Dupo Water System water quality
Dupo, IL · serves 4,684 people (2,165 connections) · Groundwater · Local government · EPA ID IL1630350
Data: U.S. EPA · How we read the data · How we check it
Buys water from Illinois American Water – East St Louis. Treated water bought from another system can carry that system's contaminants.
Summary
PFAS above the 2024 federal limits. Systems have until 2029 to meet the PFAS limits.
Is it an emergency? No: PFAS limits are about years of exposure, not a glass of water, and nothing in EPA's data calls for you to stop drinking the water today. If your utility ever issues a boil-water or do-not-drink notice, follow it.
- PFAS
- Above limitPFOS above the federal limit in EPA's 2023–2025 testing (PFOS 5.05 ppt vs a limit of 4 ppt, where ppt = parts per trillion).
- Lithium
- Above screening levelHighest result 24 ppb. EPA uses 10 ppb to decide what to study further. It is not a health limit, and there is no federal limit for lithium. About 1 in 4 systems tested were above it.
- Lead
- Below action level0 ppb (parts per billion) at the 90th percentile: 9 in 10 homes sampled were at or below it. Action level 15 ppb, falling to 10 ppb in Nov 2027. Monitoring period Jan 2024 – now, still in progress (results reported so far). Your home's pipes can make yours higher.
- Violations
- None health-basedNo health-based violations since 2016.
- Pregnant, or mixing baby formula with tap water? Babies drink more water for their size, so PFAS exposure matters more for them. Consider bottled water or a filter certified for PFAS for formula, and ask your doctor. Health effects.
- To lower your PFAS exposure now, a home filter certified for PFAS reduction works (reverse osmosis, or activated carbon certified to NSF/ANSI 53 or 58). Filters for these results.
- Built before 1986, or not sure what your service line is made of? Check your service line and test your tap. Utility data can't show your pipes.
- Tested your own tap? Compare your result with these numbers. Moving? Compare this system with another.
- Read Dupo Water System's annual water quality report (Consumer Confidence Report). It lists every regulated contaminant tested and is usually on the utility's website or mailed with your bill, and you can also request it at (618) 286-4200. EPA: how to find it.
PFAS (“forever chemicals”)
EPA UCMR 5: 1 entry point tested May 2025 to Nov 2025. "Average" is the highest entry-point average (non-detects counted as zero), the way EPA compares UCMR 5 results to the limits. ppt = parts per trillion. These results do not determine compliance.
| Contaminant | Highest average |
|---|---|
| PFOA Not detected Limit 4 ppt | – |
| PFOS Above limit Limit 4 ppt | 5.05 ppt 1.26× the limit |
| PFHxS Detected, below limit Limit 10 ppt | 1.55 ppt 16% of the limit |
| PFNA Not detected Limit 10 ppt | – |
| HFPO-DA (GenX) Not detected Limit 10 ppt | – |
| Hazard Index (a combined score for PFHxS, PFNA, GenX and PFBS, where above 1 is over the limit) Detected, below limit Limit 1 | 0.16 |
| PFBS Detected, below limit Guideline 2,000 ppt | 3.4 ppt |
| PFBA Not detected Guideline 6,000 ppt | – |
| PFHxA Not detected Guideline 3,000 ppt | – |
For context: the PFOS average is higher than at 98% of the Illinois systems EPA tested.
29 PFAS tested, 3 detected at least once. "Not detected" means below EPA's reporting limit (about 2 to 20 ppt depending on the chemical), not proven zero. PFAS not listed were not detected. The limits for PFHxS, PFNA, GenX and the Hazard Index were proposed for rescission in May 2026. That proposal is not final. Systems have until 2029 to meet the limits.
Lithium
Detected in 2 of 2 samples. Highest result 24 ppb. EPA's non-enforceable screening level is 10 ppb. Above screening level The screening level is how EPA decides what to study further, not a health limit. There is no federal limit for lithium and no filter is certified to remove it. About lithium.
Lead and copper
Latest 90th percentile: 0 ppb lead (Jan 2024 – now (in progress)). Below action level
Highest since 2016: 1.6 ppb (Dec 2017).
| Monitoring period | Lead (90th pct.) |
|---|---|
| Jan 2024 – now (in progress) | 0 ppb |
| Jan 2021 – Dec 2023 | 0 ppb |
| Jan 2018 – Dec 2020 | 0 ppb |
Earlier results (9)
| Jan 2015 – Dec 2017 | 1.6 ppb |
| Jan 2012 – Dec 2014 | 1.2 ppb |
| Jan 2011 – Dec 2013 | 0 ppb |
| Jan 2009 – Dec 2011 | 0 ppb |
| Jan 2008 – Dec 2010 | 0 ppb |
| Jan 2005 – Dec 2007 | 2 ppb |
| Jan 2002 – Dec 2004 | 2 ppb |
| Jan 1999 – Dec 2001 | 0 ppb |
| Jan 1997 – Dec 1997 | 0 ppb |
Lead comes from pipes and fixtures, not the source water, so it varies home to home. The 90th percentile means 9 in 10 sampled homes were at or below it. More on lead.
Violations
Health-based violations mean a contaminant exceeded a limit or a required treatment step was missed. Monitoring and reporting violations mean required tests or reports were late or missing, so the water's quality during that time is unknown. The total includes every violation in EPA's records, most of them paperwork.
Where it serves
Dupo
ZIP codes the system reported serving: 62236, 62239, 62240, 62260
Nearby utilities
- Illinois American Water – East St Louis East St. Louis · 8 mi
- Collinsville Water System Collinsville · 16 mi · PFAS above limit
- East Alton Water System East Alton · 26 mi · PFAS above limit
- Springfield Water System Springfield · 93 mi
- Decatur Water System Decatur · 116 mi
- Illinois American Water – Lincoln Lincoln · 122 mi · PFAS above limit
Questions
Is Dupo Water System water safe to drink?
Dupo Water System has no health-based violations since 2016. EPA testing found PFAS above the 2024 federal limits, which systems must meet by 2029. Federal data can't tell you about your own pipes: lead comes from service lines and plumbing, so test your tap if your home was built before 1986. For the official word, read the utility's annual Consumer Confidence Report.
Does Dupo Water System water have PFAS?
Yes. EPA's 2023–2025 testing of Dupo Water System found 3 PFAS at least once. The highest entry-point averages were above the federal limit for PFOS: PFOS 5.05 ppt (limit 4 ppt for PFOA and PFOS, 10 ppt for the others).
What is the lead level in Dupo Water System water?
The most recent 90th-percentile lead result for Dupo Water System is 0 ppb, for the monitoring period that began Jan 2024 (still in progress). The federal action level is 15 ppb, falling to 10 ppb in November 2027. The 90th percentile means 9 in 10 homes sampled were at or below this number. Individual homes can be higher.
Check these numbers yourself
Every figure on this page comes from public EPA records. You don't have to take our word for it:
- EPA's own report for IL1630350: violations, enforcement and inspections, straight from EPA.
- EPA UCMR 5 data: the PFAS and lithium results (search the file for PWSID IL1630350).
- EPA SDWIS download: the lead results, population and violation records we use.
- The utility's annual water quality report (Consumer Confidence Report): ask Dupo Water System at (618) 286-4200, or see EPA's guide to finding it.
Found something that doesn't match? Tell us and we'll check it against EPA's records. How we check our data.
Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.