Independent maps from USGS, EWG, and state environmental agencies converge on the same four geographic patterns: firefighting-foam training grounds (mostly military and civilian airports), the two big fluorochemical manufacturers (Chemours in North Carolina, 3M in Alabama and Minnesota), biosolids-amended farmland, and unlined landfill plumes. The PFAS map is, more than anything else, a map of where these four activities happened.
The 2023 US Geological Survey nationwide tap-water study (Smalling et al., Environment International) reported that at least one PFAS compound was detected in roughly 45% of finished tap-water samples collected across the United States. The hotspots within that 45% cluster around four well-documented source types, AFFF firefighting-foam sites, fluorochemical manufacturing plants, biosolids land-application areas, and landfill leachate plumes, and every public PFAS map (USGS, EWG, state DEPs) is a rearrangement of those same four datasets.
Before looking at any individual map, it helps to know what the dots represent. Across USGS sampling, the EWG contamination map, and the patchwork of state environmental agency disclosures, PFAS groundwater hotspots fall into four archetypes. Most "named" sites in the news are one of these.
1. AFFF training and response sites. Aqueous film forming foam, used since the 1960s to suppress hydrocarbon fires, is built around PFOS and (post-2002) shorter-chain perfluorinated surfactants. Military airfields, civilian airports certified under FAA Part 139, refinery fire brigades, and municipal fire training academies repeatedly discharged AFFF onto bare ground for decades. The foam infiltrates the unsaturated zone, partitions onto the air-water interface, and rides shallow groundwater off-site. Most large plumes (kilometre-scale) in the US are AFFF plumes.
2. Fluorochemical manufacturing. A small number of plants made PFOA, PFOS, GenX (HFPO-DA) and their precursors at industrial scale: Chemours/DuPont in Parkersburg WV and Fayetteville NC, 3M in Decatur AL and Cottage Grove MN, Daikin in Decatur AL, Solvay in West Deptford NJ, Arkema in Calvert City KY. Around each plant, decades of stack emissions, wastewater discharge, and on-site disposal produced contiguous contamination of soil, surface water and aquifers measurable for tens of miles downwind and downstream.
3. Biosolids land-application areas. When PFAS-laden industrial wastewater goes through a municipal wastewater treatment plant, the carbon-fluorine bonds survive intact and partition heavily into the sludge. When that sludge is dewatered, classified as biosolids, and spread on cropland as a soil amendment, the PFAS goes with it. Maine identified this pathway first, the state's 2022 statewide biosolids review triggered farm-by-farm testing and several farm closures, and Michigan, Wisconsin and New Mexico have since flagged similar fields.
4. Landfill leachate. Consumer goods treated with PFAS (carpet, food packaging, outerwear, cosmetics) end up in municipal solid waste landfills. Rain percolating through the waste mass mobilises PFAS into leachate. In older, unlined or partially-lined cells, that leachate enters shallow groundwater directly; in modern lined cells it is captured and sent to a wastewater treatment plant, which (see archetype 3) cycles the PFAS back into biosolids or surface water discharge.
The single largest documented source category is the US Department of Defense's own AFFF use. The DoD Environmental Restoration Program, in successive annual reports to Congress, has confirmed PFAS contamination above screening levels at hundreds of military installations, current and former Army, Navy, Air Force, and National Guard sites, plus a growing list of formerly used defense sites (FUDS). The figure has grown with each new wave of preliminary assessments and site inspections, so any single "exact" number is out of date within months. The right framing is: every installation that historically maintained an aircraft crash-rescue capability or a fire training pit is being investigated, and most are coming back positive.
