Incidence and mortality of solid cancer among emergency workers of the Chernobyl accident: assessment of radiation risks for the follow-up period of 1992-2009.

This paper presents the results of a retrospective cohort study of cancer incidence and mortality among emergency workers of the Chernobyl accident, for the follow-up period 1992-2009. The cohort selected for analysis consists of 67,568 emergency workers who worked in the Chernobyl exclusion zone in 1986-1987. External radiation whole-body absorbed dose varied from 0.0001 gray (Gy) to 1.24 Gy, with a median of 0.102 Gy. Over the follow-up period 1992-2009, a total of 4,002 solid cancers of different sites were identified as the result of annual compulsory health examination, and a total of 2,442 deaths from all solid cancers in the study cohort were reported. Poisson regression was applied for the analysis of cancer incidence and mortality. The analysis of the standardized incidence ratio (SIR) has shown a statistically significant increase in cancer incidence in the cohort as compared with baseline cancer incidence among males of Russia. The average excess over the entire follow-up period is 18 % [SIR = 1.18, 95 % confidence interval (CI) 1.15; 1.22]. In contrast, however, no increase in the mortality from all cancers among the emergency workers as compared to the baseline mortality in Russian men was found. Values of excess relative risk of cancer incidence and mortality per 1 Gy (ERR Gy(-1)) are 0.47 (95 % CI 0.03; 0.96, p value = 0.034) and 0.58 (95 % CI 0.002; 1.25, p value = 0.049), respectively. These values are statistically significant.