Lung function and exposure to workplace second-hand smoke during exemptions from smoking ban legislation: an exposure-response relationship based on indoor PM2.5 and urinary cotinine levels

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 (PM(2.5)) 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 (FEV(1) in litres), forced vital capacity (FVC in litres) and forced expiratory flow as 25-75% of FVC (FEF(25-75) in l/s) were recorded.

Results: Indoor fine particulate (PM(2.5)) concentrations were 4.4 times as high in smoking premises (267.9 μg/m(3)) than in non-smoking premises (60.3 μg/m(3)) and were strongly associated with the probability of permitted smoking (R(2)=0.99). Smoking was the dominant source of particulates (R(2)=0.66). Compared with workers exposed to the lowest indoor PM(2.5) stratum (<25 μg/m(3)), lung function was lower in the three higher PM(2.5) strata (25-75, 75-175, >175 μg/m(3)) with FEV(1) -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); FEF(25-75) -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 FEV(1)/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 PM(2.5) but negatively with lung function. Consistently lower values for lung function per unit increase of indoor PM(2.5) 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.