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

Abstract

The possible confounding effect of smoking on radon-associated risk for lung cancer mortality was investigated in a case-control study nested in the cohort of German uranium miners. The study included 704 miners who died of lung cancer and 1,398 controls matched individually for birth year and attained age. Smoking status was reconstructed from questionnaires and records from the mining company's health archives for 421 cases and 620 controls. Data on radon exposure were taken from a job-exposure matrix. Smoking adjusted odds ratios for lung cancer in relation to cumulative radon exposure have been calculated with conditional logistic regression. The increase in risk per Working Level Month (WLM) was assessed with a linear excess relative risk (ERR) model taking smoking into account as a multiplicative factor. In addition, the potential impact of temporal factors on the ERR per WLM was examined. Lung cancer mortality risk increased with increasing radon exposure, yielding a crude ERR per WLM of 0.25% (95% CI: 0.13-0.46%). Adjustment for smoking led only to marginal changes of the radon-associated lung cancer risks. The adjusted ERR per WLM was very similar (0.23%, 95%-CI: 0.11-0.46%) to the crude risk and to the risk found in the Wismut cohort study. This stability of the radon-related lung cancer risks with and without adjustment for smoking suggests that smoking does not act as a major confounder in this study and presumably also not in the cohort study.

Silica dust, radon and death from non-malignant respiratory diseases in German uranium miners

“…Unfortunately, only very limited and incomplete data on smoking exist in the full cohort that could not be used. In a nested case-control study on lung cancer,33 it was shown that most Wismut miners were smokers and adjustment for smoking only marginally reduced the radon-related lung cancer risk. Smoking was broadly categorised into non-smokers defined as lifetime non-smokers or ex-smokers since 20 years or smokers.…”

Occupational dust and radiation exposure and mortality from stomach cancer among German uranium miners, 1946–2003

“…This high-socioeconomic homogeneity of the cohort should limit potential confounding associated with lifestyle factors. Furthermore, in a nested case–control study on lung cancer among Wismut miners, it could be demonstrated that nearly all miners were smokers and that the correlation with radon exposure was low 46. Another limitation is the potential misclassification of death certificates, missing information on subtypes and cancer incidence data.…”

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

“…Individual data on smoking are only available for 38% of the cohort members. A case-control study on lung cancer nested in the WISMUT cohort exhibited no indication of major confounding by smoking on the radon-related lung cancer risk 41. Given that smoking is a much stronger risk factor for lung cancer than leukaemia, it is unlikely that smoking is confounding the radiation-related leukaemia risk.…”