Inhalation of Ultrafine and Fine Particulate Matter Disrupts Systemic Vascular Function

Abstract

Epidemiological evidence suggests that inhalation of internal combustion-derived particulate matter (PM) is associated with cardiovascular mortality and morbidity. Significant increases in emergency room visits for cardiac events during high PM episodes have been documented. 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. PURPOSE: To investigate effects of PM1 (PM with an aerodynamic diameter of 0.02–1 um) inhalation during exercise on conduit artery and microvascular function. METHODS: Sixteen intercollegiate athletes performed 30-min of exercise while inhaling low or high [PM1]. 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. RESULTS: Basal brachial artery vasoconstriction was found after high [PM1] exercise (4.0%, 4.66±0.609 vs 4.47±0.625 mm diameter; P=0.0002), but not after low [PM1 exercise (−0.3%, 4.66±0.626 vs 4.68±0.613 mm diameter). FMD was impaired after high [PM1] exercise (6.8±3.58% for pre-exercise FMD vs 0.30±2.74% for postexercise FMD, P=0.0001), but not for low PM1 exercise (6.6±4.04% for pre-exercise FMD vs 4.89±4.42% for post-exercise FMD). Significant reduction in forearm muscle reperfusion estimated by reoxygenation slope to baseline after 3 min cuff ischemia was observed for high [PM1] exercise, while no difference was noted for low [PM1 exercise (55% vs 3%, P=0.0006). Brachial artery FMD response was related to muscle reoxygenation slope to baseline (R=0.50, P=0.005). CONCLUSION: Acute inhalation of high [PM1] typical of urban environments impairs both systemic conduit artery function and microcirculation. Decreased reoxygenation slope to baseline after cuff release is consistent with reduced blood flow in the muscle microvasculature. Supported by AHA 0455734U.