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A CASE-CONTROLLED STUDY OF CHILDHOOD AND ADOLESCENT HOUSEHOLD PASSIVE SMOKING (PS) AND THE RISK OF FEMALE LUNG CANCER Wang, Fu L.; Love, Edgar J. (University of Calgary, Calgary, Canada) and Dai, Xu D. Heilongjiang Inst. for Cancer Res., Harbin, China SUIOUIRY Background: Exposure to environmental tobacco smoke, i.e., passive smoking (PS), has been a public health concern. Such exposure has been related to many kinds of illness, such as cancer (especially lung cancer), cardiovascular disease, respiratory system symptoms, etc. However, how to measure this exposure and its effects on health remains a key issue. Most previous studies estimated PS from only the husband or the spouse, which is far from accurate. More importantly, the effects of early life exposure to tobacco smoke on health during adulthood have not received much attention. Only a few studies have noted the importance of exposure to tobacco smoke in early life with relation to cancer risk in adulthood, while one study did not find any association for nonsmoking women exposed to tobacco smoke during childhood. Methods: This study, using household exposure to tobacco smoke as an estimate of PS, was done to evaluate the risk of female lung cancer from PS, especially that during childhood and adolescence. This was a 1:1 paired case-control study conducted in Harbin, China during 1985-87. We face-to-face interviewed 114 female primary lung cancer cases, aged 30 to 69 years, and their hospital-based

controls, using a pre-set questionnaire. The controls were non- cancer patients, selected from the same hospital as the cases, and matched on age (± 5 years), residential area and lifetime smoking status. There were 59.pairs who ever smoked and 55 pairs who never smoked. Information on PS was collected by residence for each of the following five periods: 0-6, 7-14, 15-22, 23-30 and 31-69 years. Results: It was suggested that the risk of female lung cancer in relation to PS varied by exposure period and by sources of sidestream smoke. During childhood (age 0-14 years), although he sidestream exposure was mainly from parents, the percentage from mothers for the cases (38.5%) was higher than that for the controls (26.4%). For the older group, husbands became the major source of sidestream smoke, accounting for more than two-thirds for both the cases and controls. Further analyses show that, under the age of 14 years, the risk of lung cancer was significantly increased for household exposure to maternal smoking (odds ratio, OR=2.70, 95% CI=1.49-4.88), but not for exposure to paternal smoking (OR=1.40, 95% CI= 0.79-2.50). The risk was the highest in those who were exposed under the age of seven (OR=3.46, 95% CI=1.80-6.65) although the risk was also significant at ages 7-14 (OR=3.08, 95% CI=1.62- 5.57) and 15-22 (OR=3.10, 95% CI=1.52-6.31). Under the age of 23 years, the OR increased with amount of passive smoking (P<0.001). No significant differences were found between the cases and - 2 -

controls in the percentage of the exposure at ages 23-30 and 31-69 years. When stratified by smoking status, the risk was significantly increased for those exposed at ages 22 or younger, who have ever smoked; the risk also increased for those non-smoking pairs when exposed under the age of 15 years. It is important to note that the OR in all five exposure periods for non-smoking pairs were similar to those for all 114 pairs studied. Conclusions: The findings of this study suggest that (1) household passive smoking, particularly that during childhood, increases the risk of female lung cancer, and (2) the effects of PS on lung cancer, and possibly on other health conditions, should be assessed by different periods of exposure.