Abstract
BACKGROUND/OBJECTIVE: Wintertime thermal inversions in narrow mountain valleys create a ceiling effect, increasing concentration of small particulate matter (PM(2.5)). Despite potential health risks, many people continue to exercise outdoors in thermal inversions. This study measured the effects of ambient PM(2.5) exposure associated with a typical thermal inversion on exercise performance, pulmonary function, and biological markers of inflammation. METHODS: Healthy, active adults (5 males, 11 females) performed two cycle ergometer time trials outdoors in a counterbalanced design: 1) low ambient PM(2.5) concentrations (<12 μg/m(3)), and 2) an air quality index (AQI) ranking of "yellow." Variables of interest were exercise performance, exhaled nitric oxide (eNO), c-reactive protein (CRP), forced vital capacity (FVC), and forced expiratory volume in 1 s (FEV(1)). RESULTS: Despite a significant difference in mean PM(2.5) concentration of 9.3 ± 3.0 μg/m(3) between trials (p < .001), there was no significant difference (p = .424) in the distance covered during low PM(2.5) conditions (9.9 ± 1.7 km) compared to high PM(2.5) conditions (10.1 ± 1.5 km). There were no clinically significant differences across time or between trials for eNO, CRP, FVC, or FEV(1). Additionally, there were no dose-response relationships (p > .05) for PM(2.5) concentration and the measured variables. CONCLUSION: An acute bout of vigorous exercise during an AQI of "yellow" did not diminish exercise performance in healthy adults, nor did it have a negative effect on pulmonary function or biological health markers. These variables might not be sensitive to small changes from acute, mild PM(2.5) exposure.