Updated risk models for lung cancer due to radon exposure in the German Wismut cohort of uranium miners, 1946-2018

UNSCEAR recently recommended that future research on the lung cancer risk at low radon exposures or exposure rates should focus on more contemporary uranium miners. For this purpose, risk models in the German Wismut cohort of uranium miners were updated extending the follow-up period by 5 years to 1946-2018. The full cohort (n = 58,972) and specifically the 1960 + sub-cohort of miners first hired in 1960 or later (n = 26,764) were analyzed. The 1960 + sub-cohort is characterized by low protracted radon exposure of high quality of measurements. Internal Poisson regression was used to estimate the excess relative risk (ERR) for lung cancer per cumulative radon exposure in Working Level Months (WLM). Applying the BEIR VI exposure-age-concentration model, the ERR/100 WLM was 2.50 (95% confidence interval (CI) 0.81; 4.18) and 6.92 (95% CI < 0; 16.59) among miners with attained age < 55 years, time since exposure 5-14 years, and annual exposure rates < 0.5 WL in the full (n = 4329 lung cancer deaths) and in the 1960 + sub-cohort (n = 663 lung cancer deaths), respectively. Both ERR/WLM decreased with older attained ages, increasing time since exposure, and higher exposure rates. Findings of the 1960 + sub-cohort are in line with those from large pooled studies, and ERR/WLM are about two times higher than in the full Wismut cohort. Notably, 20-30 years after closure of the Wismut mines in 1990, the estimated fraction of lung cancer deaths attributable to occupational radon exposure is still 26% in the full Wismut cohort and 19% in the 1960 + sub-cohort, respectively. This demonstrates the need for radiation protection against radon.