BACKGROUND AND METHODS: A retrospective cohort study was conducted to estimate the effects of low-level exposure to external (penetrating) radiation on cancer mortality among 4,563 workers monitored for external radiation between 1950 and 1993 at a nuclear research and production facility in Southern California. RESULTS: Of the 875 deaths that occurred before 1995, 258 were due to cancer as the underlying cause. External comparisons of male subjects with the U.S. white male population indicated that the workers had lower rates of dying from all causes and all cancers, but a higher rate of dying from leukemia. Internal comparisons of workers exposed at different dose levels, using risk-set analyses with adjustment for confounders, demonstrated an increased mortality rate in workers exposed to 200 mSv for hemato- and lymphopoietic cancers and for lung cancer. Mortality rates for total cancers and "radiosensitive" solid cancers increased monotonically with cumulative radiation dose, but no trends were observed for "nonradiosensitive" cancers. CONCLUSIONS: Despite possible residual confounding and low precision for estimating effects on specific cancers, these findings indicate that chronic, low-level radiation exposure may have more generalized carcinogenic effects than have been observed in most previous investigations. Such effects may have become evident as a result of the relatively long follow-up period in the present study.
BACKGROUND AND METHODS: A retrospective cohort study was conducted to estimate the effects of low-level exposure to external (penetrating) radiation on cancer mortality among 4,563 workers monitored for external radiation between 1950 and 1993 at a nuclear research and production facility in Southern California. RESULTS: Of the 875 deaths that occurred before 1995, 258 were due to cancer as the underlying cause. External comparisons of male subjects with the U.S. white male population indicated that the workers had lower rates of dying from all causes and all cancers, but a higher rate of dying from leukemia. Internal comparisons of workers exposed at different dose levels, using risk-set analyses with adjustment for confounders, demonstrated an increased mortality rate in workers exposed to 200 mSv for hemato- and lymphopoietic cancers and for lung cancer. Mortality rates for total cancers and "radiosensitive" solid cancers increased monotonically with cumulative radiation dose, but no trends were observed for "nonradiosensitive" cancers. CONCLUSIONS: Despite possible residual confounding and low precision for estimating effects on specific cancers, these findings indicate that chronic, low-level radiation exposure may have more generalized carcinogenic effects than have been observed in most previous investigations. Such effects may have become evident as a result of the relatively long follow-up period in the present study.