Montana's Colstrip Plant Remains America's Dirtiest as EPA Rolls Back Mercury Rules

The Colstrip power plant in Montana remains the nation's dirtiest, emitting the highest levels of soot and mercury pollution. Recent policy shifts by the Trump administration have rolled back key regulations, raising concerns among nearby communities. The Northern Cheyenne tribe, living close to the plant, now faces heightened health risks from unchecked emissions.

Colstrip has long avoided installing basic pollution controls, unlike many other power plants. The facility burns lignite coal, a particularly dirty fuel source, and has repeatedly sought exemptions from stricter rules. In 2026, only two other U.S. plants—Antelope Valley Station and Milton R. Young Station in North Dakota—will still rely on similar coal, leaving North Dakota and Montana most exposed.

The Trump administration's Environmental Protection Agency (EPA) recently reversed the mercury air toxics rule, a move that eliminates federal limits on mercury emissions. The agency argued that upgrading pollution controls at plants like Colstrip would impose excessive costs. In contrast, the Biden EPA insists that the necessary technology is already available and affordable. Mercury, a potent neurotoxin, poses severe health risks, particularly to pregnant women, babies, and young children. It can settle in water, contaminate fish, and enter the food chain, directly threatening communities like the Northern Cheyenne tribe. Charlene Alden, the tribe's environmental protection director, has voiced alarm over the rollback, warning of lasting harm to public health. Joe Goffman, a Biden EPA official, reinforced these concerns, stating that the policy reversal will continue to expose local residents to dangerous pollution levels. The Trump EPA's decision also granted Colstrip a waiver, allowing it to bypass stricter Biden-era pollution standards entirely.

The rollback of mercury regulations leaves communities near Colstrip and similar plants without federal safeguards. With only two other lignite-burning plants remaining by 2026, North Dakota and Montana will bear the brunt of the environmental impact. Health officials and tribal leaders continue to push for stricter controls, but the current policy shift removes key protections for vulnerable populations.