Representatives of the Environmental Protection Agency (EPA) in the US have proposed going back on a previous endorsement of limits on mercury pollution.

Under former President Barack Obama, the US enacted Mercury and Air Toxic Standards (MATS) in 2011 which forced coal-fired power plants to cut mercury output. The industry has since mostly complied with the regulation; some plants were shut down while other locations upgraded their equipment to cut pollution.

On Friday, the EPA said the 2011 rule will stay in place. However, the agency proposed it was not "appropriate and necessary" to regulate these emissions "because the costs of such regulation grossly outweigh the quantified […] benefits."

The agency's reassessment of an earlier 2016 endorsement showed that complying with MATS cost the government between $7.4 billion to $9.6 billion (€6.5 billion to €8.4 billion) every year, but only brought in up to $6 million in measurable health benefits.

Read more: Trump administration plans to roll back coal regulations

Brain damage, learning disabilities and birth defects

In arguing for the limits, environmentalists have pointed at unquantifiable benefits such as reduced health care costs, cleaner air and cleaner water. Mercury can cause brain damage, learning disabilities and birth defects in children, as well as problems for women during pregnancy.

"The policy [acting EPA head] Andrew Wheeler and [President] Donald Trump proposed today means more pregnant women, young children and the elderly will be exposed to deadly neurotoxins and poisons, just so wealthy coal and oil barons can make a few extra bucks," Sierra Club Beyond Coal Campaign Director Mary Anne Hitt said in a statement.

"Virtually every coal plant in the US has already met this lifesaving standard, and now Trump is recklessly trying to roll it back," she said.

Wheeler, a noted former lobbyist for coal energy companies, was chosen by Trump as acting EPA administrator after Wheeler's predecessor, Scott Pruitt, was forced out over several embezzling scandals in July.

'Defeat from the jaws of victory'

Coal power plants are the single biggest source of mercury pollution in America, accounting for nearly half of mercury pollution in 2015, according to a recent study published by Harvard University's School of Public Health.

Senator Tom Carper, the ranking Democrat on the US Senate's Environment and Public Works Committee, spoke out against the move.

The EPA has "decided to snatch defeat from the jaws of victory" after the successful cleanup of toxins from the country's coal-plant smokestacks, Carper said.

The EPA said it would take comments on its proposal for the next 60 days and hold at least one public hearing before making a final ruling.

Friday's move was the latest step in an effort to roll back dozens of Obama-era pollution limits. Former EPA air-quality official Janet McCabe said the proposal was part of "the quiet dismantling of the regulatory framework" for the federal government's environmental protections.

Even though the proposal was made public during the holiday season and one week into the US government shutdown "this low-key announcement shouldn't fool anyone — it is a big deal, with significant implications," she said.

dj/cmk (Reuters, AP)

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