Respiratory outcomes of ultrafine particulate matter (UFPM) as a surrogate measure of near-roadway exposures among bicyclists

BACKGROUND: Studies have shown a consistent association between exposure to traffic-related air pollution and adverse health effects. In particular, exposure can be high for cyclists who travel near roadways. The objective of the current study was to examine the relationship between short-term exposure of near-road traffic emissions and acute changes in lung function among individuals who frequently bike in the Sacramento and Davis areas in California. Ultrafine particulate matter (UFPM) was used as a surrogate for near-roadway exposure in this study since the main source of this pollutant is from motor vehicle exhaust. METHODS: Thirty-two bicyclists were recruited and completed two rides on separate days during the study period of March-June, 2008. One ride was on a high traffic route paralleling a section of Interstate 80 (I-80)/Interstate Business 80 (I-80B), and a second one was on a low traffic route, such as bike paths away from major highways. The participant’s lung function was measured before and after each ride, and UFPM exposure was measured during the rides using a condensation particle counter (CPC). RESULTS: In the final linear mixed-effect model using median UFPM concentrations as the main exposure, we observed that lung function change (post–ride minus baseline measurements) shifted in the negative direction. Lung function changed by 216 mL for FVC and 168 mL for FEV(1), respectively, for an interquartile range (IQR: 12,225 to 36,833 number of particles/cm(3)) increase of UFPM concentration after adjusting for other covariates of age, sex, wind direction, and day of the week. CONCLUSIONS: This study found significant associations between increased levels of UFPM concentrations as a proxy for near road traffic pollution, and decrements in lung function measurements. Our results are related to short-term exposures, and the long-term health effects of cycling near heavy traffic require further research. Our study suggests the need to reduce traffic pollution, particularly near roads. Cyclists should plan their route to reduce their exposure where possible and further research on built environment designs may help urban planners to reduce the potential health concerns of cyclists’ exposure to traffic-related air pollution. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12940-017-0212-x) contains supplementary material, which is available to authorized users.