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

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<2.5μm in aerodynamic diameter (PM2.5), 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 24h and six preceding 24-h periods, using linear mixed models. Results: IQR increases in mean PM2.5 (7.0μg/m³) and CO (161.7 parts per billion) concentrations in the first 24h before the plasma nitrite measurement were associated with increased plasma nitrite concentrations (PM2.5: 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.