Lifetime environmental exposure to tobacco smoke and primary lung cancer of non-smoking Taiwanese women

Background For a female population with a high lung cancer mortality rate, such as Taiwanese women, who smoke relatively rarely, but live in an enviro nment with high male smoking prevalence, the risk and population burden of lung cancer due to environmental tobacco smoke (ETS) are relatively importa nt. Methods An age-matched case-control study was designed to investigate the e ffects of cumulative environmental exposure to tobacco smoke during childho od and adult life on lung cancer risk among non-smoking women in Taiwan. In formation on passive smoking from all possible sources and life periods wer e obtained from interviews with 268 and 445 lifetime non-smoking cases and controls. Conditional logistic regression and synergism 'S' index were appl ied to the data to assess the independent and joint effects of passive smok ing in different life stages while controlling for possible confounding var iables. Results Risks of contracting lung cancer among women near-distantly exposed to the highest level of ETS in childhood (>20 smoker-years) and in adult l ife (>40 smoker-years) were 1.8-fold (95% CI: 1.2-2.9) and 2.2-fold (95% CI : 1.4-3.7) higher than that among women being never exposed to ETS, and the two variables accounted for about 37% of tumours in this non-smoking femal e population. Children were found to be more susceptible to ETS than adults and such early exposure was found to modify the effect of subsequent tobac co smoke exposure in adult life based on an additive interaction model. Conclusions Environmental tobacco smoke exposure occurring in childhood pot entiates the effect of high doses of exposure in adult life in determining the development of lung cancer. Smoking prohibition would be expected to pr otect about 37% of non-smoking Taiwanese women against lung cancer.