PFAS levels refer to the measured concentrations of per- and polyfluoroalkyl substances in drinking water, blood, food, and the environment. These levels are typically reported in parts per trillion (ppt) for water and nanograms per milliliter (ng/mL) for blood. Because PFAS are extremely persistent and don’t break down naturally, even tiny concentrations matter, and regulators have set strict limits to protect public health.
How PFAS Levels Are Measured
PFAS concentrations in water are measured in parts per trillion, abbreviated as ppt (also written as nanograms per liter, or ng/L). One part per trillion is an extraordinarily small amount. To put it in perspective, 1 ppt is equivalent to one drop of water in 20 Olympic-sized swimming pools. The fact that regulators set limits at single-digit parts per trillion reflects how potent these chemicals can be at very low concentrations.
Blood levels, on the other hand, are measured in nanograms per milliliter (ng/mL). National health surveys collect blood samples to track how much PFAS the general population carries. These two measurement systems, ppt for water and ng/mL for blood, show up in nearly every PFAS discussion, so understanding both is useful for interpreting test results.
EPA Drinking Water Limits
In 2024, the EPA finalized the first enforceable federal limits for PFAS in drinking water. These Maximum Contaminant Levels (MCLs) are the legal ceiling for what public water systems can deliver to your tap:
- PFOA: 4.0 ppt
- PFOS: 4.0 ppt
- PFHxS: 10 ppt
- PFNA: 10 ppt
- GenX chemicals: 10 ppt
These limits are dramatically lower than the EPA’s earlier 2016 health advisory, which set a combined limit of 70 ppt for PFOA and PFOS together. The sharp drop reflects a growing body of evidence that health effects occur at much lower exposures than previously thought. PFOA and PFOS, the two most studied PFAS compounds, received the strictest limits because they persist longest in the body and have the strongest links to health problems.
Screening Levels for Children and Adults
The Agency for Toxic Substances and Disease Registry (ATSDR) has developed separate screening values that translate daily exposure limits into drinking water concentrations. Because children weigh less and drink more water relative to their body size, their thresholds are significantly lower:
- PFOA: 78 ppt for adults, 21 ppt for children
- PFOS: 52 ppt for adults, 14 ppt for children
- PFHxS: 517 ppt for adults, 140 ppt for children
- PFNA: 78 ppt for adults, 21 ppt for children
These are screening values, not enforceable limits. If water concentrations fall below these numbers, exposure is not expected to cause health problems. If levels exceed them, it signals the need for further evaluation, not necessarily immediate danger. The EPA’s enforceable MCLs are considerably stricter than these screening values, meaning water systems that comply with federal law will also fall well within ATSDR’s safety margins.
How European Limits Compare
The European Union takes a broader approach. Rather than setting limits for individual PFAS compounds, the EU’s updated Drinking Water Directive introduced two parameters: “PFAS Total” and “Sum of PFAS.” The limit for the sum of specific PFAS compounds is 100 ppt (0.1 micrograms per liter), while the total PFAS limit covering all detectable PFAS is 500 ppt (0.5 micrograms per liter). These became mandatory for EU member states in January 2026. The philosophy behind this approach is that PFAS rarely appear alone in contaminated water, so regulating the total burden may be more protective than targeting individual chemicals.
PFAS Levels in Blood
Nearly everyone in the United States has detectable levels of PFAS in their blood. National health survey data from 2017 to 2020 found that the 95th percentile blood concentration of PFOS (the most commonly detected compound) was 14.8 ng/mL among people aged 12 and older. For PFOA, the 95th percentile was 3.6 ng/mL. That means 95% of the population had levels at or below those numbers, while the remaining 5% had higher exposure.
These blood levels have actually declined significantly over the past two decades. Major manufacturers phased out PFOS production in the early 2000s and PFOA production followed. But because PFAS take years to leave the body (the half-life of PFOS in blood is roughly four to five years), population levels drop slowly. People living near manufacturing sites, military bases where firefighting foam was used, or contaminated water sources tend to have blood levels well above the national average.
PFAS in Food and Packaging
Drinking water isn’t the only source of exposure. PFAS have been detected in food packaging, particularly grease-resistant wrappers and containers. A recent assessment of consumer food packaging found nine different PFAS compounds across samples, with total concentrations ranging from 0.11 to 16.3 nanograms per gram. The most common compound appeared in 61% of samples across all material types. While these concentrations are low, they represent one of several everyday exposure routes that collectively contribute to the PFAS levels found in blood.
Other sources include nonstick cookware, stain-resistant fabrics, certain cosmetics, and contaminated soil or groundwater near industrial sites. For most people, diet and drinking water are the two largest contributors to total PFAS exposure.
How to Reduce Your Exposure
If your water supply has elevated PFAS levels, a certified water filter is the most direct intervention. Filters certified under the NSF/ANSI standard for PFAS reduction must bring combined PFAS concentrations down to 20 ppt or lower. Activated carbon filters and reverse osmosis systems are the two most effective technologies for home use. Standard pitcher filters vary widely in performance, so checking for NSF certification specific to PFAS is important.
You can find out what’s in your local water by checking your utility’s annual Consumer Confidence Report, which public water systems are required to publish. If you use a private well, you’ll need to arrange testing independently, as wells are not covered by federal drinking water regulations. Many state health departments offer PFAS testing for private wells at low or no cost, particularly in areas with known contamination.
Beyond water filtration, reducing contact with grease-resistant food packaging, choosing cookware without nonstick coatings, and checking product labels for PFAS-free claims can help lower your cumulative exposure over time.