Should You Filter Your Water for PFAS?

US Geological Service (USGS) research published in the journal Environment International marks the first time anyone has tested for and compared forever chemicals in tap water from both private and government-regulated public water supplies on a broad scale throughout the country. The data provide shocking results that should concern all of us about our health and safety.

Technically known as per- and polyfluoroalkyl substances (PFAS), this family of heat- and water-resistant miracle chemicals includes thousands of unique compounds, all of which contain fluorine. These compounds are known as both long- and short-chained PFAS, and they are all toxic, yet used in a wide variety of common applications, from the linings of fast-food boxes and non-stick cookware to fire-fighting foams, agricultural pesticides, school clothing, sports uniforms, and thousands of other uses. PFAS pose health risks even at very low levels measured in parts per trillion, according to the US Environmental Protection Agency (EPA). Because they break down very slowly, PFAS are commonly called “forever chemicals.”

“USGS scientists tested water collected directly from people’s kitchen sinks across the nation, providing the most comprehensive study to date on PFAS in tap water from both private wells and public supplies,” said USGS research hydrologist Kelly Smalling, the study’s lead author. “The study estimates that at least one type of PFAS — of those that were monitored — could be present in nearly half of the tap water in the U.S. Furthermore, PFAS concentrations were similar between public supplies and private wells.”

The study tested for 32 individual PFAS compounds using a method developed by the USGS National Water Quality Laboratory. The most frequently detected compounds in this study were PFBS, PFHxS, and PFOA. The interim health advisories released by the Environmental Protection Agency (EPA) in 2022 for PFOS and PFOA were exceeded in every sample in which they were detected in this study.

Geographic Distribution of Contamination

Scientists collected tap water samples from 716 locations across low-, medium-, and high-human-impact areas. The low category included protected lands; the medium category included residential and rural areas with no known PFAS sources; and the high category included urban areas and locations with reported PFAS sources, such as industrial sites or waste sites.

Most of the exposure was observed near urban areas and potential PFAS sources. This included the Great Plains, the Great Lakes, the Eastern Seaboard, and Central/Southern California, as well as military bases. The study’s results are consistent with previous research indicating that people in urban areas are at higher risk of PFAS exposure. USGS scientists estimate that the probability of PFAS not being observed in tap water is about 75 percent in rural areas and around 25 percent in urban areas.

Testing Your Water

The EPA regulates larger public water supplies and requires testing. It does not regulate smaller water utilities. In many cases, especially for smaller public or private systems and private wells, homeowners are responsible for the maintenance, testing, and treatment of their own water supplies. Testing is the only way to confirm the presence of these contaminants in your tap water. Cyclopure and Mytapscore both offer water tests for PFAS and other chemicals of concern.

Filter Effectiveness

Scientists at Duke University and North Carolina State University say that while using any filter is better than using none, many of the household filters they tested are only partially effective at removing PFAS from drinking water. Some, without maintenance, increase concentrations.

They tested seventy-six point-of-use filters and thirteen point-of-entry or whole-house systems and found their effectiveness “varied widely.”

But there was good news too. All of the under-sink reverse osmosis systems and two-stage filters achieved near-complete removal of PFAS. In contrast, the effectiveness of activated-carbon filters, used in many pitcher, countertop, refrigerator, and faucet-mounted styles, was inconsistent and unpredictable. The whole-house systems were also widely variable and, in some cases, actually increased PFAS levels in the water. However, ZeroWater pitcher filters are certified to remove PFAS.

Key Takeaways from the Study

Reverse osmosis filters and two-stage filters reduced PFAS levels, including GenX, by ninety-four percent or more.

Activated-carbon filters removed an average of 73 percent of PFAS contaminants, but results varied widely. In some cases, the chemicals were completely removed; in other cases, they were not reduced at all. Researchers found no clear trends between removal efficiency and filter brand, age, or source-water chemical levels. Changing out filters regularly is probably a very good idea, nonetheless, researchers said.

The PFAS-removal efficiency of whole-house systems using activated carbon filters varied widely. In four of the six systems tested, some PFAS levels actually increased after filtration.

In 2017, Minnesota released the results of a study for a faucet-mounted carbon filter made by PUR. The filter was tested for seven PFAS chemicals commonly found in groundwater in Washington County. The state concluded that this low-cost filter could effectively reduce PFAS contamination. Six of seven contaminants, including PFOA and PFOS, were removed below the reporting limits of 5 and 10 parts per trillion, respectively. Levels of the shorter-chain PFAS and PFBA were reduced by 75%. In addition, the Environmental Working Group reports that pitcher filters are somewhat effective at PFAS removal.

Shower filters can be helpful, too. Seek brands that are certified or independently tested for PFAS removal.