Personal exposure to environmental tobacco smoke: salivary cotinine, airborne nicotine, and nonsmoker misclassification

A Large study was conducted to assess exposure to environmental tobacco smo ke (ETS) in a geographically dispersed study population using personal brea thing zone air sampling and salivary cotinine levels. Approximately 100 sel f-reported nonsmoking subjects in each of 16 metropolitan areas were recrui ted for this investigation. Cumulative distributions of salivary cotinine l evels for subjects in smoking and nonsmoking homes and workplaces exhibited a general trend of decreasing salivary cotinine levels with decreasing tim e spent in smoking environments. Median salivary cotinine levels for the fo ur experimental cells in the study (product of smoking and nonsmoking home and workplaces) were comparable to those reported for a large national stud y of serum levels of cotinine (Third National Health and Nutrition Examinat ion Survey, NHANES III), when the latter was corrected for expected differe nces between serum and saliva concentrations. However, the most highly expo sed group in this study had a median salivary cotinine concentration approx imately a factor of 2 greater than that of the comparable group in the NHAN ES III study. Misclassification rates, both simple (for self-reported nonsm okers) and complex (self-reported Lifetime never smokers), were near the me dian of those reported for other studies. Estimated misclassification rates for self-reported lifetime never-smoking females are sufficiently high (2. 95% using a discrimination revel of 106 ng/ml) that, if used in the Environ mental Protection Agency (EPA) risk assessment related to ETS and lung canc er, would place the lower 90% confidence interval (CI) for relative risk at nearly 1.00, i.e., no statistically significant increased risk. For the 26 3 most highly exposed subjects in the study whose self-reported nonsmoking status was accurate, the correlation between airborne exposure to nicotine and average salivary cotinine is so small, on an individual basis, that it makes the relationship useless for estimating exposure on a quantitative ba sis. When subjects are grouped according to likely categories of nicotine e xposure, correlation between group median airborne nicotine exposure and sa livary cotinine level increases dramatically. The comparison improves for t he most highly exposed subjects, suggesting that such quantitative comparis ons are useful for only those subjects who are exposed to the higher levels of ETS. However, airborne nicotine exposure for most of the subjects does not account for estimated systemic levels of nicotine, based on salivary co tinine levels.