ENVIRONMENTAL TOBACCO-SMOKE AND LUNG-CANCER MORTALITY IN THE AMERICAN-CANCER-SOCIETY CANCER PREVENTION STUDY-II

Environmental tobacco smoke (ETS) has been classified as a human lung carcinogen by the United States Environmental Protection Agency (EPA), based both on the chemical similarity of sidestream and mainstream sm oke and on slightly higher lung cancer risk in never-smokers whose spo uses smoke compared with those married to nonsmokers. We evaluated the relation between ETS and lung cancer prospectively in the US, among 1 14,286 female and 19,549 male never-smokers, married to smokers, compa red with about 77,000 female and 77,000 male never-smokers whose spous es did not smoke. Multivariate analyses, based on 247 lung cancer deat hs, controlled for age, race, diet, and occupation. Dose-response anal yses were restricted to 92,222 women whose husbands provided complete information on cigarette smoking and date of marriage. Lung cancer dea th rates, adjusted for other factors, were 20 percent higher among wom en whose husbands ever smoked during the current marriage than among t hose married to never-smokers (relative risk [RR] = 1.2, 95 percent co nfidence interval [CI] = 0.8-1.6). For never-smoking men whose wives s moked, the RR was 1.1 (CI = 0.6-1.8). Risk among women was similar or higher when the husband continued to smoke (RR = 1.2, CI = 0.8-1.8), o r smoked 40 or more cigarettes per day (RR = 1.9, CI = 1.0-3.6), but d id not increase with years of marriage to a smoker. Most CIs included the null. Although generally not statistically significant, these resu lts agree with the EPA summary estimate that spousal smoking increases lung cancer risk by about 20 percent in never-smoking women. Even lar ge prospective studies have limited statistical power to measure preci sely the risk from ETS.