Has US EPA just deregulated certain PFAS in water?

Whilst some PFAS will remain regulated at already-established limits, others will become completely unregulated.

In a surprising reversal, the U.S. Environmental Protection Agency (EPA) has announced plans to rescind drinking water limits for four key per- and polyfluoroalkyl substances (PFAS), raising concern across the water monitoring community. 

The agency has pledged to maintain strict maximum contaminant levels (MCLs) for PFOA and PFOS (the two most studied and widespread PFAS).

It will now re-evaluate rules for PFHxS, PFNA, GenX (HFPO-DA), and the PFAS mixture hazard index that had been finalised under the Biden administration in 2024.

For professionals tasked with monitoring PFAS in water, this move brings regulatory uncertainty, operational challenges, and renewed questions about long-term detection and mitigation strategies for these persistent chemicals.

Let's explore this new development.

If you need to analyse PFAS in water, find your next instrument in our international directory of companies supplying environmental monitoring equipment.

Regulatory rewind

The now-rescinded 2024 rules had imposed enforceable limits of 10 parts per trillion (ppt) for PFHxS, PFNA, and GenX, based on a growing body of toxicological evidence linking these chemicals to cancer, reproductive issues, immune dysfunction, and developmental harm. 

Announced in May 2025, the EPA’s rollback states that these limits were enacted without following the proper legal procedures under the Safe Drinking Water Act (SDWA). 

According to the agency, the simultaneous issuance of preliminary regulatory determinations and proposed rules for these four substances may not have met statutory requirements.

However, critics argue that this legal technicality has opened the door to what they see as a deregulatory agenda that benefits industry at the expense of public health. 

“It’s a devastating step backwards,” said Melanie Benesh of the Environmental Working Group. “Every time we look at these chemicals, we discover they are more toxic than we thought.”

Mixing PFAS and microplastics increases toxicity, new study claims

A new study has revealed that perfluoroalkyl substances (PFAS) and PET microplastics are more toxic (to freshwater species, at least) when combined. Focusing on water fleas (Daphnia magna), a se... Read More

What are the four PFAS now off the EPA’s rulebook?

PFHxS (Perfluorohexane sulfonic acid): Known for persistence and immune toxicity. Detected in many public water systems.

PFNA (Perfluorononanoic acid): Linked to cholesterol increases and liver damage.

GenX (HFPO-DA): Replacement for PFOA, found in North Carolina’s Cape Fear River. Tied to birth defects and liver toxicity.

PFBS (Perfluorobutanesulfonic acid): Previously regulated as part of a hazard index mixture.

Implications for instrumentation and monitoring

The EPA’s decision has direct implications for utilities, regulators, and instrumentation professionals. 

While PFOA and PFOS remain under strict 4 ppt MCLs, with a new compliance deadline of 2031, the elimination of standards for PFHxS and GenX introduces ambiguity into monitoring programs. 

Utilities and labs that have invested in multianalyte PFAS testing methods using advanced LC-MS/MS instruments may now face reduced regulatory mandates for certain analytes, potentially altering testing scopes and frequency.

Yet many experts urge the industry not to scale back monitoring efforts. 

“From an instrumentation standpoint, we know that water utilities don’t only measure to comply—they measure to protect public health,” said one analytical chemist at a national laboratory. “These chemicals are still in the water. The absence of a rule doesn’t mean the absence of risk.”

Indeed, compounds like PFHxS have been found in public water systems across the country, including the Washington, D.C. area, even inside EPA’s own buildings. GenX, meanwhile, has contaminated rivers and aquifers near manufacturing sites, especially in North Carolina.

Public demand answers on PFAS in Harefield water source

Residents of Buckinghamshire and West London are calling for further investigation into a common PFAS previously detected at one of the region’s pumping stations. If you get off the 724 bu... Read More

Concerns over compliance flexibility

The EPA’s announcement also includes the creation of a “federal exemption framework” for PFAS compliance, sparking concern in some corners of the water sector. 

While the agency insists exemptions would merely allow extra time to find treatment solutions, not permission to exceed MCLs, observers worry about the precedent it sets.

“An exemption framework might open the door for utilities to argue that PFAS treatment is too costly, especially in small or rural systems,” warned Daniel Jones, emeritus professor of molecular biology at Michigan State University. “That’s not in the spirit of the Safe Drinking Water Act.”

Some in the instrumentation field see an opportunity, however. 

The delay to 2031 may enable better planning, piloting, and scaling of advanced PFAS removal technologies like reverse osmosis and nanofiltration. 

The EPA’s new PFAS OUTreach initiative aims to provide technical assistance, funding access, and tailored support for water systems, particularly those in disadvantaged communities.

PFAS regulation is still chemical-by-chemical

Underlying the controversy is a deeper frustration with the EPA’s piecemeal approach to PFAS regulation. 

Of the more than 10,000 PFAS compounds in commerce, only six had been federally regulated as of 2024, and now that list is effectively reduced to two.

Many scientists and advocates are calling for PFAS to be treated as a chemical class, rather than regulated one by one.

“This Whac-a-Mole approach doesn’t make sense from a public health or an instrumentation perspective,” said Erik Olson of the Natural Resources Defense Council. “Testing for one PFAS while ignoring others with similar structures and toxicities only delays real solutions.”

This fragmentation places an additional burden on water testing labs and monitoring professionals, who must continue to evolve multiplex detection capabilities, refine sample preparation protocols, and stay ahead of shifting regulations.

Long-chain and short-chain PFAS: what is the difference?

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals with exceptional chemical stability and unique characteristics, including resistance to water, oil, and heat. They are used extens... Read More

What happens next?

The EPA says it may return with more stringent PFAS regulations in spring 2026, following a re-evaluation of its legal framework. 

In the meantime, many state agencies and utilities are expected to maintain current monitoring programs for the rescinded compounds, especially where local contamination is known.

For instrumentation users, the message is clear: despite regulatory rollbacks, demand for PFAS detection, quantification, and removal technologies will remain strong. 

Instruments must be flexible enough to track multiple PFAS species, reliable enough for ultra-trace analysis, and scalable for both compliance and public confidence.

Whether or not these PFAS are formally regulated tomorrow, they remain in our water today.