Respiratory health of bus drivers in Hong Kong

Objective: We conducted a cross-sectional study to evaluate the lung function and respiratory symptoms of Hong Kong bus and tram drivers exposed to air pollutants. Methods: Demographic information, vital signs, pulmonary function, respiratory symptoms and blood lead levels in 358 male drivers of air-conditioned buses (ACB) were compared with 129 male drivers of non-air-conditioned buses and trams (NACB). Particulate matter (PM₁₀), carbon dioxide (CO₂) and carbon monoxide (CO) levels were measured in 16 air-conditioned and 15 non-air-conditioned trams along the same route. Results: Forced vital capacity, forced expiratory volume in 1 s and maximal voluntary ventilation were lower but blood lead levels were higher in the NACB drivers compared with ACB drivers. More NACB drivers compared to ACB drivers reported frequent productive cough, dry cough, as well as sore throat. The measured lung function parameters in the NACB drivers were lower than a cohort of personnel working in an academic environment. The work-year duration was longer and scheduled days off per month were shorter for NACB (13.4±8.8 years and 4.3±1.3 days) compared to ACB drivers (11.5±9 years and 5.4±0.8 days), respectively (P<0.001). The PM₁₀ and CO₂ levels were higher in ACB (265±83 μg/m³ and 2,114±69.6 ppm) compared to non-air-conditioned trams (161±103 μg/m³ and 500 ppm, respectively) (P<0.005). Conclusion: We hypothesise that prolonged exposure to air pollutants adversely affects lung function in our NACB drivers but air recirculation could result in higher blood lead levels in ACB drivers.