Drinking water in America may contain twice as many forever chemicals as previously thought, a new study suggests.
Researchers looked through more than 1.8 million records from the Environmental Protection Agency (EPA) monitoring per- and polyfluoroalkyl substances (PFAS), also called forever chemicals, in public water systems across the country.
They found that by classifying PFAS levels that fall below minimal reporting levels as zero, current EPA reports only capture about 44 percent of the average PFAS concentration in public water systems.
This means the burden of forever chemicals in these systems may be far greater than official reporting would suggest. PFAS have been shown to linger in the environment for long periods of time and are increasingly being linked to reproductive issues, liver damage, cancer and developmental delays in children.
The EPA data shows at least 176 million Americans use water from systems where at least one type of PFAS was detected, but more than half of test results fall below the agency’s minimum reporting threshold and are treated as zero.
The team found the greatest estimated gaps in California, followed by Texas and Florida, based on PFAS levels and the amount of people relying on these water systems.
Gehendra Kharel, first study author and associate professor at Texas Christian University, said: ‘When the levels of these chemicals are below our reporting limit, it’s often treated as zero when we calculate how widespread they are.
‘We set out to understand how treating those results as zero changes the picture of PFAS occurrence in drinking water.’
Researchers have warned that the level of forever chemicals in water may be twice as high as previous estimates suggest
Under the Safe Drinking Water Act, the EPA requires public water systems to monitor levels of 29 different kinds of PFAS in drinking water.
The agency’s minimum reporting threshold for PFAS in drinking water is four parts per trillion (ppt).
The researchers behind the new study, published in Cell Reports Sustainability, note that most individual PFAS test results in EWG’s dataset fall below this level, causing the EPA to record them as zero.
Kharel notes that while this does not suggest the water is completely PFAS-free, it often is treated as zero when agencies and researchers summarize average PFAS levels in drinking water.
In the new study, researchers analyzed water data for 25 types of PFAS that had at least one detection nationally.
They used this data to estimate the difference in reported PFAS concentrations to those found in their own analysis.
Overall, the team found that while the national average concentration of PFAS in drinking water under conventional estimates is about 2.6 nanograms per liter, the new study’s model estimates an average closer to 5.2 nanograms per liter.
The above map included in the new study measures the differences in PFAS concentrations in standard reported PFAS measures compared to those the researchers found in their own analysis. Darker shades indicate states with a larger difference in estimated PFAS concentrations using conventional methods compared to those in the study
The above map from Environmental Working Group, updated in March 2026, shows areas with PFAS levels in drinking water measuring above and below the agency’s proposed safety limits
To reduce the risk of exposure to PFAS, the EPA recommends drinking filtered water
The researchers also compared state-level estimates of PFAS concentrations using conventional methods to estimates from their model accounting for measurements that were below standard reporting limits.
Research is still uncovering the health risks tied to PFAS and exactly how much PFAS may be linked to long-term damage. The EPA notes that even small amounts of PFAS can accumulate in the body over months or years because the substances do not break down, leading to issues such as high cholesterol, reproductive issues, developmental delays, liver damage and certain kinds of cancer.
The EPA recommends drinking filtered water to cut down on exposure.
Kharel cautions that the findings are not automatically a cause for panic. He said the study ‘only estimates how PFAS measurements are summarized’ and that it ‘does not establish that every below-limit result poses a health risk.’
He notes, however, that the findings could provide a more complete picture of PFAS levels in drinking water.
He said: ‘When a water quality report says “not detected,” that means below the reporting limit, not zero.
‘Our method gives water agencies and utilities a way to account for that difference, so they can see where more testing would help and be clearer about what they do and do not know.’
