Synergistic effects of exposure to concentrated ambient fine pollution particles and nitrogen dioxide in humans

Abstract

Context: Exposure to single pollutants e.g. particulate matter (PM) is associated with adverse health effects, but it does not represent a real world scenario that usually involves multiple pollutants.Objectives: Determine if simultaneous exposure to PM and NO2 results in synergistic interactions.Materials and methods: Healthy young volunteers were exposed to clean air, nitrogen dioxide (NO2, 0.5 ppm), concentrated fine particles from Chapel Hill air (PM2.5CAPs, 89.5 ± 10.7 µg/m3), or NO2+PM2.5CAPs for 2 h. Each subject performed intermittent exercise during the exposure. Parameters of heart rate variability (HRV), changes in repolarization, peripheral blood endpoints and lung function were measured before and 1 and 18 h after exposure. Bronchoalveolar lavage (BAL) was performed 18 h after exposure.Results: NO2 exposure alone increased cholesterol and HDL 18 h after exposure, decreased high frequency component of HRV one and 18 h after exposure, decreased QT variability index 1 h after exposure, and increased LDH in BAL fluid. The only significant change with PM2.5CAPs was an increase in HDL 1 h after exposure, likely due to the low concentrations of PM2.5CAPs in the exposure chamber. Exposure to both NO2 and PM2.5CAPs increased BAL α1-antitrypsin, mean t wave amplitude, the low frequency components of HRV and the LF/HF ratio. These changes were not observed following exposure to NO2 or PM2.5CAPs alone, suggesting possible interactions between the two pollutants.Discussion and conclusions: NO2 exposure may produce and enhance acute cardiovascular effects of PM2.5CAPs. Assessment of health effects by ambient PM should consider its interactions with gaseous copollutants.