Respiratory health effects of ultrafine and fine particle exposure in cyclists

Objectives Monitoring studies have shown that commuters are exposed to high air pollution concentrations, but there is limited evidence of associated health effects. We carried out a study to investigate the acute respiratory health effects of air pollution related to commuting by bicycle. Methods Twelve healthy adults cycled a low-and a high-traffic intensity route during morning rush hour in Utrecht, The Netherlands. Exposure to traffic-related air pollution was characterised by measurements of PM10, soot and particle number. Before, directly after and 6 h after cycling we measured lung function (FEV1, FVC, PEF), exhaled NO (FENO and respiratory symptoms. The association between post-minus pre-exposure difference in health effects and exposure during cycling was evaluated with linear regression models. Results The average particle number concentration was 59% higher, while the average soot concentration was 39% higher on the high-traffic route than on the low-traffic route. There was no difference for PM10. Contrary to our hypothesis, associations between air pollution during cycling and lung function changes immediately after cycling were mostly positive. Six hours after cycling, associations between air pollution exposure and health were mostly negative for lung function changes and positive for changes in exhaled NO, although nonsignificant. Conclusions We found substantial differences in ultrafine particle number and soot exposure between two urban cycling routes. Exposure to ultrafine particles and soot during cycling was weakly associated with increased exhaled NO, indicative of airway inflammation, and decrements in lung function 6 h after exposure. A limitation of the study was the relatively small sample size.