To great applause, the U.S. Environmental Protection Agency last month proposed “maximum contamination levels” in drinking water for six per- and polyfluoroalkyl substances (PFAS) chemicals. This was the first such action that EPA had taken in more than 30 years on any drinking contaminant.

Unfortunately, despite the magnitude of this action for this handful of PFAS, there are at least 12,000 PFAS variations.

Before the applause for EPA could die down, this month, a study found 26 types of PFAS in drinking water samples from 16 states. Notably, EPA has no pending proposed standard for 20 of these PFAS. More disturbing, 12 of these PFAS are not included in EPA’s current monitoring—in other words, EPA does not even currently test for them.

Furthermore, three of these PFAS fall outside the “working definition” for PFAS that EPA adopted without any outside review in 2021. This means that EPA is not considering regulating them.

The public health implications of its chemical-by-chemical posture are much too serious to accommodate (however lamely) EPA’s scientific self-image.

In fact, EPA’s working definition is far narrower than those adopted by other entities, such as the intergovernmental Organisation for Economic Co-operation and Development (OECD) and members of the European Union. Nor is it as broad as the definition adopted by numerous states that have started regulating PFAS on their own, frustrated by the slow pace set by EPA. It is also substantially narrower than the definition EPA itself uses for research purposes and non-regulatory estimates.

Why would EPA summarily adopt a definition that leaves out thousands of PFAS?

Public Employees for Environmental Responsibility (PEER), the organization I work for, asked the agency this very question. Just four months after EPA published this working definition in 2021, we submitted a Freedom of Information Act (FOIA) request for documents that would provide a scientific explanation or justification for this new definition.

We are still waiting.

Months after our request, EPA released some 2,500 pages of documents that did not answer the question. By June 2022, when it became clear that the agency would not voluntarily produce any meaningful response, my organization filed a federal lawsuit under FOIA demanding complete production.

In the ensuing months, like a squid emitting an ink cloud to throw off a pursuer, EPA’s attempts to evade production have only grown more convoluted. This exercise, however, appears to have confirmed the information we received from inside the agency – EPA’s working definition does not appear to be the product of EPA scientific research.

This working definition suddenly appeared out of thin air, with no discernible paper trail of parentage. We suspect it actually sprung from a chemical industry lobbyist’s pen, as the financial implications of this definition are enormous. If EPA admitted the definition’s true origin that would be embarrassing, to say the least, and puncture all of the lofty rhetoric its senior officials regularly spout about the rigorous scientific integrity behind agency decision-making.

Why would EPA summarily adopt a definition that leaves out thousands of PFAS?

The public health implications of its chemical-by-chemical posture are much too serious to accommodate (however lamely) EPA’s scientific self-image. Only aiming to regulate a handful of PFAS dooms the agency’s “PFAS Strategic Roadmap” to failure.

In 2022, EPA issued non-binding Health Advisories for four PFAS chemicals. For two of those chemicals –PFOS and PFOA – the indicated levels of concern were expressed in parts per quadrillion. This advisory suggests that just about any detectable levels of these two chemicals are injurious to human health.

But the manufacture of PFAS and PFOA in the United States has largely ended. These first-generation PFAS chemicals have been replaced by new variations of PFAS that are proving just as toxic. EPA’s current regulatory approach cannot possibly keep up with an unending stream of industry replacements.

Moreover, EPA’s decision to approach PFAS also does not address the fact that many PFAS variants can degrade into terminal end products that are themselves PFAS.

One trait all PFAS have in common is their persistence. They do not break down readily in the environment, hence they are called “forever chemicals.” Many bioaccumulate in our bodies and biomagnify in the food chain.

Thus, it is critical that EPA abandon the fundamental folly of its chemical-by-chemical, whack-a-mole approach to PFAS regulation. Instead, EPA should treat PFAS as a class of chemicals regulated in the same manner as the European Union and other countries.

As more and more studies detect varieties of PFAS in the environment outside the narrow purview EPA has staked out, the inexplicable and irresponsible nature of its present regulatory posture only becomes more evident.