Water in Wisconsin.
Milwaukee and the southeast draw Lake Michigan water. The 1993 Milwaukee Cryptosporidium outbreak — affecting 400,000 people — remains the largest U.S. waterborne disease outbreak in modern history. Madison and Marinette face active PFAS contamination concerns.
Milwaukee's 1993 Cryptosporidium outbreak remains the largest documented waterborne disease event in U.S. history.
How Wisconsin regulates drinking water.
Federal SDWA primacy. State PFAS standards adopted 2022 (PFOA 70 ng/L, PFOS 70 ng/L individually). Active Marinette / Tyco firefighting-foam remediation.
Wisconsin Department of Natural Resources — Drinking Water and Groundwater Program
Wisconsin's water history, in order.
The contamination events, regulatory shifts, and major settlements that define how this state thinks about drinking water today.
- 1993
Milwaukee Cryptosporidium outbreak — 400,000 sick, 50+ deaths — largest U.S. waterborne disease event in modern history.
- 2017
Marinette PFAS contamination from Tyco firefighting foam identified.
- 2022
Wisconsin sets state MCLs for PFOA and PFOS.
The actual water you drink.
The physical rivers, aquifers, lakes, and reservoirs that feed Wisconsin's public water systems. Source quality is the foundation of tap quality — and where the long-term protection fights happen.
- lakeLake Michigan
Milwaukee and southeast WI.
- lakeLake Superior
Duluth-Superior.
- riverMississippi River
Western WI.
- aquiferSandstone Aquifers
Statewide groundwater.
Source-water mix
~50% surface water (Lake Michigan + Lake Superior), ~50% groundwater
Major cities served
Milwaukee · Madison · Green Bay · Kenosha · Racine
Who actually serves the water.
The largest public water systems in Wisconsin by population served. Click your ZIP after to see the full live EWG report for your specific utility.
- Milwaukee Water WorksMilwaukee870Kserved
- Madison Water UtilityMadison270Kserved
- Green Bay Water UtilityGreen Bay200Kserved
Where the contamination comes from.
Every state has a different industrial fingerprint. The industries below are the dominant historical and active contamination sources in Wisconsin's drinking water systems.
Tyco Fire Products (Marinette / Peshtigo) firefighting-foam PFAS contamination affected hundreds of households. Kewaunee County dairy CAFOs drive nitrate exposure. Paper mill legacy in Fox River chlorinated organics.
What state data flags most consistently.
Drawn from EPA SDWIS sampling records, EWG state summaries, and regional regulatory action over the past five years. Read the full deep dive on each.
Lead
A neurotoxic metal that leaches from old pipes and solder. No safe level for children.
PFAS (Forever Chemicals)
A class of ~15,000 synthetic chemicals that don't break down. Now regulated for the first time.
Nitrate
Fertilizer and animal waste runoff. Acutely dangerous for infants under 6 months.
Trihalomethanes (TTHMs)
Byproducts of chlorinating water. Linked to bladder cancer at chronic exposure.
Risk isn't evenly distributed.
Milwaukee residents in pre-1986 housing face significant lead exposure. Marinette / Peshtigo residents face PFAS. Kewaunee County dairy-farm region faces nitrate.
Milwaukee alone has ~70,000 lead service lines.
~25% on private wells. Northeastern WI agricultural region (Kewaunee County) has the most-documented nitrate exposure.
What's coming for Wisconsin's water.
Great Lakes warming drives toxic algal blooms (Green Bay). Karst region (door county, southwest WI) groundwater faces contamination from extreme rainfall. Lake Superior thermal regime changes affect Duluth-area systems.
Voluntary statewide
WI DNR provides voluntary technical assistance; Milwaukee and Madison have published voluntary results.
Five questions for your next Consumer Confidence Report.
Your utility is required to send you a Consumer Confidence Report annually. Most are dense and procedural. These are the questions worth following up on for Wisconsin specifically.
- 1
If I'm in Marinette / Peshtigo area, is my well in the Tyco PFAS contamination zone?
- 2
What is my system's PFOA + PFOS measured value vs. WI's state MCLs (70 ng/L each)?
- 3
If I'm in Kewaunee County, when was my well last tested for nitrate?
Most state regulators allow public records requests for the underlying lab reports behind your CCR — your utility should be able to provide them on request.
What's changed in Wisconsin water law.
Drinking water regulation moves at the state level as much as the federal level. Below are notable recent bills and regulatory actions specific to Wisconsin.
- 2022
WI PFAS MCLs set — PFOA and PFOS at 70 ng/L individually.
For lead: NSF/ANSI 53. For Marinette PFAS: state of Wisconsin provides bottled water and POE filtration to confirmed impacted households.
We don't recommend brands — the NSF/ANSI certification number matters more than the name on the box.
This is the state. Your address is the answer.
State-level patterns don't tell you about your specific tap. Run your ZIP for the live EWG contaminant report on your utility — or build a personalized Water File for your household.
Source-water mix, utility counts, lead-service-line estimates, and private-well shares are approximate, drawn from EPA SDWIS public data and state primacy-agency summaries. Contaminant rankings reflect EWG state-level monitoring data and regional regulatory action — they are not exhaustive. Timeline events are publicly documented. See methodology for the full sourcing. Search EPA SDWIS for Wisconsin