Daily exposure to environmental tobacco smoke: smokers vs nonsmokers in California.

OBJECTIVES: This study examined the differences in environmental tobacco smoke exposure between smokers and non-smokers. METHODS: A probability sample of 1579 California adults completed a 1-day time diary of a full day's activities in which they reported whether any smoker was present during each activity. RESULTS: Some 61% of respondents reported at least some environmental tobacco smoke exposure in these diary accounts (for an average of up to 5 hours per day), and potential exposure rose monotonically with number of cigarettes actively smoked. Heaviest smokers reported about four times as much such exposure as nonsmokers. CONCLUSIONS: Because smokers lead life-styles that expose them to far higher levels of environmental tobacco smoke exposure, that factor needs to be controlled in studies estimating the effects of active smoking.