WASHINGTON – The EPA announced plans Thursday to regulate a set of harmful chemicals found in drinking water systems that serve millions of Americans.

The process, which is likely to take months at least, is designed to set a maximum contaminant level for polyfluoroalkyl substances (PFAS), a man-made substance found in commercial household items such as food packaging, cleaners, water-repellent fabrics, Teflon-coated cookware and cleaning products.

Contaminants are also found in firefighting foams, which have seeped into groundwater sources that reach millions of drinking taps.

Environmental advocates and congressional Democrats criticized the move as little more than a stalling tactic to protect industry interests, given the health risks known about the chemicals.

The chemicals have been linked to reproductive and developmental, liver and kidney, and immunological effects. Research has shown they can contribute to low infant birth weights, thyroid problems and some cancers.

“The action plan commits EPA to take important steps that will improve how we research, monitor, detect and address PFAS," Andrew Wheeler, the Environmental Protection Agency's acting administrator, said at a news conference in Philadelphia.

By the end of the year, the agency will propose a regulatory determination, which is the next step legally required under the Safe Drinking Water Act to establish a "maximum contaminant level" for the chemicals, Wheeler said. The agency is reviewing whether similar chemicals should be regulated, he said.

The EPA plans to list the harmful chemicals as contaminants under its Superfund program, which would give the agency more authority to pursue polluters.

Despite the move, environmental groups slammed the EPA for moving too slowly. Several states already have taken to steps to limit or ban PFAS and highlighted their risks to the public.

“This so-called plan is actually a recipe for more PFAS contamination, not less,” said Scott Faber, senior vice president for government affairs at the Environmental Working Group. “It’s shameful that the EPA has taken two decades to produce a plan that allows increased exposure to compounds whose makers have used the American people as guinea pigs and, with the EPA’s complicity, covered it up.”

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The organization has studied the issue for almost 20 years. It estimates that more than 1,500 drinking water systems, serving up to 110 million Americans, may be contaminated with some levels of those chemicals.

The EPA established health advisory levels at 70 parts per trillion. Setting a "maximum contaminant level" as part of a regulation would require regular monitoring and give the agency more power to crack down on violators.

A study in 2016 by university researchers and published by the National Institutes of Health found that more than 6 million Americans were provided tap water above the 70 parts per trillion standard.

Delaware Sen. Tom Carper, the top Democrat on the Senate Environment and Public Works Committee, called Wheeler's announcement "insufficiently protective."

“It has taken the EPA nearly a year just to kick the can even further down the road," Carper said. "While EPA acts with the utmost urgency to repeal regulations, the agency ambles with complacency when it comes to taking real steps to protect the water we drink and the air we breathe."

At Thursday's news conference, Wheeler was asked whether he thought the EPA's standard should be more aggressive, considering the scientific research that moved some states to reduce PFAS exposure.

"We feel right now that 70 parts per trillion is a safe level for drinking water," he responded. "As we go forward with the (regulation), we'll be looking to see whether or not lower levels are required, according to where the science directs us."