Review of Methods of Dose Estimation for Epidemiological Studies of the Radiological Impact of Nevada Test Site and Global Fallout

Abstract

Methods to assess radiation doses from nuclear weapons test fallout have been used to estimate doses to populations and individuals in a number of studies. However, only a few epidemiology studies have relied on fallout dose estimates. Though the methods for assessing doses from local and regional compared to global fallout are similar, there are significant differences in predicted doses and contributing radionuclides depending on the source of the fallout, e.g. whether the nuclear debris originated in Nevada at the U.S. nuclear test site or whether it originated at other locations worldwide. The sparse historical measurement data available are generally sufficient to estimate external exposure doses reasonably well. However, reconstruction of doses to body organs from ingestion and inhalation of radionuclides is significantly more complex and is almost always more uncertain than are external dose estimates. Internal dose estimates are generally based on estimates of the ground deposition per unit area of specific radionuclides and subsequent transport of radionuclides through the food chain. A number of technical challenges to correctly modeling deposition of fallout under wet and dry atmospheric conditions still remain, particularly at close-in locations where sizes of deposited particles vary significantly over modest changes in distance. This paper summarizes the various methods of dose estimation from weapons test fallout and the most important dose assessment and epidemiology studies that have relied on those methods.

Ultrasound-Detected Thyroid Nodule Prevalence and Radiation Dose from Fallout

“…However, the analysis described here used a more sophisticated dose reconstruction, known as the "joint U.S./Russian methodology", based on the combined experience of dosereconstruction scientists in Russia and the U.S. related to nuclear test explosions carried out by the two countries (11,25). The method is similar, with some unique aspects, to methods used in other studies (3,26,27) to estimate doses from nuclear weapons testing fallout. While the dose estimation methodology is based on much accumulated experience, the dose reconstruction estimates are preliminary in the sense that we are currently seeking additional subject information to refine individual dose estimates and better quantify their uncertainties.…”

“…The amounts of 131 I and 133 I deposited on the ground at each site from each test were derived from measured exposure rates, using the LLNL data described earlier, according to a well-established methodology (28,35) that has been used in other reconstructions of dose from fallout (32,36,37).…”

“…The radioiodine concentration in milk peaks a few hours after fallout deposition is complete and decreases with time according to weathering processes from vegetation surfaces and radioactive decay. Standard models and reference values (3,24,26,27) were used to estimate the radioiodine concentrations in milk and milk products and their conversion to thyroid dose (39,40). Finally, in the absence of published surveys of village diets in Kazakhstan for the period of interest, our assumed daily rates of consumption of milk and milk products were based on responses to the questionnaire administered to study participants at the time of the thyroid examinations, averaged with unpublished IRME archival data from regional dietary surveys (B. I. Gusev, personal communication) that determined typical per capita daily consumption rates for various fresh milk products and that were used as default values when individual data were lacking.…”

Accounting for Shared and Unshared Dosimetric Uncertainties in the Dose Response for Ultrasound-Detected Thyroid Nodules after Exposure to Radioactive Fallout

“…Methods for estimation of doses from external and internal irradiation by fallout from nuclear testing, with particular emphasis on fallout from the Nevada Test Site (NTS), have been discussed elsewhere in detail [e.g., Simon et al (16, 17) and Beck et al (18)], and formed much of the basis for the dose-estimation methods used in 2008 and in the current article. Modifications to the methods for the NTS dose reconstruction based on joint discussions between U.S. and Russian investigators were discussed by Simon et al (19), Gordeev et al (20, 21) and Beck et al (18). Specific details about contamination from the SNTS were discussed by Gordeev et al (20–22).…”

A New Era of Low-Dose Radiation Epidemiology

“…It is also important to capture temporal characteristics (e.g., age and time since first exposure), all sources of individual exposure, biologically relevant latency periods, and to incorporate sources of uncertainty for external [20][21][22] and internal [23] radiation exposures. Since epidemiologic studies are usually launched several years to decades after initial radiation exposure, radiation doses of exposed individuals must be reconstructed for the relevant time period(s) [24][25][26][27][28].…”