National-Scale Air Quality Data Assessment: Initial Findings from the Near-Road NO2 Monitoring Program

Abstract:

In 2010, the U.S. Environmental Protection Agency (EPA) revised the National Ambient Air Quality Standards (NAAQS) for nitrogen dioxide (NO₂) to include a primary health-based standard for hourly NO₂. NO₂ is a reactive gas that is emitted from motor vehicles, such as cars, trucks, and off-road equipment, as well as non-mobile sources, and is known to adversely affect human respiratory health. In conjunction with the NAAQS revision, EPA has mandated air quality monitoring next to selected major roadways throughout the United States that are in large urban areas where peak hourly NO₂ concentrations are expected. Monitoring began in phases during 2012–2015 and included nitrogen dioxide (NO₂), carbon monoxide (CO), and particulate matter smaller than 2.5 microns (PM_2.5) at 40 monitoring sites nationwide. We conducted a national-scale review of near-road air pollutant concentrations, identified areas where high concentrations of NO₂, PM_2.5, and CO occurred, and evaluated how concentrations varied by factors such as location, distance to roadway, fleet mix characteristics, and traffic volume. We present the findings from our national near-road data assessment for the 2014 monitoring year.