Plasma nitrite is an indicator of acute changes in ambient air pollutant concentrations

Abstract

Context: Endothelial dysfunction has been suggested as a potential mechanism by which ambient air pollution may cause acute cardiovascular events. Recently, plasma nitrite has been developed as a marker of endothelial dysfunction.

Objectives: We examined the changes in plasma nitrite concentration associated with increases in ambient air pollutant concentrations in the previous 7 d.

Materials and methods: We linked up to three measurements of plasma nitrite concentrations obtained from 49 students to 24-h average concentrations of five criteria air pollutants [particle mass < 2.5 µm in aerodynamic diameter (PM_2.5), carbon monoxide (CO), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), and ozone (O₃)] measured at two monitoring sites closest to Rutgers University campus (6–15 miles) in New Jersey during the years 2006–2009. We examined the change in plasma nitrite associated with each interquartile-range (IQR) increase in pollutant concentration in the previous 24 h and six preceding 24- h periods, using linear mixed models.

Results: IQR increases in mean PM_2.5 (7.0 µg/m³) and CO (161.7 parts per billion) concentrations in the first 24 h before the plasma nitrite measurement were associated with increased plasma nitrite concentrations (PM_2.5: 15.5 nanomolar; 95% confidence interval (CI): 2.4, 28.5; CO: 15.6 nanomolar; 95% CI: 2.4, 28.9). Increased plasma nitrite associated with IQR increases in O₃ and SO₂ concentrations over longer lags were observed.

Discussion and conclusion: Rapid increases in plasma nitrite following exposure to ambient air pollutants support the hypothesis that ambient air pollution is associated with inducible nitric oxide synthase-mediated systemic inflammation in humans.

• Air pollution
• ambient air pollutants
• plasma nitrite concentration

Acknowledgements

We would like to thank the staff at the Computational Chemodynamics Laboratory at the Environmental and Occupational Health Sciences Institute for their help in the acquisition of the ambient air pollutant measurements and weather data used in the analysis. We acknowledge the generous participation of our volunteer subjects, and the dedication and expertise of the research staff at EOHSI who made these experiments possible.