In a letter to the EPA last summer, utilities and regulatory and labor groups said mercury emissions had been reduced by almost 90 percent over the past decade.
Ann Weeks, senior counsel for the Clean Air Task Force, an environmental group, criticized the rule as "bean counting", and said, "This is not tax law".
The EPA is not seeking to remove the mercury limitations, outlined under the 2011 Mercury and Air Toxics Standards, but critics are saying the proposed change in calculations sets a unsafe precedent for future regulations associated with public health.
The mercury regulation also costs the coal industry $9.6 billion annually, making it among the most expensive regulations the EPA has ever had to enforce.
Under the direction of acting administrator Andrew Wheeler, the EPA is now questioning whether it was appropriate to include these additional benefits. The Obama administration estimated that the measure would prevent as many as 11,000 premature deaths from asthma, other respiratory diseases or heart attacks.
A proposal Friday from the Environmental Protection Agency challenges the basis for the Obama regulation. The federal government is required to take into account both the costs and health benefits when considering pollution regulations.
Blues reject Bayern's £13.5m bid for Callum Hudson-Odoi
According to the Daily Mail , Die Roten have tabled a £13million offer for the 18-year-old ahead of the January transfer window. Bayern's league rivals Borussia Dortmund have also shown interest in Hudson-Odoi, but have not made an official approach yet.
Merkel, Macron urge Russia to release Ukrainian sailors
The 2015 Minsk summit laid out a ceasefire and global monitoring in eastern Ukraine, but a pro-Russian insurgency has persisted. Merkel and Macron had demanded on Friday the "immediate and unconditional release of all illegally detained Ukrainian sailors".
Viewing, funeral service set for fallen Newman police corporal Ronil Singh
The announcement of arrests comes after a statewide manhunt for the suspect accused of killing Mr Singh the day after Christmas. The Newman Police Department has announced plans are underway to hold Corporal Singh's funeral on 5th January.
But the new EPA finding would conclude it's not "appropriate" for the agency to regulate the toxic emissions.
Janet McCabe, a former air-quality official in the Obama administration's EPA, called the proposal part of "the quiet dismantling of the regulatory framework" for the federal government's environmental protections.
The proposal, which revisits a 2011 rule limiting mercury emissions from coal plants, argues that the EPA lacked justification to curb the neurotoxin in the first place because many benefits stemmed from the overall drop in air pollution that would occur once power companies adopted new technologies. The standards help meet the country's commitments under the Minamata Convention on Mercury.
US coal-fired power generation has fallen more than 40 percent since a peak in 2007, while natural gas-fired generation soared by about the same amount, according to the Energy Information Administration. It's the latest administration effort on behalf of the country's coal industry.
Trump's industry allies, including Robert Murray, CEO of private coal mining giant Murray Energy Corp, had complained that the MATS rule contributed to the demise of the coal business by triggering hundreds of coal-fired power plant shutdowns and driving coal demand to its lowest in decades.
In December the administration proposed a revision that would allow coal-fired generators to emit more Carbon dioxide per megawatt-hour of electricity generated.