Benign and Malignant Thyroid Disease Among Those Exposed as Children to Fallout from the Chornobyl Accident[unreadable] The Chernobyl nuclear reactor accident in Ukraine in 1986 contaminated large parts of Belarus, northwestern Ukraine, and bordering Russian provinces. A case-control study in Belarus, with individual dose estimates, demonstrated a statistically significant link between thyroid cancer and radiation dose from fallout related to the Chornobyl accident. With the assistance of the Department of Energy (DOE) and the Nuclear Regulatory Commission (NRC), NCI has organized long-term follow-up studies of benign and malignant thyroid disease among those exposed as children to fallout from the Chornobyl accident in Belarus and in Ukraine. To date, the thyroid glands of approximately 12,000 subjects in each country have been screened biennially. A prevalence analysis of thyroid cancer based on data from the first screening has been completed and a manuscript is under review at a leading journal. A paper on autoimmune thyroiditis is in preparation.[unreadable] [unreadable] Cancer Mortality Among the Population Exposed to Radioactive Waste Dumped in the Techa River Adjacent to the Mayak Nuclear Facility in Russia[unreadable] Villagers living along the banks of the Techa River in Russia were exposed to chronic external and internal radiation from the Mayak nuclear facility. Cancer mortality is being evaluated in a cohort of approximately 30,000 people who received large doses of radiation from the radioactive waste dumped into the river. Current efforts focus on improving data quality, tracing the population for vital status information, and on statistical analyses. Ans association between cancer mortality and radiation dose has been observed.[unreadable] [unreadable] Thyroid Nodules as a Measure of Radiation Risk Among a Population of 3000 Residents in Kazakhstan Exposed as Children to Fallout from Nuclear Testing at the Semipalatinsk Test Site[unreadable] Thyroid nodule prevalence, ascertained by ultrasound screening, was used as a biomarker for radiation-related risk in a population of 3000 childhood residents of villages in Kazakhstan affected by radioactive fallout from nuclear bomb tests at the nearby Semipalatinsk Test Site. An ongoing dose reconstruction, based on Russian models for fallout deposition, archival and interview data on residence at the time of fallout events, source and consumption of milk and milk products, and models for iodine transport from pasture to food, yielded individual estimates of thyroid dose from external and internal radiation sources. Preliminary estimates of dose response for nodule prevalence suggest that the relative biological effectiveness of radiation from ingested 131-I compared to gamma rays from external sources is about 70% and is unlikely to be less than 20%.[unreadable] [unreadable] Lung Cancer and High Levels of Indoor Radon in China[unreadable] Data from a comprehensive case-control study of lung cancer in rural China in which high levels of indoor radon increased lung cancer risk was pooled with data from another large case-control study of lung cancer and radon conducted in a more urban area of China. Results from both studies were consistent with meta-analyses of indoor studies and from miner data suggesting that long-term exposure to radon in homes increases lung cancer risk. A measurement sub-study conducted over a three-year period found that temporal variation in radon levels represented the greatest source of uncertainty in radon measurements. Adjusting for this uncertainty in measurement increased the excess risk estimates of lung cancer by 50-100%. This suggests that radon studies using similar dosimetry may underestimate radon effects.[unreadable]