Abstract

The Wismut cohort includes 58,982 male workers, first employed between 1946 and 1989 at the Wismut uranium mining company in Germany. The cohort is characterised by a long average duration of follow-up (37 years), large number of deaths (25,438) and nearly complete follow-up (97%) by end of 2008. Annual exposures to radon progeny, external gamma radiation and long-lived radionuclides were retrospectively assessed using a comprehensive job-exposure matrix. Data on occupational exposure to silica, fine and arsenic dust are available for all cohort members, and for part of them on smoking.

The range of cumulative radon exposure in Working Level Months (WLM) is broad (Median = 33, Mean = 280, Max = 3,224 WLM). Mortality from lung cancer was statistically significantly associated with radon (n = 3,500; ERR/100 WLM = 0.20), with risk effect modification by time since exposure, age at exposure and exposure rate. The group of deaths from cancers other than lung cancer showed a lower, but also significantly elevated risk (n = 3,887; ERR/100 WLM = 0.014). Notable was the excess for the group of cancers of the extra-thoracic airways (n = 234; ERR/100 WLM = 0.04, p = 0.12). In the sub-cohort of miners hired after 1959, which is characterised by very low exposure rates, a statistically significant excess of lung cancer in relation to radon was found (n = 334; ERR/100 WLM = 1.3). A similar pattern of risk was observed in the sub-cohort of low exposed millers, who never worked underground (n = 159; ERR/100 WLM = 3.4).

Recently, the follow-up has been extended by five years to end of 2013, including now 29,751 deaths. In addition, a linkage of the cohort with the East Germany cancer registry (1960–2013) is prepared. Future focus of the Wismut study and within the international pooling activities is to investigate in more detail the radon-related risk for cancer sites other than lung cancer and the risk of lung cancer at low radon exposures or exposure rates.