Introduction: Cycling is currently promoted at the municipal, provincial and national level as a form of active transportation that increases physical activity while at the same time reducing traffic congestion, traffic-related air pollution and greenhouse gas emissions. While at a population level the health benefits of exercise via cycling are estimated to substantially exceed any health impacts related to air pollution exposure and injuries from traffic accidents , cyclists are known to experience elevated exposures to traffic-related air pollutants. Combined with exposure to elevated concentrations of air pollutants, cyclists also are subject to substantially increased inhaled doses due to their level of exertion and consequently increased inhalation rate. Therefore, given that cyclists experience exposures to relatively high concentrations of traffic-related air pollutants and that their inhalation of these pollutants is increased, it is important to evaluate the potential health impacts of this scenario. Research on the potential health impacts related to exercise (cycling) and urban air pollution exposure can help inform public communication strategies related to air quality and its health impacts. In addition, as our previous work suggests substantial variability in air pollution exposures to cyclists that is related to the route type and the levels of traffic along cycling routes, there is potential for transportation planners to promote increased cycling by enhancing infrastructure while at the same time developing routes that also minimize exposure to air pollution. The cyclist population is also interested in information regarding the air pollution exposures and potential health impacts related to cycling.

The objective of this study is to investigate the relationship between traffic-related air pollution exposure, and respiratory and cardiovascular health impacts in commuting cyclists. Specifically, the investigators propose to:

1. determine commuting cyclists' exposure to traffic-related air pollutants (PM 2.5, PM10, ultrafine particulate, black carbon) while cycling along two different bicycle routes in the city of Vancouver;
2. estimate the pollutant dose received by each cyclist, and relate this to the health effects observed; and
3. determine if there is a change in lung function, endothelial function, and C-reactive protein level related to the level of air pollution exposure and dose

Inclusion Criteria:

• Age 19- 39
• male or female
• able to bicycle comfortably on city streets for 1 hour

Exclusion Criteria:

• Smokers of any substance (smoking more than 1x every 2 weeks)
• Must be of height to safely ride a test bike (<5'2", >6'5" )
• Diagnosed asthma or active allergy (hav fever) symptoms
• Irregular menstrual cycle, pregnant, breastfeeding, non-monocyclic contraceptive medication or device
• Taking medication for heart or lung condition
• Answers yes to any questions on physical activity readiness questionnaire (PAR-Q)
• requires pain medication daily
• visual or hearing impairment that prevents safe cycling on streets with motor vehicles