PFAS Explained: The 'Forever Chemicals' in Your Water

What PFAS are

PFAS stands for per- and polyfluoroalkyl substances — a class of about 15,000 different synthetic chemicals built around an unusually strong carbon-fluorine bond. That bond doesn't exist in nature, and once these chemicals are made, almost nothing in nature breaks them apart. That's why they're called "forever chemicals."

They've been manufactured since the 1940s for products that need to resist water, oil, heat, or stains: non-stick cookware, water-repellent fabric, fast-food wrappers, firefighting foam, dental floss, cosmetics, and thousands of industrial applications.

How they got into your water

PFAS get into drinking water through industrial discharge, leakage from landfills, use of firefighting foam at airports and military bases, and runoff from areas where PFAS-containing biosolids were applied to fields. Once they enter groundwater, they stay there.

A 2023 USGS study estimated that at least 45% of U.S. tap water contains detectable PFAS. The contamination doesn't respect city/well boundaries — both surface water utilities and private wells are affected.

The new EPA limits (April 2024)

PFOA: 4 parts per trillion (ppt)

PFOS: 4 ppt

PFHxS, PFNA, HFPO-DA ("GenX"): 10 ppt each

Mixtures of these compounds: a calculated Hazard Index of 1.0

These were the first new federal drinking water standards for any chemical contaminant since the 1990s. Public water systems must achieve compliance by 2029. Private wells are not covered.

Why the limits are in parts per trillion

A part per trillion is roughly one drop in a thousand Olympic swimming pools. The EPA's health-based goals (MCLGs) for PFOA and PFOS are actually zero — the enforceable limit of 4 ppt is the lowest level labs can reliably measure with current technology.

Health concerns from peer-reviewed research include immune system effects (reduced vaccine response in children), increased cholesterol, liver effects, decreased birth weight, increased risk of kidney and testicular cancer, and thyroid disease.

How labs test for PFAS

The two primary methods are EPA Method 533 and EPA Method 537.1. Both use liquid chromatography paired with tandem mass spectrometry (LC-MS/MS). They differ in which PFAS compounds they target — Method 533 covers more short-chain compounds; Method 537.1 covers the long-chain compounds most often discussed in the news.

Sample collection is unusually picky. PFAS are in so many consumer products that contamination during collection is a real risk. Don't use plastic bottles for collection (unless lab-provided), don't wear clothing treated with stain repellent, don't use hand cream, and don't write on the sample bottle with a permanent marker.

Treatment options

Granular Activated Carbon (GAC): Effective for long-chain PFAS like PFOA and PFOS. Less effective for short-chain compounds.

Reverse osmosis (RO): The most broadly effective for all PFAS types. Practical for a single tap (under-sink); not always practical whole-house.

Ion exchange resins (anion-specific): Effective and increasingly used in municipal treatment.

Boiling does NOT remove PFAS — it concentrates them. Pitcher filters that are not specifically certified for PFAS (NSF/ANSI 53 with the PFOA/PFOS claim, or NSF/ANSI 58 for RO) will not reliably remove them.