Exposure misclassification bias in studies of environmental tobacco smoke and lung cancer.

It is now recognized that exposure to environmental tobacco smoke (ETS) in the workplace and other settings outside the home may be equally as important as residential ETS exposure. This review examines the sources of misclassification in the assessment of workplace ETS exposure in questionnaire-based epidemiologic studies. Cogent to this discussion is the role of misclassification of ever smokers as never smokers, which is important in studies of both workplace and residential ETS exposure and lung cancer and is discussed first. The collective evidence from studies that have used direct or indirect approaches to estimate smoker misclassification shows that although some misclassification of ever smokers as never smokers exists in studies of ETS and lung cancer, the potential bias from the misclassification of smokers is unlikely to explain the observed increased risk of lung cancer associated with ETS exposure.