Abstract
We examined two near-road monitoring sites where the daily PM2.5 readings were among the highest of any near-road monitoring location in the U.S. during 2014–2016: Denver, Colorado, in February 2014 and Indianapolis, Indiana, in November 2016. At the Denver site, which had the highest measured U.S. near-road 24-hr PM2.5 concentrations in 2014, concentrations exceeded the daily National Ambient Air Quality Standards (NAAQS) on three days during one week in 2014; the Indianapolis site had the second-highest number of daily exceedances of any near-road site in 2016 and the highest 3-year average PM2.5 of any near-road site during 2014–2016. Both sites had hourly pollutant, meteorological, and traffic data available, making them ideal for case studies. For both locations, we compared air pollution observations at the near-road site to observations at other sites in the urban area to calculate the near-road PM2.5 “increment” and evaluated the effects of changes in meteorology and traffic. The Denver near-road site consistently had the highest PM2.5 values in the Denver area, and was typically highest when winds were near-downwind, rather than directly downwind, to the freeway. Complex Denver site conditions (near-road buildings and roadway alignment) likely contributed to higher PM2.5 concentrations. The increment at Indianapolis was also highest under near-downwind, rather than directly downwind, conditions. At both sites, while the near-road site often had higher PM2.5 concentrations than nearby sites, there was no clear correlation between traffic conditions (vehicle speed, fleet mix) and the high PM2.5 concentrations.
Highlights
Air pollution is recognized to be elevated near major roads [1,2,3,4,5] and, in 2010, the U.S EnvironmentalProtection Agency (EPA) mandated that near-road air quality be measured in selected U.S metropolitan areas [6]
We examine two cases—Denver, Colorado, and Indianapolis, Indiana—where some of the highest near-road PM2.5 concentrations have been observed under the U.S near-road monitoring program
We examine data at the Denver Interstate Highway 25 (I-25) near-road site on three days during February 2014 when PM2.5 concentrations were above the National Ambient Air Quality Standards (NAAQS) threshold of 35 μg/m3, and at the Indianapolis I-70 near-road site on three days during November 2016 when PM2.5 concentrations were above the NAAQS threshold of 35 μg/m3
Summary
Air pollution is recognized to be elevated near major roads [1,2,3,4,5] and, in 2010, the U.S Environmental. Protection Agency (EPA) mandated that near-road air quality be measured in selected U.S metropolitan areas [6]. As of 2018, 70 near-road monitors were operational under the EPA mandate, measuring a number of pollutants. We examine two cases—Denver, Colorado, and Indianapolis, Indiana—where some of the highest near-road PM2.5 concentrations have been observed under the U.S near-road monitoring program. These in-depth case studies complement separately published national-scale reviews of EPA-mandated near-road air pollutant measurements [7,8]. Public Health 2019, 16, 1634; doi:10.3390/ijerph16091634 www.mdpi.com/journal/ijerph
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