Environmental tobacco smoke and lung function in employees who never smoked: the Scottish MONICA study

OBJECTIVES To investigate the relation between lung function in employees and exposure to environmental tobacco smoke (ETS) at work and elsewhere. METHODS Never smokers in employment (301) were identified from the fourth Scottish MONICA survey. They completed a self administered health record, which included details of exposure to ETS, and attended a survey clinic for physical and lung function measurements, and for venepuncture for estimation of serum cotinine. Differences in lung function in groups exposed to ETS were tested by analysis of variance (ANOVA), the exposure-response relation by a linear regression model, and a case-control analysis undertaken with a logistic regression model. RESULTS Both men and women showed effects on forced expiratory volume in the first second (FEV1) and forced vital capacity (FVC) from exposure to ETS—higher exposure going with poorer lung function. This was found at work, and in total exposure estimated from ETS at work, at home, and at other places. Linear regression showed an exposure-response relation, significant for ETS at work, total exposure, and exposure time/day, but not at home or elsewhere. Compared with those not exposed to ETS at work, those who were exposed a lot had a 254 ml (95% confidence interval (95% CI) 84 to 420) reduction in FEV1, and a 273 ml (60 to 480) reduction in FVC after adjusting for confounders. Although lung function was not significantly associated with serum cotinine in all the data, a significant inverse relation between cotinine concentration and FVC occurred in men who had had blood collected in the morning. Case-control analysis also showed a significant exposure-response relation between ETS, mainly at work, and lung function. A higher exposure measured both by self report and serum cotinine went with lower lung function. CONCLUSION The exposure-response relation shows a reduction in pulmonary function of workers associated with passive smoking, mainly at work. These findings endorse current policies of strictly limiting smoking in shared areas, particularly working environments.