Forever Chemicals (PFAS) Explained: A Simple Guide

What makes them "forever"

PFAS stands for per- and polyfluoroalkyl substances. They are a family of synthetic chemicals built around carbon-fluorine bonds, which are among the strongest bonds in organic chemistry. This bond strength is what gives PFAS their useful properties (resistance to water, oil, heat, and stains) and also what makes them nearly indestructible in the environment. A PFAS molecule released into water, soil, or air today will remain intact for decades, centuries, or longer. No natural process breaks them down efficiently.

There are over 12,000 known PFAS compounds. They have been manufactured since the late 1940s. The two most studied and regulated, PFOS (perfluorooctane sulfonic acid) and PFOA (perfluorooctanoic acid), were phased out of US manufacturing by the mid-2010s but persist in the environment and in the blood of virtually every person tested. The CDC\'s National Health and Nutrition Examination Survey (NHANES) has detected PFAS in the blood of over 98% of Americans sampled.

Where PFAS are used

PFAS are used in thousands of consumer and industrial products because of their resistance to water, grease, and heat:

Product category	Examples	PFAS function
Non-stick cookware	Teflon, ceramic-coated pans	Creates slippery, non-stick surface
Waterproof clothing	Gore-Tex, many outdoor jackets	Repels water from fabric
Food packaging	Microwave popcorn bags, fast food wrappers, pizza boxes	Grease resistance
Firefighting foam	AFFF (aqueous film-forming foam)	Smothers fuel fires
Stain-resistant fabrics	Scotchgard, treated carpets and upholstery	Repels stains and liquids
Cosmetics	Some foundations, mascaras, lip products	Smooth application, water resistance
Industrial applications	Chrome plating, semiconductor manufacturing, wire insulation	Chemical resistance, electrical insulation

How PFAS get into drinking water

PFAS enter water supplies through several pathways:

• Military bases and airports: AFFF firefighting foam has been used extensively at military installations and airports for decades. Foam runoff seeps into groundwater. The Department of Defense has identified over 700 installations with known or suspected PFAS contamination.
• Manufacturing facilities: Factories that produce or use PFAS discharge wastewater containing these chemicals. The 3M plant in Decatur, Alabama, and the DuPont plant in Parkersburg, West Virginia, are well-documented examples.
• Landfill leachate: Consumer products containing PFAS break down in landfills, and PFAS-laden water (leachate) seeps into groundwater.
• Wastewater treatment plants: Conventional treatment does not remove PFAS. Water discharged from treatment plants contains PFAS from household and industrial sources, which enters rivers and streams used as drinking water sources downstream.
• Agricultural runoff: Biosolids (treated sewage sludge) used as fertilizer can contain PFAS, which then leach into groundwater.

Health effects

The health effects of PFAS exposure have been studied extensively, particularly through the C8 Science Panel, which examined health outcomes in communities near the DuPont plant in West Virginia. Key findings from that panel and subsequent research:

• Cancer: The C8 panel found probable links between PFOA exposure and kidney cancer and testicular cancer. The International Agency for Research on Cancer (IARC) classified PFOA as carcinogenic to humans (Group 1) in 2023.
• Thyroid disease: Both PFOS and PFOA are associated with thyroid dysfunction, which affects metabolism, energy, and development.
• Immune system: PFAS exposure is associated with reduced vaccine antibody response, particularly in children. A 2012 study in JAMA found that children with higher PFAS blood levels had lower antibody concentrations after routine vaccinations.
• Reproductive effects: Associated with preeclampsia during pregnancy, reduced fertility, and lower birth weight. See our guide on water quality and pregnancy.
• Cholesterol: PFAS exposure is consistently associated with elevated cholesterol levels, even at low doses.
• Liver effects: Studies have found associations between PFAS exposure and liver damage markers.

The 2024 EPA rule

In April 2024, the EPA finalized the first-ever national drinking water standard for PFAS. This rule sets maximum contaminant levels (MCLs) for six PFAS compounds:

PFAS compound	MCL (maximum allowed)	Notes
PFOS	4 parts per trillion (ppt)	Among the lowest MCLs ever set for any contaminant
PFOA	4 ppt	Among the lowest MCLs ever set
PFNA	10 ppt	Individual limit
PFHxS	10 ppt	Individual limit
HFPO-DA (GenX)	10 ppt	Replacement chemical for PFOA
Mixture of 2+ PFAS	Hazard index of 1	Accounts for combined exposure

Key timeline: water utilities must begin monitoring by 2027 and must comply with the limits by 2029. The EPA estimated that 6 to 10 percent of public water systems will need to take action, affecting 66 to 100 million people. The federal government allocated $9 billion through the Bipartisan Infrastructure Law to help small and disadvantaged communities pay for PFAS treatment.

How to check your water for PFAS

1. Check your city\'s data: Search your city on CheckMyTap to see PFAS levels from EPA monitoring data (UCMR5).
2. Read your utility\'s CCR: Some utilities have begun voluntary PFAS testing and report results in their Consumer Confidence Report.
3. Test your own water: Home PFAS testing through certified labs costs $100 to $200. This is especially worthwhile if you are on a private well near a known contamination source.

How to remove PFAS from your water

Three filtration technologies are effective against PFAS:

Technology	PFAS removal	Certification to look for	Cost
Reverse osmosis	90-99%	NSF 58	$150-$400 under-sink
Activated carbon (granular or block)	60-95% depending on type and contact time	NSF P473 or NSF 53	$50-$200
Ion exchange resin	90-99%	NSF P473	$200-$500 (whole-house)

For home use, a reverse osmosis system at the kitchen sink provides the most reliable PFAS removal. Look for systems tested and certified to NSF 58 or NSF P473 specifically for PFAS reduction. Not all filters that claim to remove PFAS have been independently tested. See our PFAS filter buying guide for specific product recommendations.

PFAS beyond drinking water

Drinking water is one exposure route, but not the only one. PFAS also enter your body through food (especially food packaged in PFAS-treated containers), indoor dust (from treated carpets and furniture), personal care products, and occupational exposure. Reducing drinking water exposure through filtration is the single easiest step because it addresses the most concentrated and consistent source for most people.

Related resources

• PFAS filter buying guide
• PFAS and pregnancy
• Microplastics in tap water
• Check your city\'s PFAS levels