Lifetime Risks for Lung Cancer due to Occupational Radon Exposure: A Systematic Analysis of Estimation Components.

Lifetime risk estimates play a key role in many areas of radiation research. Here, the focus is on the lifetime excess absolute risk (LEAR) for dying from lung cancer due to occupational radon exposure based on uranium miners cohort studies. The major components in estimating LEAR were systematically varied to investigate the variability and uncertainties of results. Major components of the LEAR calculation are baseline mortality rates for lung cancer and all causes of death, risk model and exposure scenario. Sex-averaged mortality rates were chosen from a mixed Euro-American-Asian population, in addition to mortality rates to represent heavy and light smokers. Seven radon-related lung cancer risk models derived from different uranium miners cohorts were compared. As exposure scenarios, occupational exposure of two working level months (WLM) from age 18-64 years was considered, and three scenarios from the German uranium miners cohort. Further components were modified in sensitivity analyses. The LEAR was compared to other lifetime risk measures. With a range from less than 0.6 × 10-4 to over 8.0 × 10-4, LEAR per WLM estimates were influenced heavily by the choice of risk models. Notably, mortality rates, particularly lung cancer mortality rates, had a strong impact on LEAR per WLM across all models. The LEAR per WLM exhibited only low variation to changes in exposure scenarios for all risk models, except for the BEIR VI model fitted on the pooled 11 miners study. All assessed lifetime risk measures displayed a monotonically increasing relationship between exposure and lifetime risk at low to moderate exposures, with minor differences between ELR, REID, and LEAR (all per WLM). RADS yields the largest lifetime risk estimates in most situations. There is substantial variation in LEAR per WLM estimates depending on the choice of underlying calculation components. Reference populations and mortality rates should be selected with care depending on the application of lifetime risk calculations. The explicit choice of the lifetime risk measure was found to be negligible. These findings should be taken into consideration when using lifetime risk measures for radiation protection policy purposes.