PFAS Chemicals in Tap Water
PFAS are a large family of persistent synthetic chemicals. Individual compounds have different reference values, monitoring histories, and treatment claims.
5 compound guides5 with a federal MCL3 treatment methods named
A family label, not a compound
The family includes many fluorinated compounds designed to resist heat, oil, stains, and water. A family label is useful for orientation, but it is not a substitute for identifying the specific compound in a water record.
Reference values and enforceable limits apply to named PFAS compounds or defined mixtures. PurityMap therefore keeps each compound’s benchmark and measurement context attached to its own guide. In 2024 the U.S. EPA set the first enforceable national limits for several PFAS, including a maximum of 4.0 ng/L each for PFOA and PFOS.
- Industrial discharge
- Firefighting foam
- Legacy consumer-product manufacturing
- Legacy stain-resistant treatments
- Fluoropolymer / chemical manufacturing discharge
Five PFAS with federal limits
Each has its own limit. Three are also limited together through a hazard index.
EPA's 2024 drinking-water rule set maximum contaminant levels of 4.0 ng/L for PFOA and for PFOS, and 10 ng/L for PFHxS, PFNA and HFPO-DA (GenX). In May 2026 EPA proposed keeping the PFOA and PFOS limits, with the option of until 2031 to comply, and rescinding the other three. Until a final rule, all five limits apply.
Four checks before you act
- STEP 1Identify the named analyte
A family name may contain compounds with different standards and health contexts.
- STEP 2Keep the measurement attached
Read the value with its unit, qualifier, sampling period, reporting limit and source.
- STEP 3Compare only with the stated reference
PurityMap does not turn unlike compound results into a family score or safety verdict.
- STEP 4Verify the treatment claim
The product certification must name the compound or reduction claim.
Three methods, each named by the compound guides
A technology name is only a starting point. Confirm the product’s certification names the compound before choosing equipment.
- Activated carbon (GAC)
Named by 5 of 5 compound guides in this family.
PFOAPFOSPFHxSGenXPFNA - Anion exchange
Named by 5 of 5 compound guides in this family.
PFOAPFOSPFHxSGenXPFNA - Reverse osmosis
Named by 5 of 5 compound guides in this family.
PFOAPFOSPFHxSGenXPFNA