Free Illinois water report: PFAS & lead levels for every water system, worst-affected cities, and EPA violations. Check your ZIP.
Illinois' water supply reflects the state's geographic divide: the Chicago metro in the northeast draws from Lake Michigan – one of the largest freshwater bodies on Earth – while the rest of the state relies on a mix of rivers, reservoirs, and groundwater. The state's approximately 12.5 million residents are served by about 4,300 public water systems, overseen by the Illinois Environmental Protection Agency (Illinois EPA).
Chicago's Lake Michigan supply is managed by the Department of Water Management, which operates two of the largest water purification plants in the world. The Jardine and South Water Purification plants together serve about 5.3 million people – the city's 2.7 million residents plus over 100 suburban communities that purchase Chicago water. Lake Michigan provides abundant, relatively clean source water, but the journey from lake to tap involves infrastructure that includes century-old distribution mains and an estimated 400,000 lead service lines – more than any other American city.
Downstate Illinois presents a different picture. Communities draw from the Illinois, Mississippi, and Sangamon rivers, from smaller reservoirs, and from groundwater wells tapping various aquifer systems. Agricultural contamination – particularly nitrates and atrazine from corn and soybean farming – is the primary water quality challenge outside the Chicago metro. According to USGS monitoring data, several Illinois waterways regularly exceed recommended levels for agricultural chemicals.
The EPA's UCMR5 monitoring has confirmed PFAS detections at public water systems across Illinois, from the Chicago suburbs to downstate communities. The contamination pattern reflects the state's mix of military installations, airports, industrial facilities, and landfills that have served as PFAS sources.
Illinois has been working to establish state-specific PFAS standards. The Illinois EPA has set health-based guidance levels for PFOA and PFOS and is developing enforceable standards through the regulatory process. The state is evaluating MCLs for multiple PFAS compounds, aiming to provide protections that go beyond the 2024 federal limits. Until state MCLs are finalized, Illinois follows the federal standards of 4 ppt for PFOA and PFOS.
The contamination picture varies significantly across the state. Lake Michigan water, processed through Chicago's treatment plants, generally shows lower PFAS levels than groundwater-dependent communities near contamination sources. Downstate systems that draw from rivers also face PFAS, as wastewater treatment plant effluent – a known PFAS pathway – discharges into many of the same rivers that downstream communities use for drinking water.
Naval Station Great Lakes, located in North Chicago along the Lake Michigan shore, is the most prominent military PFAS source in Illinois. As the Navy's only boot camp, Great Lakes has trained every enlisted sailor since 1911 and has used AFFF extensively in firefighting training over the decades. The Navy has confirmed PFAS in groundwater on and around the base.
The contamination at Great Lakes is complicated by the base's proximity to Lake Michigan and to North Chicago and Waukegan – communities that use both lake water and groundwater. While PFAS migration toward the lake is a concern, the more immediate issue is contamination of local groundwater wells used by nearby residents and businesses.
Scott Air Force Base near Belleville in the Metro East (St. Louis metro) area is another installation under PFAS investigation. The base has a long history of AFFF use and sits above groundwater that serves surrounding communities.
The former Chanute Air Force Base in Rantoul, which closed in 1993, has documented environmental contamination including PFAS from its operational years. Cleanup at former military installations often proceeds more slowly than at active bases, and Chanute's contamination continues to be monitored.
Other Illinois military sites under PFAS assessment include the Rock Island Arsenal and various Air National Guard facilities. The Department of Defense has included these installations in its nationwide PFAS investigation program. See our military bases page for current status.
Illinois has taken a more active regulatory approach to PFAS than many midwestern states. The Illinois EPA has established health-based guidance levels, conducted targeted investigations at potential PFAS sources, and is working toward enforceable drinking water standards.
The state's UCMR5 data has added significantly to the understanding of PFAS distribution across Illinois. With 4,300 public water systems, the state's dataset is one of the larger ones in the country. Results have confirmed contamination near expected sources – military bases, airports, industrial sites – and also revealed detections in communities without obvious point sources, suggesting diffuse contamination pathways.
According to Illinois EPA data, approximately 1.2 million Illinois residents rely on private wells. In agricultural areas, these wells face nitrate and pesticide exposure in addition to potential PFAS. The state does not require PFAS testing for private wells, though Illinois EPA recommends testing for homeowners near known contamination sources.
The Illinois legislature has been active on PFAS policy. The state passed the PFAS Reduction Act, which restricts PFAS in certain products including firefighting foam, and has funded PFAS monitoring and response activities through the Illinois EPA.
For background on PFAS science and health effects, see our PFAS guide.
Illinois's water quality depends heavily on whether you are in the Chicago metro or downstate, and on your proximity to contamination sources.
1. Check your ZIP code at the homepage to see monitoring data specific to your water system. We compile UCMR5, Illinois EPA, and utility data in one view. 2. Chicago residents: your primary concern may be lead rather than PFAS. If your home was built before 1986, it likely connects to the water main through a lead service line. Run water for 3-5 minutes before drinking after periods of stagnation, and consider a filter certified to NSF/ANSI 53 for lead. Our water filter guide covers both lead and PFAS filtration. 3. Downstate residents near military bases, airports, or industrial facilities: a reverse osmosis filter is the most effective option for PFAS. If you are on a private well, testing is recommended – for PFAS and for nitrates. 4. Request a detailed water report for your address to see how your area's data compares to state guidance levels and federal standards.
Illinois has some of the best source water in the country (Lake Michigan) and some of the oldest infrastructure delivering it. Check your specific location to see where your water quality stands.