Mortality among female workers at a thorium-processing plant

The mortality patterns among a cohort of 677 female workers at a thorium-processing plant are reported for the period from 1940 to 1982. Of the 677 women, 165 were reported dead; 459 were still alive; and 53 (7.8%) were lost to follow-up. The standardized mortality ratios from all causes (0.74), all cancers (0.53), and circulatory diseases (0.66) were significantly below those for the general US population. In this cohort, 5 deaths due to lung cancer and 1 death from leukemia were observed, with 4.53 and 1.69 deaths expected, respectively. No deaths from cancer of the liver, pancreas, or bone were observed. Poisson regression analysis was used for an internal comparison within the cohort. The results of the Poisson regression analysis showed no significant effect on mortality rates of all causes and cancers from the study factors, including job classification, duration of employment, and time since first employment