Updated cancer mortality among uranium miners on the Colorado Plateau: interactions of radon exposure with smoking and temporal factors

Abstract

Objectives Understanding of long-term lung cancer risks from radon decay products (RDP) exposure derives largely from studies of uranium miners. We aimed to compare mortality for lung and other cancers to the general population, to estimate excess absolute rate (EAR) and excess relative rate (ERR) from RDP exposure, and to estimate the joint effects of RDP and cigarette smoking in extended follow-up of a cohort of 4137 male uranium miners from the US Colorado Plateau. Methods We extended mortality follow-up through 2016 and re-evaluated RDP exposure against original work history and mine records. We calculated standardised mortality ratios (SMRs) compared with a regional population, evaluated EAR of lung cancer mortality using standardised rate ratios and modelled ERR using Cox proportional hazards regression. We evaluated interactions of RDP with smoking pack-years, attained age (AA) and time-since-exposure (TSE). Results There were 695 lung cancer deaths, including 146 among never-smokers and light smokers. The overall SMR was >4; the EAR per unit RDP exposure increased substantially with smoking pack-years and decades of follow-up. Lung cancer ERR decreased with AA and TSE. ERR attenuation at high exposure rates was smaller than observed elsewhere. Joint effects of RDP and smoking were submultiplicative but greater-than-additive, appearing closer to multiplicative at lower RDP exposures. Pancreas was the only other site showing a significantly positive ERR per unit exposure. Conclusions Excess rates of lung cancer mortality persist throughout the lifespan among this cohort of uranium miners. Information about RDP-smoking interactions is of interest for occupational and general population exposure.