1 in 5 Americans May Have PFAS in Their Tap Water, Study Finds

When you fill a glass at the tap, you expect the water to be clean and safe—not brimming with cancer-linked PFAS chemicals. Unfortunately, this may be the reality for countless Americans relying on groundwater sources for their drinking water, according to a new scientific study by the U.S. Geological Survey (USGS).

PFAS, short for per- and polyfluoroalkyl substances, are synthetic compounds used in various consumer and industry products since the 1940s. Scientists have studied these so-called “forever chemicals” extensively throughout the decades and even linked them to serious health issues. Now, the USGS estimates that millions of Americans may have PFAS in their drinking water, particularly if it comes from untreated groundwater serving public and private wells.

In this article, we’ll break down this groundbreaking study, highlight the potential harms of PFAS exposure, and share how you can minimize exposure to these pervasive chemicals in drinking water at home.

Understanding the Scope of PFAS Contamination in U.S. Groundwater

The purpose of the USGS study has a lot to do with the EPA’s Unregulated Contaminant Monitoring Rule 5 (UCMR-5). Under this rule, testing is required for 29 PFAS chemicals in public water systems serving over 3,300 people and 800 smaller systems from 2023 to 2025. However, it excludes over 90% of small systems under that size group and private wells that supply water to about 13% of the U.S. population. Besides, the exact locations and depths of UCMR 5 samples were undisclosed, supposedly to protect water security.

Considering this, researchers sought to address these gaps.

How the Study Was Conducted

To derive PFAS contamination estimates, the research team analyzed 1,238 groundwater samples collected by USGS scientists. These samples came from untreated domestic wells from three networks across the U.S. between 2019 and 2022. The researchers considered factors such as urban development and well depth to assess the likelihood of PFAS contamination.

After feeding the collected data into an advanced machine learning algorithm, the team was able to estimate how many people in a given area relying on groundwater for drinking water may be exposed to PFAS contamination before any treatment. They could also predict the regions that are likely to be impacted, even if they had not been tested yet.

The researchers tested for the presence of 24 common PFAS, including perfluorobutane sulfonate (PFBS), perfluorooctane sulfonate (PFOS), and perfluorooctanoate (PFOA).

Findings

The findings were both alarming and enlightening. Between 71 and 95 million Americans, or more than 20% of the country’s population, in the lower 48 states may rely on untreated groundwater containing detectable levels of PFAS for their drinking water supplies. Also, over one-third (37%) of all groundwater samples contained at least one PFAS.

The study found that California and Florida have the most residents reliant on public water supplies that use PFAS-tainted groundwater. For private well supplies, Michigan, Florida, North Carolina, Pennsylvania, New York, and Ohio had the highest populations dependent on potentially contaminated groundwater. Of all the areas sampled, the Biscayne Principal Aquifer in southern Florida showed the highest median concentration of PFAS at 29 nanograms per liter for the 24 PFAS compounds analyzed.

Comments from Study Authors

Andrea Tokranov, USGS research hydrologist and lead author of this study, said this about the findings: “This study’s findings indicate widespread PFAS contamination in groundwater that is used for public and private drinking water supplies in the U.S. This new predictive model can help prioritize areas for future sampling to help ensure people aren’t unknowingly drinking contaminated water.”

When asked who this study could benefit, Tokranov explained: “This is especially important for private well users, who may not have information on water quality in their region and may not have the same access to testing and treatment that public water suppliers do.”

Furthermore, the researchers say they hope their model will help people at high risk of exposure to be more aware of their risk and push for testing. They said: “The results are available for public consumption, which allows homeowners to evaluate results in their region and determine if home testing or treatment are options they would like to pursue.”

How do PFAS get into U.S. groundwater?

While the study did not say precisely how PFAS ended up in U.S. groundwater supplies, these chemicals generally can do so through several pathways.

Industrial Discharges

Many commercial and industrial industries produce or use PFAS in manufacturing processes. Sometimes these chemicals are improperly released directly into water bodies or through air emissions that eventually settle into water and soil. These industries include textile and leather treatment, paper products, and metal plating facilities. The chemicals can then seep into groundwater and contaminate drinking water sources.

Landfill Leachate

When certain hazardous materials break down in landfills and compost sites, PFAS can leach out and eventually end up in groundwater. Generally, landfills and compost sites are designed with a safety feature to prevent this. Still, sometimes there’s none, or it fails, allowing the PFAS to enter the soil during heavy precipitation and percolate into groundwater sources.

Wastewater Treatment Plants

Sewage treatment plants remove most contaminants from water, so it’s safer for the environment. However, pollutants like PFAS can still slip through. As a result, the chemicals are released back into the water table. From there, they can enter groundwater systems, especially where surface water and groundwater are closely connected.

Firefighting Foam

Aqueous film-forming foams in firefighting, particularly at airports, military bases, and firefighting training areas, have been a significant source of PFAS contamination. These foams are highly effective at suppressing fuel fires but contain high PFAS concentrations. When used, they can quickly infiltrate soil and eventually reach groundwater, creating long-lasting contamination plumes.

Learn more: How AFFF Firefighting Foam Can Pollute Drinking Water

Is there a safe level of exposure to PFAS in drinking water?

