ISSUES IN THE COMPARISON OF RISK ESTIMATES FOR THE POPULATION IN THE TECHA RIVER REGION AND ATOMIC-BOMB SURVIVORS

Plutonium production in the former Soviet Union began in 1949 at the M ayak Production Association located between the cities of Chelyabinsk and Ekaterinbourg in the southern Ural mountains about 1200 km east of Moscow. During the first few years of Mayak's operation, almost 30,00 0 people living on the banks of the Techa River received significant i nternal and external exposures as a consequence of the release of larg e quantities of radioactive materials from Mayak. Studies of levels of radioactive contamination and health effects in this population began in the early 1950s. A systematic follow-up of a fixed cohort that inc ludes al people who were living in Techa River villages in 1949 was be gun about 30 years ago. In this paper we describe the Techa River coho rt, outline the nature of the exposures and discuss the status of foll ow-up for the period from 1950 through 1989. While noting the limitati ons of the current epidemiological follow-up data, we also compare the demographic and mortality structure of the Techa River cohort with th e Life Span Study cohort of Japanese atomic bomb survivors. It is seen that, despite a number of limitations, the current data suggest that the risks of mortality from leukemia and other cancers increase with i ncreasing radiation dose in the Techa River cohort. This finding sugge sts that, with continued improvements in the quality of the follow-up and dosimetry, the Techa River cohort has the potential to provide qua ntitative estimates of the risks of chronic low-dose-rate radiation ex posures for an unselected general population that will be an important complement to the estimates based on the Life Span Study that are use d as the primary basis for numerical assessments of radiation risk. (C ) 1997 by Radiation Research Society.