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

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 (PM(2.5)CAPs, 89.5 ± 10.7 µg/m³), or NO₂+PM(2.5)CAPs 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 PM(2.5)CAPs was an increase in HDL 1 h after exposure, likely due to the low concentrations of PM(2.5)CAPs in the exposure chamber. Exposure to both NO₂ and PM(2.5)CAPs 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 PM(2.5)CAPs alone, suggesting possible interactions between the two pollutants.

DISCUSSION AND CONCLUSIONS

NO₂ exposure may produce and enhance acute cardiovascular effects of PM(2.5)CAPs. Assessment of health effects by ambient PM should consider its interactions with gaseous copollutants.