The Environmental Protection Agency imposed the first federal limits on PFAS, or "forever chemicals," in drinking water, allowing the government to enforce limits on the levels of toxic chemicals linked to cancer and other health risks in public water systems across the country.

PFAS, or per-and polyfluoroalkyl substances, are a class of nearly indestructible chemicals found in a wide range of items, such as non-stick pans, firefighting foam, microwave popcorn packaging and other water-repellent products.

The new rules will mandate that public water systems monitor and inform the public of levels of PFAS in drinking water. Up to 10% of the 66,000 water systems that the new rule applies to may need to reduce the PFAS levels in their water, according to the EPA.

Under the new regulations, water systems will have three years to complete an initial test for current levels of PFAS in their water supply. If the levels are too high, they must reduce them within five years.

"This new standard will reduce PFAS exposure for approximately 100 million people," EPA Administrator Michael Regan said at a press briefing on Wednesday.

The EPA first proposed limits to the same six types of PFAS last March.

Under the new limits, the agency will cap levels of PFOA and PFOS, two of the most widely used types of PFAS, in drinking water, at 4 parts per trillion, the lowest level that most labs can detect the chemicals in water. The EPA set a goal of eliminating the two chemicals from water levels entirely.

"They're the ones that probably have the most proven health harm that we've studied," Ariana Spentzos, science and policy associate at the Green Science Policy Institute, said of the two chemicals. Setting zero as "the goal level really is acknowledging that there's no safe level for those particular chemicals," she added.

The new rules cap limits of other PFAS chemicals, including PFNA, PFHxS, and "GenX Chemicals," at a slightly higher level of 10 parts per trillion. Those same chemicals, along with PFBS, are also limited when they are mixed together.

Courtney Carignan, an assistant professor at Michigan State University and member of the university's Center for PFAS Research, said "PFHxS is excreted from the body the most slowly" and could take eight years or more to exit the body, compared with PFOA and PFAS, which take about 3 to 5 years.

The Biden administration also said it would set aside $1 billion of funding authorized by the infrastructure law passed in Nov. 2021 to go towards testing and treatment of public water systems and helping owners of private wells address PFAS contamination.

Data released by the EPA last month from an ongoing five-year review of water systems across the country showed at least 70 million Americans get their water from systems with high enough levels of PFAS to require reporting to the agency, according to a USA TODAY investigation.

Out of about 3,800 water systems reviewed, 1,245 contained levels of at least one of the toxic chemicals mandating reporting. Those included systems in large urban areas like Salt Lake City, Sacramento, California, Madison, Wisconsin and Louisville, Kentucky, according to the data.

Eleven states have imposed their own regulations on PFAS, and Delaware and Virginia are in the process of passing regulations.

Spentzos said efforts to regulate PFAS only accelerated recently, even though there have been warning signs about their safety for decades. "Things have really picked up in the last five to 10 years, but the harms of this have been known for a long time."

More:EPA detected "forever chemicals" in water systems serving 46 million. Is yours on our map?

'Long, growing list' of negative health effects of PFAS

PFAS can seep into the ground around factories and plants where they are used and end up in nearby water supplies, said Carignan.

"They're also extremely mobile and they can travel with the water cycle," Carignan said. "This is one of the properties that's made them problematic, along with the fact that they've been found to be toxic."

Some PFAS have been found to have negative effects on multiple systems of the body, even at relatively low levels in drinking water, Carignan said.

Research has linked PFAS with certain diseases, including kidney, testicular and breast cancer, Carignan said. It can also affect fetal development. Some types of PFAS, including PFOA and PFOS, can also decrease the body's immune response, leaving it more vulnerable to disease.

"There's some studies showing effects possibly on the brain and neurodevelopment," as well as bone density, Carignan said. "It is sort of this long, growing list."

Cybele Mayes-Osterman is a breaking news reporter for USA Today. Reach her on email at [email protected]. Follow her on X @CybeleMO.