Rolling back public health protections from air pollution

The Union of Concerned Scientists reports that the EPA's January 25, 2018, withdrawal of the "once in, always in" (OIAI) policy allows industrial facilities to be reclassified from "major sources" to "area sources" of hazardous air pollutants (HAPs). This reclassification removes the requirement for facilities to use Maximum Achievable Control Technology (MACT), which the authors estimate was used by 70 percent of major sources in 2014 to keep emissions at or below thresholds of 10 or 25 tons per year. The document warns that area sources are not regulated or inspected as stringently, potentially increasing emissions of toxic substances like chlorine, benzene, and styrene. The analysis identifies at least 21 states at risk of increased pollution, with specific high-risk clusters in Louisiana's "Cancer Alley," Houston, Chicago, and the New York-Newark urban area.

• The EPA withdrew the "once in, always in" (OIAI) policy on January 25, 2018, which previously required any industrial facility determined to be a major source of hazardous air pollutants (HAPs) to permanently employ Maximum Achievable Control Technology (MACT) to reduce emissions.
• Under the new guidance, major sources can be reclassified as "area sources" if their potential to emit HAPs falls below specific thresholds (10 tons per year for a single chemical or 25 tons per year for combined chemicals). Area sources are not subject to the same stringent regulation, inspection, or MACT requirements as major sources, which may lead to increased pollution.
• The document identifies specific U.S. regions where hazardous air pollution could increase: at least 21 states are affected, including 42 facilities in Louisiana's "Cancer Alley," 37 of 50 facilities in Houston, 35 of 41 in Chicago, and 26 of 28 in the New York-Newark urban area.
• The analysis lists the top ten hazardous air pollutants by volume and toxicity emitted by major sources in 2014, including chlorine, hydrochloric acid, styrene, manganese compounds, xylene and mixed isomers, benzene, n-hexane, naphthalene, 1-3-butadiene, and chloromethane.

APA

Union of Concerned Scientists (2018). Rolling back public health protections from air pollution. https://www.ucs.org/resources/epa-decision-increases-air-pollution-risk

Chicago

Union of Concerned Scientists. Rolling back public health protections from air pollution. 2018. https://www.ucs.org/resources/epa-decision-increases-air-pollution-risk.

Wikipedia

{{cite report |author=Union of Concerned Scientists |title=Rolling back public health protections from air pollution |date=20 April 2018 |url=https://www.ucs.org/resources/epa-decision-increases-air-pollution-risk |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{unionofconcernedscientists2018rolling, author = {{Union of Concerned Scientists}}, title = {{Rolling back public health protections from air pollution}}, institution = {Union of Concerned Scientists}, year = {2018}, month = apr, url = {https://www.ucs.org/resources/epa-decision-increases-air-pollution-risk}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }