This study found an SMR for lung cancer of 88 (48 observed, 54.6 expected; 95% CI 65–117). Additionally, the mortality for the two subcohorts who had higher exposure to uranium based on job categorization (as categorized by urine uranium levels) showed similar SMRs. The SMR was lower in the heavily exposed subcohorts than in the entire cohort, which is evidence against a meaningful association. There was no pattern of increasing cancer mortality with longer employment or when assuming a 15-year latency period.
The level of exposure of this cohort was relatively low. Only 50 percent worked at the plant more than 5 years, and the turnover of employees was 15–25 percent every 5 years. Further, the study did not have the power to detect small differences in increased risk of lung cancer for several reasons: the period of follow-up was relatively short (a maximum of 28 years and only 17 years for 40 percent of the cohort); according to the urinary uranium levels, relatively few workers had high levels of exposure to uranium; and members of the cohort were relatively young at the end of the follow-up period.
There was no increase in lung cancer deaths in this cohort (21 observed, 21.7 expected; SMR 97, 95% CI 60–148). Results for lung cancer deaths were similar when the standard of comparison was white male residents of Erie and Niagara counties. Of the employees studied, 38 percent had an annual internal exposure that exceeded 100 mSv (10 rem) per year. The cohort of 995 workers was relatively young, with 64 percent aged 16–35 years at the date of hire. The vast majority of employees began work from 1943 to 1945, and 56 percent worked less than a year. A weakness of the study is the small number of workers, which means that the comparison of heavily exposed workers to less exposed workers lacked the power to detect small differences between the two groups.
This study of workers at the Oak Ridge uranium processing plant from 1943 to 1947 found an SMR for lung cancer of 109 (95% CI 97–121). These numbers changed only slightly after corrections for incomplete ascertainment of deaths. For the 2,051 men who worked in the areas most highly exposed to uranium dust (first stage chemistry areas), the SMR was 97 for lung cancer. Lung cancer results were similar when analyses were restricted to men who had worked in heavily exposed areas for a year or more; based on 66 observed cases, the SMR was 106. Results were also similar when unexposed workers at Oak Ridge were used as the comparison group. The only suggestion of an increased risk of lung cancer was seen when men working in the heavily exposed areas were subdivided