Learn
PFAS in drinking water — what 2024's new MCLs actually mean
April 2024: EPA finalized the first enforceable drinking-water Maximum Contaminant Levels for six PFAS compounds. The action levels are the lowest in any contaminant rule's history — and the compliance window is short.
Published 2026-04-25 · Last reviewed 2026-04-25 · methodology
What PFAS is
Per- and polyfluoroalkyl substances (PFAS) are ~15,000 synthetic chemicals used since the 1940s in non-stick coatings, fire-fighting foam, water-repellent fabrics, food packaging.
Once in groundwater, PFAS persist for decades — hence 'forever chemicals'. Linked to thyroid disease, kidney cancer, immune-system suppression, and developmental effects.
About 45% of US tap water has detectable PFAS per a 2023 USGS sampling study.
The 2024 MCL rule
Six compounds regulated: PFOA, PFOS (each MCL 4.0 ppt), PFHxS, PFNA, GenX (each MCL 10.0 ppt), plus a Hazard Index for PFHxS+PFNA+GenX+PFBS mixtures.
PFOA + PFOS at 4 parts per trillion — that's roughly 4 drops in 20 Olympic swimming pools. The detection limit is ~2 ppt; many utilities will be required to install treatment because they can't meet 4 ppt without removal.
Compliance schedule: monitoring required by 2027; treatment in place by 2029. Some communities pushing back on cost; lawsuits filed by utility-trade associations.
Where PFAS shows up most
Near military bases (firefighting-foam runoff): especially around Air Force facilities + Navy training areas.
Near manufacturing facilities: 3M (Minnesota, Alabama, Belgium); DuPont/Chemours (West Virginia, North Carolina Cape Fear basin); Solvay (NJ).
Downstream of paper mills, textile plants, electroplating facilities — historically.
Cape Fear basin (Wilmington NC), Hoosick Falls (NY), Decatur (AL), and Parkersburg (WV) are documented hotspots.
Reading utility PFAS results
Pre-2024 testing was voluntary; many utilities have UCMR (Unregulated Contaminant Monitoring Rule) results from UCMR3 (2013-2015) and UCMR5 (2023-2025). Compare your utility's UCMR5 to the new MCLs.
If your utility shows PFOA above 4 ppt OR PFOS above 4 ppt → treatment is required by 2029. Most utilities will install granular activated carbon (GAC) filters or ion-exchange resin.
If you're on a private well + you live near a documented hotspot, get a PFAS test ($300-500 typical). Reverse-osmosis filtration handles PFAS.
What zipradar shows
EPA SDWIS data per utility — though PFAS-specific compliance data lags behind pre-2027 monitoring.
Where UCMR5 results are public, we'll surface them per ZIP starting Q3 2026.
We don't show speculative PFAS risk; we show measured violations. If a utility hasn't tested yet under the new rule, we say so explicitly.
Related zipradar topics
More from /learn/
- Flood zones explained — what AE, X, and VE actually mean
- EPA Radon Zones — what 1, 2, and 3 mean and when you should test
- FBI UCR and NIBRS — what crime statistics actually show (and don't)
- Lead and Copper Rule 2024 — the federal lead-pipe inventory mandate
- Property tax millage — what 'mill' means and how your bill is computed
- AQI explained — what 50, 100, 150 actually mean for your lungs
- School district boundaries — how to confirm yours and why it matters
- Wildfire Hazard Potential — what the USFS scale means and how to defend your home
- EPA SDWIS — how to read drinking-water violations and what they actually mean
- Deed records — what they show and what they don't
- Zoning codes — what R-1, C-2, M-1, MU mean and why your house is one
- Homestead exemption — state-by-state property tax savings
- Reading FBI UCR national crime trends — what 2020–2025 actually shows
- AirNow + wildfire smoke — when AQI is a real-time tool
- Radon and real estate — what disclosure laws and home tests actually require
- Wildfire insurance in 2026 — why premiums spiked and what to do
- NCES Common Core of Data — what district boundaries actually mean for buyers
- EPA SDWIS — reading drinking-water violations without panicking
- FEMA flood zones — AE vs. X vs. VE in plain English
- County assessor data — how millage rates and assessments actually combine
- NSOPW — why zipradar deep-links instead of caching the registry
- FEMA LOMA — when your home is wrongly in a flood zone (and how to appeal)
- NCES SABS — the only authoritative US school attendance map
- Deed activity by ZIP — what aggregated transfers tell you about market trends
- Buying a house — the 12-dimension data checklist before you sign
- Private well water — what to test when EPA SDWIS doesn't cover you
- County recorder vs. county assessor — they sound the same, they're not
- Zoning overlays — historic, flood, environmental layers that change what you can build
- Lead in paint vs. lead in pipes — same metal, different exposure
- EPA Superfund + Brownfields — what 'contaminated site nearby' actually means
- Property tax escrow — why your monthly payment changes after you close