The Environmental Protection Agency is loosening some of its rules for "major" sources of air pollution.
The agency is withdrawing a policy often referred to as "once in always in." The policy meant that companies producing a lot of toxic emissions had to use the best possible pollution control technology available, even if they managed to bring their pollution emissions back down below a certain level.
Under the new rules, plants or factories that fall below that threshold won't have to use those best pollution controls.
Fossil fuel companies have long opposed the old policy. And the EPA says it furthers the Trump administration's goal of cutting regulatory burdens on companies.
But environmental groups say the move will lead to major increases in hazardous pollutants like mercury, arsenic and lead.