Arsenic in Drinking Water in North Dakota
What residents of North Dakota 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, North Dakota Department of Environmental Quality, USGS · Last reviewed: 2025-01-01
Quick Answer
Is arsenic in drinking water a concern in North Dakota?
Yes. North Dakota has documented arsenic occurrence in glacial aquifer systems and in the Cretaceous shale formations that underlie much of the state. Multiple North Dakota public water systems have historically exceeded the arsenic MCL, particularly in communities dependent on local groundwater rather than Missouri River water. North Dakota is one of the upper Midwest states with the most documented small community arsenic issues.
Where does arsenic come from in North Dakota's water?
Glacial drift aquifers and Cretaceous shale geology are the primary arsenic sources in North Dakota. Cretaceous-age Pierre Shale and related formations underlying the Missouri Coteau region contain naturally elevated arsenic. Glacial till and associated aquifers across the state can also mobilize arsenic under reducing conditions. Communities in the Coteau region dependent on local groundwater — rather than Missouri River water from the Mid-Dakota Rural Water System — face the highest risk.
What should North Dakota residents know?
Communities in the Missouri Coteau region of central and western North Dakota dependent on local groundwater face the most direct arsenic risk. North Dakota NDDEQ has worked with multiple small communities on arsenic treatment compliance. Rural private well owners in counties with documented elevated arsenic from Cretaceous shale geology should test independently.
Key Facts
| EPA MCL | 10 µg/L (10 ppb) |
| MCLG | Zero |
| Primary source | Cretaceous Pierre Shale geology (Missouri Coteau region); glacial drift aquifer sediments |
| Regional solution | Mid-Dakota Rural Water System delivers Missouri River water to some communities — reducing arsenic exposure for connected users |
| State regulator | North Dakota Department of Environmental Quality (NDDEQ) |
| Health effects | Bladder, lung, skin cancer; cardiovascular; diabetes risk |
| Effective treatment | Reverse osmosis (NSF/ANSI 58) or activated alumina |
Why Arsenic Matters in North Dakota
North Dakota's arsenic problem is connected to its Cretaceous bedrock geology. The Pierre Shale and related formations that underlie much of the Missouri Coteau contain naturally elevated arsenic that has been documented in groundwater across a wide area. The state's Mid-Dakota Rural Water System delivers Missouri River water to many communities, reducing arsenic exposure for those connected to the system — but communities not connected remain dependent on local groundwater with elevated arsenic. North Dakota NDDEQ has pursued treatment assistance funding for affected small communities.
North Dakota Arsenic Program
North Dakota DEQ monitors arsenic under federal SDWIS and has documented elevated arsenic in the glacial aquifer systems that supply much of rural North Dakota's water. Several North Dakota small water systems required treatment after the 2006 MCL tightening. Private well owners drawing from glacial aquifers in the James River Valley and Missouri Coteau regions face elevated arsenic risk.
Largest North Dakota Water Utilities
No arsenic violations on record in EPA SDWIS for North Dakota utilities in our database. Browse the largest utilities to review their full water quality record.
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
Communities in the Missouri Coteau region of central North Dakota (McIntosh, Logan, LaMoure, Dickey, Emmons, Kidder, Stutsman, and surrounding counties) dependent on local groundwater face the highest arsenic risk. Private well users in counties with documented elevated Cretaceous shale arsenic should test.
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 North Dakota
- 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 North Dakota Department of Environmental Quality-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 North Dakota, 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
North Dakota State Overview
All utilities and water quality data
North Dakota 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.
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North Dakota Department of Environmental Quality ↗