Low-level radon exposure and lung cancer in the Pooled Uranium Miners Analysis (PUMA)

Abstract

BACKGROUND AND AIM: Radon, a ubiquitous gas, and its progeny are a leading environmental and occupational cause of lung cancer. To better inform radiation protection standards by estimating risk, we assembled an international cohort study of workers employed in uranium mining in Canada, the Czech Republic, France, Germany, and the United States. METHODS: We focus on miners employed during the more contemporary period of the uranium mining industry when radon exposures tended to be comparatively low, and individual exposure data are available. A cohort of 56,614 male uranium miners first employed in 1960 or later was assembled and followed to ascertain causes of death. Estimates of excess relative rate (ERR) per working level month (WLM) of cumulative radon progeny exposure for mortality from lung cancer were derived by internal Poisson regression. RESULTS:In the follow-up period a total of 1217 lung cancer deaths occurred, accumulating 1.9 million person-years at risk. The relative rate of lung cancer increased in a linear fashion with cumulative exposure to radon progeny, lagged 5 years (ERR/100 WLM=1.34; 95% CI: 0.89, 1.89). Attained age was a clear modifier of this association, showing a decrease in ERR/WLM with increasing attained age. Further potential modifiers are age at exposure or time since exposure and exposure rate. CONCLUSIONS:PUMA provides the most precise and informative estimates to-date of the association between low-level exposure to radon progeny and lung cancer mortality. The results strengthen the basis for radiation protection standards for radon and its progeny. KEYWORDS: Ionizing radiation, Occupational exposures, Risk assessment,International collaboration