure," page 113 in Proceedings of the 5th International Congress of the Znternutional Radiation Protection Assocktion (Pergamon Press, New York). COHEN,L. (1966). "Radiation response and recovery: Radiation principles and their relation to clinical practice," in The Biological Basis ofRadiation Therapy, E. E. Schwartz, Ed. (Lippencott Publishers, New York). DAVIS,F., BOICE,J., KELSEY,J., AND MONSON, R. (1987). "Cancer mortality after multiple fluoroscopic examinations of the chest," J. Natl. Cancer Inst.78,645. DEAN,P. N. AND LANCHAM, W. H. (1969). 'Tumorigenicity of small highly radioactive particles," Health Phys. 16,79. DEAN,P. N., LANCHAM, J. AND HOLLAND, L. M. (1970). "Skin response to a point sou& of fissioned uranium-235 carbide." Health Phys. 19,3. DUNN,J., LEVIN,E., LINDEN,G., AND HARZFELD,L. (1965). "Skin cancer as a cause of death," Calif. Med., 102,361. EADS,D. L. (1972). "Application of a ret-dose slide rule relating dose, time, area-volume, quality, and anatomic factors," in Frontiers of Radiation Thercpy and Oncology, Vaeth, J. M. Ed. (University Park Press, Baltimore).

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ELLIS. F. (1942) "Tolerance dose in radiotherapy with 200 keV x rays," Brit. J. Radiol. 15,348. EPSTEIN,E., EP~EIN, N., BRAGG,K., AND LINDEN; G. (1968). "Metastases from quamow cell carcinomas of the skin." Archiv. Dermabl.; 97,245. S. Z. (1969). "Acute lesions in skin produced by FORBES,P. D. AND MIKHAIL, radioactive microspher&s,"oral presentation a t the annual meeting of the Radiation Research Society, 1970, abstract in Radiat. Res. 39,493. FRY, R.J.M., STORER,J.B., AND BURNS,F J . (1986). "Radiation induction of cancer of the skin," Brit. J. Radiol. Suppl. 19,58. GEORGE, L. A. AND BUSTAD, L. K. (1966). "Comparative effects of beta irradiation of swine, sheep, and rabbit skin," page 491 in Swine in Biomedical Research, Bustad, L. K . and McClellan, R. O., Eds. (Battelle Memorial Institute, Richland, Washington). GILES, G., MARKS,R., AND FOLEY,P. (1988). "Incidence of non-melanocytic skin cancer treated in Australia," Brit. Med. J. 296, 13. HAY, J., DUNCAN, W., AND KER, G. (1984). "Subsequent malignancies in patients irradiated for testicular turnours," Brit. J. Radiol. 57,597. HILDRETH,N., SHORE,R., HEMPELMANN; L., AND ROSENSTEIN, M., (1985). "Risk of extrathyroid tumors following radiation treatment in infancy for thymic enlargement," Radiat. Res., 102,378. HOPEWELL, J.W. (1986). "Mechanisms of the action of radiation on skin and underlying tissues," Brit. J. Radiol. Suppl. 19,39. HOPEWELL, J. W., COGGLE, J. E., WELLS,J., HAMLET, R., WILLIAMS, J. P. AND CHARLES, M. W. (1986)."The acute effectsof different energy betaemittera on pig and mouse skin," Brit. J. Radiol., Suppl. .19,47. HRUBEC, Z., BOICE,J., MONSON,R., AND ROSENSTEIN, M. (1989). "Breast cancer after multiple chest fluoroscopies: Second follow-up of Massachusetts women with tuberculosis," Cancer Res. 49,229. ICRP (1984).International Commission on Radiological Protection. Nonstoc h t i c Effectsofionizing Radiation, ICRP Publication 41, Volume 14, No. 3 (Pergamon Press, New York). INPO (1987). Institute of Nuclear Power Operations. "Hot particle exposyes," presentation by W.R. Kindley to NCRP ScientificCommittee 80-1 on Hot Particles on the Skin, Denver, Colorado, Dec. 9,1987. KOPP,A. (1979). "Computer analysis of 3531 basal-cell carcinoma8 of the skin." J. Dermatol. 6,267. LOEVINGER, R. (1956). "The dosimetry of beta sources in tissue, the point 80urce function," Radiology 66,55. LOEVINGER, R., JAPHA,E. M. AND BROWNELL, G. L. (1956). "Discrete radioisotope sources," page 693 in RadiationDosimetry, Hine, G. J..and Brownell, G. L., Eds. (Academic Press, New York). Moru~z,A. R. AND HENRIQUE,F.W. (1952). "Effect of beta rays on the skin as a function of the energy, intensity and durationof irradiation, II," Lab. Invest. 1,167. N A m R C (1980). National Academy of SciencedNationalResearch Council. TheEffectson Populations ofExposure to Low Levels oflonizing Radiation: 1980, BEIR 111(National Academy Press, Washington). NCRP (1975).National Council on Radiation Protection and Measurements.

