No short-term respiratory effects among particle-exposed employees in the Stockholm subway

Exposure to traffic-related air pollution is associated with adverse respiratory effects, but it is not known whether the high exposure to particles prevailing in the subway system may affect the respiratory system. We investigated airway inflammation and lung function among particle-exposed subway employees.

We studied 81 workers. All participants were non-smokers, aged 25-50 years. Three exposure groups were formed according to particulate matter (PM) levels obtained during an occupational hygienic investigation: 30 platform workers [average PM(2.5) 63 µg/m(3) and DataRAM (MIE Inc, Billerica, Waltham, MA, USA) 182 µg/m(3)], 30 subway drivers (19 µg/m(3) and 33 µg/m(3)), and 21 ticket sellers (10 µg/m(3) and 13 µg/m(3)). We measured the fractional exhaled nitric oxide (FENO) of all workers before and after a workday. We also measured the peak expiratory flow (PEF) and forced expiratory volume in one second (FEV(1)) of platform workers and ticket sellers five times a day over two weeks. We calculated the arithmetic means of PEF and FEV(1) during exposed and unexposed time for every individual.

There was no significant increase in FENO after work among platform workers, subway drivers or ticket sellers (the means of percentual individual change were -7%, +2% and -4% respectively). The averages of the ratios (exposed to unexposed time) of PEF and FEV(1) were above 1.0 for both ticket sellers (1.016 and 1.002 respectively) and platform workers (1.022 and 1.005).

Our observations do not indicate any short-term respiratory effects of particle exposure in the subway among the employees, with respect to airway inflammation or lung function.