Polluting under the Radar: Emissions, Inequality, and Concrete Batch Plants in Houston.

Small industrial sources collectively release large amounts of pollution, including particulate matter (PM) that contributes to air quality problems in the United States and elsewhere. We study one such type of industrial facility, concrete batch plants, and analyze PM emissions and siting patterns of 131 plants located in Harris County, Texas. We find that concrete batch plants in Harris County are collectively a major pollution source, contributing between 38 and 111 tons of primary PM 2.5 emissions (between 26%-76% of PM 2.5 from the median Texas oil refinery) and between 109 and 493 tons of primary PM 10 emissions (between 64%-290% of PM 10 from the median refinery). Estimates from an integrated assessment model suggest that health damages from the PM 2.5 emissions alone amount to $29 million annually, reflecting two additional premature deaths per year. We further find that concrete batch plants in Harris County are disproportionately located in census tracts with more low-income, Hispanic, and Black populations, thereby raising important environmental justice questions. On the basis of these findings, we argue that small pollution sources require more air quality monitoring and emissions reporting and that regulatory agencies should consider cumulative environmental and health impacts of these sources as part of the permitting process.