A case-control study of lung cancer and environmental tobacco smoke among nonsmoking women living in Shanghai, China

Introduction: The incidence of lung cancer in women living in China is among the highest in the world but it does not appear that tobacco smoking is a major risk factor for lung cancer. As tobacco smoking is highly prevalent in Chinese men, exposure to environmental tobacco smoke (ETS) may play an important role in the development of lung cancer in Chinese women who never smoked. We conducted the present investigation because previous studies did not account for dietary habits or indoor air pollution from Chinese-style cooking and they did not assess the effect of occupational exposure to ETS. Methods: A population-based, case-control study was conducted to evaluate the relationship between lung cancer and exposure to ETS among nonsmoking women living in Shanghai, China. Five-hundred and four women diagnosed with incident, primary lung cancer between February 1992 and January 1994 were identified through the population-based Shanghai Cancer Registry. A control group of 601 nonsmoking women was selected randomly from the Shanghai Residential Registry, and was approximately frequency-matched to the age distribution of the lung cancer cases. Information on lifetime domestic and occupational exposure to ETS was obtained through face-to-face interviews. Adjusted odds ratios (OR) and 95% confidence intervals (CI) were estimated by unconditional logistic regression. Results: The OR for ever exposed to ETS from spouses was 1.1 (95% CI: 0.8-1.5), and the OR for ever exposed to ETS at work was 1.7 (95% CI: 1.3-2.3). Furthermore, the OR increased with increasing number of hours of daily exposure to ETS in the workplace and with increasing number of smoking co-workers. No associations were found for exposure to ETS during childhood. Conclusions: The main findings of the present study are that long-term occupational exposure to ETS, both alone or in combination with exposures at home, conferred an increased risk of lung cancer among women who never smoked. The inconsistency of the results regarding exposure to ETS at home and at work may have been due to lower exposures at home.