There’s a lot of uncertainty around what’s considered a “safe” level of PFAS in drinking water.

In 2022, the EPA advised that any amount of these chemicals in tap water can be dangerous. But on April 10, 2024, the agency finalized its first-ever federal limits on PFAS in water, capping PFOS and PFOA—the two most common PFAS—at four parts per trillion (ppt). This is the lowest level most labs can detect the chemicals in water.

Their non-enforceable health-based goal for both PFAS, however, is zero. Per the EPA, this limit reflects the latest science showing that there is no level of exposure to these contaminants without risk of health impacts.

The EPA also regulated four other PFAS in water with a maximum contaminant level (MCL) of 10 ppt for each. These chemicals include PFBS, PFNA, PFHxS, and GenX. Under the rule, the level detected of these four chemicals will be compared to a “Health-Based Water Concentration” for the chemical. Afterward, the values for each of these are added together. If the combined concentration exceeds the EPA’s hazard index or any individual MCL is exceeded, this is considered a violation.

What are the health risks from PFAS exposure?

PFAS aren’t called “forever chemicals” for no reason. They combine carbon and fluorine molecules to form a strong chemical bond, which explains why they don’t break down or do so extremely slowly. Because of this, PFAS can remain in our bodies for an incredibly long time and even accumulate in our tissues and organs over time.

As noted by the EPA, even tiny levels of exposure to PFAS are linked to several diseases and health risks, including:

Interference with the body’s natural hormones.
Increased cholesterol levels and/or risk of obesity.
Increased risk of some cancers, including prostate, kidney, and testicular cancers.
Reduced ability of the body’s immune system to fight infections, including reduced vaccine response.

Pregnant women, infants, and children are even more susceptible to the adverse effects of PFAS. Some additional health effects linked to PFAS for pregnant women and children include:

Developmental effects or delays in children, such as low birth weight, accelerated puberty, bone variations, or behavioral changes.
Reproductive effects such as decreased fertility or increased high blood pressure in pregnant women.
Decreased response to vaccines

A review by a panel of experts examining research on PFAS toxicity found evidence linking these chemicals to several other health issues. However, more research is needed to confirm these findings. The potential health risks include:

inflammatory bowel disease
reduced fertility
breast cancer
an increased likelihood of miscarriage
developing high blood pressure and preeclampsia during pregnancy

Beyond that, current research indicates that prenatal exposure to PFAS may have long-term consequences for children. Babies exposed before birth might face a higher risk of obesity, early-onset puberty, and reduced fertility later in life

Learn more: The Toxic Effects of PFAS in Drinking Water

How can you reduce your risk of PFAS in drinking water at home?

If a water test or water quality report indicates that your water is contaminated with PFAS, or you want peace of mind, it is worth investing in a water filtration system for your home.

The EPA has found that reverse osmosis (RO) and activated carbon filters are the most effective at reducing PFAS in drinking water, so let’s look at how these systems work.

How Reverse Osmosis Filters Remove PFAS from Drinking Water

Reverse osmosis is considered the “gold standard” for addressing high PFAS concentrations in water. During filtration, the system uses pressure to force the unfiltered water through a semipermeable RO membrane with super-tiny pores. The membrane separates the water molecules from unwanted substances, effectively trapping contaminants and impurities like PFAS, lead, microplastics, arsenic, and some bacteria in the membrane’s pores while allowing water to pass through. Now filtered, the water passes to the other side of the membrane and is collected in a tank. The remaining trapped contaminants are flushed away as wastewater.

Learn more: Reverse Osmosis Water Filtration Explained

How Activated Carbon Filters Remove PFAS from Drinking Water

Activated carbon filters, like the SpringWell CF1 Whole-House Water Filter, reduce PFAS in water through adsorption. Activated carbon is a porous material with a large surface area. As water passes through it, the activated carbon traps the PFAS molecules in the pores of its surface area. If any, the water flows to the next filtration stage.

Learn more: Activated Carbon Filters: What Do They Remove from Water?

What about bottled water?

Many people perceive bottled water as a safer alternative to tap water, but it might not be as pure as some believe. According to Consumer Reports, many bottled waters have tested positive for PFAS, heavy metals, and other contaminants.

Most bottled water is also packaged in plastic, typically polyethylene terephthalate (PET). There are concerns that this packaging can leach micro-nano plastics and chemicals like phthalates, bisphenols, and antimony into the water inside.

On top of that, the manufacturing and disposal of bottled water plastic is a major source of various chemicals that ultimately enter and contaminate the surface and groundwater sources that supply our drinking water. And as explained in a previous article, buying bottled water can outpace the cost of a high-quality water filtration system for your home in the long run.

Final Thoughts

The USGS’s latest discovery of another PFAS crisis shows us how widespread this problem has become and should be a wake-up call to pay more attention to our drinking water quality. Plus, given the health risks associated with these persistent chemicals, we should try our best to limit our exposure, primarily through water supplies.

With that in mind, use your best judgment and consider investing in a reverse osmosis filter or activated carbon system, mainly if you rely on well water or live in high-risk areas like California, Florida, Michigan, North Carolina, Pennsylvania, New York, or Ohio.