Exposure to radon progeny and cancer mortality, excluding lung cancer, in the cohort of Newfoundland Fluorspar Miners between 1950 and 2016.

The increased risk of lung cancer from radon progeny among Newfoundland fluorspar miners is well established. In the present study, an internal cohort analysis was conducted to investigate whether radon progeny is also associated with increased mortality from other cancers. Consequently, associations between cumulative radon progeny and cancer mortality (excluding lung cancer) were evaluated in a cohort of 2,110 miners. Mortality was ascertained from 1950 to 2016. Individual-level exposure to radon progeny in working level months (WLM) was determined for each miner during their employment. For cancers with at least ten deaths, Poisson regression was used to estimate excess relative risks (ERRs). Cancer site-specific relative risks were derived for mortality from common cancers within the cohort, specifically: colorectal, prostate, stomach and all cancers (excluding lung cancer). Relative risks were adjusted for age, calendar period, and the number of cigarettes smoked daily determined from smoking surveys. In total, 260 cancer deaths, excluding lung cancer, were identified during follow-up. The relative risk of death from these cancers was 1.26 (95% confidence interval (CI): 0.92, 1.75) among underground miners with a cumulative exposure of ≥ 50 WLM when compared to those with < 1 WLM. The ERR per 100 WLM for cancer mortality (excluding lung cancer) was 0.02 (95% CI=-0.01 to 0.05). No statistically significant increased risks with increasing exposure were found for bladder, colorectal, pancreatic, and stomach cancer. Overall, these findings provide modest evidence that radon progeny contributes to increased risks of cancer mortality (excluding lung cancer) among fluorspar miners. However, the precision of the estimates is limited by the small size of the cohort, which restricts the ability to draw firm conclusions regarding specific cancer sites. Future research should consider pooling data from radon-exposed occupational cohorts to better understand the association between radon exposure and the risk of cancers other than lung cancer.