Clean Air – Environmental and Energy Law Program

Regulatory Tracker

EPA VOC and Methane Standards for Oil and Gas Facilities

The Biden EPA finalized three rules regulating methane emissions from the oil and gas sector. One of the rules, the Waste Emission Charge, has been repealed under the Congressional Review Act. The Trump EPA included the other two, the methane emission reduction and GHG reporting rules, as slated for rollback.

December 4, 2025

Regulatory Tracker

Clean Car Rules — Corporate Average Fuel Economy Standards/Greenhouse Gas Standards

The Trump EPA issued a proposal to rescind the Endangerment Finding and the GHG standards for light, medium, and heavy-duty vehicles.

December 3, 2025

Regulatory Tracker

National Ambient Air Quality Standards (NAAQS) for Particulate Matter (PM)

The CAA requires EPA to review and set primary and secondary standards for PM NAAQS every 5 years. The Biden EPA strengthened the standard in March 2024. On November 25, 2025, EPA requested the D.C. Circuit vacate the 2024 rule.

November 24, 2025

Regulatory Tracker

Once In Always In Guidance for Major Sources under the Clean Air Act

Congress repealed the 2024 rule using the Congressional Review Act. EPA states the 2020 rule is the current standard which allows a major source to reclassify as an area source if the source reduces HAP emissions.

November 12, 2025

Regulatory Tracker

New Source Review

EPA establishes the baseline requirements for new source review (NSR) permits, which are then issued by state and local air pollution agencies. In 2025, EPA has made multiple changes to the NSR program easing permitting requirements for new and existing sources.

October 29, 2025

Regulatory Tracker

Ethylene Oxide (EtO) Emissions Standards for Commercial Sterilizers

The Biden EPA strengthened regulation of ethylene oxide (EtO) emissions from commercial sterilization facilities, which environmental groups and industry petitioners challenged in the D.C. Circuit. The Trump EPA plans to roll back the rule and invited industry to apply for exemptions.

October 22, 2025

Regulatory Tracker

Hydrofluorocarbons and the Kigali Amendment to the Montreal Protocol

In 2022, the US Senate ratified the Kigali Amendment, which committed the US to reducing the use of HFCs. EPA has issued multiple rules to implement the mandate.

October 17, 2025

Regulatory Tracker

Mercury and Air Toxics Standards

In June 2025, the EPA proposed a rule to rescind the 2024 mercury and air toxics standards (MATS) for power plants. Trump has exempted 74 electric generating units from the 2024 MATS.

October 16, 2025

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The Endangerment Finding and the DOE Climate Science Report

Video: Jody Freeman and other Harvard faculty experts discuss what’s at stake for current and future climate regulation.

October 8, 2025