PFAS in Drinking Water: What You Need to Know
What PFAS are, the 2024 EPA rule (4 ppt), which filters reduce them, and how to check your water.
PFAS (per- and polyfluoroalkyl substances) are a group of over 14,000 synthetic chemicals that have been manufactured and used in consumer products and industrial processes since the 1940s. They are called “forever chemicals” because they do not break down naturally in the environment or the human body.
What Are PFAS?
PFAS are a family of chemicals characterized by strong carbon-fluorine bonds. They have been used in non-stick cookware, stain-resistant fabrics, food packaging, firefighting foams (AFFF), and many industrial applications. The most studied compounds are PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonic acid), though newer “short-chain” replacements like GenX are also of concern.
PFAS enter drinking water through industrial discharge, military and civilian firefighting training sites, wastewater treatment plants, and contaminated groundwater. The EPA's UCMR 5 monitoring program has detected PFAS in approximately 3,500 public water systems, and independent research suggests an estimated 176 million Americans have detectable levels in their drinking water.
The 2024 EPA PFAS Rule
On April 10, 2024, the EPA finalized the first-ever national drinking water standard for PFAS. The key limits are:
| Compound | MCL (Enforceable Limit) | MCLG (Health Goal) |
|---|---|---|
| PFOA | 4 parts per trillion (ppt) | Zero |
| PFOS | 4 ppt | Zero |
| PFHxS | 10 ppt | 10 ppt |
| PFNA | 10 ppt | 10 ppt |
| GenX (HFPO-DA) | 10 ppt | 10 ppt |
| Mixtures of 2+ PFAS | Hazard Index of 1.0 (unitless) | |
Public water systems have until 2029 to comply. Private wells are not covered by this rule.
Health Effects
According to the EPA, exposure to certain PFAS has been associated with:
- Increased risk of certain cancers (kidney, testicular)
- Liver effects and elevated cholesterol
- Immune system effects, including reduced vaccine response
- Thyroid disease
- Developmental effects during pregnancy
The EPA set the MCLG (health goal) for PFOA and PFOS at zero, indicating that no safe level of exposure has been identified. Research is ongoing and the full scope of health effects is not yet known.
Which Filters Reduce PFAS?
Three filtration technologies have demonstrated effectiveness at reducing PFAS in peer-reviewed research and NSF-certified testing:
Activated Carbon (GAC & Carbon Block)
High-quality carbon block filters certified under NSF 53 or P473 can reduce PFOA and PFOS. Granular activated carbon (GAC) is less consistent. Look for the specific PFAS certification - not all carbon filters are effective.
Reverse Osmosis
RO systems certified under NSF 58 are effective at reducing a broad range of PFAS compounds, including short-chain variants that carbon may miss. Generally the most comprehensive option for PFAS reduction.
Ion Exchange
Anion exchange resins can be highly effective for PFAS, especially short-chain compounds. Less common in residential point-of-use systems but used in whole-house and point-of-entry applications.
UV treatment, water softeners, and standard sediment filters do not reduce PFAS. Use our Contaminant Matcher to find filters certified for PFAS reduction in your area.
How to Check Your Water
- Municipal water:Request your utility's Consumer Confidence Report (CCR), or check the EWG Tap Water Database by ZIP code for independent testing results.
- EPA UCMR 5 data:The EPA's latest monitoring round specifically tested for 29 PFAS compounds in public water systems. Results are publicly available on the EPA UCMR website.
- Private wells: PFAS is not tested by utilities for private wells. Order a PFAS-specific test from a certified laboratory. Costs typically range from $200–$400.
Sources
Educational guidance only - consult your water utility or a certified lab for situation-specific recommendations.