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REFERENCES

Alpha-Emitting Particles in Lungs, NCRP Report No. 46 (National Council on Radiation Protection and Measurements, Bethesda, Maryland). NCRP (1987).National Council on Radiation Protection and Measurements. Recommendations on Limits for Exposure to Ionizing Radiation, NCRP Report No. 91 (National Council on Radiation Protection and Measurements, Bethesda, Maryland). PATERSON, R. (1948). The Treatment of Malignunt Disease by Radium and X-mys (Arnold, London). PAVER,K., POYZER, K., BURRY,N., AND DEAKIN,M. (1973). "The incidence of basal cell carcinoma and their metastases in Australia and New Zealand," Aust. J. Dermatol. 14, 53. RON,E., MODAN, B., AND BOICE,J. (1988). "Mortality after radiotherapy for ringworm of the scalp," American J. Epidemiol., 127,713. E., AND WEINSTEIN, R. (1986)."RadiationSCHNEIDER, A., SHORE-FREEDMAN, induced thyroid and other head and neck tumors: Occurrence of multiple tumors and analysis of risk factors," J. of Clin. Endocrinol. Metabol. 63, 107. SCHNEIDER A, SHORE-FREEDMAN E,AND RON E.(1988) Personal colllmunications. (Michael Reese Hospital, Chicago and U.S. National Cancer Institute, Betheada, Maryland). SEVC,J. (1988). Personal communication. (Institute of Hygiene and Epidemiology, Prague). J. (1978). "Alpha irradiation of the skin SEVCOVA M, SEVEJ , AND THOMAS and the possibility of late effects," Health Phys. 35,803. J. SEVCOVA, M., SEVC,J., AUGUSTINOVA, J., DRAGON, J., AND KORDACOVA, (1984). "Incidence of skin basalioma in miner and non-miner groups, Comparison of epidemiological studies," Ceskoslovenska Dennatologie, 69, 1. SHORE,R., ALBERT,R., REED,M., HARLEY,N. AND PASTERNACK, B. (1984). "Skin cancer incidence among children irradiated for ringworm of the scalp," Radiat. Res. 100, 192. SHORE,R., HILDRETH,N., WOODARD, E., DVORETSKY, P., HEMPELMANN. L., AND PASTERNACK, B. (1986). "Breast cancer among women given X-ray therapy for acute postpartum maatitis," J. Natl. Cancer Inst. 77,689. SHORE,R.E. (1989). "Overview of radiation-induced skin cancer in humans," Int. J. Radiat. Biol., In press. ULBERG, J. C. AND KOCHENDORFER, D. B. (1966). Model for estimating beta dose to tissue from particle debris in aerospace nuclear applications, USNRDLTR-1107 (United States Technical Information Service, Springfield, Virginia). VAN DAAL,W., GOSLINGS,B., HERMANS, J., RUITER,D., SEPMEYER, C., VINK, W., AND THOMAS, P. (1983). "Radiation-induced head and M., VANVLOTEN neck turnours: Is the skin as sensitive as the thyroid gland? Europ. J. Cancer Clin. Oncol. 19,1081. VANVLOTEN,W., HERMANS,J., AND VAN DAAL,W. (1987). "Radiationinduced skin cancer and radiodermatitis of the head and neck," Cancer, 69,411. WARNOCK, R. V., BRAY,L. G., COOPERT. L., GOLDIN,E. M., KNAPP,P. J.,

REFERENCES

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LEWISM. M. AND RIGBY,W. F. (1987). "A health physics program for operation with failed fuel," Radiat. Prot. Manage. 4,21. D.,AND WW, D. (1975). "Metastatic basal cell carcinoma," Med. WEEDON, J. Austral. 2,177. WELLS.J. (1986). "Problems associated with localized skin exposures." Brit. J. Radiol.. Supple. 19, 146. WELLS, J. AND CHARLES, M. W. (1979). Tho Development of Criteria for Limiting the Non-uniform Zrtadiutwn of Skin, Central Electricity Generating Board Report RD/B/N4565 (Central Electricity Generating Board, London). WELLS,J., CHARLES, M. W., PEELS,D. M., HANSEN, L., HOPEWELL, J. W., AND COCGLE, J. E. (1982). 'Won-uniform irradiation of skin: Criteria for limiting non-stochasticeffects," inRadidwnPI.otection-Admances in Theory and Practice, (Society for Radiological Protection, Great Britain).

