Characteristics of the cohort of workers at the Mayak nuclear complex

At Branch No. 1 of the Russian State Research Center "Biophysics Institute" , a registry has been created of workers at the "Mayak" Production Associat ion, the first nuclear complex in Russia. This registry includes 18,830 per sons hired at Mayak's nuclear reactors and radiochemical and plutonium prod uction plant between 1948 and 1972. Twenty-five percent of these workers ar e women. As of December 31, 1994, the vital status is known for approximate ly 90% of the cohort members. A total of 5,118 persons have died. The cause for 97% of total deaths has been ascertained. The cohort members were expo sed to both external gamma radiation and internal radiation from incorporat ed plutonium. The plutonium body burden has been measured in 30% of the coh ort members with potential for plutonium exposure. External gamma-ray doses were in the range from tenths of milligrays to about 10 Gy, and plutonium body burdens were up to about 260 kBq. In view of the nature of the Mayak w orker cohort, it has the potential to provide reasonably precise, quantitat ive estimates of the long-term health effects associated with chronic low-d ose-rate exposure to external gamma radiation as well as internal radiation from plutonium. However, a number of issues must be addressed before credi ble risk estimates can be obtained from this cohort. These issues include t he development of an appropriate internal comparison group and/or external rates and separating of the effects of internal and external exposures on r isk estimates. (C) 1999 by Radiation Research Society.