Environmental tobacco smoke exposure and pulmonary function among adults in NHANES III: Impact on the general population and adults with current asthma

The impact of environmental tobacco smoke (ETS) exposure on adult pulmonary function has not been clearly determined. Because adults with asthma have chronic airway inflammation, they may be a particularly susceptible group. Using data from the Third National Health and Nutrition Examination Survey (NHANES III), I examined the cross-sectional relationship between serum cotinine, a biomarker of ETS exposure, and pulmonary function among 10,581 adult nonsmokers and 440 nonsmoking adults with asthma whose cotinine and spirometry data were available. I generated residuals, which are observed minus predicted values (based on Crapo equations), for forced expiratory volume in 1 sec (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio to adjust for age, sex, and height. In addition, I used multivariate linear regression to control for sociodemographic characteristics and previous smoking history. Most adults with and without asthma had detectable serum cotinine levels, indicating recent ETS exposure (85.7% and 83.4%, respectively). Among nonsmoking male participants, I found no evidence that ETS exposure was related to decreased pulmonary function. In the nonsmoking female stratum, the highest cotinine tertile was associated with a lower FEV1 [-100 mL; 95% confidence interval (CI), -143 to -56 mL], FVC (-119 mL; 95% CI, -168 to -69 mL), and FEV1/FVC ratio (-1.77%; 95% CI, -2.18% to -1.36%). Among women with asthma, the highest cotinine tertile was also associated with decreased FEV1 (-261 mL; 95% CI, -492 to -30 mL), FVC (-291 mL; 95% CI, -601 to 20 mL), and FEV1/FVC ratio (-1.6%; 95% CI, -3.3% to 0.19%). In conclusion, ETS exposure is associated with decreased pulmonary function in adult females, especially those with asthma. This analysis should provide further impetus for public policies that promote smoke-free environments.