Study of Thyroid Diseases in Young Persons Near Chernobyl
The Chernobyl nuclear power plant accident in the former Soviet Union in 1986 exposed large numbers of people in Ukraine, Belarus and Russia to radioactive iodines, principally I-131 which concentrates in the thyroid gland (Hatch, et al. 2005; Cardis and Hatch, 2011). From 1998 to 2007/8, biennial thyroid screening examinations were conducted among approximately 25,000 individuals exposed to the accident as children or adolescents in Ukraine and Belarus. The initial report from Ukraine provides convincing evidence in support of earlier reports of a 5-6 fold radiation-related increase in thyroid cancer among those who were young at the time of the accident and includes individual dose estimates on all subjects. The data show a strong, approximately linear dose-response relationship. Other studies in Ukraine include individuals exposed in utero to radioiodines, who may have a raised risk of thyroid neoplasia. The relationships between radiation and autoimmune thyroiditis, follicular adenoma, hyperthyroidism and hypothyroidism have also been assessed. Current efforts utilize national cancer registries for follow-up and various strategies for maintaining contact with these cohorts.
Study of Leukemia Risk in Chernobyl Clean-up Workers
Following the accident at the Chernobyl nuclear power plant, hundreds of thousands of clean-up workers from Ukraine were exposed primarily to external radiation with those sent earliest receiving the highest doses (185 mGy in 1986, 112 mGy in 1987 and 47 mGy in 1988-89). To date, studies of cancer among clean-up workers have focused on leukemia. The Radiation Epidemiology Branch (REB) in collaboration with the Research Center for Radiation Medicine in Ukraine has conducted a case-control study of leukemia and other hematological diseases based on a large cohort of male clean-up workers (~110,000), with individual doses to the bone marrow estimated using a new method developed for this study. Findings from the first phase of the study based on cases diagnosed between 1987-2000 have been summarized in three companion papers (Methods, Dosimetry, Risk analysis) published in Radiation Research (vol. 170, 2008). The study was extended to accrue cases for an additional six years.