Estimating lung cancer risk with exposure to environmental tobacco smoke

Estimates of lung cancer in nonsmokers due to exposure to environmental tob acco smoke (ETS) in the workplace or in the home may be developed in severa l ways. Estimates may be based on a) models developed using the full range of data in smokers; b) models developed using data restricted to smokers wi th a low smoking rate, for example, less than or equal to 10 cigarettes per day: c) models developed using data from studies of residential exposure t o ETS of nonsmokers, with exposures based on smoking rates of spouses; and d) models using data from studies of occupational exposure to ETS of nonsmo kers. Methods a and b require an estimate of cigarette equivalent exposure for ETS as well as assumptions on the cigarette equivalent dose to target c ells from ETS and on the comparability of lung cancer risk per unit dose fr om smokers and nonsmokers. Summary relative risks (RRs) and 95% confidence intervals (CI) from ETS studies of nonsmokers with exposures based on smoki ng patterns of spouses are 1.24 (1.1, 1.4) for females and 1.34 (1.0, 1.8) for males, whereas the RR estimate for occupational ETS exposure and its 95 % CI is 1.39 (1.2, 1.7). Using RR estimates for ETS exposure, cigarette equ ivalents for ETS range from 0.1 to 1.0, based on a range of descriptive and biologically motivated models in active smokers; a cigarette equivalent is 0.2 based on a comparison of log-linear trends in RR with number of cigare ttes smoked per day in active smokers and in spouses of nonsmokers.