Radon and lung cancer in the pooled uranium miners analysis (PUMA): highly exposed early miners and all miners.

OBJECTIVES: Radon is a ubiquitous occupational and environmental lung carcinogen. We aim to quantify the association between radon progeny and lung cancer mortality in the largest and most up-to-date pooled study of uranium miners. METHODS: The pooled uranium miners analysis combines 7 cohorts of male uranium miners with 7754 lung cancer deaths and 4.3 million person-years of follow-up. Vital status and lung cancer deaths were ascertained between 1946 and 2014. The association between cumulative radon exposure in working level months (WLM) and lung cancer was modelled as the excess relative rate (ERR) per 100 WLM using Poisson regression; variation in the association by temporal and exposure factors was examined. We also examined analyses restricted to miners first hired before 1960 and with <100 WLM cumulative exposure. RESULTS: In a model that allows for variation by attained age, time since exposure and annual exposure rate, the ERR/100 WLM was 4.68 (95% CI 2.88 to 6.96) among miners who were less than 55 years of age and were exposed in the prior 5 to <15 years at annual exposure rates of <0.5 WL. This association decreased with older attained age, longer time since exposure and higher annual exposure rate. In analyses restricted to men first hired before 1960, we observed similar patterns of association but a slightly lower estimate of the ERR/100 WLM. CONCLUSIONS: This new large, pooled study confirms and supports a linear exposure-response relationship between cumulative radon exposure and lung cancer mortality which is jointly modified by temporal and exposure factors.

Lung Cancer and Radon: Pooled Analysis of Uranium Miners Hired in 1960 or Later.

BACKGROUND: Despite reductions in exposure for workers and the general public, radon remains a leading cause of lung cancer. Prior studies of underground miners depended heavily upon information on deaths among miners employed in the early years of mine operations when exposures were high and tended to be poorly estimated. OBJECTIVES: To strengthen the basis for radiation protection, we report on the follow-up of workers employed in the later periods of mine operations for whom we have more accurate exposure information and for whom exposures tended to be accrued at intensities that are more comparable to contemporary settings. METHODS: We conducted a pooled analysis of cohort studies of lung cancer mortality among 57,873 male uranium miners in Canada, Czech Republic, France, Germany, and the United States, who were first employed in 1960 or later (thereby excluding miners employed during the periods of highest exposure and focusing on miners who tend to have higher quality assessments of radon progeny exposures). We derived estimates of excess relative rate per 100 working level months (ERR/100 WLM) for mortality from lung cancer. RESULTS: The analysis included 1.9 million person-years of observation and 1,217 deaths due to lung cancer. The relative rate of lung cancer increased in a linear fashion with cumulative exposure to radon progeny (ERR/100 WLM=1.33; 95% CI: 0.89, 1.88). The association was modified by attained age, age at exposure, and annual exposure rate; for attained ages <55 y, the ERR/100 WLM was 8.38 (95% CI: 3.30, 18.99) among miners who were exposed at ≥35 years of age and at annual exposure rates of <0.5 working levels. This association decreased with older attained ages, younger ages at exposure, and higher exposure rates. DISCUSSION: Estimates of association between radon progeny exposure and lung cancer mortality among relatively contemporary miners are coherent with estimates used to inform current protection guidelines. https://doi.org/10.1289/EHP10669.

Mortality in Underground Miners in a Former Uranium Ore Mine­Results of a Cohort Study Among Former Employees of Wismut AG in Saxony and Thuringia.

