Arsenic in Drinking Water in Minnesota
What residents of Minnesota need to know about arsenic in drinking water — including natural geological sources, private well risk, which utilities have documented violations, and how to remove arsenic from tap water.
Source: EPA SDWIS, Minnesota Department of Health, USGS · Last reviewed: 2025-01-01
Quick Answer
Is arsenic in drinking water a concern in Minnesota?
Yes — Minnesota has one of the highest rates of private well arsenic occurrence of any state in the upper Midwest. The state's glacial aquifer geology, particularly in the prairie and agricultural regions of central and western Minnesota, creates naturally elevated arsenic in groundwater from mineral sediment chemistry. Minnesota MDH has conducted extensive private well testing programs and documented arsenic as a top priority for well owners.
Where does arsenic come from in Minnesota's water?
Glacial drift aquifer geology is the dominant arsenic pathway in Minnesota. Glacial till, outwash sands, and buried valley aquifers across central and western Minnesota contain arsenic-bearing iron oxide minerals that release arsenic under reducing geochemical conditions. The Prairie Pothole region, with its organic-rich sediments and reducing groundwater chemistry, has particularly elevated arsenic occurrence. The Cretaceous shale formations in western and southern Minnesota also contribute arsenic.
What should Minnesota residents know?
Minnesota MDH actively promotes private well testing for arsenic and has documented elevated concentrations in numerous counties. The state has subsidized testing programs and provides free consultation to private well owners. Rock, Pipestone, Murray, Nobles, Jackson, Martin, Faribault, and surrounding southwest Minnesota counties have among the highest documented arsenic rates in the state.
Key Facts
| EPA MCL | 10 µg/L (10 ppb) |
| MCLG | Zero |
| Primary source | Glacial drift and Cretaceous shale aquifer geology — reducing conditions mobilize natural arsenic in mineral sediments |
| Highest occurrence | Southwest Minnesota Prairie Coteau/Pothole region — 20%+ of wells exceeding MCL in some counties |
| State program | MDH provides well arsenic data viewer by township and subsidized testing programs |
| State regulator | Minnesota Department of Health — national leader in private well arsenic assessment |
| Health effects | Bladder, lung, skin cancer; cardiovascular; diabetes risk |
| Effective treatment | Reverse osmosis or activated alumina — iron oxidation (iron/manganese) filters also effective in MN iron-rich water |
Why Arsenic Matters in Minnesota
Minnesota has taken a national leadership role in private well arsenic assessment and has produced some of the most comprehensive county-level arsenic occurrence data in the country. Studies by MDH and USGS have documented arsenic as the most frequently detected health-based drinking water contaminant in Minnesota private wells. Southwest Minnesota's Prairie Coteau and Prairie Pothole regions have particularly high occurrence rates — over 20% of private wells in some counties exceed the 10 ppb MCL. Minnesota MDH maintains a well arsenic data viewer that allows residents to check occurrence rates in their township.
Minnesota Arsenic Program
Minnesota MDH has one of the most active arsenic monitoring programs in the country, having identified the glacial aquifer system — particularly the Buried Artesian Aquifer in the northeast and the Prairie du Chien-Jordan aquifer in the southeast — as high-arsenic zones. Approximately 40% of Minnesota's private well water comes from aquifers with elevated arsenic potential. MDH provides free arsenic testing resources and maintains a detailed county-level arsenic occurrence map.
Minnesota Utilities With Arsenic Violation Records
The utilities listed below have at least one arsenic violation on record in EPA's SDWIS database. Violations may be open or resolved — see individual utility pages for current status and risk level.
How Does Arsenic Get Into Drinking Water?
Arsenic in drinking water is almost always naturally occurring — it leaches from arsenic-bearing rocks and minerals into groundwater over time. New England granite, Southwest volcanic geology, and Upper Midwest glacial aquifers are the primary high-risk formations. It has no taste, odor, or color.
