| Case-control studies of haematological malignancies and of thyroid cancer among Chernobyl accident recovery workers (liquidators) in Belarus, the Russian Federation and the Baltic States Studies of cancer risk among Chernobyl accident recovery workers (liquidators) were conducted in Belarus, the Russian Federation and Baltic States. Two collaborative case-control studies - one of haematological malignancies and the other of thyroid cancer risk - were set-up to estimate the radiation-induced risk of these diseases among liquidators of the Chernobyl accident and, in particular, to study the effect of exposure rate. The design of both studies is similar. The study population consists of the approximately 65 000 Belarusian and 66 000 Russian (residing in five regions of the Russian Federation), and 15 000 Estonian, Latvian and Lithuanian liquidators who worked in the 30 km zone around the Chernobyl reactor in the period 26 April 1986 to 31 December 1987, and who have been identified through the national Chernobyl Registries in Belarus and the Russian Federation, and through the rosters of the established Baltic liquidator cohorts. The two studies include: 107 cases of thyroid cancer and 117 cases of malignancies of lymphoid and hematopoietic tissue diagnosed both retrospectively and prospectively between 1 January 1999 and 31 December 2000; 904 controls matched with the case on age, gender and region of residence at the time of the accident. A method, entitled RADRUE (Realistic Analytical Dose Reconstruction with Uncertainty Estimation), was developed (and extensively tested) to assess individual dose to the bone marrow and to the thyroid from external radiation received by the liquidators during their clean up missions. Internal doses to the thyroid due to the intake of 131I were also calculated for the liquidators who worked on the industrial site during the first few weeks after the accident. Internal doses were also calculated for the liquidators who were residents of contaminated settlements of Gomel and Mogilev regions (oblasts) of Belarus and were returning home every evening or after weekly shift work and consumed locally produced contaminated milk or vegetables. The results of the study of the haematological malignancies have been published in the Radiation Research in 2008 (1). For all haematological malignancies combined, a significantly elevated OR was seen at doses of 200 mGy and above. The Excess Relative Risk (ERR) per 100 mGy was 0.60 (90% confidence interval (CI): -0.02, 2.35). The corresponding estimate for leukemia excluding chronic lymphoid leukemia (CLL) was 0.50 (90%CI 0.38, 5.7). It is slightly higher than, but statistically compatible with, those estimated from A-bomb survivors and recent low dose-rate studies. |