Adverse Reproductive Outcomes in Families of Atomic Veterans The Feasibility of Epidemiologic Studies (1995) / Chapter Skim
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8. FEASIBILITY OF THE STUDY OF ADVERSE REPRODUCTIVE OUTCOMES IN THE FAMILIES OF VETERANS EXPOSED TO IONIZING RADIATION
8. FEASIBILITY OF THE STUDY OF ADVERSE REPRODUCTIVE OUTCOMES IN THE FAMILIES OF VETERANS EXPOSED TO IONIZING RADIATION
Pages 62-73
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From page 62... ...
Fourth, how reliable are the individual dose estimates? Fifth, what mechanisms are available for identifying adverse reproductive outcomes?
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From page 63... ...
, the means do not exist to obtain information on adverse reproductive outcomes among their children and grandchildren in a suitably complete and unbiased manner to estimate the risk, if any, stemming from exposure to ionizing radiation. SIZE OF THE SAMPLE OR COHORT REQUIRED To determine the size of an epidemiologic study seeking to respond to the concerns of the Atomic Veterans, two somewhat different, but related questions can be posed: 1.
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From page 64... ...
What is the maximum relative risk one could expect to find among the Atomic Veterans' children given what is known about the effects of ionizing radiation from studies in animals and humans? Consider, for example, the appearance of major congenital malformations among the children of exposed Atomic Veterans.
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From page 65... ...
BEIR V (NRC, 1990) estimated genetic risks from ionizing radiation for seven kinds of disorders: clinically severe and mild autosomal dominant, X linked, autosomal recessive, unbalanced translocations, trisomies, and congenital abnormalities.
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From page 66... ...
Again, less than one additional case would be expected due to the radiation. The committee did not count the large genetic disease burden usually referred to as diseases of complex etiology, but these are expected to have relative risks at least as small as the ones considered here.
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From page 67... ...
From Table 8, assuming a background rate of 3% for major congenital birth defects present at birth, a total study population of 100,000 individuals (unexposed and exposed) would be required to detect a relative risk of 1.5.
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From page 68... ...
External dose is that received from a radiation source outside the body such as radioactive materials on the ground or on equipment such as vehicles. For the exposed Atomic Veterans, the biggest components were gamma rays and beta rays, but only a small fraction of the beta radiation could penetrate the clothing and skin to reach the gonads, the specific organ of interest here.
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From page 69... ...
Although a few veterans were exposed to neutrons, the bulk of the recorded doses were from gamma radiation. In some cases there was the potential for materials containing radioactive particles to be inhaled or ingested, and efforts were made to include doses from these particles in the dose estimates.
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From page 70... ...
However, the committee believed that comprehensive dose reconstructions may be feasible for a limited subset of Atomic Veterans. Although the DNA dose data are unsuitable for dose-response analysis, they may provide a rough estimate of the magnitude of doses received by the Atomic veterans.
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From page 71... ...
The organ of concern for this study is the gonads, but within the other uncertainties in doses, the dose to the gonads can be taken to be the same as the estimated dose to the whole person. IDENTIFICATION OF ADVERSE REPRODUCTIVE OUTCOMES Study of reproductive outcomes among Atomic Veterans requires being able to identify both normal and abnormal outcomes in an unbiased manner.
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From page 72... ...
Even for infant deaths by other causes, there is great variability in the accuracy and completeness of recording of causes of deaths. To study the health conditions of greatest concern and health outcomes for which a biological mechanism related to paternal exposure can be postulated, unbiased information is even less likely to be available than for other types of adverse reproductive outcomes.
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From page 73... ...
Study of mental retardation in the children of Atomic Veterans would require access to school records that include information on standardized test scores. Such records are unlikely to be available.
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