Air pollution exposure and subclinical health impacts in commuter cyclists

Background: Cycling is a form of active transportation, resulting in health benefits via increased physical activity. Less is known of traffic-related air pollution exposures and the resulting physiological responses experienced by urban commuter cyclists. The aim of this study was to measure systemic inflammation and lung function changes amongst cyclists by comparing responses between high and low- air pollution routes. Methods: Male and female participants (n = 38) rode an instrumented bicycle for approximately 1- hour along a Residential and a Downtown designated bicycle route in a randomized crossover trial during the summer and fall of 2010 and 2011. Heart rate, power output, location and particulate matter air pollution (PM₁₀, ₂₅, and ₁ and particle number concentration [PNC]) were measured at 6- second intervals during trials. Endothelial function [RHI], lung function, and blood measurements of C-reactive protein [CRP], Interleukin-6 [IL-6], and 8-hydroxy-2’-deoxyguanosine [8-OHdG] were assessed within one hour pre- and post-trial. A subset of 23 participants each completed a post-ride cycle ergometer minute ventilation (V̇E) measurement to estimate air pollution intake, based on heart rate measurements. Results: Geometric mean (GM) PNC exposures and intakes were higher along the Downtown (GM exposure = 16 226 particles/cm³; intake = 4.54 x 10¹⁰ particles) compared to the Residential route (GM exposure = 10 011 particles/cm³; intake = 3.13 x 10¹⁰ particles). The mean V̇E cycling: rest ratio was 3.0. In linear mixed-effect regression models, post-cycling RHI was 22% lower following the Downtown route compared to the Residential route (RHI of -0.38, 95% CI of -0.75 to -0.02), but this was not associated with exposure or intake of measured air pollutants. IL-6 and 8-OHdG levels increased after cycling trials along the Downtown route, but no significant association was found with PNC exposure or intake in mixed effect models. Conclusions: Although air pollution exposures and intakes were higher along the Downtown route and RHI was significantly decreased following trials on this route, this decrease was not associated with air pollution exposure or intake. This suggests other drivers of systemic inflammation related to cycling on the Downtown route may have been responsible for the observed association.Medicine, Faculty ofPopulation and Public Health (SPPH), School ofGraduat