Exposure and mortality in a cohort of German nuclear power workers

A historical cohort study of German nuclear power workers was set up to investigate the overall and cancer mortality risk related to a long-term low-level exposure to ionising radiation. The cohort was part of an international collaborative study whose pooled analyses were carried out at the International Agency for Research on Cancer (IARC), Lyon, and published recently. Due to delays in data collection, data from the German cohort were not included in these analyses. This cohort includes 4,844 employees who worked in any of 10 nuclear power plants, between 1 January 1991 and 31 December 1997. Sixty-eight deaths among men were observed in 31,000 person years, and none among women. Standardized mortality ratios (SMRs) were computed for all causes of death, all cancers, cardiovascular diseases, external causes, and all other causes. Overall, a strong healthy worker effect was observed (all-cause SMR = 0.54, 95% CI 0.42-0.67), and no increase in total cancer mortality was seen (SMR = 0.66, 95% CI 0.43-0.95). These results are in line with and complement IARC results. Figures are yet too small for stable risk estimates and further work is therefore under way to include more power plants, and to extend the follow-up until the year 2005.