Attorneys general from five states have raised objections to an Environmental Protection Agency (EPA) rollback of Obama-era regulations that stipulate how coal-fired power plants dispose of waste containing arsenic, lead and mercury.

The lawyers representing Maryland, Pennsylvania, Illinois, Michigan, and Vermont expressed concerns about the proposed changes, which would weaken rules dealing with the residue from burning coal, called coal ash, in a Tuesday comment addressed to EPA Administrator Andrew Wheeler Andrew WheelerOvernight Energy: Smoke from wildfires has reached Europe | EPA postpones environmental justice training | UN report: Countries have failed to meet a single target to protect wildlife in last decade EPA postpones environmental justice training after White House memo OVERNIGHT ENERGY: House Democrats tee up vote on climate-focused energy bill next week | EPA reappoints controversial leader to air quality advisory committee | Coronavirus creates delay in Pentagon research for alternative to 'forever chemicals' MORE.

“When power plants burn coal, the resulting waste—coal combustion residuals, or coal ash—includes a host of toxic chemicals, such as arsenic, lead, and mercury,” they wrote. “These chemicals pose numerous dangers to human health, including cancer, cardiovascular effects, and neurological effects.”

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Their comment acknowledged that states are free to impose stricter regulations than the federal government, but noted that waters within their borders are connected to out-of-state waters and could be tainted by pollution produced in those states.

“Our states thus rely on federal regulation to ensure a stable nationwide regulatory floor protecting against pollution crossing our borders,” the attorneys general wrote.

An EPA official told The Hill in an email that the agency “will consider all timely filed public comments as part of the rulemaking process.”

The agency has previously defended the proposed changes as supporting “the Trump Administration’s commitment to responsible, reasonable regulations by taking a commonsense approach, which also protects public health and the environment.”