What on-road emissions may contribute to PM2.5 pollution?
PM2.5 is made up of direct pollutant emissions from vehicle tailpipes and brake and tire wear, as well as reentrained road dust from paved and unpaved roads and construction dust emissions from highway and transit construction. In addition, PM2.5 can also be formed from precursor emissions of oxides of nitrogen (NOx), volatile organic compounds (VOCs), sulfur oxides (SOx), and ammonia (NH3). See EPA’s May 6, 2005 final rule for more information regarding when PM2.5 precursor emissions are considered in regional analyses in PM2.5 nonattainment and maintenance areas.