A representative slice from publicly released DoD inventories and ATSDR exposure assessments:
| Installation | State | Notes |
|---|---|---|
| Wurtsmith Air Force Base (former) | MI | Closed 1993. Plume documented in shallow aquifer, Van Etten Lake. Cornerstone of Michigan MPART action. |
| Pease Air Force Base (former) | NH | Haven well shut 2014. ATSDR Pease exposure assessment cohort. |
| Joint Base Cape Cod / Massachusetts Military Reservation | MA | AFFF plume into Sagamore lens, public-supply wells affected. |
| Naval Air Warfare Center Warminster & NAS Willow Grove | PA | Drove the ATSDR Horsham/Warminster/Warrington exposure assessment. |
| Peterson Space Force Base / former Peterson AFB | CO | Widefield aquifer, Security/Fountain/Widefield. ATSDR El Paso County assessment. |
| England Air Force Base (former) | LA | Now Alexandria International Airport, classic dual military/Part 139 footprint. |
| Tyndall Air Force Base | FL | Multiple AFFF release areas, on-base and downgradient sampling ongoing. |
| Eielson Air Force Base | AK | Off-base private wells in Moose Creek impacted; bottled water provided. |
This is a representative sample, not a ranking. The DoD's own list (published periodically on the Office of the Assistant Secretary of Defense for Energy, Installations, and Environment site) is the authoritative source and continues to grow. Civilian Part 139 airports show the same pattern with less consistent disclosure, because state environmental agencies, not DoD, lead those investigations.
If AFFF is the most widespread PFAS source, the Chemours Fayetteville Works site in Bladen County, North Carolina is the most thoroughly litigated. The plant, originally a DuPont facility before the 2015 spin-off, manufactured fluoropolymer process aids including HFPO-DA, the "GenX" compound DuPont developed as a short-chain replacement for PFOA. In 2017, NC State University researchers and the Wilmington StarNews revealed that GenX and a family of related fluorinated ethers had been discharging into the Cape Fear River for years, contaminating the drinking-water intakes serving roughly 200,000 customers of the Cape Fear Public Utility Authority downstream.
The legal response is captured in State of North Carolina ex rel. NCDEQ v. The Chemours Company FC, LLC, Bladen County Superior Court file number 17-CVS-580. The consent order was signed in February 2019 and has been amended several times since. Its key provisions: Chemours must capture and treat process wastewater, eliminate air emissions of PFAS to a 99%+ standard, provide whole-house filtration to private well owners whose wells exceed defined PFAS thresholds, and fund downstream utility treatment improvements. CFPUA's Sweeney Water Treatment Plant brought full-scale granular activated carbon online in October 2022, and finished-water PFAS values at CFPUA are now routinely below the new federal MCLs per the utility's published quarterly sampling. Communities upstream and on Cape Fear tributaries continue to be sampled.
The other major US fluorochemical hotspot of comparable scale sits on the Tennessee River in north Alabama. The 3M Decatur plant manufactured PFOA, PFOS, and related perfluorinated surfactants for decades, with documented river discharges and on-site land disposal. Downstream public water systems, including those serving Decatur, the West Morgan-East Lawrence Water Authority, and points west, recorded elevated PFOA and PFOS in finished water in the late 2000s and 2010s. West Morgan-East Lawrence ultimately installed a granular activated carbon plus reverse osmosis treatment train, funded in part by settlement proceeds.
3M's 2023 multi-district settlement with US public water systems, valued at $10.3–$12.5 billion over thirteen years and approved by the US District Court for the District of South Carolina, resolved the bulk of the utility-side civil claims nationwide, but it did not resolve the underlying contamination at Decatur. State-level enforcement under the Alabama Department of Environmental Management, along with separate Tennessee Riverkeeper litigation, continues. The 3M facility, like Fayetteville, anchors a hotspot whose footprint extends well beyond the fence line of the plant itself.
Michigan is the cleanest case study of what happens when a state actually goes looking. The Michigan PFAS Action Response Team (MPART) was created in 2017, and the Department of Environment, Great Lakes, and Energy (EGLE) ran statewide sampling of every community water supply, plus targeted investigations at known industrial and military sites. The MPART public dashboard catalogues sites of investigation with a level of granularity no other state matches.
Two of the marquee cases:
Wolverine World Wide, Rockford. Decades of Scotchgard-treated leather scrap and tannery sludge were disposed in the House Street dump and other unlined sites in Kent County. PFAS migrated into the shallow aquifer that supplies hundreds of private wells in Plainfield and Algoma townships. Wolverine entered a consent decree, has provided bottled water and whole-house filtration, and is funding municipal water-line extensions. This is a textbook biosolids/industrial-disposal hotspot.
