A monumental federal plan would require most fossil fuel power plants to slash their greenhouse gas pollution by 90% by 2040 — or shut down.

The Biden administration plan, announced on Thursday, could limit the amount of climate change-causing emissions released. If implemented, for the first time in U.S. history, the amount of greenhouse gasses emitted from the nation’s 3,400 power plants, which are responsible for 25% of the nation’s carbon emissions, would be capped.

As the U.S. inches closer to reducing pollutants from power plants that have historically caused harm throughout vulnerable communities, regulating these facilities’ emissions will have environmental justice implications. Across the country, low-income Black people are exposed to the most pollution from power plants and have the highest risk of death from such pollution. Nearly 80% of Black Americans live near a coal-fired power plant, compared with 56% of white people.

“By proposing new standards for fossil fuel-fired power plants, EPA is delivering on its mission to reduce harmful pollution that threatens people’s health and well-being,” said Michael Regan, the first Black man to head the Environmental Protection Agency.

If passed in conjunction with two other recent recommendations by the Biden administration regarding methane leaks from oil and gas wells and the country’s transition to electric vehicles, it would put the nation on track to meet the EPA goals to cut the country’s emissions roughly in half by 2030.

The EPA estimates that by 2030 the emission caps will have prevented about 1,300 premature deaths, more than 800 hospital and emergency room visits, more than 300,000 asthma attacks, 38,000 school absences, and 66,000 lost workdays.

The landmark proposal is expected to meet sharp opposition from conservative lawmakers, including from Democratic West Virginia Sen. Joe Manchin, who has said he would oppose all of Biden’s future appointees to positions within the EPA unless the administration dropped the regulation.

This isn’t the first time such a proposal has been levied by a Democratic president. In 2014, then-President Barack Obama’s Environmental Protection Agency released a similar plan that was ultimately blocked by the U.S. Supreme Court and then rolled back by President Donald Trump. A future administration could also follow the same path and weaken Biden’s regulation.

Read More: Air Pollution and Its Impact on Black Communities, Explained

The proposal, which would help avoid more than 600 million metric tons of carbon emissions over the next two decades, depends on setting caps on pollution rates, which power plant operators would have to meet. The proposal does not enforce how power plants must meet the requirements, but they could do it by using new technologies or switching their fuel source.

The plan sets specific targets for plants based on their size, operating frequency, and their lifespan. For example, roughly 25% of coal-fired power plants are set to retire by 2029, so they may not have to install new pollution controls.

The regulation has received general praise from public health and environmental justice groups nationwide, who were initially fearful that the pollution limits would depend on controversial carbon capture technology. The proposal suggests that plants use the technology, but does not mandate it.

Carbon capture works by capturing carbon emissions before they’re released into the air and pumping them deep underground. Some environmental justice advocates argue the pipeline needs for this technology would lead to more potential toxic accidents in Black communities.

“Today’s proposed rule from the Biden Administration to dramatically cut greenhouse gas emissions from US power plants is critical recognition that we must cut climate pollution if our communities are to survive,” said Ozawa Bineshi Albert, co-executive director of the Climate Justice Alliance, a national nonprofit representing 89 rural and urban community-based environmental justice organizations.

“But if we are to combat climate change, we must do so with real, viable solutions — not unproven technologies that only promise to continue the legacy of dumping pollutants onto frontline communities.”

The EPA will take public comment on the proposal for 60 days after officially entering it into the Federal Register, meaning the proposal could still be strengthened or weakened before it reaches Congress.

In its current iteration, the EPA estimates that limiting pollution from these plants would produce economic and health benefits worth up to $85 billion by 2042 by lowering hospital costs for illnesses, creating new jobs to reach the standard, and limiting the amount of sick days workers across the country would need to take.

The Biden administration is attempting to push forward its three most ambitious climate proposals before 2024 in case Republicans win control of Congress. The new Congress could overturn the regulations if the policies aren’t approved within 60 days of the next elected Congress.

Adam Mahoney is the climate and environment reporter at Worldacad. Twitter @AdamLMahoney