Mercury is released into the atmosphere when coal is burned in a power plant. It doesn’t remain there. Before settling in soil, lakes, and rivers, where bacteria transform it into methylmercury, a neurotoxic that builds up in fish tissue and becomes more concentrated at each stage of the food chain, it travels—sometimes several of miles. Lake bass, pike, swordfish, and tuna. The most weight is carried by the fish at the top. The Mercury and Air Toxics Standards were created in 2012 with the intention of blocking this pathway at its origin.
The 2024 revisions to those regulations tightened that disruption even more. They increased particulate matter standards for coal plants, tightened limits on mercury from lignite-fired plants, and mandated continuous real-time emissions monitoring so that local communities and regulators could actually see what was coming out of the stacks. The EPA completed the revocation of those 2024 revisions on February 19, 2026. Waterways and coal-fired power stations are now separated by the 2012 requirements.
It’s important to remember the figures that the EPA’s own study linked to this repeal. By 2035, the agency projected that the rollback will increase mercury emissions by about 8,189 pounds per year, a 23 percent increase above what the 2024 regulation would have permitted. This represents a halt to further progress rather than a return to pre-2012 conditions when compared to the baseline set by the success of the original MATS rule, which reduced mercury emissions from coal plants by approximately 90% between 2012 and 2021, from about 29 tons per year to a fraction of that.
The EPA used cost savings—an estimated $670 million freed up for power plants by eliminating what it described as “unnecessary” and onerous requirements—as reason for approving that increase. In its cost-benefit analysis, the EPA made no effort to estimate the additional mercury’s negative effects on the environment and human health. One of the aspects of the rules that critics found most concerning was the imbalance in that accounting.
The portion of the rollback that is less well-known to the general public but greatly worries environmental experts and regulators is the removal of continuous emissions monitoring. In order to give regulators continuous data instead of sporadic snapshots, the 2024 regulation mandated that coal and oil plants build systems that track particle emissions in real time. The implementation of the remaining 2012 standards relies on interval testing, which generates windows during which non-compliance may go undetected, in the absence of such ongoing monitoring.
The most recent finalized national mercury emissions data available is from 2024, with 2025 data not expected until summer 2026, according to WRAL’s reporting from North Carolina, where Duke Energy operates coal plants. This means that the rollback’s short-term effects won’t be detectable in official data for a while. The CEMS requirement was created expressly to solve this transparency issue.
Pregnant women, nursing mothers, and young children—especially newborns whose brains are still developing—are the groups most at danger from elevated methylmercury in fish, as the EPA has repeatedly noted in its own guideline materials. Both the placental and blood-brain barriers are crossed by methylmercury, and there is a wealth of reliable scientific research on its effects on neurological development.
Because of this known risk, the EPA has its own fish consumption warnings that still advise pregnant women to stay away from high-mercury fish like swordfish and king mackerel. These recommendations are unaffected by the removal of the 2024 MATS updates. It modifies the path of mercury into the water that gives rise to the fish that are the subject of the advisories.
Looking at the timetable, there’s a sense: between April and July of 2025, 71 coal plants were granted two-year exemptions from the current mercury restrictions; in February of 2026, the stricter 2024 requirements were repealed; and now, legal challenges are pending in the D.C. Circuit—that the institutional ability that generated the 90% mercury reduction over a fourteen-year period is being questioned, not merely a regulatory wording.
The legal challenges are being monitored by the Harvard Environmental and Energy Law Program. According to experts quoted by WRAL, the present deregulatory tsunami is exceptionally broad in scope and raises long-term concerns about how future environmental standards will be set and defended. It’s still unclear if and when the courts will step in. The coal plants continue to burn.
