Mortality among the Chernobyl emergency workers: Estimation of radiation risks (preliminary analysis)

This paper presents results of the analysis of mortality among Chernobyl ac cident emergency workers who are resident in Russia. The analysis is based on information for the cohort of emergency workers (males) from six regions of Russia including 65,905 persons with documented external doses in the r ange 0.005-0.3 Sv. These data were gathered during the period 1991 to 1998 and cover a total of 426,304 follow-up person-y. In this period, 4,995 deat hs occurred in the cohort under study. The mortality analysis was performed for four groups of causes of death (ICD-9 codes): (1) malignant neoplasms (140-239); (2) cardiovascular diseases (390-459); (3) injuries, poisoning a nd violent deaths, (800-999); and (4) the remainder (other than the above). The standardized mortality rate for groups 1, 3, and 4 is less than unity and varies from 0.6 to 0.9. For group 2 (death from cardiovascular diseases ) the standardized mortality rate conforms with the control within 95% conf idence intervals. The control was the mortality rate (males) for the corres ponding ages in Russia in general and the internal control, the spontaneous mortality among emergency workers, derived from the equation of the observ ed and expected number of cases in the followed up cohort. Dose response of mortality was studied. Statistically significant radiation risks were obta ined for mortality from malignant neoplasms (515 cases) and cardiovascular diseases (1,728 cases). The values of the excess relative risk per unit dos e (ERR Sv(-1)) for malignant neoplasms and cardiovascular diseases are esti mated as 2.11 (1.31, 2.92 95% CI) and 0.54 (0.18, 0.91 95% CI) (for externa l control), 2.04 (0.45, 4.31 95% CI) and 0.79 (0.07, 1.64 95% CI) (for inte rnal control), respectively. The risk of death from all noncancer causes is close to zero and not statistically significant.