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 over sixty 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: Officers President Vice President Secretary and Treasurer Assistant Secretary Assistant Treasurer

WARREN K . SINCLALR S. JAMES ADEISTEIN W.ROGERNEY CARLD. HOBELMAN JAMES F.BERG

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Members A. ALAN MOGHISSI ETHELS. GILBERT MARYELLENO'CONNOR ROBERTA. GOEPP JOEL E. GRAY ANDREWK. POZNANSKI NORMAN C. RASMVSSEN ARTHURW. GUY CHESTER R. RICHMOND ERICJ. HALL MARVIN R O S W ~ M NAOMIH. HARLEY N. ROTHENBERG LAWRENCE WILLIAMR. HENDEE LEONARD A. SAGAN DONALD G. JACOBS KEITHJ. SCHIAGER A. EVER= JAMES, JR. BERNDKAHN ROBERTA. SCHLENXER R. KASE WILLLAM J. SCHULL KENNETH ROYE. SHORE CHARLES E. LAND WARREN GEORGE R. LEOPOLD K. SINCLAIR PAULSLOVIC RAYD. LLOYD RICHARD A. TELL HARRY R. MAXON W w L. TEMPLETON ROGER0.MCCLELLAN JAMES E. MCLAUGHLIN THOMAS S. TENPORDE BARBARA J. MCNEIL J . W. T H I E ~ ~ E N THOMAS F. MEANEY J O H N E. TILL B. MEWOLD ROBERT ULLRICH CHARLES L. MENDELSOHN ARTHURC. U ~ N MORTIMER GEORGE FREDA. M E ~ E R L. VOELZ A. MIUS WLLUAM GEORGE M. W m m MARV~N ZISKIN DADEW. MOELLER

Honorary Members ~ L W O NS. TAYLOR, Honomry I President

ROBERT 0.GORSON JOHN H. HARLEY JOHN W. HEALY LOUISH. HEMPELMANN. JR PAUL C. HODGES GEORGE V. LEROY WILFRIDB. MANN KARLZ. MORGAN ROBERT J . NELSEN

WESLEY L. NYBORG

HARALD H. ROSSI L. RUSSELL WILLIAM JOHN H. RUST EUGENEL. SAENGER J. NEWELLSTANNARD JOHN B. STORER ROYC. THOMPSON EDWARD W. W E B S ~ R HAROLD0.WYCKOFF

Currently, the f o l l o w i n g subgroups are actively engaged in formulating recommendations: SC 1

SC 16 SC 40

Basic Radiation Protection Criteria SC 1-1 Probability of Causation for Genetic and Developmental Effects SC 1-2 The Assessment of Risk for Radiation Protection Purposes X-Ray Protection in Dental Offices Biological Aspects of Radiation Protection Criteria

THE NCRP SC 40-1 Atomic Bomb Survivor Dosimetry Owrational Radiation Safetv Sk 46-2 Uranium Mining aAd Milling-Radiation Safety Programs SC 46-3 ALARA for Occupationally Exposed Individuals in Clinical Radiology SC 46-4 Calibration of Survey Instrumentation SC 46-5 Maintaining Radiation Protection Records SC 46-7 Emergency Planning SC 46-8 Radiation Protection Design Guidelines for Particle Accelerator Facilities SC 46-9 ALARA a t Nuclear Plants SC 46-10 Assessment of Occupational Doses from Internal Emitters SC 46-11 Radiation Protection During Special Medical Procedures Conceptual Basis of Calculations of Dose Distributions Internal Emitter Standards SC 57-2 Respiratory Tract Model SC 57-6 Bone Problems SC 57-8 Leukemia Risk SC 57-9 Lung Cancer Risk SC 57-10 Liver Cancer Risk SC 57-12 Strontium SC 57-14 Placental Transfer SC 57-15 Uranium Human Population Exposure Experience Radiation Exposure Control in a Nuclear Emergency SC 63-1 Public Knowledge About Radiation SC 63-2 Criteria for Radiation Instruments for the Public Environmental Radioactivity and Waste Management SC 64-6 Screening Models SC 64-7 Contaminated Soil as a Source of Radiation Exposure SC 64-8 Ocean Disposal of Radioactive Waste SC 64-9 Effects of Radiation on Aquatic Organisms SC 64-10 Xenon SC 64-1 1 Disposal of Low Level Waste Quality Assurance and Accuracy in Radiation Protection Measurements Biological Effects and Exposure Criteria for Ultrasound Biological Effects of Magnetic Fields Microprocessors in Dosimetry Efficacy of Radiographic Procedures Radiation Exposure and Potentially Related Injury Radiation Received in the Decontamination of Nuclear Facilities Effects of Radiation on the Embryo-Fetus Guidance on Occupational and Public Exposure Resulting from Diagnoatic Nuclear Medicine Procedures Practical Guidance on the Evaluation of Human Exposures to Radiofrequency Radiation Extremely Low-Frequency Electric and Magnetic Fields Radiation Biology of the Skin (Beta-Ray Dosimetry) Assessment of Exposures from Therapy Identification of Research Needs ICCommittee

