LUNG-CANCER AND EXPOSURE TO TOBACCO-SMOKE IN THE HOUSEHOLD

The relation between passive smoking and lung cancer is of great public health importance. Some previous studies have suggested that exposure to environmental tobacco smoke in the household can cause lung cancer, but others have found no effect. Smoking by the spouse has been the most commonly used measure of this exposure. In order to determine whether lung cancer is associated with exposure to tobacco smoke within the household, we conducted a population-based case–control study of 191 patients with histologically confirmed primary lung cancer who had never smoked and an equal number of persons without lung cancer who had never smoked. Lifetime residential histories including information on exposure to environmental tobacco smoke were compiled and analyzed. Exposure was measured in terms of “smoker-years,” determined by multiplying the number of years in each residence by the number of smokers in the household. Household exposure to 25 or more smoker-years during childhood and adolescence doubled the risk of lung cancer (odds ratio, 2.07; 95 percent confidence interval, 1.16 to 3.68). Approximately 15 percent of the control subjects who had never smoked reported this level of exposure. Household exposure of less than 25 smoker-years during childhood and adolescence did not increase the risk of lung cancer. Exposure to a spouse's smoking, which constituted less than one third of total household exposure on average, was not associated with an increase in risk. The possibility of recall bias and other methodologic problems may influence the results of case–control studies of environmental tobacco smoke. Nonetheless, our findings regarding exposure during early life suggest that approximately 17 percent of lung cancers among nonsmokers can be attributed to high levels of exposure to cigarette smoke during childhood and adolescence. (N Engl J Med 1990; 323:632–6.) THE 1972 Surgeon General's report dealt with the health consequences of passive smoking or environmental tobacco smoke for the first time.1 In 1986 the entire report was devoted to the issue; it concluded that “involuntary smoking is a cause of disease including lung cancer in healthy non-smokers.”2 More than a dozen epidemiologic studies have assessed the relation between passive smoking and lung cancer.3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 The findings have ranged from no detectable increase in risk10,17 to a moderate (about twofold), statistically significant increase.4 5 6 7 Most studies have found only small elevations in risk, which are frequently not statistically significant.3,8,9 In a meta-analysis of. © 1990, Massachusetts Medical Society. All rights reserved.