Radiation Exposure and Cancer Mortality Among Nuclear Power Plant Workers: a Meta-analysis / 예방의학회지

OBJECTIVES: We conducted a meta-analysis to investigate the relationship between low external doses of ionizing radiation exposure and the risk of cancer mortality among nuclear power plant workers. METHODS: We searched MEDLINE using key words related to low dose and cancer risk. The selected articles were restricted to those written in English from 1990 to January 2009. We excluded those studies with no fit to the selection criteria and we included the cited references in published articles to minimize publication bias. Through this process, a total of 11 epidemiologic studies were finally included. RESULTS: We found significant decreased deaths from all cancers (SMR = 0.75, 95% CI = 0.62 - 0.90), all cancers excluding leukemia, solid cancer, mouth and pharynx, esophagus, stomach, rectum, liver and gallbladder, pancreas, lung, prostate, lymphopoietic and hematopoitic cancer. The findings of this meta-analysis were similar with those of the 15 Country Collaborative Study conducted by the International Agency for Research on Cancer. A publication bias was found only for liver and gallbladder cancer (p = 0.015). Heterogeneity was observed for all cancers, all cancers excluding leukemia, solid cancer, esophagus, colon and lung cancer. CONCLUSIONS: Our findings of low mortality for stomach, rectum, liver and gallbladder cancers may explained by the health worker effect. Yet further studies are needed to clarify the low SMR of cancers, for which there is no useful screening tool, in nuclear power plant workers.

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 Department 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 316,619 Person-Years of which 28 (34.6% of the total) deaths belonged to the monitored Radiation Worker category having a database of 112,363 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 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 DAE populations.

A cancer mortality study in Bombay-based atomic energy community: 1975-1987.

Cancer deaths recorded by the centralised health services of the Department of Atomic Energy (DAE) among its employees and their families stationed in Bombay during 1975-1987 have been analysed. Expected number of deaths due to cancer in the study group has been estimated by using the age-sex-specific cancer death rates reported for Bombay resident population for the year 1983. The size of the database for the entire DAE community is about 702,000 person years and the number of cancer deaths observed in 154. Analysis has been done separately for employees and their families, individually for important groups of cancer sites such as respiratory organs, digestive organs, breast, genito-urinary organs and lymphatic and haematopoietic systems. The standardised mortality ratios are generally lower than 100, which may partly be due to the 'healthy worker effect' in the DAE community and partly because of its differences in the social class distribution and the concomitant differences in lifestyle with respect to the comparison group of Bombay city.