BACKGROUND: From 1946 to 1990, more than 400 000 people were employed by Wismut AG, a Soviet/Soviet-German corporation (German abbreviation: SAG/ SDAG), in the East German states of Saxony and Thuringia. In the early years in particular, employees were exposed to large amounts of radon and respirable crystalline silica. METHODS: In a cohort of 35 204 former underground employees of Wismut AG, mortality was analyzed in comparison to the general male population of East Germany, and the pertaining standardized mortality ratios (SMRs) were calculated. RESULTS: 18 510 persons in the study cohort died in the follow-up period 1960-2013. Mortality from lung cancer was 2.36 higher in the study cohort than in the general population (95% confidence interval, [2.28; 2.45]); the associated SMRs rose markedly with increasing radon exposure. Mortality from silicosis and other types of pneumoconiosis was elevated by a factor of 22.62 [21.20; 24.11], and the associated SMRs rose exponentially with increasing exposure to respirable crystalline silica. Mortality from both of these causes was still markedly elevated more than 20 years after Wismut AG had ceased its activities. Mortality from a wide range of other diseases was elevated as well, with the following SMRs: stomach cancer, 1.28 [1.17; 1.40]; liver cancer, 1.34 [1.15; 1.55]; all tumors other than lung cancer, 1.06 [1.02; 1.09]; infections, 1.18 [1.01; 1.38]; cerebrovascular diseases, 1.33 [1.26; 1.41]; and influenza/pneumonia, 1.13 [1.01; 1.27]. Mortality from a small number of other causes was found to be markedly lowered in the study cohort (mental illness, renal diseases, and nervous system diseases). The role of occupational risk factors, lifestyle differences and other reasons for the latter results is unclear. CONCLUSION: Underground miners employed by Wismut AG displayed marked excess mortality due to silicosis/other pneumoconiosis and lung cancer. The contribution of individual occupational risk factors for these and other causes of death with increased SMR are being further investigated in analyses within the study cohort.

PUMA - pooled uranium miners analysis: cohort profile.

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.

Analysis of mortality in a pooled cohort of Canadian and German uranium processing workers with no mining experience.

PURPOSE: Long-term health risks of occupational exposures to uranium processing were examined to better understand potential differences with uranium underground miners and nuclear reactor workers. METHODS: A cohort study of mortality of workers from Port Hope, Canada (1950-1999) and Wismut, Germany (1946-2008) employed in uranium milling, refining, and processing was conducted. Poisson regression was used to evaluate the association between cumulative exposures to radon decay products (RDP) and gamma-rays and causes of death potentially related to uranium processing. RESULTS: The pooled cohort included 7431 workers (270,201 person-years of follow-up). Mean RDP exposures were lower than in miners while gamma-ray doses were higher than in reactor workers. Both exposures were highly correlated (weighted rho = 0.81). Radiation risks of lung cancer and cardiovascular diseases (CVD) in males were increased but not statistically significant and compatible with risks estimated for miners and reactor workers, respectively. Higher RDP-associated CVD risks were observed for exposures 5-14 years prior to diagnosis compared to later exposures and among those employed <5 years. Radiation risks of solid cancers excluding lung cancer were increased, but not statistically significant, both for males and females, while all other causes of death were not associated with exposures. CONCLUSIONS: In the largest study of uranium processing workers to systematically examine radiation risks of multiple outcomes from RDP exposures and gamma-rays, estimated radiation risks were compatible with risks reported for uranium miners and nuclear reactor workers. Continued follow-up and pooling with other cohorts of uranium processing workers are necessary for future comparisons with other workers of the nuclear fuel cycle.

Leukaemia mortality and low-dose ionising radiation in the WISMUT uranium miner cohort (1946-2013).

OBJECTIVES: To examine the risk of death from leukaemia in relation to occupational chronic low-level external and internal radiation exposure in a cohort of 58 972 former German uranium miners with mortality follow-up from 1946 to 2013. METHODS: The red bone marrow (RBM) dose from low-linear energy transfer (LET) (mainly external γ-radiation) and high-LET (mainly radon gas) radiation was estimated based on a job-exposure matrix and biokinetic/dosimetric models. Linear excess relative risks (ERR) and 95% CIs were estimated via Poisson regression for chronic lymphatic leukaemia (CLL) and non-CLL. RESULTS: The mean cumulative low-LET and high-LET RBM doses among the 86% radiation-exposed workers were 48 and 9 mGy, respectively. There was a positive non-significant dose-response for mortality from non-CLL (n=120) in relation to low-LET (ERR/Gy=2.18; 95% CI -0.41 to 6.37) and high-LET radiation (ERR/Gy=16.65; 95% -1.13 to 46.75). A statistically significant excess was found for the subgroup chronic myeloid leukaemia (n=31) in relation to low-LET radiation (ERR/Gy=7.20; 95% CI 0.48 to 24.54) and the subgroup myeloid leukaemia (n=99) (ERR/Gy=26.02; 95% CI 2.55 to 68.99) for high-LET radiation. The ERR/Gy tended to be about five to ten times higher for high-LET versus low-LET radiation; however, the CIs largely overlapped. Results indicate no association of death from CLL (n=70) with either type of radiation. CONCLUSIONS: Our findings indicate an increased risk of death for specific subtypes from non-CLL in relation to chronic low-LET and high-LET radiation, but no such relation for CLL.