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Why Legal Tap Water Is Not Always Safe: The 2026 GenX Case Study
July 2, 2026
Eric Roy, PhD | Chief Scientist
When your utility publishes its annual water quality report (ie Consumer Confidence Report), there are several reference numbers listed for each contaminant. One is the Maximum Contaminant Level Goal (MCLG), which is a "health only" threshold that science says causes no known harm. The other is the Maximum Contaminant Level (MCL), which is the legal limit. While the MCLG is based only on toxicology, the MCL balances toxicology against cost and feasibility for the municipality to attain. For many contaminants the two numbers are further apart than people expect.
Take PFOA and PFOS, the two most studied PFAS (ie forever chemicals). The MCLG for each is zero, because the EPA's toxicological assessment found that there is no known safe level for these compounds in drinking water. Despite this toxicological profile, EPA set a regulatory limit of four parts per trillion, which corresponds with the lowest concentration water systems can reliably measure and treat at the municipal scale. While it'd be ideal for the "health only" and "legal" limits to be the same thing, this type of compromise is pretty easy to justify.
GenX is an example where this compromise gets harder to accept. GenX is another PFAS, and in 2024 the EPA ruled that the compound posed a high enough risk that the cost to regulate it was justified by the public health benefit, and assigned GenX a legally-enforceable MCL of 10 ppt. Fast forward 2 years to May 2026, and EPA proposed to remove that limit entirely. The reason it gave for the removal was procedural, that the original 2024 rule had been issued through an improper process, and it acknowledged that the underlying health assessment used to justify the regulation in the first place remained valid.
Weeks after proposing to rescind the GenX regulation, the EPA and DOJ announced a settlement with Chemours, the company that makes GenX, worth more than $450 million, which includes a requirement to control 99 percent of the GenX released from its plants. A settlement of this scale shows that there's no credible debate over the toxicity of PFAS.
This is one of those moments that is hard to comprehend, because in the span of weeks the EPA made Chemours pay almost a half billion dollars over its PFAS pollution, and also proposed taking the same chemicals off the list of regulated drinking water contaminants.
This type of informational whiplash is confusing to the public, because they're reading about the health problems associated with PFAS in drinking water, but their water provider is saying that their drinking water meets all federal regulations. The frustrating thing, as a scientist that has worked in water for several decades, is knowing that they're actually talking about two completely different things. The real problem is that the toxicity doesn't switch on and off in the same way that regulations can. Fortunately, once you know this, you can act based on safety. Depending on your situation, this could mean getting your water tested, reviewing the water quality report your city already publishes, or choosing to protect your home’s water.
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