Environmentalists are up in arms over moves by Donald Trump’s administration to ease restrictions on coal power plants that would allow mercury and other toxins to be released into the air.

Officials are considering loosening regulations set up under Barack Obama that have helped to dramatically cut pollution that can cause respiratory illnesses, as well as learning disabilities and other birth defects in children.

The Environmental Protection Agency (EPA) says the cost of regulation outweighs the savings and benefits to human health and the environment, and it wants to change the way the calculations will be made.

Under the 2011 Mercury and Air Toxic Standards (Mats), coal-burning power plants were required to install expensive equipment to cut output of mercury and other polluting chemicals.

The regulation led to a drop in mercury emissions from coal-fired power plants of an estimated 85 per cent.

The proposal is the latest in a long line of steps by President Trump to scrap steps to protect the environment taken under Mr Obama.

The environment has been targeted more than any other policy area under Mr Trump, with changes including allowing oil and gas drilling in Alaksa’s Arctic National Wildlife Refuge; loosening rules on capturing methane when drilling for energy; rubber-stamping oil pipelines; ending the Clean Power Plan, repealing the Clean Water Rule, and increasing use of carbon-emitting fossil fuels, as well as pulling out of the Paris accord on climate change.

Coal power plants in the US are the largest single man-made source of mercury, which enters the food chain, mostly through fish.

The World Health Organization says mercury is one of the top 10 chemicals or groups of chemicals of major public health concern.

But since August, the agency has been reconsidering the justification for the regulation that curbs emissions.

Now officials propose using a different cost analysis to evaluate whether it is needed, a move that will go out for a 60-day public consultation.

It paves the way for looser rules and for coal mining companies to challenge the environmental protection in court.

The agency says the crackdown has produced only a few million dollars a year in measurable health benefits and is not “appropriate and necessary” — the test under the country’s Clean Air Act.

The change could set a precedent reaching far beyond mercury rules. “It will make it much more difficult for the government to justify environmental regulations in many cases,” said Robert N Stavins, a professor of environmental economics at Harvard University, The New York Times reported.

The Trump administration has been trying to support the US coal industry, which has been struggling to compete with natural gas and other cheaper, cleaner forms of energy.

Hal Quinn, head of the National Mining Association, claimed that the Obama administration had carried out “perhaps the largest regulatory accounting fraud perpetrated on American consumers” when it calculated that the health benefits would outweigh the cost of equipment upgrades.

Profits corporate polluters rake in while making our kids sick will officially take priority over the health of the public and the environment Mary Anne Hitt

But Democratic Senator Tom Carper, condemned the plan, saying the Trump administration was playing with numbers, ignoring “clear health, environmental and economic benefits to come up with a bottom line that suited the administration’s deregulatory aims”.

Janet McCabe, a former air-quality official in the Obama administration’s Environmental Protection Agency, said that coming one week into a government shutdown, and in the lull between Christmas and New Year, “this low-key announcement shouldn’t fool anyone — it is a big deal, with significant implications”.

US environmental group the Sierra Club condemned the “dangerous and disgraceful” plan.

Mary Anne Hitt, director of the Beyond Coal campaign of the Sierra Club, said: “Trump and Andrew Wheeler [acting head of the agency] just put coal in the stocking and mercury in the drinking water of American moms and kids, in a cynical and dangerous move days after Christmas.

“If this disgraceful proposal is finalised, it will mean that profits corporate polluters rake in while making our kids sick will officially take priority at the EPA over the health of the public and the environment.

“The policy… 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.

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

Additional reporting by agencies