The proposed rule follows a legal petition by environmental groups last August asking the EPA to end exemptions to its 2015 coal ash rule that had enabled utilities across the country to sidestep responsibility for handling up to a half a billion tons of cancer-causing toxic waste.

The proposal requires safe management of coal ash that was dumped in currently unregulated areas, including inactive power plants with surface impoundments that are no longer in use. These facilities were not covered by the 2015 rule issued by former President Barack Obama's administration.

Coal ash contains hazardous pollutants including arsenic, chromium, lead, and mercury, which have been linked to cancer, heart and thyroid disease and other illnesses. It tends to have a larger impact on low-income, minority communities living near power plants.

"Many of these communities have been disproportionately impacted by pollution for far too long. This proposal will better protect their health and our environment," said EPA Administrator Michael Regan.

The groups that filed the petition last year, represented by Earthjustice, found that the EPA exempted coal ash heaps at 566 landfills and dumps at 242 coal plants in 40 states.

Now, plant owners in states including Illinois, Indiana, Tennessee, New Mexico and Florida with some unregulated coal ash dumps would be required to monitor and clean up all coal ash at a given site, Earthjustice said.

"Power plants will finally lose their hall pass to leave coal ash wherever they dumped it," said Lisa Evans, senior counsel for Earthjustice, adding EPA should strengthen the proposal to include coal ash that was used as construction fill at playgrounds, schools, and throughout neighborhoods.

The rule comes days after the EPA proposed what could become the first-ever rules aimed at curbing carbon dioxide from new and existing power plants, which could hasten the closure of coal plants around the country by requiring installation of carbon capture technology starting in 2030.