Studies of Populations Exposed to Occupational Sources of Radiation

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Markers of Cosmic Radiation Exposure Among Flight Crew A biodosimetry study to assess cosmic radiation exposure and frequency of chromosome aberrations by fluorescence in situ hybridization among 83 pilots and 51 university faculty with minimal flying experience. The mean frequency of translocations did not differ between the airline pilots and a comparison group of university faculty, however there was a significant increasing trend among the pilots for number of years flying commercial aircraft and translocation frequency. In addition, radiation exposure from personal diagnostic procedures among the pilots was positively associated with translocation frequencies after adjustment for age and number of years flying. Some diet and vitamin supplements were also associated with translocation frequency. Cancer and Other Mortality Risks in a Cohort of U.S. Radiologic Technologists In 1982, the REB, initiated a nationwide cohort study of all cancer incidence and mortality among 146,022 U. S. radiologic technologists. The cohort with 73% females, and very high response rates offers a rare opportunity to study effects of occupational protracted low- to moderate-dose radiation exposure on breast and thyroid cancer, the two most sensitive organ sites for radiation carcinogenesis in women. All other cancer and non-cancer serious disease outcomes are also being evaluated in relation to protracted low-to-moderate dose exposures. Presently we are expanding the scope of the study to include a study of skin cancer in relation to radiation exposure and variation in levels of circulating vitamin D. Cancer Mortality in Russian Nuclear Workers A cohort of 26,000 Mayak nuclear facility workers is being studied because they comprise a unique occupational group for protracted exposure to external radiation at high doses and for exposure to plutonium. Improved dosimetry and updated mortality data confirm earlier findings of external dose-response relationships for leukemia and for all solid cancers. Mortality analyses have clearly demonstrated that risks for lung cancer, liver cancer and bone cancer increase with increasing dose from plutonium. Dose-response analyses of cancer mortality in relation to in utero radiation exposure from maternal employment at the Mayak facility are underway. Chernobyl Leukemia Study This is a joint US-Ukrainian case-control study of leukemia and other hematological diseases in a cohort of clean-up workers in Ukraine following the Chornobyl accident, carried out from 1986 to 2006 - one of the largest analytical studies performed in Chornobyl liquidators, taking into account the whole period of observation since the accident, cohort size (approximately 110,000) and collective dose. A total of137 cases of leukemia have been ascertained in the cohort, including 79 cases with chronic lymphocytic leukemia (CLL). With a case-control ratio of 1:5, this number of cases would provide adequate power to test the hypothesis of an association between radiation and leukemia risk. The study should also have adequate power to test the hypothesis that the risk is different from that seen in the atomic bomb survivors study if the previously suggested pattern of CLL increases is confirmed. The study is conducted by scientists of the Ukrainian Research Center for Radiation Medicine (RCRM), scientists from the U.S. National Cancer Institute (NCI) and scientists and consultants from Columbia University, New York (through a contract with NCI). Dosimetry for Nuclear Medicine Patients Despite the growing use of nuclear medicine procedures in the United States, very little is known regarding patterns of exposure in medical radiation workers. 20% of radiologic technologists in the U.S. radiologic technologist (USRT) study have reported working as nuclear medicine technologists at some time in their job history. In November 2010, REB held a focus-group discussion in which 8 to 10 experts provided input on historical practices. Based on these findings, as well as the literature, we have developed a detailed interview work module for radiologic technologists working with nuclear medicine procedures. We plan to refine this module based on feedback from a second meeting of a subset of focus group attendees, and to perform extensive pilot testing of the new nuclear medicine module. Germline Genetic Variation and Risk of Chromosome Aberrations among Mayak Nuclear Workers REB is elucidating the contribution of germline genetic variation to the frequency of chromosomal aberrations in a cohort of workers at the Mayak nuclear weapons facility. These workers were exposed to external gamma and internal plutonium radiation. Studies of UV and cancer at various sites in the USRT cohort The USRT cohort study includes self-reported data on lifetime UV radiation exposure, host susceptibility to adverse UV radiation effects, as well as various determinants of vitamin D exposure over time in a sub-cohort. We have examined and plan to continue to examine the association between UV radiation exposure and various cancer outcomes, including the particular patterns of UV radiation exposure that may relate to cancer risk, to examine the determinants of vitamin D and to assess tracking of vitamin D status over time Leukemia and Other Cancer Incidence in Baltic Clean-up Workers All cancer incidence through 1998 was evaluated in two cohorts, comprising 10,000 clean-up workers, from Estonia and Latvia, who were sent to Chornobyl (Ukraine) following the reactor accident in 1986. Workers received an average radiation dose of approximately 10 cGy. Leukemia risk incidence was not significantly elevated in this group compared to the general population. Thyroid cancer incidence was increased, but this appeared to have been due, at least in part, to thyroid screening. The study is being extended to include a cohort of 7,000 clean-up workers from Lithuania and additional years of follow-up. Incidence of Cancers in Female Flight Attendants We are investigating the risk of breast cancer and incidence of other cancers in a study of 9,631 female flight attendants due to cosmic radiation exposure. Surveys from living or proxy respondents have been collected from 6,341 female flight attendants. Confirmation of cancer diagnoses from death certificates or medical records is ongoing.