This study investigated the effects of particulate matter (PM) with aerodynamic diameter 0.02-1 μm (noted as PM 1 ) inhalation during exercise on conduit artery and microvascular function. Inhalation of internal combustion-derived PM is associated with cardiovascular mortality and morbidity. Direct action of PM on the vascular endothelium is likely, as a substantial fraction of ultrafine PM translocates from the alveoli to the circulatory system. Sixteen intercollegiate athletes performed 30 min of exercise while inhaling low or high PM 1 . Flow-mediated brachial artery dilation (FMD) using high-resolution ultrasonography with simultaneous measurements of forearm oxygen kinetics using near infrared spectrophotometry (NIRS) was done before and after exercise. Basal brachial artery vasoconstriction was found after high PM 1 exercise (4.0%, 4.66 ± 0.609 to 4.47 ± 0.625 mm diameter; p = .0002), but not after low PM 1 exercise (−0.3%, 4.66 ± 0.626 to 4.68 ± 0.613 mm diameter). FMD was impaired after high PM 1 exercise (6.8 ± 3.58% for preexercise FMD and 0.30 ± 2.74% for postexercise FMD, p = .0001), but not after low PM 1 exercise (6.6 ± 4.04% for preexercise FMD and 4.89 ± 4.42% for postexercise FMD). Reduction in forearm muscle reperfusion estimated by reoxygenation slope-to-baseline after 4 min cuff ischemia was observed for high PM 1 exercise (55% vs. 3%, p = .0006); no difference was noted for low PM 1 exercise. Brachial artery FMD was significantly correlated to muscle reoxygenation slope-to-baseline (r = .50, p = .005). Acute inhalation of high [PM 1 ] typical of urban environments impairs both systemic conduit artery function and microcirculation. The observed decrease reoxygenation slope-to-baseline after cuff release is consistent with reduced blood flow in the muscle microvasculature.

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In spite of epidemiological evidence concerning vehicular air pollution and adverse respiratory/cardiovascular health, many athletic fields and school playgrounds are adjacent to high traffic roadways and could present long-term health risks for exercising children and young adults. Particulate matter (PM 1 ,0.02-1.0 µm diameter) number counts were taken serially at four elementary school athletic/playground fields and at one university soccer field. Elementary school PM 1 measurements were taken over 17 days; measurements at the university soccer field were taken over 62 days. The high-traffic-location elementary school field demonstrated higher 17-day [PM 1 ] than the moderate and 2 low traffic elementary school fields (48,890 ± 34,260, 16,730 ± 10,550, 11,960 ± 6680, 10,030 ± 6280, respective mean counts; p < .05). The 62-day mean PM 1 values at the university soccer field ranged from 115,000 to 134,000 particles cm −3 . Lowest mean values were recorded at measurement sites furthest from the highway (∼34,000 particles cm −3 ) and followed a second-order logarithmic decay (R 2 = .999) with distance away from the highway. Mean NO 2 and SO 2 levels were below 100 ppb, mean CO was 0.33 ± 1.87 ppm, and mean O 3 was 106 ± 47 ppb. Ozone increased with rising temperature and was highest in the warmer afternoon hours (R = .61). Although the consequence of daily recess play and athletic activities by school children and young athletes in high ambient [PM 1 ] conditions has not yet been clearly defined, this study is a critical component to evaluating functional effects of chronic combustion-derived PM exposure on these exercising schoolchildren and young adults. Future studies should examine threshold limits and mechanistic actions of real-world particle exposure.

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