Clean Air – Environmental and Energy Law Program

Regulatory Tracker

Regional Haze Rule

Through two state plan approvals, EPA finalized a new policy that eases all states’ Regional Haze planning obligations. Environmental groups are challenging the approvals.

December 11, 2025

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 One of the rules, the Waste Emission Charge, was repealed using the Congressional Review Act. In Sept. 2025, EPA proposed to delay the GHG reporting rules until 2034. In Nov. 2025, EPA finalized the deadline exemptions for certain provisions regulating methane emissions from new and existing oil and gas sources.

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Congress repealed the 2024 rule using the Congressional Review Act.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 24, 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 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

In 2024, EPA strengthened regulation of ethylene oxide (EtO) emissions from commercial sterilization facilities. In July 2025, the Trump administration exempted 41 facilities from the rule, prompting challenges from public health and environmental nonprofits.

October 22, 2025

Regulatory Tracker

Hydrofluorocarbons and the Kigali Amendment to the Montreal Protocol

In 2022, the U.S. Senate ratified the Kigali Amendment, which committed the U.S. to reducing the use of HFCs. EPA issued multiple rules to implement the mandate. In Oct. 2025, EPA issued a proposed rule to loosen requirements and compliance deadlines for air conditioning, retail food refrigeration, and other sectors.

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