On Wednesday, the Environmental Protection Agency stunned scientists and local officials across the country by issuing new health advisories for toxic “forever chemicals” found in thousands of U.S. drinking water systems, potentially affecting millions of people.

The new advisories reduce the safe level of the chemical PFOA by more than 17,000 times what the agency previously declared to be protective of public health, to just four “parts per quadrillion.” The safe level of PFOS, a related chemical, was reduced by a factor of 3,500. Because of their extreme resistance to disintegration, the chemicals belong to a class of chemicals known as per- and polyfluoroalkyl substances (PFAS). They have been linked to various cancers, low birthweights, thyroid disease, and other health issues.

The presence of PFOA, PFOS, and other PFAS chemicals in drinking water has been tracked by the Environmental Working Group, a national environmental nonprofit. Water systems are not required to test for the chemicals because they are not yet officially regulated. However, their long-term use in a variety of products such as Teflon and other nonstick cookware, clothing, food packaging, furniture, and numerous industrial processes has resulted in their widespread presence in the environment and drinking water.

According to Scott Faber, senior vice president of the group, at least 1,943 public water supplies across the country have been found to contain some amount of PFOS and PFOA. And there are likely many more that contain the chemicals but have not been tested, according to Faber, potentially putting millions of Americans in danger.

Previous research has found that Americans have been exposed to the chemicals for decades.

For years, scientists have been concerned about how a large class of chemicals, numbering in the thousands, may be affecting public health in the United States. PFOA has been linked to kidney and testicular cancers, ulcerative colitis, thyroid disease, and other serious illnesses in highly contaminated communities such as Parkersburg, West Virginia.

Other studies, however, have discovered that a variety of PFAS may be toxic even at extremely low levels found in the general population, potentially affecting the immune system, birth weights, cholesterol levels, and even cancer risk.

According to Philippe Grandjean, a PFAS researcher at the Harvard T.H. Chan School of Public Health who has advocated for extremely protective PFAS limits, the chemicals have no acute toxicity. Consumers should not expect to become ill immediately after consuming amounts found in drinking water.

PFAS, on the other hand, operate in the background, with risks accruing over a lifetime of consumption. His research indicates that PFAS can reduce immune response in children. They may contract more infections than they would normally. Vaccinations are less effective, an effect that may extend to COVID-19 vaccination, a question that researchers are now investigating.

The EPA said in releasing the new health advisories that they fit into a larger picture outlined in the agency’s “Strategic Roadmap.” This includes plans to propose formal drinking water regulations for PFOS, PFOA, and possibly other chemicals this fall. The agency also claims to be taking a comprehensive approach to PFAS, with plans to clean up contamination hotspots, address PFAS in consumer products, and provide assistance to impacted communities.

According to a press release, the agency is releasing the first $1 billion of a total $5 billion in grant funding from the bipartisan infrastructure law passed last year to assist contaminated communities. An additional $6.6 billion may be available through existing loan programs for water and sewer utilities.

The costs of removing and disposing of PFAS are exorbitant. A single water well filter can cost up to $500,000. While the new funding is beneficial, Remmel believes it is only a “drop in the bucket” compared to what is required across the country.

Costs will eventually have to be passed on to water customers, who have already seen their rates rise dramatically over the last decade as utilities invested in other priorities such as replacing lead pipes and outdated sewer infrastructure. Remmel wants the EPA to do a better job of engaging at the local level to help with the public health and financial burdens caused by PFAS.