Tobacco Documents Online

22-P.}OV-1993 1 3:22 FROM TO 0!0i~^'-.1'2`30r~3 T -' P.OMi00 available classify never-smoking women as'exposed* or'unezposed' to ETS based on self- or proxy-reported smoking in the subject's environment, usually according to whether or not a woman is married to a smoker. In addition, 17 studies provide sufficient information for highest exposure group and exposure-responst: analyses. Other analyses of the data include adjusting for the potential upward bias of smoker misclssif'sc«.tion (S~c:io3 S..2); examining confounders, effect modifiers, and sources of potzntial biu (Stction 5.4); attid pooling aualitatively higher ranked studies (Section 5.5). It is hoped that by analy.zittg the data in several different ways, a clear picture will emerge (Sectioti 5.6). Throughout this chapter, one-tailed tests of sigcifi;,ance (p • 0.05) are used, which increases the statisticai ability (power) to detect an effect. The 90% confidence intervals used for the analyses performed are consistent with the use of the one-tailed test. The justification for this usage is based on the a priori hypothesis (from the plausibility of a lung cancer effect documented in Chapters 3 and 4) that a positive association exists between exposure to ETS and lung cancer. Epidemiologic evidence of an association between passive smoking and lung cancer first appeared 10 years ago in a prospective cohort study in Japan (Hirayatna, 1981a) and a case-control study in Greece (Trichopoulos et at., 1983). Both studies concluded that the lung cancer incidence and mortality in nonsmoking women was higher for women married to smokers than for those married to nonsmokers. Although there are other sources of exposure to ETS, particularly outside the home, the assumption is that women married to smokers are exposed to more tobacco smoke, on average, than women married to nonsmokers. These two studies, particularly the cohort study from Japan, evoked considerable critical response. ihLy also aroused the interest of public health epidemiologists, who initiated additiona( studies. At the request of two Federal agencies--the U.S. Environmental Protection Agency (Office of Air and Radiation) and the U.S. Department of Health and Human Services (Office of Smoking and Health)--the National Research Council (NRC) formed a committee on passive smoking to evaluate the methods for assessing exposure to ETS and to review the literature on the health consequences. The committee's report (NRC, 1986) addresses the issue of lung cancer risk in considerable detail and includes summary analyses of the evidence from 30 ease-control and 3 cohort (prospective) studies. It concludes,'Considering the evidence as a whole, exposure to ETS increases the incidence of lung cancer in nonsmokers.' . The NRC committee was particularly concerned about the potential bias in the study results caused by the fact that current and former smokers may have incorrectly reported themselves as lifelong nonsmokers (never-smokers). Using reasonable assumptions for misreported smoking habits, the committee determined that a plausible range for the true relative 5-2