Situated in a former sand and gravel pit just a few hundred feet from the Kennebec River in central Maine, the Riverside Station pumps half a million gallons of fresh groundwater every day. The well station processes water from two of five wells on either side of the river operated by the Greater Augusta Utility District, or GAUD, which supplies drinking water to nearly 6,000 local households. Most of them reside in Maine’s state capital, Augusta, just a few miles to the south. Ordinarily, GAUD prides itself on the quality of its water supply. "You could drink it out of the ground and be perfectly safe," said Brian Tarbuck, GAUD's general manager.

But in March 2021, environmental sampling of Riverside well water revealed trace levels of per- and polyfluoroalkyl substances (PFAS), or "forever chemicals," as they're better known. The levels at Riverside didn't exceed Maine's drinking water standard of 20 parts per trillion (ppt), which was a relief, Tarbuck said. Still, he and his colleagues at the utility were wary. PFAS have been linked to a variety of health problems, and Maine lawmakers at the time were debating an even stricter limit for the chemicals. Tarbuck knew a lower standard was coming someday. The only question was when.

As it turns out, a tougher standard is expected early this year. That's when the US Environmental Protection Agency is set to finalize an enforceable cap on PFAS in drinking water that will require GAUD and thousands of other utilities around the country to update their treatment methods. The standard, which in regulatory terms is called a maximum contaminant level, or MCL, limits permissible amounts of the two most studied and ubiquitous PFAS compounds—PFOA and PFOS—to just 4 ppt in drinking water each. Roughly equivalent to a single drop in five Olympic-size swimming pools, this is the lowest concentration that current analytical instruments can reliably detect "within specific limits of precision and accuracy during routine laboratory operating conditions," according to the EPA. Four other PFAS—PFHxS, PFNA, PFBS, and HFPO-DA (otherwise known as GenX Chemicals)—will be regulated by combining their acceptable levels into a single value. Utilities will have three to five years to bring their systems into compliance.

Agency officials estimate that between 3,400 and 6,300 water systems will be affected by the regulation, which is the EPA's first ever PFAS standard and the first MCL set by the agency for any chemical in drinking water in over 25 years. PFOA and PFOS account for the majority of anticipated exceedances.

GAUD is now gearing up to spend $3 to 5 million on PFAS removal technology, according to Tarbuck, much of which will be passed on to its customers in the form of higher water bills. Nationally, the price tag of meeting the standard could top $37 billion in upfront costs, in addition to $650 million in annual operating expenses, according to the American Water Works Association, or AWWA, a nonprofit lobbying group representing water utilities. That's far higher than the EPA's cost estimate of $777 million to $1.2 billion and a significant burden for an industry already contending with other costly priorities, such as boosting cybersecurity and "replacing all those antiquated, leaking big water pipes that transport the water from the treatment plant to the service line” that connects to homes, said Marc Edwards, a professor of civil and environmental engineering at Virginia Tech. Chris Moody, the AWWA's regulatory technical manager, said most of the money will be spent in the next several years, as utilities race to install PFAS removal systems and other infrastructure needed to meet compliance deadlines.

In proposing the limits, EPA officials said that they had leveraged the latest science to protect the public from PFAS pollution. Environmental groups welcomed the move as long overdue. But the standard has drawn widespread criticism from the water utility industry and some scientists who say that in many places, small drops in PFAS water levels will matter little for exposure or health. “There are other strategies that get us to safer, public health protective approaches to PFAS that don’t involve the really strict standard that EPA is putting forward," said Ned Calonge, an associate dean for public health practice at the Colorado School of Public Health and chair of a 2022 National Academies of Sciences report on PFAS exposure, testing, and clinical follow-up.

EPA officials estimate that between 3,400 and 6,300 water systems will be affected by the regulation, which is the agency's first-ever PFAS standard

A key issue, critics say, is that the standard ensnares too many utilities with very small PFAS exceedances. Roughly 98 percent of drinking water utilities in the country, including GAUD, have maximum PFOA and PFOS levels below 10 ppt, according to the AWWA. When the levels are already so low, further reductions of a few parts per trillion "is not going to have much effect on total exposure intake," wrote Ian Cousins, an environmental chemist at Stockholm University and one of the world's leading researchers on PFAS exposure, in an email to Undark.

Drinking water is only one among many different pathways by which people can be exposed to PFAS. The chemicals are also in agricultural produce, fish, meat, outdoor soil, household dust, nonstick cookware, cosmetics, fast-food wrappers, stain- and water-resistant fabrics, and other products. Just how much these sources each contribute to PFAS exposure is a subject of ongoing research. But the EPA estimates that Americans get 80 percent of their PFAS intake from sources other than drinking water, and according to Cousins, dietary contributions likely account for most human exposure. The US Food and Drug Administration has required the phase out of some PFAS in food packaging. But "food is contaminated via bioaccumulation in agricultural and marine food chains," Cousins said. "We cannot clean up our food in the same way that we can add a treatment process to our drinking water."