Abstract
BackgroundCycling and other forms of active transportation provide health benefits via increased physical activity. However, direct evidence of the extent to which these benefits may be offset by exposure and intake of traffic-related air pollution is limited. The purpose of this study is to measure changes in endothelial function, measures of oxidative stress and inflammation, and lung function in healthy participants before and after cycling along a high- and low- traffic route.MethodsParticipants (n = 38) bicycled for 1 h along a Downtown and a Residential designated bicycle route in a randomized crossover trial. Heart rate, power output, particulate matter air pollution (PM10, PM2.5, and PM1) and particle number concentration (PNC) were measured. Lung function, endothelial function (reactive hyperemia index, RHI), C-reactive protein, interleukin-6, and 8-hydroxy-2′-deoxyguanosine were assessed within one hour pre- and post-trial.ResultsGeometric mean PNC exposures and intakes were higher along the Downtown (exposure = 16,226 particles/cm3; intake = 4.54 × 1010 particles) compared to the Residential route (exposure = 9367 particles/cm3; intake = 3.13 × 1010 particles). RHI decreased following cycling along the Downtown route and increased on the Residential route; in mixed linear regression models, the (post-pre) change in RHI was 21% lower following cycling on the Downtown versus the Residential route (−0.43, 95% CI: -0.79, −0.079) but RHI decreases were not associated with measured exposure or intake of air pollutants. The differences in RHI by route were larger amongst females and older participants. No consistent associations were observed for any of the other outcome measures.ConclusionsAlthough PNC exposures and intakes were higher along the Downtown route, the lack of association between air pollutant exposure or intake with RHI and other measures suggests other exposures related to cycling on the Downtown route may have been influential in the observed differences between routes in RHI.Trial registrationClinicalTrials.gov, NCT01708356. Registered 16 October 2012.
Highlights
Cycling and other forms of active transportation provide health benefits via increased physical activity
Mean concentrations of particle number concentration (PNC) were significantly higher along the Downtown route (16,870 pt/cm3) compared to the Residential route (10,840 pt/cm3, Table 2)
Improvements in endothelial function were observed after cycling along the low traffic Residential route, while cycling along the Downtown route led to a mean decrease in endothelial function measures
Summary
Cycling and other forms of active transportation provide health benefits via increased physical activity. Studies have consistently shown the physiological impacts of acute exposure to particulate matter (PM), linking it with changes in vascular tone [14,15,16], cardiovascular morbidity and mortality [17, 18], oxidative stress [19], pulmonary inflammation [20], and stimulation of pulmonary irritant receptors [21, 22]. These studies only serve to demonstrate the acute health effects of PM exposure in the home and laboratory, environments that lack elements present during a cycling trip that may further impact the effect of PM exposure on health. Increased respiration rates due to physical effort involved while cycling leads to increased inhalation of polluted air [23, 24]
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