Illinois Water Quality: 2.9% of Systems Over the PFAS Limit

Water quality by state

Is Illinois tap water safe? 2.9% of systems averaged PFOA/PFOS over the EPA limit

2.9% of Illinois’s 443 public water systems with a full set of results (13 systems) averaged PFOA or PFOS above the EPA’s 4 ppt limit in the EPA’s UCMR5 monitoring (2023-2025), using EPA’s own sampling-location average method. Nationally the figure is 11.4%, so Illinois ranks #30 of the states with enough data.

EPA UCMR5 PFAS (2023-2025)
Illinois
2.9%
Systems with a full set of results443
Averaged PFOA/PFOS over 4 ppt13 (2.9%)
Over another EPA limit (SYR, 2012-2019)25.8% of 2264
These are the systems’ own EPA UCMR5 monitoring results — “reported above the limit,” not “in violation.” The EPA limit (4 ppt for PFOA and for PFOS) is a running annual average, so a system counts here when the AVERAGE of a full set of results at one of its sampling locations is above the limit — EPA’s own method. That is an occurrence flag, not a compliance finding: real compliance is determined from quarterly samples reported to the state. Enforcement phases in through 2029-2031.

Illinois systems with the highest PFOA/PFOS location averages

Water systemAnalyteHighest location average
Crest HillPFOA12.4 ppt
East AltonPFOA12.2 ppt
GalesburgPFOA11.0 ppt
FreeportPFOS10.8 ppt
AbingdonPFOA9.2 ppt
This is a statewide summary — not your tap.

Check what your specific utility reported for YOUR ZIP code, and the exact filter that handles it: Check your water by ZIP →

Which PFAS show up most in Illinois

  • PFBA (82 systems)
  • PFPeA (58 systems)
  • PFHxA (40 systems)
  • PFBS (39 systems)
  • PFHxS (19 systems)

Beyond PFAS, 25.8% of 2264 Illinois systems in the EPA Six-Year-Review record (2012-2019) reported at least one of arsenic, nitrate, TTHM, HAA5, fluoride, gross alpha, radium, or uranium above its EPA limit. That is a 2012-2019 snapshot, not current.

Common questions about Illinois water

Is Illinois's tap water safe to drink?

In the EPA’s UCMR5 data, 2.9% of Illinois’s systems with a full set of results averaged PFOA or PFOS above the 4 ppt limit. That is an occurrence flag on public systems, not a verdict on your home’s tap. These are system-level records for public water systems, not a reading of any individual home’s tap, and they do not cover private wells. Confirm your own utility’s current Consumer Confidence Report, and test your tap if you’re unsure.

Does Illinois have PFAS in its drinking water?

In EPA UCMR5 monitoring, 13 of Illinois’s 443 public water systems with a full set of results averaged PFOA or PFOS above the EPA’s 4 ppt limit. Rates are over the water systems that reported a FULL set of UCMR5 results in this state (the only ones EPA’s method can average) — not all systems, and not population. A state that tested more systems can show more detections simply because it looked harder.

How do I check my specific Illinois water system?

Enter your ZIP on the water checker to see what YOUR utility reported and the filter that handles it.

Neighboring states

WisconsinIowaMissouriKentuckyIndiana

See the full 50-state water-quality index and the national PFAS data study.

Rates are over the water systems that reported a FULL set of UCMR5 results in this state (the only ones EPA’s method can average) — not all systems, and not population. A state that tested more systems can show more detections simply because it looked harder.

Sources: EPA UCMR5 occurrence data, Feb 2026 release (~95% complete; final reporting 2026) (2026-06), public domain; beyond-PFAS: EPA Six-Year Review (SYR4, compliance monitoring 2012-2019) + current state Drinking Water Watch (CA, FL). Computed by scripts/build_state_water_data.py. Built 2026-07-25. Every figure is traceable to the committed EPA data.