Radon and risk of extrapulmonary cancers: results of the German uranium miners' cohort study, 1960–2003

Abstract

Data from the German miners' cohort study were analysed to investigate whether radon in ambient air causes cancers other than lung cancer. The cohort includes 58 987 men who were employed for at least 6 months from 1946 to 1989 at the former Wismut uranium mining company in Eastern Germany. A total of 20 684 deaths were observed in the follow-up period from 1960 to 2003. The death rates for 24 individual cancer sites were compared with the age and calendar year-specific national death rates. Internal Poisson regression was used to estimate the excess relative risk (ERR) per unit of cumulative exposure to radon in working level months (WLM). The number of deaths observed (O) for extrapulmonary cancers combined was close to that expected (E) from national rates (n=3340, O/E=1.02; 95% confidence interval (CI): 0.98–1.05). Statistically significant increases in mortality were recorded for cancers of the stomach (O/E=1.15; 95% CI: 1.06–1.25) and liver (O/E=1.26; 95% CI: 1.07–1.48), whereas significant decreases were found for cancers of the tongue, mouth, salivary gland and pharynx combined (O/E=0.80; 95% CI: 0.65–0.97) and those of the bladder (O/E=0.82; 95% CI: 0.70–0.95). A statistically significant relationship with cumulative radon exposure was observed for all extrapulmonary cancers (ERR/WLM=0.014%; 95% CI: 0.006–0.023%). Most sites showed positive exposure–response relationships, but these were insignificant or became insignificant after adjustment for potential confounders such as arsenic or dust exposure. The present data provide some evidence of increased risk of extrapulmonary cancers associated with radon, but chance and confounding cannot be ruled out.

Radon exposure and oropharyngeal cancer risk

“…Nevertheless, not all of them have a really significant number of oral/pharyngeal cancer cases. The studies with the highest sample size are the American Cancer Society study with 1.2 million people, and the German cohort of uranium miners which included a sample of 58,987 miners [18,20,23,26]. The sample size of the remaining studies ranged between 1294 subjects in the Swedish iron miner cohort [16] and 5098 subjects in the French uranium miner cohort [25].…”

“…From this year onwards data were obtained weekly and monthly, respectively, and from 1983 until the end of the study the incorporation of α dosimeters made possible individualised measurements for each worker. In the German uranium miner cohort [18,20,23,26] the measurement data were obtained with a mathematical estimation using a job exposure matrix, taking into account annual data from location and type of work from 1955. In the Canadian fluorspar miners cohort [15] that started in 1933, the measurement was individualised for each worker depending on their working place with daily data from 1968.…”

“…In the French cohort [25], there were 33 cases in 5098 subjects studied between 1946 and 1999, with an O/E = 0.91. The German cohort [18] observed 99 cases in a sample of 58,987 miners, with an O/E = 0.80 after a follow-up from 1946 to 1989. In this last case, increasing the sample size did not show a significant difference in the SMR dates obtained.…”

Accounting for Smoking in the Radon-Related Lung Cancer Risk Among German Uranium Miners: Results of a Nested Case-Control Study

“…These categories of WLM agree with those chosen for the analyses of the cohort (Kreuzer et al , 2008. For all ORs, 95% confidence intervals (CIs) were computed.…”

“…Recently, first results from the currently largest single cohort study on underground miners -the Wismut cohort including about 59,000 German uranium miners -have been published Kreuzer et al 2006Kreuzer et al , 2008Kreuzer et al , 2009). In accordance with results from other miners studies, a statistically significant linear increase in risk for lung cancer mortality with increasing cumulative exposure to radon progeny has been found in the Wismut cohort .…”