NUREG/CR-1728, Forwards NUREG/CR-1728, Feasibility of Epidemiologic Investigations of Health Effects of Low Level Ionizing Radiation. Comments of Interagency Scientific Review Group Encl
| ML19340C820 | |
| Person / Time | |
|---|---|
| Issue date: | 12/04/1980 |
| From: | Goldsmith R, Parsont M NRC OFFICE OF STANDARDS DEVELOPMENT |
| To: | NRC OFFICE OF STANDARDS DEVELOPMENT |
| Shared Package | |
| ML19340C821 | List: |
| References | |
| RTR-NUREG-CR-1728 NUDOCS 8012170519 | |
| Download: ML19340C820 (10) | |
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t MEMORANDUM FOR: All Recipients of NUREG/CR-1728, "The Feasibility of Epidemiologic Investigations of the Health Effects of Low-Level Ionizing Radiation" FR0ti:
Robert Goldsmith flichael A. Parsont, Project Officers
SUBJECT:
REPORT OF THE INTERAGENCY SCIENTIFIC REVIEW GROUP This attachment to NUREG/CR-1728 contains coments by an Interagency Scientific Review Group which was established by Memorandum of Under-standing between the Nuclear Regulatory Comission and the Environmental Protection Agency. The Scientific Review Group, which inclut'ed representa-tives of the Nuclear Regulatory Comission, the Environmental Protection Agency and the Department of Health and Human Services, developed the scope of work for this study and monitored its technical progress.
& J.s4L Rnbert idsmith, Project icer e
Michael A.
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REPORT OF THE INTERAGENCY SCIENTIFIC REVIEW GROUP ON EQUIFAX'S FINAL REPORT: THE FEASIBILITY OF EPIDEMIOLOGIC INVESTIGATIONS OF THE HEALTH EFFECTS OF LOW-LEVEL IONIZING RADIATION October 31, 1980 Nuclear Regulatory Comc.ission Environmental Protection Agency A
Frank J Arsenault Gerald J. Rausa Office of Nuclear Regulatory Research Office of Research & Development Karl R. Coller i liam A. Mills, Chairman Office of Standards Development Office of Radiation Programa Department of Health & Human Services
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Charlotte Silverman Bureau of Radiological Health L
REPORT OF THE INTERAGENCY SCIENTIFIC REVIEW GROUP ON EQUIFAX'S FINAL REPORT:
THE FEASIBILITY OF EPIDEMIOLOGIC INVESTIGATIONS OF THE HEALTH EFFECTS OF LOW-LEVEL IONIZING RADIATION Under a Memorandum of Understanding (MOU) co-signed by NRC and EPA and published in the Federal Register 44:3793 (January 18, 1979), a scientific review group (SRG) was established.
The SRC's membership and responsibilities were stated in the MOU as follows:
2.
Preparatioc of the technical scopes of work for the pre-liminary planning and design studies, selection of the type of organizations most appropriate to conduct such studies and monitoring of the technical progress and the effort, will be accomplished under the direction of a five member scientific review group.
It will consist of members of the professional staffs of NRC, EPA, and the Department of Health, Education, and Welfare (HEW),
two members designated by NRC and two by EPA with each other's agreement.
EPA will select, with NRC's agreement, the chairperson of this group.
- and, 6.
After review of the report by the scientific review group, the report will be sent to the Commission and j
the Administrator of EPA for final approval prior to l
transmittal to the Congress.
In accord with this MOU, the SRG has carried out its responsibilities under item #2 and submits this report to complete its task under item #6.
ACTIVITIES OF THE SRG 1.
Development of contract scope of work.
The SRG carefully considered the objectives of this mandated effort and developed a scope of work commensurate with these objectives.
2 The task requirement has been found to be quate for directing the effort and no redefinition of the scope has been necessary.
2.
Evaluation of bidders proposals.
A panel of NRC and EPA staff members evaluated the proposals in response to the advertised RFP and recommended to the NRC Director, Office of Standards Development, the awarding of the contract to Equifax, Inc.,
Dr. Nancy A. Dreyer, Principal Investigator.
3.
Review of Effort.
The SRG periodically reviewed progress of the contractor, including face-to-face discussions with the Equifax staff.
These reviews and discussitns were designed to ensure that the contractor was addressing the scope of work in a manner consistent with the SRG's expectations.
Advice was offered to and generally accepted by Equifax during the conduct of the study.
However, the contractor is responsible for the content of the final report, and the opinions and judgments of the contractor are not necessarily those of the SRG members.
SRG COMMENTS ON FINAL REPORT 1.
The final report satisfactorily meets the requirements of the scope of worx and provides a general overview of the feasibility of conducting definitive epidemiologic studies of populations exposed to
3 low-levels of ionizing radiation.
The study included the identification of populations which are possible candidates for epidemiologic studies of low-level exposures to ionizing radiation.
It provides a useful starting point for those who may contemplate the conduct or the support of epidem-i iologic studies which, because the dose and expected risks are low, would have to involve large populations for long periods of time with conse-quently large costs.
In this respect, the report's usefulness extends to concerns with many sources of low-level exposures in the environment and workplace besides ionizing radiation.
The SRG did not expect this report to be a detailed treatise or to represent a rigorous treatment of all questions concerned with esti. mating the biological effects of low-dose radiation.
2.
The sRG racepts the general conclusion "...that no single, outstanding candidate population is available for study, i.e.,
there is no one population that can be expected to yield an unambiguous answer of high statistical certainty, that presumably would define precisely the low-level radiation risk."
