Epidemiological evidence of lung cancer risk from radon is based mainly on studies of underground miners where occupational exposures were, historically, relatively high in comparison to residential indoor exposure. However, radiation protection measures have caused radon levels in uranium mines to decrease significantly in more recent periods. Miners' occupational exposure is limited to their working years while they are exposed to environmental radon at home over their entire lifetime. Even during their limited working years, workers spend much more time at home than in workplaces. The biological effect of radon in mines cannot be distinguished from the biological effect of residential radon. Therefore, for an exposure-risk relationship study of former uranium miners, excess radon-induced lung cancer cases should be related to the combined radon exposure cumulated in workplaces and at homes in excess of the radon exposure of the reference population. This is especially important when residential radon levels differ or vary significantly between miners and the reference population over the course of extended follow-up years. This paper reviews some recent studies on former uranium miners, shares what seems controversial to the author and wonders whether lifetime exposure at home to widely varying radon concentrations can actually impact the quality of exposure assessment, and hence impact the results of the exposure-risk relationship.

• Keywords
• Exposure assessment, Radon-222, Risk assessment, Uranium miners,
• MeSH
• Housing MeSH
• Adult MeSH
• Risk Assessment MeSH
• Mining * MeSH
• Middle Aged MeSH
• Humans MeSH
• Neoplasms, Radiation-Induced epidemiology   MeSH
• Occupational Diseases epidemiology   MeSH
• Occupational Exposure * MeSH
• Air Pollutants, Radioactive * MeSH
• Radon * MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Uranium * MeSH
• Air Pollution, Indoor MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Czech Republic epidemiology   MeSH
• France epidemiology   MeSH
• Names of Substances
• Air Pollutants, Radioactive * MeSH
• Radon * MeSH
• Uranium * MeSH

OBJECTIVES: Epidemiological studies of underground miners have provided clear evidence that inhalation of radon decay products causes lung cancer. Moreover, these studies have served as a quantitative basis for estimation of radon-associated excess lung cancer risk. However, questions remain regarding the effects of exposure to the low levels of radon decay products typically encountered in contemporary occupational and environmental settings on the risk of lung cancer and other diseases, and on the modifiers of these associations. These issues are of central importance for estimation of risks associated with residential and occupational radon exposures. METHODS: The Pooled Uranium Miner Analysis (PUMA) assembles information on cohorts of uranium miners in North America and Europe. Data available include individual annual estimates of exposure to radon decay products, demographic and employment history information on each worker and information on vital status, date of death and cause of death. Some, but not all, cohorts also have individual information on cigarette smoking, external gamma radiation exposure and non-radiological occupational exposures. RESULTS: The PUMA study represents the largest study of uranium miners conducted to date, encompassing 124 507 miners, 4.51 million person-years at risk and 54 462 deaths, including 7825 deaths due to lung cancer. Planned research topics include analyses of associations between radon exposure and mortality due to lung cancer, cancers other than lung, non-malignant disease, modifiers of these associations and characterisation of overall relative mortality excesses and lifetime risks. CONCLUSION: PUMA provides opportunities to evaluate new research questions and to conduct analyses to assess potential health risks associated with uranium mining that have greater statistical power than can be achieved with any single cohort.

• Keywords
• Radon, cancer, cardiovascular, low-level ionising radiation, uranium miners,
• MeSH
• Risk Assessment MeSH
• Miners * MeSH
• Cohort Studies MeSH
• Cigarette Smoking epidemiology   MeSH
• Humans MeSH
• Lung Neoplasms epidemiology   mortality   MeSH
• Neoplasms, Radiation-Induced epidemiology   mortality   MeSH
• Occupational Diseases epidemiology   MeSH
• Occupational Exposure adverse effects   MeSH
• Radon adverse effects   MeSH
• Uranium * MeSH
• Check Tag
• Humans MeSH
• Male MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, U.S. Gov't, P.H.S. MeSH
• Geographicals
• Europe epidemiology   MeSH
• North America epidemiology   MeSH
• Names of Substances
• Radon MeSH
• Uranium * MeSH

