PFAS
PFOS in your water
Is PFOS in drinking water dangerous?
It depends on the level and how long you're exposed. The EPA legal limit (MCL) for PFOS is 4 ppt, but health-based goals (EPA MCLG / WHO) are often stricter, at 0.004 ppt. Meeting the legal limit isn't the same as zero risk — test your water to know your level.
How do you remove PFOS from water?
PFOS is treated by Reverse Osmosis and Whole-House Carbon Filter. Choose a system independently certified to NSF/ANSI standards to reduce PFOS, and test your water first to confirm the level.
Source: EPA MCL / MCLG; WHO guidelines; NSF/ANSI · 2026
Health effects
PFOS is another "forever chemical" from older firefighting foams and consumer coatings. Like PFOA it accumulates in the body and is linked to immune, thyroid, liver, and developmental effects. EPA set an enforceable limit for it in 2024.
The health-based goal vs. the legal limit
The federal legal limit (MCL) is the maximum allowed by law. The health-based goal (EPA MCLG / WHO) is a health target — it is often stricter than the legal limit, and it is not itself a legal limit.
Health-based goal (EPA MCLG / WHO)
0.004 ppt
Federal legal limit (MCL)
4 ppt
Source: EPA MCL / MCLG; WHO guidelines · 2026
Not affiliated with or endorsed by EWG.
What removes PFOS
Semipermeable membrane filtration
Reverse Osmosis
Pushes water through a fine membrane that removes the dissolved solids most filters miss.
Look for: NSF/ANSI 58 certification
How it works→Activated carbon adsorption
Whole-House Carbon Filter
A point-of-entry carbon bed that strips chlorine, chloramine, and chemical taste from every tap.
Look for: NSF/ANSI 42 certification
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Is PFOS in your water?
Check your city's public record, then book a free 30-minute test to confirm what's in your home.