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 (PM_2.5CAPs, 89.5 ± 10.7 µg/m³), or NO₂+PM_2.5CAPs 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 PM_2.5CAPs was an increase in HDL 1 h after exposure, likely due to the low concentrations of PM_2.5CAPs in the exposure chamber. Exposure to both NO₂ and PM_2.5CAPs 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 PM_2.5CAPs alone, suggesting possible interactions between the two pollutants.

Discussion and conclusions: NO₂ exposure may produce and enhance acute cardiovascular effects of PM_2.5CAPs. Assessment of health effects by ambient PM should consider its interactions with gaseous copollutants.

Keywords::

• Air pollution
• cardiovascular effects
• heart rate variability
• mulipollutants
• particulate matter

Acknowledgements

The authors are indebted to Ms. Maryann Bassett, Ms. Jacqueline Carter, Ms. Lisa Dailey, Ms. Shirley Harder, Ms. Heidi Hiers, Ms. Tracey Montilla, Mr. Michael Schmitt, Mr. Robert Silbajoris, and Ms. Joleen Soukup for their expert medical and technical assistance in the execution of this study.

Declaration of interest

The research described in this article was funded by the intramural grants of U.S. EPA and has been reviewed and approved for publication by the U.S. EPA National Health Effects and Environmental Research Laboratory. Approval does not signify that the contents necessarily reflect the views and policies of the U.S. EPA, nor does mention of the trade names or commercial products constitute endorsement or recommendation for use. The authors declare they have no competing financial interests relevant to the study.

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