Objectives: The causes of lung cancer among nonsmokers are not clearly understood. To further evaluate the relation between passive smoke exposure and lung cancer in nonsmoking women, we conducted a population-based, case-control study.
Methods: Case patients (n = 618), identified through the Missouri Cancer Registry for the period 1986 through 1991, included 432 lifetime nonsmokers and 186 ex-smokers who had stopped at least 15 years before diagnosis or who had smoked for less than 1 pack-year. Control subjects (n = 1402) were selected from driver's license and Medicare files.
Results: No increased risk of lung cancer was associated with childhood passive smoke exposure. Adulthood analyses showed an increased lung cancer risk for lifetime nonsmokers with exposure of more than 40 pack-years from all household members (odds ratio [OR] = 1.3; 95% confidence interval [CI] = 1.0, 1.8) or from spouses only (OR = 1.3; 95% CI = 1.0, 1.7). When the time-weighted product of pack-years and average hours exposed per day was considered, a 30% excess risk was shown at the highest quartile of exposure among lifetime nonsmokers.
Conclusions: Ours and other recent studies suggest a small but consistent increased risk of lung cancer from passive smoking. Comprehensive actions to limit smoking in public places and worksites are well-advised.