Key Points

• The dominant pattern is litigation against EPA efforts to undo Biden-era or long-standing climate and air-pollution protections.
• Two main regulatory targets stand out: Mercury and Air Toxics Standards for coal plants and the 2009 endangerment finding used for greenhouse-gas regulation.
• Plaintiffs include states, cities, environmental groups, health groups, and Alaskan tribes, showing broad coalition resistance.
• The most consistent substantive claim is that EPA rollbacks lack a reasoned basis and conflict with the Clean Air Act and prior Supreme Court precedent.
• Public health effects are a recurring frame, especially risks from mercury, heavy metals, and weakened emissions monitoring.
• The issue is legally and institutionally coherent, with challenges concentrated in the D.C. Circuit and centered on federal rulemaking authority.
• The signal appears moderate and current, with little historical drift beyond the legal foundation supplied by older standards and court decisions.