Drinking water contaminated with PFAS directly linked to dangerous blood toxin levels

People in U.S. communities with higher PFAS in public drinking water also tend to carry more of these chemicals in their blood. The most important number is this: 7.1 percent of residents in high exposure areas had blood levels above 20 ng/mL, compared with 2.8 percent in low exposure areas.

The study drew on 1,599 deidentified blood samples from matched U.S. zip codes categorized by water system PFAS exposure. Those results were presented in Chicago at a national diagnostics meeting.

Drinking water and PFAS levels

The team examined how PFAS (per- and polyfluoroalkyl substances) in local water relate to PFAS found in people’s blood. They paired areas with high and low water exposure and kept age and sex distributions similar across groups.

Wen Dui of Quest Diagnostics led the research team that analyzed the samples and interpreted the findings. That point matters because it shows a laboratory group connecting population exposure with clinical testing.

“Drinking water is one of the most important routes for exposure to environmental contaminants, including PFAS,” said Dui.

Doctors now have a clearer yardstick for interpreting PFAS blood results, thanks to National Academies of Sciences, Engineering, and Medicine (NASEM), independent science advisors to government. The guidance uses the sum of nine PFAS to flag exposure levels that may require more follow up.

“There is an increased risk of adverse effects above 20 ng/mL.” That language frames the clinical meaning of the 7.1 percent with high summed PFAS.

The same guidance links higher PFAS exposures with problems such as kidney cancer, lower infant growth, abnormal cholesterol, and reduced antibody response.

It also recommends extra clinical testing and exposure reduction once the 20 ng/mL threshold is exceeded.

Developing PFAS water standards

Federal regulators have set enforceable limits for several PFAS in public water systems using the maximum contaminant level, which is the highest legally allowed concentration in drinking water thresholds. 

The new standards include 4 parts per trillion for PFOA and PFOS, which are among the most studied PFAS. That bar is extremely low, reflecting both improved detection and concern about health effects at small doses.

The rule also regulates certain PFAS mixtures through a hazard index, which adds risk scores when several compounds show up together. In practice, that drives more monitoring and more treatment upgrades in systems that exceed the limits.

Science behind the blood test

To measure exposure in people, the Quest team used a serum assay built to quantify the nine PFAS recommended by NASEM. Here, serum, the liquid part of blood after clotting, gives a stable window into cumulative exposure.

Quest scientists previously validated a precise serum method that can measure these nine PFAS together and report the total. That summation aligns the lab test with how clinicians interpret health risk.

Summing across nine common PFAS helps standardize results even when individual compounds vary from place to place.

It also streamlines follow up, since the 20 ng/mL cut point is tied to the total rather than any one chemical.

Broadening the search

PFAS are nearly everywhere, from nonstick pans to water resistant fabrics and some firefighting foams. A national study estimated that at least 45 percent of U.S. tap water contains one or more PFAS.

These substances enter water when manufacturing waste streams, landfill leachate, or legacy firefighting foam residues move into rivers and aquifers. Once in the environment, many PFAS persist for years in soil and water.

Communities have begun tracking sources, upgrading filters, and planning long term cleanup. Those steps take time, but they lower exposure for many people who cannot switch sources quickly.

What this link does not prove

This study shows correlation, not causation, between higher PFAS in water and higher PFAS in blood. It does not prove that water exposure alone is responsible for any one person’s result.

People also encounter PFAS through food contact materials, indoor dust, and some specialty products. Those pathways can add up, even when water meets current standards.

Using zip code level water data can misclassify exposure for households that use private wells or bottled water. Remnant specimens can also underrepresent people who rarely access the health system.

What you can do now

Start with your local water utility’s Consumer Confidence Report, which lists detected contaminants and treatment steps. If PFAS are not listed, ask whether testing is planned and when results will be posted.

If you are concerned about household exposure, look for point of use filters that are certified to reduce PFAS. Certification marks help separate marketing claims from performance.

If you receive a PFAS blood test, share the result with a clinician who understands the NASEM thresholds. That visit can guide sensible next steps and keep follow up focused on the highest benefit actions.

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