EPA mercury rollback raises health and transparency concerns in North Carolina

When coal is burned at power plants, mercury released into the air does not simply disappear. It can travel for dozens of miles before settling into soil and waterways, where it enters the food chain and concentrates in fish that people eat.

That pathway is at the center of new concerns after the Environmental Protection Agency repealed a 2024 update to the Mercury and Air Toxics Standards (MATS). The rule had tightened pollution controls and required power plants to continuously monitor certain emissions.

Federal officials say the rollback will lower costs and maintain reliable energy. Public health advocates and some scientists say it could lead to more toxic pollution and less transparency.

Chris Frey, an environmental engineering professor at North Carolina State University and a former assistant administrator at the EPA, said the 2024 rule was part of a routine federal review that found pollution-control technology had improved.

“The 2024 rule did was it increased the regulation for controlling particle emissions from power plants,” Frey said. “By reducing the particle emissions, it reduces the emissions of many toxic metals.”

Those metals include mercury, arsenic, chromium and nickel, which are released during coal combustion and can pose risks ranging from cancer to neurological damage.

The rollback also removes a requirement for continuous emissions monitoring systems that provided real-time data about pollution levels.

“There’s a saying in business that things get done that get measured,” Frey said. “If you measure something, you’re likely to pay more attention to it and manage it better.”

The EPA says repealing the 2024 rule will save about $670 million and that the older 2012 mercury standards remain protective of public health. At the same time, the agency has stopped calculating the economic value of lives saved and health costs avoided in some air pollution rules, saying it plans to revise how those benefits are measured.

The tighter 2024 standards were not scheduled to take effect until July 2027, meaning many utilities had not yet been required to comply. State regulators say that nationwide, the repeal could allow some plants to avoid future upgrades designed to further reduce toxic emissions.

In North Carolina, the Department of Environmental Quality said most coal units were already meeting the stricter limits before they took effect. Two coal units at Duke Energy’s Mayo plant would have needed upgrades to comply by 2027. A Duke spokesperson said those upgrades for filterable particulate matter are still planned.

Mercury remains a central public health concern because of how it moves through the environment. Once airborne mercury settles into lakes and rivers, it can transform into methylmercury, a potent neurotoxin that builds up in fish and increases in concentration up the food chain.

“For subsistence fisher people who catch fish locally, the concern is that they’re getting exposure to methylmercury,” Frey said. The compound is “especially toxic” and can affect the nervous system, particularly in unborn babies and children.

North Carolina already has statewide fish consumption advisories tied to mercury contamination.

Frey said 2024 mercury emissions standards were expected to cut roughly 1,000 pounds of pollution per year. 

“Repealing the 2024 rule would be expected to increase the amount of mercury emitted,” he said.

Coal-fired power plants are the largest human-caused source of mercury emissions in the United States, accounting for more than 40% of the nation’s total, according to the EPA.

Duke Energy, which operates coal plants in North Carolina, said it does not expect emissions to increase and will continue monitoring and reporting air toxics emissions under existing federal requirements.

The most recent finalized national mercury emissions data available is from 2024, with 2025 data expected to be released in summer 2026.

The debate over mercury standards is unfolding amid a broader wave of environmental deregulation.

“It is very unusual to see such a broad set of rollbacks of dozens of standards,” Frey said. “Every one of those actions is undoing a standard that was protecting public health.”

He added that the dismantling of EPA research programs raises long-term questions about the agency’s scientific capacity and how future environmental standards will be developed and defended.

Legal challenges to the mercury rollback are widely expected and could take years to resolve. In the meantime, the change leaves regulators, utilities and the public to grapple with how much protection is enough — and how much risk is acceptable.