Kevin King, senior principal consultant at SLR, looks at how the new enforceable contaminant limits governing PFAS challenge conventional environmental cleanup and pollution control approaches.

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The US Environmental Protection Agency (EPA)’s recent adoption of the national primary drinking water regulation (NPDWR) criteria for six per- and polyfluoroalkyl substances (PFAS) – otherwise known as ‘forever chemicals’ – include numerical maximum contaminant levels (MCLs) of 4.0 parts per trillion (ppt) for two substances: perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). Those individual criteria are supplemented by an enforceable limit on four other PFAS – including perfluorobutane sulfonic acid (PFBS), hexafluoropropylene oxide-dimer acid (HFPO–DA or GenX), perfluorononanoic acid (PFNA), and perfluorohexanesulfonic acid (PFHxS) – using a hazard index approach to protect human health when these chemicals are present together. PFAS are seemingly coming at us from all directions, but understandably EPA has initially focused on the water we drink.  

The implications of these enforceable criteria on an estimated 155,000 public drinking water suppliers in the US are immense, considering 3M’s recent settlement agreement of $10.3bn dollars only covers 11,000 of these water utilities’ costs. That settlement has been judged by many to be an early drop in the bucket for major PFAS manufacturers. 3M’s total PFAS liability has been estimated to potentially be as high as $140bn. These new criteria, however, are also likely to increase the complexity and cost of remediating contaminated industrial sites – especially those located in areas where groundwater is a potential potable resource. 

In Connecticut, approximately 93% of the state lies within ”GA”-classified groundwater areas meaning the groundwater is classified as suitable for direct human consumption without treatment. Connecticut currently has PFAS criteria for groundwater based on a sum of five different PFAS (including PFOA and PFOS) set at 70ppt and adopting the new MCLs may tighten that standard considerably. The CT Department of Energy & Environmental Protection (DEEP) has hinted it intends to move to individual cleanup criteria. 

Cleanup criteria at the ppt level means impactful concentrations of PFAS can be found almost everywhere as ambient concentrations are not specifically tied to a point release. A 2022 article in Environmental Science & Technology by Ian Cousins, et al of the University of Stockholm puts the ubiquity of PFAS into ominous context:

• “… international drinking water guidelines for PFAS are now close to, or even lower than, levels in precipitation.”

• “…the levels of PFOS in rainwater are shown to often exceed the US EPA drinking water health advisory for PFOS except for two studies conducted in remote regions (in Tibet and Antarctica).”

I acknowledge that PFAS criterion and health advisories change at a pace not previously experienced in the environmental industry, and higher enforceable criteria may have since superseded the advisories Cousins’ referenced. We could view those advisory levels as obsolete until one considers that the new regulation includes MCL goals (MCLG) for PFOA and PFOS of zero (essentially the analytical method detection limit for the best labs in the market). These statements describe a sobering situation that presents new challenges to the environmental field that, up to now, had a solid handle on delineating contaminant releases and designing remediation protective of human health and the environment. 

Unlike every other contaminant the environmental industry has dealt with since the EPA was formed in 1970, exposure to PFAS is not limited to the water we drink and the air we breathe. It’s not just localized near manufacturing facilities or places where aqueous film-forming foam (AFFF) was deployed to douse a fire. It is widely present in our food supply, in our homes, in our cars, and the medical devices designed to keep us healthy. Ultimately, the best PFAS remediation strategy may be to get upstream of the problem however you can. But as Cousins observes, we may have already crossed a global tipping point, and our only feasible options now are limited to understanding where we have exposure and mitigating the worst of them. 

Source control/reduction will play a part, but even the best technologies implemented at full scale are probably only reducing concentrations in source areas by 90-95% and at very high expense. Unfortunately, PFAS reductions of that magnitude still leave impactful concentrations of PFAS in the environment, recognizing that safe levels are defined at low ppt levels. 

Strategies to reduce PFAS exposure are now well into a new phase focused on not making the problem worse than it already is. Environmentally friendly alternatives to PFAS products are being sought in many industries but progress is slow. As a society, we need to seek materials that can degrade naturally and avoid the mistake of creating another class of recalcitrant compounds with effects that could linger “forever”.