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 m in aerodynamic diameter ( PM ( 2.5 ) ) , carbon monoxide ( CO ) , sulfur dioxide ( SO ) , nitrogen dioxide ( NO ) , and ozone ( O ) ] measured at two monitoring sites closest to Rutgers University campus ( 6-15 miles ) in New Jersey during the years 2006-2009 .