| Abstract
| - Background. The effects of workplace second-hand smoke (SHS) on lung function remain uncertain because of a lack of objective measures for SHS exposures. Objective. To determine whether an exposure-response association exists between lung function and two different markers of SHS based on indoor fine particulate (PM2.5) and urinary cotinine levels in non-smoking catering workers. Design. A cross-sectional study during a 1.5-year exemption of licensed catering premises from smoke-free legislation. Participants. 186 non-smoking catering workers aged 18-65 years in Hong Kong were recruited. A declared non-smoking status was accepted in workers with exhaled breath carbon monoxide levels <6 ppm and urinary cotinine levels <100 ng/ml. Main outcome measures. Lung function measures of forced expiratory volume in 1s (FEV1 in litres), forced vital capacity (FVC in litres) and forced expiratory flow as 25-75% of FVC (FEF25-75 in l/s) were recorded. Results. Indoor fine particulate (PM2.5) concentrations were 4.4 times as high in smoking premises (267.9 μg/m3) than in non-smoking premises (60.3 μg/m3) and were strongly associated with the probability of permitted smoking (R2=0.99). Smoking was the dominant source of particulates (R2=0.66). Compared with workers exposed to the lowest indoor PM2.5 stratum (<25 μg/m3), lung function was lower in the three higher PM2.5 strata (25-75, 75-175, >175 μg/m3) with FEV1 −0.072 (95% CI −0.123 to −0.021), −0.078 (95% CI -0.132 to −0.024), −0.101 (95% CI −0.187 to −0.014); FEF25-75 −0.368 (95% CI −0.660 to −0.077), −0.489 (95% CI −0.799 to −0.179), −0.597 (95% CI −0.943 to −0.251); and FEV1/FVC (%) −2.9 (95% CI −4.8 to −1.0), −3.2 (95% CI −5.1 to −1.4) and −4.4 (95% CI −7.4 to −1.3), respectively. Urinary cotinine was associated positively with indoor PM2.5 but negatively with lung function. Consistently lower values for lung function per unit increase of indoor PM2.5 were found. Conclusion. Lung function is inversely associated with workplace SHS. Workplace exemptions and delays in implementing smoke-free policies and current moves to relax legislation are a major threat to the health of workers.
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