on Comparison of Radiation Exposures

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Ad Hoc Group on Plutonium Ad Hoc Group on Radon Ad Hoc Group on Video Display Terminals Study Group on Compartive Risk l b k Force on Occupational Exposure Levels

In recognition of its responsibility to facilitate and stimulate cooperation among organizations concerned with the scientific and related aspects of radiatio? 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 ~ e d i c aPhysics i American College of Nuclear Physicians American College of Radiology American Dental Association American Industrial Hygiene Association American Institute of Ultrasound in Medicine American Insurance Services Group American Medical Association American Nuclear Society American Occupational Medical Association American Podiatric 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 Bioelectromagnetics Society College of American Pathologists Conference of Radiation Control Program Diredors Electric Power Reeearch Institute Federal Communications Commission Federal Emergency Management Agency Genetics Society of America Health Physics Society Institute of Nuclear Power Operations National Electrical Manufacturers Association National Institute of Stand* and Technology Nuclear Management and Resources Council Radiation Research Society Radiological Society of North America

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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 Sta@s 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 a n interest in radiation protection and measurements. This liaison relationship provides: (1)an opportunity 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 draR 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: Australian Radiation Laboratory Commissariat a 1'Energie Atomique (France) Commission of the European Communities Defense Nuclear Agency Federal Emergency Management Agency Japan Radiation Council National Institute of Standards and Technology National Radiological Protection Board (United Kingdom) National Research Council (Canada) Office of Science and Technology Policy Office of Technology k s s m e n t Ultrasonics Institute of Australia United States Air Force United States A m y 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

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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 Academy of Dermatology American kssociation of Physicists in Medicine American College of Nuclear Physicians American College of Radiology American College of Radiology Foundation American Dental Association American Hospital Radiology Administrators American Industrial Hygiene Association American Insurance Services Group American Medical Association American Nuclear Society American Occu~ationalMedical Association American osteopathic College of Radiology 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 American Veterinary Medical Association American Veterinary Radiology Society Association of University Radiologists Battelle Memorial Institute Center for Devices and RadiologuA Health College of American Pathologists Committee on Radiation Research and Policy Coordination Commonwealth of Pennsylvania Defense Nuclear Agency Eastman Kodak Company Edison Electric Institute Edward Mallinckrodt, Jr. Foundation EG&G Idaho, Inc. Electric Power Research Institute Federal Emergency Management Agency Florida Institute of Phosphate Research Genetics Society of ~ r n e h c a Health Physics Society Institute of Nuclear Power Operations James Picker Foundation Martin Marietta Corporation National Aeronautics and Space Administration National Association of Photographic Manufacturers National Cancer Institute

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National Electrical Manufacturers Association National Institute of Standards and Technology Nuclear Management and Resources Council Radiation Research Society Radiological Society of North America Richard Lounsbery Foundation Sandia National Laboratory 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 Vietoreen, Incorporated

To 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 to 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 Ave., Suite 800 Bethesda, Md 20814 The currently available publications are listed below.

Proceedings of the Annual Meeting No. 1

2 3 4

5 6

7

Title Perceptions of Risk, Proceedings of the Fifteenth Annual Meeting, Held on March 14-15,1979 (Including Taylor Lecture No. 3) (1980) Quantitative Risk in Standards Setting, Proceedings of the Sixteenth Annual Meeting, Held on April 2-3, 1980 (Including Taylor Lecture No. 4) (1981) CritEcal Issues in Setting Radiation Dose Limits, Proceedings of the Seventeenth Annual Meeting, Held on April 8-9,1981 (Including Taylor Lecture No. 5) (1982) Radiation Protection and New Medical Dugnostic Procedures, Proceedings of the Eighteenth Annual Meeting, Held on April 6-7,1982 (Including TayIor Lecture No. 6) (1983) Environmental Radioactivity, Proceedings of the Nineteenth Annual Meeting, Held on April 6-7, 1983 (Including Taylor Lecture No. 7) (1984) Some Issues Important in Developing Basic Radiation Protection Recommendations, Proceedings of the Twentieth Annual Meeting, Held on April 4-5, 1984 (Including Taylor Lecture No. 8) (1985) Radioactive Waste,Proceedings of the Twenty-first Annual Meeting, Held on April 3-4, 1985 (Including Taylor Lecture No. 9) (1986)

