Pooled analysis of cancer mortality cases among the employees in five units of the Department of Atomic Energy in India

Available data on cancer mortality in the combined employee populations of five units of the Dept. of Atomic Energy, namely those in Mumbai, Tarapur, Kalpakkam, Hyderabad and Alwaye, with study periods ranging between 13 and 21 years, have been analysed. Data are available only on those still serving, i.e., subjects in the age group 20-59 yrs., and not on the retired employees and this is the major constraint in the study. A total of 81 cancer deaths have been recorded in the combined database of 316619 person-years (PY) of which 28 (34.6% of the total) deaths belonged to the monitored radiation worker category having a database of 112363 PY(35.5% of the total). Background age-specific cancer death rates of the urban Indian population have been constructed by averaging the only available age-specific cancer mortality data published by the Bombay Cancer Registry for Mumbai, Nagpur and Pune cities. Using this as a tentative national urban baseline, the estimated standardised mortality ratio (SMR) for combined DAE employees works out to be 111 with 95% CI:80-138. The SMR for the radiation workers alone is 108(95% CI:72-156) as compared to the SMR of 113 (95% CI:84-149) for the non-radiation workers. The relative risk of radiation workers as opposed to non radiation workers is 0.96(95% CI:0.64 - 1.39); analysis on individual types of cancer also leads to similar results. It is seen clearly that the radiation workers are not at any extra risk of cancer as compared to non-radiation workers. Nor does a comparison with the restricted national base-line data available for cities like Mumbai, Pune and Nagpur indicate any statistically significant risk of cancer in Department of Atomic Energy (DAE) populations. (author)