Having announced its intentions in May last year, the US Environmental Protection Agency (EPA) hasnow formally proposed new rules limiting drinking water levels for six per- and polyfluoroalkyl substances (PFAS).
In 2024, president Joe Biden put in place the first ever national, legally enforceable drinking water standards to protect US communities from exposure to PFAS. They set limits at 4 parts per trillion (ppt) for the two most well-known substances, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), and 10ppt for four other PFAS chemicals – perfluorohexane sulfonate (PFHxS), perfluorononanoic acid (PFNA), PFBS, hexafluoropropylene oxide-dimer acid (HFPO-DA, or GenX), and mixtures of these three, plus perfluorobutane sulfonic acid (PFBS) – under the US Safe Drinking Water Act.
PFAS – also known as ‘forever chemicals’ – are a family of an estimated 15,000 synthetic chemicals that have been widely used in consumer products globally since the 1950s. They all share a characteristic carbon chain with multiple fluorine atoms attached. They do not degrade easily in the environment because the carbon–fluorine bond is among the strongest in existence. The unique properties of these substances confer characteristics like repellence to oil, grease and water, as well temperature resistance and friction reduction. This helps to create products that are non-stick and stain-resistant, for example.
However, PFAS are also highly mobile in the environment and they bioaccumulate, as well as biomagnify, up the food chain. PFOA and PFOS – the best studied of these substances – have been linked to serious health conditions like reproductive and developmental disorders, reduced immune function and certain types of cancer.
In May 2025, EPA administrator Lee Zeldin announced that the agency intended to allow water companies two additional years (until 2031) to comply with the 4ppt limits on PFOS and PFOA, and completely repeal the limits on the remaining substances. At the time, experts told Chemistry World there was no scientific reason to reverse these limits, and that doing so would be a ‘tremendous setback to common sense water stewardship’.
In announcing the proposals on 18 May, Zeldin said the Biden administration had ‘cut corners’ and failed to follow the law when regulating PFAS in drinking water. ‘We are fixing that error with standards water systems can actually implement and that will hold up to scrutiny, while addressing PFOA and PFOS, two of the best-studied PFAS with well-documented health impacts,’ he stated.
The head of the US Department of Health the Human Services (HHS), Robert Kennedy, described PFAS contamination as ‘a serious public health challenge that demands rigorous science, clear standards, and practical solutions.’ His department is ‘advancing gold-standard research’ to better understand PFAS exposure, toxicity, and long-term health impacts on Americans, he said.
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