What Is the EPA? Environmental Protection, Climate Rules, and the Deregulation Battle

The EPA administers more than a dozen major federal environmental laws. Its four core areas of responsibility are:

Air Quality: Under the Clean Air Act (1970, amended 1990), the EPA sets National Ambient Air Quality Standards (NAAQS) for six "criteria pollutants": particulate matter, ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, and lead. States must submit implementation plans showing how they will meet these standards. The EPA also regulates emissions from cars and trucks (setting fuel economy standards jointly with the Department of Transportation) and from power plants and factories.

Water Quality: Under the Clean Water Act (1972), the EPA regulates discharges of pollutants into US waters and sets quality standards for surface waters. Under the Safe Drinking Water Act (1974), it sets standards for public water systems. The EPA's definition of what waters fall under its jurisdiction — the "Waters of the US" (WOTUS) question — has been one of the most litigated issues in environmental law, with the Supreme Court significantly narrowing federal jurisdiction in Sackett v. EPA (2023).

Hazardous Waste and Superfund: The EPA oversees cleanup of contaminated sites under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, known as Superfund, 1980). Over 1,300 sites appear on the National Priorities List. Cleanup can take decades and cost billions per site.

Toxic Chemicals: Under the Toxic Substances Control Act (TSCA), the EPA reviews new chemicals before they enter commerce and can restrict or ban existing ones. The 2016 Lautenberg Chemical Safety Act strengthened the EPA's authority after decades of criticism that TSCA was too weak to protect against chemicals like asbestos and PFAS ("forever chemicals").

The Trump administration's second term (2025–) has initiated an extensive deregulatory agenda at the EPA, described by the administration as eliminating "job-killing regulations" and restoring American energy dominance:

• Power Plant Rules: The Biden-era rule requiring existing coal plants and new natural gas plants to capture 90% of carbon emissions was withdrawn. The administration cited cost and feasibility concerns.
• Vehicle Emissions: The Biden EPA had set aggressive tailpipe emissions standards designed to accelerate electric vehicle adoption. The Trump EPA proposed loosening these standards significantly.
• Methane Rules: The Biden administration had finalized strict rules limiting methane leaks from oil and gas operations. These are being reconsidered under the Congressional Review Act and EPA rulemaking.
• PFAS Regulation: The Biden EPA had set the first-ever federal drinking water limits for six PFAS compounds. The Trump administration has signaled it will revisit these rules, potentially loosening limits.
• Endangerment Finding: The most consequential potential action — reconsidering or rescinding the 2009 finding that greenhouse gases endanger public health. If rescinded, it would eliminate the legal basis for nearly all federal climate regulation. Industry groups and Democratic AGs have filed opposing legal briefs.

The EPA's regulatory authority has been shaped and constrained by a series of landmark Supreme Court decisions:

Massachusetts v. EPA (2007): The Supreme Court ruled 5-4 that greenhouse gases are air pollutants under the Clean Air Act and that the EPA must determine whether they endanger public health. This ruling directly led to the 2009 endangerment finding and all subsequent climate regulation.

West Virginia v. EPA (2022): In a 6-3 ruling, the Supreme Court held that the EPA had exceeded its authority under the Clean Air Act by adopting the Obama-era Clean Power Plan, which would have shifted electricity generation away from coal toward renewables at the grid level. The Court invoked the "major questions doctrine" — the principle that agencies need clear congressional authorization for actions of vast economic and political significance. This ruling significantly limits the EPA's ability to use the Clean Air Act as a broad climate tool without new legislation from Congress.

Sackett v. EPA (2023): A 9-0 ruling that significantly narrowed the EPA's jurisdiction over wetlands under the Clean Water Act. Only wetlands with a "continuous surface connection" to navigable waters fall under federal protection. Millions of acres of previously protected wetlands lost federal coverage.