Arsenic in Drinking Water in Oklahoma
What residents of Oklahoma 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, Oklahoma Department of Environmental Quality, USGS · Last reviewed: 2025-01-01
Quick Answer
Is arsenic in drinking water a concern in Oklahoma?
Yes. Oklahoma has documented arsenic in the Ogallala Aquifer in the Oklahoma Panhandle and in alluvial aquifer systems throughout the state. Multiple Oklahoma public water systems have required arsenic treatment, particularly in the Panhandle and rural western Oklahoma where the Ogallala is the primary water source. Oklahoma also has arsenic from naturally occurring sources in the Ouachita Mountain region of southeastern Oklahoma.
Where does arsenic come from in Oklahoma's water?
The Ogallala (High Plains) Aquifer in the Oklahoma Panhandle and western Oklahoma counties is the primary arsenic source for communities in these areas. Alluvial aquifer systems along the Arkansas, Canadian, and Cimarron rivers also have documented naturally occurring arsenic. The Ouachita Mountain region in southeastern Oklahoma has arsenic from sulfide mineral geology similar to the Arkansas Ouachitas.
What should Oklahoma residents know?
Oklahoma Panhandle communities in Cimarron, Texas, and Beaver counties dependent on the Ogallala face the most direct arsenic risk. Rural western Oklahoma communities on alluvial aquifer systems should verify their system's compliance. Private well owners in the Ouachita Mountain counties of southeastern Oklahoma should test for arsenic.
Key Facts
| EPA MCL | 10 µg/L (10 ppb) |
| MCLG | Zero |
| Primary source | Ogallala Aquifer (Panhandle/western Oklahoma); alluvial river aquifers; Ouachita Mountain sulfide geology (SE Oklahoma) |
| State regulator | Oklahoma Department of Environmental Quality (DEQ) |
| Health effects | Bladder, lung, skin cancer; cardiovascular; diabetes risk |
| Effective treatment | Reverse osmosis or activated alumina |
Why Arsenic Matters in Oklahoma
Oklahoma's arsenic concerns reflect its geological diversity — from the Ogallala Aquifer of the High Plains in the Panhandle to the mineral-rich Ouachita Mountains in the southeast. The Panhandle's dependence on the Ogallala for drinking water in an extremely arid region means arsenic treatment is both critical and costly for these small, remote communities. Oklahoma DEQ has worked with affected communities on compliance assistance and treatment funding.
Oklahoma Arsenic Program
Oklahoma DEQ monitors arsenic under federal SDWIS. Oklahoma's geology — particularly the Arbuckle Mountains and the western volcanic and sedimentary zones — has naturally elevated arsenic in some groundwater. Several Oklahoma small water systems in the western portion of the state required treatment after the 2006 MCL change. Private well owners in western Oklahoma should test.
Oklahoma 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
Oklahoma Panhandle communities in Cimarron, Texas, and Beaver counties, western Oklahoma communities on alluvial aquifer systems, and southeastern Oklahoma private well users in the Ouachita Mountain counties (McCurtain, Pushmataha, Latimer, Le Flore) face the most relevant arsenic risk.
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 Oklahoma
- 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 Oklahoma 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 Oklahoma, 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
Oklahoma State Overview
All utilities and water quality data
Oklahoma 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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Oklahoma Department of Environmental Quality ↗