PFOS (Perfluorooctane Sulfonate) in Drinking Water: Health Risks, Sources, and How to Remove It
PFOS (Perfluorooctane Sulfonate) is a synthetic organic chemical contaminant that has been widely used in industrial and consumer applications. As an organic compound of significant health concern, the Environmental Protection Agency (EPA) has established a Maximum Contaminant Level (MCL) of 0.004 μg/L for this substance in drinking water. Because of its persistence and potential risks, monitoring and regulating its presence in drinking water is highly critical.
Health Effects
Exposure to PFOS in drinking water is associated with serious health risks, including an increased risk of cancer. Additionally, this contaminant can cause thyroid effects and impact the immune system. Due to these potential health outcomes, minimizing exposure to PFOS in drinking water is strongly recommended.
How PFOS (Perfluorooctane Sulfonate) Gets Into Tap Water
PFOS enters drinking water supplies through various industrial and specialty applications. Major sources of this contaminant include the runoff and soil infiltration from firefighting foam, waste from metal plating facilities, and residues from the production of stain repellents. These activities can release the chemical into the environment, where it may eventually contaminate local groundwater or surface water sources.
How to Remove PFOS (Perfluorooctane Sulfonate) From Your Water
Several water treatment technologies are effective at reducing PFOS levels in drinking water. Treatment systems utilizing granular activated carbon, ion exchange, or reverse osmosis can successfully filter and remove this contaminant. Consumers looking to treat their water should ensure their chosen systems are properly maintained and certified for contaminant removal.
Should You Test Your Water?
To determine if PFOS is present in your water supply, you can review your local utility's annual Consumer Confidence Report or check WaterQ's database. Private well owners should consider testing their water through a certified laboratory, especially if they live near areas where potential sources are located. You can also look up your local water system on WaterQ or check the PFOS (Perfluorooctane Sulfonate) data page for reported levels in your area.
Frequently Asked Questions
Is PFOS (Perfluorooctane Sulfonate) dangerous in drinking water?
Yes, PFOS is considered a significant concern in drinking water due to its potential health effects. Exposure to this organic contaminant is linked to an increased cancer risk, thyroid effects, and adverse impacts on the immune system.
How does PFOS (Perfluorooctane Sulfonate) get into tap water?
PFOS primarily enters tap water supplies from areas where firefighting foam has been used, or from industrial activities like metal plating and the manufacturing of stain repellents.
How can I remove PFOS (Perfluorooctane Sulfonate) from my water?
You can remove PFOS from your drinking water using treatment methods such as granular activated carbon, ion exchange, or reverse osmosis systems.
Source: EPA National Primary Drinking Water Regulations and WaterQ National Database. For more contaminants, visit our contaminant library.
What actually removes pfas ("forever chemicals")
PFAS are the clearest case where the default advice fails. A standard carbon pitcher is not PFAS-rated and independent testing has repeatedly shown poor reduction. What works is reverse osmosis, or carbon whose media has been specifically tested to the NSF/ANSI 53 PFOA/PFOS claim or NSF P473. Check for that exact wording — "reduces contaminants" on the box means nothing here.
Works
- Reverse osmosis (NSF 58)The broadest removal available at home: arsenic, nitrate, fluoride, PFAS, TDS.
- PFAS-rated carbon (NSF 53 PFOA/PFOS or P473)Carbon with media specifically tested against PFAS. Ordinary carbon is not.
- Anion exchangeWhole-house option for nitrate and uranium on well water.
Will not fix this
- Basic activated carbon (NSF 42)
- Ion-exchange water softener
- UV disinfection (NSF 55)
- Ion-exchange pitcher
- Boiling Makes it worse — evaporation concentrates what's left behind.
Test before you buy.PFAS ("forever chemicals") can't be seen, tasted or smelled, and the right hardware depends on the concentration you actually have. A certified lab test costs a fraction of the wrong filtration system. Start with your local water quality report, and get a mail-in lab test if you're on a private well.
Options that carry the right certification
Ordered cheapest-adequate first. Prices are indicative bands and move often.
| Product | Certification | Upfront | Per year | |
|---|---|---|---|---|
| AquaTru Countertop Reverse OsmosisCountertop | NSF/ANSI 42, 53, 58, 401 and P473 certified.Catch:Takes counter space and you refill a tank by hand. Wastes some water as brine, like all RO. | $400–500 | $80–130 | Check price |
| Aquasana AQ-5200 Under-SinkUnder-sink | NSF/ANSI 42, 53, 401 and P473 certified.Catch:Carbon, not RO — no meaningful fluoride, nitrate or arsenic reduction. | $110–160 | $80–120 | Check price |
| Clearly Filtered Water PitcherPitcher | Independently lab-tested against NSF/ANSI 42, 53, 401 and P473 protocols. Note: tested to those methods, not NSF-listed.Catch:Expensive per gallon and slow to filter. Verify current test reports before relying on the fluoride and PFAS claims. | $80–110 | $90–130 | Check price |
| APEC ROES-50 EssenceUnder-sink | Built with WQA-certified components to NSF/ANSI 58.Catch:Needs an under-sink drain connection and a spare hole for the dedicated faucet. Strips minerals — some people dislike the flat taste. | $180–240 | $50–80 | Check price |
Certification listings change. Before buying, confirm the current listing for the exact model in the NSF certified products database — a manufacturer's marketing page is not a certification. WaterQ earns a commission on purchases made through these links at no extra cost to you; see our affiliate disclosure. This is general information, not medical or engineering advice.
For a full breakdown of certifications, running costs and the models worth considering, see our buying guide for pfas ("forever chemicals").