Cancer incidence among liquidators of the Chernobyl accident: solid tumors, 1986-1995.

The paper considers information about cancer incidence (solid tumors) among liquidators of the Chernobyl accident, which occurred in April 1986. The information was accumulated in the Russian National Medical and Dosimetric Registry (RNMDR) in the period from 1986 to early 1996. The RNMDR contains individual dosimetric and annual check-up data on liquidators resident in Russia. This paper presents results for male liquidators who had no oncological diseases before arrival to the 30-km zone and for whom the following information was available: confirmed dose of external radiation, birth date, date of arrival to the 30-km zone, time spent in the 30-km zone, and results of medical check-ups. The number of liquidators under study is 114,504, i.e., about 68% of all those registered in the RNMDR. The average dose of the studied cohort is 108 mGy; the average age at first arrival to the 30-km zone is 34.3 y; the total number of person-y is 797,781. The cohort of liquidators is briefly characterized. Cancer incidence in liquidators is compared to that of the population of Russia as a whole by calculating standardized incidence ratio (SIR). The values of SIR with 95% confidence intervals for all solid tumors and malignant neoplasms of the digestive system were 1.23 (1.15; 1.31) and 1.11 (1.01; 1.24), respectively. Assessment of radiation risks for the same classes of diseases has revealed a statistically significant increase in cancer incidence with external radiation dose. This study also shows that statistically significant excesses in the incidence of malignant neoplasms of the respiratory system have not been observed.