Taconite plants on Minnesota’s Iron Range will now get two extra years to comply with a rule that would have forced them to cut how much mercury they release into the air.

A proclamation signed by President Donald Trump on Thursday notes that the rule “places significant burdens on a sector critical to the Nation’s industrial foundation,” and also noted that the steel made with taconite pellets is used “in national defense systems, critical infrastructure, and a broad range of industrial applications.”

Joy Anderson, an attorney at the Minnesota Center for Environmental Advocacy, called the move “really unfortunate” because the rule had been many years in the making. She said that taconite operations are responsible for about half the mercury emissions to air in Minnesota.

“We’ve made the coal plants put on air emissions equipment to clean up their emissions,” she said. “The taconite [plants], so far, have not had to do it.”

The move comes after the White House announced earlier this year that a range of companies could ask for exemptions from some Clean Air Act rules by sending the request to an EPA email address. A spokesman for U.S. Steel, which operates two taconite plants in Minnesota, confirmed the company had made such a request.

“The 2024 Taconite Rule is not supported by science and would impose unprecedented costs while setting technologically unachievable standards. This Presidential exemption is fair, reasonable and necessary,” a statement from U.S. Steel said.

Cleveland-Cliffs owns four plants, and hailed the proclamation in its own statement. The prior rule had been put in place without regard for “the impact it presented to the domestic iron ore industry and thousands of good paying jobs these operations sustain,” the company said.

Both steel firms had previously filed lawsuits challenging the emissions rule.

The plants granted an exemption in the proclamation are U.S. Steel’s Keetac and Minntac plants in Mountain Iron, and Cliffs’ plants associated with Hibbing Taconite, United Taconite, Northshore Mining and Minorca. Two Cliffs facilities in Michigan were also granted the reprieve.

Also on Thursday, Trump issued three other proclamations with two-year delays on Biden environmental rules related to medical device sterilizers, coal plants and chemical manufacturers. None of the affected facilities is in Minnesota.

The mercury rule, finalized under the Biden Administration last year, was projected to reduce mercury emissions by a third, while also cutting down on hydrofluoric and hydrochloric acid and lung-damaging fine particles.

Mercury is a potent neurotoxin that harms developing fetuses and children. In some forms it also causes serious nervous system and reproductive issues in adults. Global airborne mercury emissions from several sources have led to widespread contamination in fish. As a result, people are warned to avoid eating too much fish from waterbodies across Minnesota.

Prior to the Biden rule, mercury emissions from taconite had never been limited under the Clean Air Act, according to EPA.

Some have argued that the rule did not go far enough. Several environmental groups and the Fond du Lac Band of Lake Superior Chippewa sued to challenge the Biden-era rule last year.

As of EPA’s most recent filing in late May, that case is on hold, because the agency is “is evaluating the issues raised by the administrative petitions and assessing next steps.”

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