It is well established that high radon exposures increase the risk of lung cancer mortality. The effects of low occupational exposures and the factors that confound and modify this risk are not clear and are needed to inform current radiation protection of miners. The risk of lung cancer mortality at low radon exposures (< 100 working-level months) was assessed in the joint cohort analysis of Czech, French, and Canadian uranium miners, employed in 1953 or later. Statistical analysis was based on linear Poisson regression modeling with grouped cohort survival data. Two sensitivity analyses were used to assess potential confounding from tobacco smoking. A statistically significant linear relationship between radon exposure and lung cancer mortality was found. The excess relative risk per working-level month was 0.022 (95% confidence intervals: 0.013-0.034), based on 408 lung cancer deaths and 394,236 person-years of risk. Time since exposure was a statistically significant modifier; risk decreased with increasing time since exposure. A tendency for a decrease in risk with increasing attained age was observed, but this was not statistically significant. Exposure rate was not found to be a modifier of the excess relative risk. The potential confounding effect of tobacco smoking was estimated to be small and did not substantially change the radon-lung cancer mortality risk estimates. This joint cohort analysis provides strong evidence for an increased risk of lung cancer mortality from low occupational radon exposures. The results suggest that radiation protection measures continue to be important among current uranium miners.

• Keywords
• Cohort, Epidemiology, Lung cancer, Radon, Risk, Smoking, Uranium mining,
• MeSH
• Miners * MeSH
• Cohort Studies MeSH
• Tobacco Smoking MeSH
• Middle Aged MeSH
• Humans MeSH
• Lung Neoplasms epidemiology   mortality   MeSH
• Neoplasms, Radiation-Induced epidemiology   mortality   MeSH
• Occupational Diseases epidemiology   MeSH
• Occupational Exposure adverse effects   MeSH
• Radon adverse effects   MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Uranium * MeSH
• Check Tag
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Czech Republic epidemiology   MeSH
• France epidemiology   MeSH
• Canada epidemiology   MeSH
• Names of Substances
• Radon MeSH
• Uranium * MeSH

The aim of the present study was to evaluate the risk of lung cancer from combined exposure to radon and smoking. Methodologically, it is based on case-control studies nested within two Czech cohort studies of nearly 11,000 miners followed-up for mortality in 1952-2010 and nearly 12,000 inhabitants exposed to high levels of radon in homes, with mortality follow-up in 1960-2010. In addition to recorded radon exposure, these studies use information on smoking collected from the subjects or their relatives. A total of 1,029 and 370 cases with smoking information have been observed in the occupational and environmental (residential) studies, respectively. Three or four control subjects have been individually matched to cases according to sex, year of birth, and age. The combined effect from radon and smoking is analyzed in terms of geometric mixture models of which the additive and multiplicative models are special cases. The resulting models are relatively close to the additive interaction (mixing parameter 0.2 and 0.3 in the occupational and residential studies, respectively). The impact of the resulting model in the residential radon study is illustrated by estimates of lifetime risk in hypothetical populations of smokers and non-smokers. In comparison to the multiplicative risk model, the lifetime risk from the best geometric mixture model is considerably higher, particularly in the non-smoking population.

• MeSH
• Mining MeSH
• Smoking adverse effects   MeSH
• Humans MeSH
• Lung Neoplasms epidemiology   etiology   MeSH
• Air Pollutants, Radioactive adverse effects   MeSH
• Radon adverse effects   MeSH
• Risk MeSH
• Case-Control Studies MeSH
• Uranium MeSH
• Environmental Exposure adverse effects   analysis   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Czech Republic epidemiology   MeSH
• Names of Substances
• Air Pollutants, Radioactive MeSH
• Radon MeSH
• Uranium MeSH