In our view, those populatie s with low-level exposure (as defined in the report) which were selected by the contractor for detailed evaluation of their merits for providing useful scientific information were representative and the best choices that could be made.
In accepting tl'is conclusion, however, the SRG emphasizes that the route to
- The Contractor " defines low-level ionizing radiation as a single i
dose of 5 rem (whole-body) or less and chronic doses that accumulate at the rate of less than 5 rem per year."
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4 understanding low-dose risks probably lies not directly through the study of very large populations exposed to low levels of ionizing radiation, but indirectly, through the furtherance of fundamental knowledge in radiobiol-ogy, especially knowledge of mechanisms of action from which dose-response models may be derived, together with epidemiologic studies of human populations exposed to higher doses to which these models may be applied.
Pr esent knowledge of the ef fects of radiation on man derives from long-term studies of such populations as patients exposed to radiation for the trea tment or diagnosis of disease, radium-dial painters, underground uranium miners, and Japanese atomic-bemb survivors.
These populations received higher doses at both high and icw dose rates.
Such studies should be continued and extended in order to provide information on the many determinants of biologic effects other than mere magnitude of dose; i.e., radiation quality, dose-rate, host factors, and other environmental risk factors. Knowledge of such determinants as derived from human observations at the intermediate and high dose levels makes possible better estimates of risk in the low-dose region.
3.
The report suggests that, however small the chance may be that large, low-dose epidemiologic studie.s will yield the definitive quantita-tive estimates that are desired for the low-dose region, nonscientific reasons may dictate that one or more such studies shall be done.
The report does not note the hazards that may accompany such studies. When studies having low power to distingu.ah between real increases in disease rates an' chance oc.urrences are conducted they may, merely by chance,
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yield estimates that have statistical but not real significance.
The likelihood is that such estimates will be biased, that is, result in over-estimates of the true uncerlying risks,.and that this bias will not be readily appreciated or understood.
Studies of low statistical power cannot be counted on to demonstrate that effects are "small," even if they are.
In this light, the SRG agrees with the authors of the contract report concerning the ascertair; ment of feasibility before starting epidemiological studies. To quote the report, page 53, "Owing to the great difficulties in carrying out studies on the health effects -- it is of particular impor-tance to estimate the informativeness and feasibility of the suggested studies before finally deciding upon them, and to do so in terms that can be readily understood by the concerned public."
4.
The report recommends that a national registry be established of radiation workers, primarily to support investigation of cancer.
It further states that "The registry could also provida information on compli-ance with occupational safety regulations and to assess the merit of safety standards." The report details deficiencies in present. record systems that the development of such a registry might be expected to correct. The SRG holds that the registry concept, particularly for those workers employed in nuclear work, is worthy of serious consideration in the interests of i
occupational protection, and would be a useful asset in the event that a large national study of these workers should be needed in the future.
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6 5.
Some epidemiologic studies involving populations exposed at low doses and low dose rates may be warranted for reasons other than to derive quantitative risk estimates.
In this context, the contractor recommends three occupational groups as candidate po;ulations "if prospective studies are to be co,docted."
These populations are nuclear power plant workers, DOE-facility workers (selected on the basis of > 5 rem cumulative dose),
and radiologic technologists. However, studies of radiation workers at DOE facilities and nuclear shipyard workers are already being supported by the Federal Government.
Since these two groups are among the larFest and have the best available data, it would seem advisable to avait the results of these two studies before expanding the scope to include other similar low-dose populations.
The SRC strongly supports continuation of these studies and encourages that adequate resources be provided to expedite their progress.
In the same context, the contractor also recommends as a candidate population, with environmental exposures, those persons in Utah, Nevada, and Arizona exposed to fallout from nuclear weapons tests at the Nevada Test Site.
The fiRG sees some public health and social value in exploratory studies of the frequency of thyroid cancer and leukemia among these citizens.
Howes er, it does not believe that such studies would be likely to produce reliable estimates of the quantitative risk of cancer from Icu-dose exposure.
Only environmental readings are systematically available, not doses to individuals, thereby allowing only estimates of maximum and average doses.
Further, the thyroid dose from I-131 through r
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the f ood chain would have to be known before the radiati3n risk could be derived from observations of any excess thyroid cancers.
6.
Task 2(a)(ii) in Phase II of the contract requires that an upper-bound of risk for radiation-Induced cancer be described, and allows the contractor to select appropriate models to illustrate.
In doing so, the contractor selected as the upper-bound of the risk estimrtes the top of the range given in the BEIR III report for the linear quadratic (LQ-L designation) dose /effect relationship, i.e.,
the relative risk estimates.
The opinion of the SRG is that, as an upper-bound estimate, a more appropriate model for this would have been the linear (L-L designation) relationship.
The effect of selecting the linear model would be a risk estimate about twice as large for the upper-bound. Further, it would have been helpful to know how high the "true" value would have to be, for t'iose populations selected for detailed evaluation, in order to have reasonable statistical power of demonstrating with confidence a positive finding.
It mi gh t show whether or not such values of risk estimates are inconsistent with what we know of background levels of radiation and the incidence of I
spontaneous cancer.
7.
The Scientific Review Group considers that the contractor's I
l report is suitable for publication and recommends that this report of the SRG accompany the contractor's report when sent to the Congress.
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8 ACKNOWI.EDGEMENTS The members of the SRC wish to acknowledge the significant contributions made by Dr. Gilbert Beebe of NCI and Drs. David Rubinstein and Shlomo Yaniv of NRC.
Also, special notes of appreciation are due to Drs. Michael Parsont and Robert Goldsmith of NRC for their many afforts in completing this study and its review.
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