Multiscale Vehicle Traffic Air Pollutant Exposure and Equity Analysis in the United States using a Novel Emissions Exposure Surrogate

We estimate the emission density of directly emitted (primary) nitrogen oxides (NOX) and fine particulate matter (PM2.5) from on-road vehicle traffic for each census block in the United States (U.S.) and use these data as a new spatially refined and computationally efficient exposure surrogate. Our analysis using block level emission density estimates reveals in new detail the widespread extent of vehicle traffic emission exposure hotspots, the large impact of medium- and heavy-duty truck traffic on exposure, and environmental justice concerns that encompass nearly every county in the U.S. We find that emissions from trucks contribute to 46% of NOX and 50.4% of PM2.5 exposure from vehicle traffic in the U.S. We also find statistically significant associations between where greater proportions of people of color or people with lower incomes and higher traffic emission exposures in over 88% of the counties in the U.S. The magnitude of these disparities is often substantial. Our findings are notable in that traffic related emission exposure hotspots and related exposure inequalities are not limited to just the large metropolitan areas that have been the focus of much of the prior transportation and air quality literature. They are in fact much more widespread than previously shown.