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Nonionizing Electromagnetic Radiation and Ultrasound, Proceedings of the Twenty-second Annual Meeting, Held on April 2-3,1986 (Including Taylor Lecture No. 10) (1988) New Dosimetry at Hiroshima and Nagasaki and Its Implications for Risk Estimates, Proceedings of the Twenty-third Annual Meeting, Held on April 543,1987 (Including Taylor Lecture No. 11)(1988). Radon, Proceedings of the Twenty-fourth Annual Meeting, Held on March 30-31,1988 (Including Taylor Lecture No. 12) (1989). Symposium Proceedings

The Control of Exposure of the Public to Ionizing Radiation in the Event of Accident or Atlack, Proceedings of a Symposium held April 27-29,1981(1982)

Laurieton S.Taylor Lectures No. 1 2 3 4

5 6

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Title and Author

The Squares of the Natural Numbers in Radiation Protection by Herbert M. Parker (1977) Why be Quantitative About Radiation Risk Estimates? by Sir Edward Pochin (1978) Radiation Protection40mpts and Trade Offsby Hymer L. Friedell (1979) [Available also in Perceptions of Risk, see above] From "Quantity of Radiation" and "Dose" to 'iExposure" and "Absorbed DoseJ'-An Historical Review by Harold 0.Wyckoff (1980) [Available also in QuantitativeRisks in Standards Setting, see abovel How Well Can We Assess Genetic Risk? Not Very by James F. Crow (1981) [Available also in Critical Issues in Setting Radiation Dose Limits, see abovel Ethics, Trade-offs and Medical Radiation by Eugene L. Saenger (1982) [Available also in Radiation Protection and New Medical Diagnostic Approaches, see abovel The Human Environment-Past, Present and Future by Merril Eisenbud (1983) [Available also in Environmental Radioactivity, see above]

NCRP PUBLICATIONS

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Limitation and Assessment in Radiation Protection by Harald H. Rossi (1984) [Available also in Some Issues Important in Developing Basic Radiation Protection Recommen&tions, 8ee abovel Truth (and Beauty) in Radiation Measurement by John H. Harley (1985)[Availablealso in Radioactive Waste, see above] Nonionizing R a d M n B ~ e c t s Cellular : Properties and Interactions by Herman P. Schwan (1986) [Available also in Nonionizing Electromagnetic Radiations and Ultrasound, see abovel How to be Quantitative about Radiation Risk Estimates by Seymour Jablon (1987) [Available also in New Dosimetry at Hiroshima and Nagasaki and its Implications for Risk Estimates, see above] How Safe is Safe Enough? by Bo Lindell(l988) [Available also in Radon, See abovel Radiobiology and Radiation Protection: The Past Century and Prospects.for the Future by Arthur C. Upton (1989) NCRP Commentaries No. 1

Title Krypton-85 in the Atmosphere-With Specific Reference to the Public Health Signifiance of the Proposed Controlled Release at Three Mi& Island (1980) Preliminary Evaluation of Criteria fir the Disposal of Tmnsumnic Contaminated Waste (1982) Screening Techniques for Determining Compliance with Environmental Standards (19861, Rev. (1989) Guidelines for the Release of Waste Water f h m Nuclear Facilities with Special Reference to the Public Health Significance of the Proposed Rekase of Treated Waste Waters at Three Mile Island (1987) Living Without Landfills (1989)

NCRP Reporta No. .8

Title Control and Removal of Radioactive Contamination in Labomtories (1951)

