Commuters’ air pollution exposure and acute health effects

Abstract

People spend a substantial proportion of their time in traffic. In Europe, the average daily time in traffic is one to one and a half hour. Because of high in-traffic exposures and because most of the journeys are made during rush hours, the one to one and a half hour in traffic contributes disproportionately to total daily exposure to traffic related air pollution. So far a limited number of studies compared particulate matter exposures of different groups of commuters. There is limited evidence of health effects of the typically short but high exposures in traffic. Long-term exposure to traffic-related air pollution as well as short-term (daily) changes in traffic-related pollutants are related to cardiopulmonary mortality and morbidity. The TRAVEL study (Transport Related Air pollution, Variance in commuting, Exposure and Lung function) examined air pollution exposures of different groups of commuters and acute health effects of typical short exposures in traffic. In-traffic exposures of particle number (PN), PM2.5, PM10 and soot were measured in the city of Arnhem during morning rush hour. Exposures were measured in diesel and in electric trolleybuses, in diesel and in petrol cars, and along a high- and low-traffic bicycle route. Exposure levels in diesel buses were 20 to 40% higher than in electric trolley buses, though not for PM10, that mainly derives from other sources than diesel exhaust. Exposure levels between new diesel and new petrol cars did not differ. Cyclists air pollution exposure was 40 and 35% lower on the low-traffic route compared to the high-traffic route for ultrafine particles and soot, respectively, not for PM10 or PM2.5. PM10 and soot exposures of cyclists were lowest, whereas PN exposure in electric buses was lowest. Because of their increased minute ventilation, the inhaled doses of all studied air pollutants were highest for cyclists. Inhaled doses of electric bus passengers were lowest for all studied air pollutants except for PM10. Lung function, airway resistance, exhaled NO (nitric oxide, marker for airway inflammation) were measured and blood samples were taken before and after exposure in the 34 healthy, adult volunteers. Associations were found between in-traffic exposure to PN and soot and changes in lung function, airway resistance and exhaled NO. PN, PM10 and soot were associated with peak expiratory flow directly following but not six hours after exposure. PN and soot were associated with increased exhaled NO after car and bus trips but not after bicycle trips. PN inhaled dose was associated with an increase in airway resistance directly following exposure, but not six hours later. There were no associations between air pollutant exposures and blood inflammation markers. There were inconsistent associations between air pollution exposure and blood cell counts and coagulation markers. The study showed that air pollution exposure is affected by commuting mode, fuel type and route. Two hour exposure in traffic is associated with respiratory health effects, but no associations were found between exposure and blood markers of inflammation and coagulation and blood cell counts within hours following exposure.