Mortality among workers in a thorium-processing plant--a second follow-up

A second follow-up of mortality was carried out for workers employed in a thorium-processing plant between 1915 and 1973. The study group comprised 3796 workers (3119 men and 677 women). Of the whole group, 926 (761 men and 165 women) were deceased and 2620 (2161 men and 459 women) were still alive, while 250 (6.6%) were lost to follow-up. For the male workers, the standardized mortality ratio (SMR) for all causes of death was 1.12 with a 95% confidence interval (95% CI) of 1.05-1.21. The SMR for the male workers was also significantly increased for all cancers (SMR 1.23, 95% CI 1.04-1.43) and lung cancer (SMR 1.36, 95% CI 1.02-1.78). For the female workers, the SMR was 0.74 (95% CI 0.63-0.86) for all causes and 0.53 (95% CI 0.35-0.78) for all cancers. The results of a Poisson regression analysis showed that there was no significant effect of the selected factors on lung cancer mortality.