NCRP PUBLICATIONS

Maximum Permissible Body Burdens and Maximum Permissibk Concentrations of Radionuclides in Air and in Water fbr Occuputional Exposure (1959)[Includes Addendum 1 issued in August 19631 Measurement of Neutron Flux and Spectra for Physical and Biological Applications (1960) Measurement of Absorbed Dose ofNeutrons and Mixtures ofNeutrons and Gamma Rays (1961) Stopping Powers for Use with Cavity Chambers (1961) Safe Handling of Radioactive Materials (1964) Radiation Protection in Educational Institutions (1966) Dental X-Ray Protection (1970) Radiation Protection in Veterinary Medicine (1970) Precautions in the Management of Patients Who Have Received ThempeuticAmounts of Radionuclides (1970) Protection Against Neutron Radiation (1971) Protectton Against Radintion from B m c h y t h e m ~Sources (1972) Specifications of Gamma-Ray Brachytherapy Sources (1974) Radiological Factors Affecting Decision-Making in a Nuclear Attack (1974) Krypton-85 in the Atmosphere-Accumulation, Biologi cal Significance, and Control Technology (1975) Alpha-Emitting Particles in Lungs (1975) Tritium Measurement Techniques (1976) Structural Shielding Design and Evaluation for Medical Use of X Rays and Gamma Rays of Energies Up to 10 MeV (1976) Environmental Radiation Measurements (1976) Radiation Protection Design Guidelines for 0.1-1 00 MeV Partick Accelerator Facilities (1977) Cesium-137 from the Environment to Man: Metabolism and Dose (1977) Review of NCRP Radiation Dose Limit for Embryo and Fetus in Occupationally Exposed Women (1977) Medical Radiation Exposure of Pregnant and Potentially Pregnant Women (1977) Protection of the Thyroid G h n d in the Event ofReleases of Radioiodine (1977) Znstrumentution and Monitoring Methods for Radiation Protection (1978) A Handbook of Radioactivity Measurements Procedures, 2nd ed. (1985)

NCRP PUBLICATIONS

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Operational Radiation Safety Program (1978) Physical, Chemical, and Biological Properties of Radiocerium Relevant to Radiation Protection Guidelines (1978) Radiation Safety Training Criteria for Industrial Radiography ( 1978) Tritium in the Environment (1979) Tritium and Other Radionuclide Labeled Organic Compounds Incorporated in Genetic Material (1979) Influence o f Dose and Its Distribution in Time on DoseResponse Relationships for Low-LET Radiations (1980) Manugement of Persons Accidentally Contaminated with Radionucl&s (1980) Mammography (1980) Radiofreqency Electromagnetic Fields-Properties, Quantities and Units, Biophysical Interaction, and Measurements (1981) Radiation Protection in Pediatric Radiology (1981) Dosimetry of X-Ray and Gamma-Ray Beams for Radiation Therapy in the Energy Range 10 keV to 50 MeV (1981) Nuclear Medicine-Factors Influencing the Choice and Use ofRadionuclides in Diagnosis and Therapy (1982) Operational Radiation Safety-Training (1983) Radiation Protection and Measurement for Low Voltage Neutron Genemtors (1983) Protection in Nuclear Medicine and Ultrasound Diagnostic Procedures in Children (1983) Biological Effects of Ultrasound: Mechanisms and Clinical Implications (1983) Iodine-129: Evaluation of Releases from Nuclear Power Genemtion (1983) Radiological Assessment: Predicting the Transport, Bioaccumulation, and Uptake by Man ofRadionuclides Released to the Environment (1984) Exposures from the Uranium Series with Emphasis on Radon and its Daughters (1984) Evaluation of Occupational and Environmental Exposures to Radon and Radon Daughters in the United States (1984) Neutron Contamination from Medical Electron Accelerators ( 1984) Induction of Thyroid Cancer by Ionizing Radiation (1985) Carbon-14 in the Environment (1985)

SI Units in Radiation Protection and Measmments (1985) The Experimental Basis for A bsorbed-Dose Calculations in Medical Uses of Radionuclides (1985) General Concepts for the Dosimetry of Internally Depsited Radionuclides (1985) Mammogmphy-A User's Guide (1986) Biological Effects and Exposum Criteria for Radiofkquenq Electromagnetic Fields (1986) Use of Bioassay Procedures for Assessment of Internal Radionuclide Deposition (1987) Radiation Alarms and Access Control Systems (1987) GeneticE m o f I n t e d yDeposited Radionuclides (1987) Neptunium: Radiation Protection Guidelines (1987) Recommendations on Limits for Exposure to Ionizing Radiation (1987) Public Radiation Exposure j b m Nuclear Power Generation in t h United States (1987) Ionizing Radiation E1cposm of thePopulation of the United States (1987) Exposure of the Population in the United States and Canadu from Natural Background Radiation (1987) Radiation Exposure of the U.S. Population from Consumer Products and Miscellaneous Sources (1987) Comparative Carcinogenesis of Ionizing Radiation and Chemicals (1989) MeasurementofRadonand Radon Daughters inAir (1988) Guidance on Radiation Received in Space Activities (1989) Quality Assurance for Diagnostic Imaging Equipment (1988) Exposure of the U.S. Population from Diagnostic Medical Radiation (1989) Exposure of the U.S. Population From Occupational Radiation (1989) Medical X-Ray, Electron Beam and Gamma-Ray Protection For Energies Up T o 50 MeV (Equipment Design, Performance and Use) (1989) Control of Radon in Houses (1989) Radiation Protection for Medical and Allied Health Personnel (1989) Limits of Exposure to "Hot Particles" on the skin (1989) Binders for NCRP Reports are available. Two sizes make it possible to collect into small binders the "old series" of reports (NCRPReports Nos. 8-30) and into large binders the more recent publications (NCRP

