Environmental tobacco smoke and lung cancer risk in nonsmoking women.

BACKGROUND: Exposure to environmental tobacco smoke (passive smoking) has been suggested to be a cause of lung cancer, although early epidemiologic studies have produced inconsistent results. PURPOSE: We conducted an epidemiologic case-control study to assess the relationship between exposure to environmental tobacco smoke and lung cancer risk among women who have never smoked (i.e., having smoked for a total of less than 6 months or having smoked less than 100 cigarettes in their lifetimes). METHODS: Case patients (n = 210) were women with histologically confirmed primary carcinomas of the lung who were lifetime nonsmokers. They were identified through hospital tumor registries and the Florida Cancer Data System of the Statewide Cancer Registry. Community-based control women (n = 301) were also lifetime nonsmokers and were identified through random-digit dialing. Details on childhood and adulthood exposures to environmental tobacco smoke were ascertained through interviews with the study participants themselves or with surrogate respondents. Risks were calculated in terms of smoke-years, defined as the sum of the reported years of exposure to cigarette smoke from each smoker in the household. RESULTS: The risk of lung cancer more than doubled for women who reported 40 or more smoke-years of household exposure during adulthood (odds ratio [OR] = 2.4; 95% confidence interval [CI] = 1.1-5.3) or 22 or more smoke-years of exposure during childhood and adolescence (OR = 2.4; 95% CI = 1.1-5.4). Risks were highest for non-adenocarcinoma lung cancers, although modest elevations in risk were also observed for adenocarcinomas. When a surrogate respondent other than the patient's husband provided information on exposure, the risk estimates were considerably lower. CONCLUSION: These findings suggest that long-term exposure to environmental tobacco smoke increases the risk of lung cancer in women who have never smoked.