Full arsenic overview — geology maps, health effects, all 50 statesWho Should Pay Closest Attention
Southwest Minnesota counties — Rock, Pipestone, Murray, Nobles, Jackson, Martin, Faribault, Blue Earth — have the highest documented arsenic rates. Central Minnesota counties including Otter Tail, Pope, Stearns, and Grant also show elevated occurrence. Private well owners throughout Minnesota should test, as MDH's data shows arsenic can occur in any county.
Private well owners near mining districts or agricultural areas
Residents in states with documented volcanic or geothermal geology
Long-term consumers of water from small groundwater systems
Households in homes built before 1960 with older well casings
Residents whose well water has never been tested for arsenic
Anyone living in a state where bedrock wells are common
How to Check Your Situation in Minnesota
- 1
Identify your water source. If you use a public utility, use the ZIP lookup on this page to find your system and check its compliance record.
- 2
If on public water, review your utility's most recent Consumer Confidence Report (CCR) for arsenic monitoring data. The MCL is 10 ppb — your report should show recent test results.
- 3
If on a private well, order an arsenic test from a Minnesota Department of Health-certified laboratory. A basic arsenic test costs $15–$40. The state agency website maintains a certified lab list.
- 4
Test your well at the tap — not just at the wellhead. The entire water distribution system within your home can affect water quality.
- 5
If your test shows arsenic above 5 ppb, install certified treatment immediately. If above 10 ppb, do not use the water for drinking or cooking until treatment is installed.
- 6
Retest after installing treatment to confirm it is working as certified. Replace filter media on the manufacturer's schedule — an exhausted filter may not perform as rated.
Treatment Options for Arsenic
Boiling does not remove arsenic — it concentrates it. Standard activated carbon filters (Brita, etc.) do not effectively remove arsenic. Certified treatment is required.
NSF/ANSI Standard 58 — Reverse Osmosis
RO systems certified to NSF/ANSI 58 remove 85–95% of arsenic. Under-sink installation. Most effective for removing multiple contaminants simultaneously. Replace membranes and pre-filters on schedule.
Activated Alumina Filters
Activated alumina is specifically designed for arsenic and fluoride removal. Point-of-use or whole-house options available. Must be certified by NSF International or WQA for arsenic reduction. Requires periodic media regeneration or replacement.
Iron/Manganese Oxidation Filters
Effective for arsenic in iron-rich well water, which is common in the Midwest and New England. Oxidation converts dissolved iron and arsenic to a form that can be filtered out. Best when arsenic is co-occurring with high iron levels.
What does NOT work for arsenic
Standard activated carbon filters (Brita, refrigerator filters, most pitcher filters) do NOT effectively remove arsenic. Boiling concentrates arsenic. Water softeners do not remove arsenic. Only use products with NSF certification specifically for arsenic reduction.
Take Action Now
If you use a private well in Minnesota, test for arsenic — especially if you are in a region with granite, volcanic, or sedimentary geology. A basic arsenic test costs $15–$40 at a state-certified lab.
Public water users: check your utility's Consumer Confidence Report (CCR) for arsenic results. The EPA MCL is 10 ppb — any detection warrants attention.
If arsenic is detected above 10 ppb (or even below it, given MCLG is zero), install an NSF/ANSI 58-certified reverse osmosis system for drinking and cooking water.
Standard carbon filters do NOT remove arsenic — do not rely on a Brita or refrigerator filter for arsenic protection.
Frequently Asked Questions
Related Pages
Arsenic — National Overview
All U.S. utilities with arsenic records
Minnesota State Overview
All utilities and water quality data
Minnesota Well Water Guide
Testing, risks & certified labs for private wells
Reverse Osmosis Guide
Removes 85–95% of arsenic
Best Arsenic Filter Guide
What actually works (carbon doesn't)
PFAS in Drinking Water
The 'forever chemical' contamination overview
All Contaminants
Complete reference library
Data Sources & Provenance
All data on this page is sourced from official U.S. government or public datasets.
Find Your Utility
State Regulator
Minnesota Department of Health ↗