NCRP PUBLICATIONS

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Reports Nos. 32-106). Each binder will accommodate from five to seven reports. The bin ers carry the identification "NCRP Reports" and come with label h lders 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. NCRP Reports Nos. 8,22 Volume II. NCRP Reports Nos. 23,25,27,30 Volume 111. NCRP Reports Nos. 32,35,36,37 Volume IV. NCRP Reports Nos. 38,40,41 Volume V. NCRP Reports Nos. 42,44,46 Volume VI. NCRP Reports Nos. 47,49,50,51 Volume VII. NCRP Reports Nos. 52,53,54,55,57 Volume VIII. NCRP Reports No. 58 Volume IX. NCRP Reports Nos. 59,60,61,62,63 Volume X. NCRP Reports Nos. 64,65,66,67 Volume XI. NCRP Reports Nos. 68,69,70,71,72 Volume XII. NCRP Reports Nos. 73,74,75,76 Volume XIII. NCRP Reports Nos. 77,78,79,80 Volume XIV. NCRP Reports Nos. 81,82,83,84,85 Volume XV. NCRP Reports Nos. 86,87,88,89 Volume XVI. NCRP Reports Nos. 90,91,92,93 Volume XVII. NCRP Reports Nos. 94,95,96,97 (Titles of the individual reports contained in each volume are given above). The following NCRP Reports are now superseded andlor out of print: No.

1 2 3 4 5 6

Title X-Ray Protection (1931).[Superseded by NCRP Report No. 31 Radium Protection (1934).[Superseded by NCRP Report No. 41 X-Ray Protection (1936).[Superseded by NCRP Report No. 61 Radium Protection (1938).[Superseded by NCRP Report No. 131 Safe Handling of Radioactive Luminous Compounds (1941).[Outof Print] MedicalX-Ray Protection U p to Two Million Volts (1949). [Superseded by NCRP Report No. 181

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Safe Handling of Radioactive Isotopes (1949). [Superseded by NCRP Report No. 301 Recommendations for Waste Disposal of Phosphorus32 and Iodine-131 for Medical Users (1951). [Out of Print] Radiological Monitoring Methods and Instruments (1952). [Superseded by NCRP Report No. 571 Maximum Permissible Amounts of Radioisotopes in the Human Body and Maximum Permissible Concentrations i n 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 Radiations from Radium, Cobalt-60 and Cesium-137 (1954). [Supersededby NCRP Report No. 241 Protection Against Betatrondynchrotron Radiations Up to 100 Million Electron Volts (1954). [Superseded by NCRP Report No. 511 Safe Handling of Cadavers Containing Radioactive Zso topes (1953). [Superseded by NCRP Report No. 211 Radioactive Waste Disposal in the Ocean (1954). [Out of Print] Permissible Dose from External Sources of Ionizing Radiation (1954) including Maximum Permissible Exposure to Man, Addendum to National Bureau of Standards Handbook 59 (1958). [Superseded by NCRP Report No. 391 X-Ray Protection (1955). [Superseded by NCRP Report No. 261 Regulation of Radiation Exposure by Legislative Means (1955). [Out of Print] Protection Against Neutron Radiation Up to 30 Million Electron Volts (1957). [Superseded by NCRP Report No. 381 Safe Handling ofBodies Containing Radioactive Isotopes (1958). [Superseded by NCRP Report No. 371 Protection Against Radiations from Sealed Gamma Sources (1960). [Superseded by NCRP Report Nos. 33, 34, and 401 MedicdX-Ray Protection Up to Three Million Volts (1961). [Superseded by NCRP Report Nos. 33,34,35, and 361 A Manual of Radioactivity Procedures (1961). [Superseded by NCRP Report No. 581