Wurtsmith Air Force Base, Oscoda. A former Strategic Air Command base, closed in 1993. AFFF training-pit contamination produced one of the longest-studied PFAS groundwater plumes in the country, discharging into Clark's Marsh and Van Etten Lake. The site is the federal-AFFF poster child within Michigan and one of the reasons MPART exists. EGLE's ongoing sampling around the former base continues to find PFAS in surface water and biota at concentrations that have triggered fish and foam advisories.
Michigan's broader statewide community-water-supply survey, completed in 2018–2020 and updated since, found detectable PFAS in a meaningful minority of systems but rarely at levels above the state's own MCLs, consistent with the national pattern: PFAS is widespread at low concentrations and locally severe near known sources.
The most cited single dataset on US tap-water PFAS is Smalling et al., "Per- and polyfluoroalkyl substances (PFAS) in United States tapwater: Comparison of underserved private-well and public-supply exposures and associated health implications," published in Environment International in 2023. USGS scientists collected paired source-water and finished tap-water samples from 716 locations across the country between 2016 and 2021, spanning private wells and public-supply taps in residential, commercial, rural, and urban settings.
The headline finding: at least one PFAS analyte was detected in approximately 45% of finished tap-water samples. The detection frequency was similar between private wells and public-supply taps when both drew from impacted source zones. The geographic pattern in the USGS data tracks population density and proximity to known sources, urban Eastern Seaboard, the Great Lakes basin, central and southern California, and the Front Range of Colorado all showed elevated detection rates, while the Northern Plains and parts of the Mountain West showed comparatively fewer detections.
The USGS framing is important: the 45% is a detection frequency, not a regulatory exceedance rate. Most detections were below the new federal 4 ng/L MCLs for PFOA and PFOS, and the study explicitly does not characterise an individual's exposure. What it does is establish that PFAS in US drinking water is a national, not a regional, baseline, on top of which the hotspots described above stack as elevated local plumes.
Three resources, in the order most people should use them:
EWG PFAS Contamination Map. The Environmental Working Group's interactive map at ewg.org/interactive-maps/pfas_contamination compiles state DEP data, UCMR results, DoD disclosures, and ATSDR exposure assessments into a single dot-map of confirmed contamination sites and detecting utilities. It is the fastest "is my area on the map" check. EWG is an advocacy organisation and its framing is pointed, but its underlying data citations are public-record and verifiable.
USGS PFAS dashboards. The US Geological Survey publishes a PFAS data portal with the underlying Smalling et al. sampling locations and the broader National Water Quality Assessment results. This is the right source for non-advocacy, peer-reviewed sampling data.
Your state DEP / DEQ / EGLE / DNR. Most states with active PFAS programs (Michigan, New Jersey, North Carolina, Wisconsin, Minnesota, Massachusetts, New Hampshire, New York, Pennsylvania, Maine, Colorado, Vermont) publish their own sampling results, often at higher resolution and with more local context than any national source. Search "[state name] PFAS dashboard" and you will land on the right page.
Once you know whether your area has a documented hotspot, the next questions are utility-specific. For a $15 brief on your ZIP that pulls UCMR 5 data, hotspot context, the regulated-compound list, and a filtration matrix, see the order page. For the underlying methodology, see the methodology and the full sources list. If you want to read sideways into the science and regulation: the C8 Science Panel guide explains the original PFOA epidemiology, the EPA April 2024 MCL guide covers what the new federal rule actually requires, the UCMR 5 explainer walks through how to read the EPA monitoring data, the state-vs-federal guide covers which states are stricter than EPA, and the filter certification guide explains why NSF 53 P473 and NSF 58 are the only two certifications that mean "removes PFAS."
Last reviewed: 30 June 2026. We update each guide when a primary source (EPA, USGS, ATSDR, or a named state agency) publishes new data.
State UCMR-5 baseline, hotspot match if your utility appears on any of the maps above, the six federally-regulated PFAS with their MCLs, and a filtration matrix with 2024 prices. Instant PDF.
