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As the US wrestles with how to deal with widespread PFAS pollution in drinking water supplies, most utilities are lacking advanced filtration systems that could protect public health from not just PFAS but an array of harmful contaminants, according to a new study.
Small, rural communities are the least likely to have the advanced systems in place, the study notes.
Among the contaminants that the advanced systems can reduce are the water disinfectant byproducts trihalomethanes and haloacetic acid, according to the study from the Environmental Working Group (EWG), which was published Thursday in the journal ACS ES&T Water. Both byproducts are considered potential carcinogens.
“The majority of systems impacted by PFAS contamination lack advanced water treatment,” the authors wrote. “A nationwide installation of treatment for PFAS removal could present an opportunity for overall public water quality improvement.”
Though a number of hazardous chemicals and other substances commonly contaminate water sources, the issue of how to tackle per- and polyfluoroalkyl substances (PFAS) is currently a top concern.
PFAS — also known as “forever chemicals” for their persistence in the environment — are linked to certain cancers, thyroid disease, liver damage and immune system problems, among other health problems. A July analysis of EPA data by the Natural Resources Defense Council found over 73 million people in the US are exposed to toxic PFAS chemicals in their tap water.
This widespread contamination has created problems for water treatment utilities and a patchwork of state and federal PFAS drinking water standards. The study estimates just 8% of US water systems are equipped with filters that can remove PFAS. And 98% of systems that have PFAS detections do not have treatment targeting the chemicals — a number that study co-author and EWG science analyst Varun Subramaniam called “staggering.”
Advanced water filtration systems that have been put in place at some utilities include granular activated carbon, ion exchange and reverse osmosis. The cost and complexity has slowed widespread adoption of such advanced systems, and recent moves by the Trump administration has further slowed progress.
The Biden administration put in place nationwide drinking water regulations for six PFAS in 2024, which would force more utilities to put advanced filtration in place. In May, however, the EPA announced it is dropping drinking water limits on four types of PFAS and delaying the deadline for drinking water systems to comply with standards for two of the most toxic forms of PFAS.
While water utility groups applauded the EPA’s walkback citing the high costs of compliance, Subramaniam said the rules passed under Biden would have been a “catalyst for broader drinking water improvements.”
“PFAS are almost ubiquitous, occurring all across the country … and almost always as part of a mixture of several contaminants,” he said.
EPA “undervalued” benefits of advanced filtration
EWG researchers examined data from the EPA’s national water monitoring program and found that PFAS was detected along with pollutants such as trihalomethanes, haloacetic acid, heavy metals and nitrates in 64% of 1,083 systems.
In looking closer at 19 water treatment utilities that had installed advanced filtration between 2018 and 2022, levels of trihalomethanes and haloacetic acid dropped on average 42% and 50%, respectively, from before the installation of advanced filtration to after.
Trihalomethanes and haloacetic acid are groups of chemicals that can form in water when chlorine or other disinfectants contact organic and inorganic matter in water. These byproduct chemicals are regulated by the EPA.
These decreases were larger than what the EPA previously estimated.
“EPA has undervalued the benefits” of advanced filtration in removing these contaminants, Subramaniam said, adding that they also found reductions in certain PFAS compounds but the sample size was too small to estimate the decreases. While they didn’t examine decreases in other contaminants such as nitrates and heavy metals, he said they would expect advanced filtration to significantly reduce those as well.
“EPA has undervalued the benefits.” – Varun Subramaniam, EWG
Sydney Evans, EWG senior science analyst and lead author of the study, said reverse osmosis is generally the most effective advanced filtration method for removing contaminants. But it can also be expensive.
Cost is “certainly the largest challenge to public water systems that are considering advanced filtration methods,” Dan Hartnett, chief policy officer at the Association of Metropolitan Water Agencies (AMWA), said.
He said the association contracted a report that estimated annual household cost to pay for the advanced treatment methods under the Biden administration’s rule would vary based on system size, but overall would average an additional $230 per household per year.
“The numbers were significantly higher for the smallest water systems,” he added.
The new EWG study found only 7% of very small water systems serving fewer than 500 people — and with more limited resources — use advanced filtration, while 28% of the largest utilities use the technologies.
“Regardless of what kind of filtration, we saw the same trend across the entire dataset — small systems are continuing to struggle to install these,” Subramaniam said.
In 2024 the EPA estimated the total cost for community water systems to install PFAS-removing treatment systems and comply with the standards put forth by Biden’s EPA was about $1.5 billion annually, but health-related cost savings would cancel out the cost.
However, the American Water Works Association (AWWA) estimated the cost for utilities would range from more than $2.5 to $3.2 billion annually.
Evans said the pushback is understandable as “there are certainly costs to installing these treatments … which is why it’s so important to consider all of the benefits.”
“It’s really important to look at the entire breadth of benefits – you’re not just removing PFAS, but reducing all these other contaminants,” Evans said.
Changes to PFAS drinking water standards
The study comes as PFAS water standards in the US are in flux. In May the EPA announced it intends to rescind limits set under former President Biden on four types of PFAS widely found in drinking water – perfluorononanoic acid (PFNA), perfluorohexane sulfonate (PFHxS), perfluorobutane sulfonate (PFBS) and GenX — and delay the due date for utilities to comply with standards for two of the most toxic forms of PFAS — perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) — from 2029 to 2031.
While the move was widely criticized by health advocates, EPA Administrator Lee Zeldin said in a statement at the time that the agency would “work to provide common-sense flexibility in the form of additional time for compliance … [and] support water systems across the country.”
The AMWA along with the AWWA applauded the EPA’s May announcement, saying in a joint statement that “allowing communities time to make fiscally sound decisions based on thoughtful evaluation of compliance alternatives is simply good policy.”
The two groups filed a lawsuit against the EPA challenging the process used to develop the drinking water standards under Biden.
Featured image: The Peace River Manasota Regional Water Supply Authority water treatment plant in Lakewood Ranch, Florida. (Credit: Florida Water Daily/flickr)