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Exposure to Radiation i n a n Emergency (1962). [Superseded by NCRP Report No. 421 Shielding for High Energy Electron Accelerator Installations (1964). [Superseded by 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-Ray Protection for Energies Up to 10 MeV-Structural Shielding Design and Evaluution (1970). [Superseded by NCRP Report No. 491 Basic Radiation Protection Criteria (1971). [Superseded by NCRP Report No. 911 Review of the Current State of Radiation Protection Philosophy (1975). [Superseded by NCRP Report No. 911 Natuml Background R a d i d o n in the United States (1975). [Superseded by NCRP Report No. 941 Radiation Protection for Medical and Allied Health Personnel [Superseded by NCRP Report No. 1051 Radiation Exposure from Consumer Products and Miscellaneous Sources (1977). [Superseded by NCRP Report No. 951 A Handbook on Radioactivity Measurement Procedures. [Superseded by NCRP Report No. 58,2nd ed.] Other Documents The following documents of the NCRP were published outside of the NCRP Reports and Commentaries series: "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) Dose Effect Modibing Factors In Radiation Protection, Report of Subcommittee M-4 (Relative Biological Effectiveness) of the National Council on Radiation Protection and Measurements, Report BNL 50073 (T-471) (1967) Brookhaven National Laboratory (National Technical Information Service, Springfield, Virginia). X-Ray Protection Standards for Home Television Receivers, Interim Statement of the National Council on Radiation Protection and

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Measurements (National Council on Radiation Protection and Measurements, Washington, 1968) Specification of Units of Natuml Uranium and Natural Thorium (National Council on Radiation Protection and Measurements, Washington, 1973) NCRP Statement on Dose Limit for Neutrons (National Council on Radiation Protection and Measurements, Washington, 1980) Control of Air Emissions of Radionuclides (National Council on Radiation Protection and Measurements, Bethesda, Maryland, 1984)

Copies of the statements published in journals may be consulted in libraries. A limited number of copies of the remaining documents listed above are available for distribution by NCRP Publications.

Index Acute deep ulceration, 14,21,23,25 Acute ulceration, 21,22 Acute necrosis, 9,10,20,21 Additional reeearch. 26 ALARA, 4 Atrophy of dermis, 6 Average dose. 27 Berger equation, 16 Beta particle dose, 16 Berger equation, 16 Loevinger equation, 16 Beta particle emission rate, 3 Biological effects, 4 Blistering, 6 Dermal thinning, 14 Deterministic effects, 4. 14 (see nonetochastic effects) 4 Dose limits, 16 Dry desquamation. 4.5.6.7.10,

14.18

Erythema, 4,7,8,10,14 erythema dose, 5 Experiments with hot particles, 18 Exposure limits, 23,25 recommendations, 25 Extrapolation chamber, 9, 10,11, 14,27 Hot particles, 1,2,3, 5,6, 14,26 biological effects of, 6 definition of, 2 nonstochastic effecta, 5 not in skin contact, 26 other names, 1 radioactivity of, 1 radiobiological effects of, 3 sources of, 1 stochastic risks, 14 Hot particle experiments, 6.7 human, 7 monkey, 6 swine, 7 Human exposures, 22 Human study, 7.18

Hyperpigmentation, 8 Ieoeffect dosee, 5 Interphase cell death, 5 Large area irradiation, 5 erythema doee, 5 ulceration dose, 5 Late nonstochastic effects, 4,5 atrophy of dermis, 5 atrophy of hair follicles, 5 atrophy of sweat glands, 5 changes, in pigmentation, 5 fibrosis of dermis, 5 late necrosis, 5 Lifetime risk estimates, 13 skin cancer, 13 Loevinger equation. 16 Medical evaluation, 25 Mild erythema, 10 Moist desquamation, 4,5,8 Monkey experiments, 6,18,21 Non-melanoma skin cancer, 11,12 Nonstochasticdecta (determiWceffecte), 4,5,6,7,8,9,10,14

acute, 4 acute necrosis, 9, 10 blistering, 6 chronic, 4 dermal thinning, 14 dry desquamation, 4, 5,6, 7, 10, 14 erythema, 4, 7,8, 10, 14 hot particles, 5 hyperpigmentation, 8 large area irradiation, 5 late, 4 latency of, 4 mild erythema. 10 moist desquamation. 4.5.8 pigment changes, 14 prolonged erythema, 4 small area irradiation, 5 ulceration, 4,7, 10

54

INDEX

Pigmentation changes, 5, 14 Point dose, 27 Prolonged erythema, 4 Radiation protection philosophy, 4 Radiobiological effects, 3 hot particles, 3 Safety factor, 23 Skin cancer, 12,13 lifetime risk estimates, 13 risk estimates, 12

Stochastic risks, 11.14 non-melanoma skin cancer, 11 Superticial ulceration, 18,21 Swine experiments, 7.19 Threshold dose, 14, 20, 21 acute deep ulceration, 14,21 "Toleranee"doses, 5 Ulceration, 4, 7, 10, 19, 20 threshold, 19 threshold dose, 20 Ulceration dose, 5