The Science on PFAS Was Decades Ahead of the Law

By Dr. Eric Roy, PhD

I have spent almost 25 years working in water quality, including responding to the Flint lead crisis and testifying before Congress. PFAS is the clearest example I have seen of science moving faster than drinking-water regulation. EPA established the first enforceable federal limits in April 2024, more than fifty years after the early evidence of harm began to appear.

For the two best-studied PFAS, PFOA and PFOS, warning signs appeared early and became harder to dismiss as the evidence accumulated. As early as 1970, internal industry records described PFOA as "highly toxic when inhaled and moderately toxic when ingested." By 1981, internal DuPont records had raised concerns about birth defects among children born to women who worked with C8. Independent research filled in the picture over time. In 2012, the C8 Science Panel found a probable link between PFOA exposure and six conditions, including kidney and testicular cancer. The National Toxicology Program concluded in 2016 that PFOA and PFOS are presumed immune hazards to humans. By 2022, the National Academies found sufficient evidence of an association between PFAS exposure and four health outcomes, including kidney cancer and decreased antibody response.

In my experience, this is where public expectations become disconnected from how drinking-water regulation actually works. Before EPA can establish an enforceable limit, the agency must evaluate the toxicology and determine how widespread it is in public water systems, whether laboratories can measure it using EPA standard methods, whether water systems can treat it at scale, and what nationwide compliance will cost.

While there was no federal drinking-water standard, there were some federally facilitated responses that aligned with scientific understanding at the time. For example, EPA created a voluntary stewardship program in 2006 that asked eight manufacturers to reduce PFOA emissions and product content by 95 percent by 2010 and work toward elimination by 2015.

States also began writing their own drinking-water rules. For example, New Jersey was the first state to establish an enforceable limit for PFNA in 2018. New Hampshire followed quickly with limits for four PFAS (PFOA, PFOS, PFNA, PFHxS) in 2019. However, without a consistent federal standard, the level of protection depended on the state.

EPA issued the first national PFAS drinking-water regulation in 2024. The rule established individual limits for five PFAS and a Hazard Index standard for mixtures that included a sixth compound. While this was a major step toward aligning policy with science, the rule was challenged almost immediately in court. In May 2026, EPA announced two separate proposed rules. The first would rescind the individual standards for PFHxS, PFNA, and GenX, along with the Hazard Index mixture standard, leaving federal limits for PFOA and PFOS in place. The second would preserve the PFOA and PFOS limits but allow eligible drinking-water systems to request up to two additional years, until 2031, to comply.

EPA's stated rationale for the rescission was not based on any change in the science. Instead, the agency argued that the 2024 rule had used an unlawful procedure under the Safe Drinking Water Act.

By the time EPA finalized the first federal drinking water standard for PFAS in 2024, the scientific concern had been developing for more than fifty years. During that time, manufacturers changed chemistries and states wrote their own standards. The public, meanwhile, had to weigh headlines calling out health risks against assurances from their water systems that the water met all federal standards. That assurance held only because the law had not yet caught up with the science.

Sources