Arsenic in Drinking Water in Arizona
What residents of Arizona 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, Arizona Department of Environmental Quality, USGS · Last reviewed: 2025-01-01
Quick Answer
Is arsenic in drinking water a concern in Arizona?
Yes — Arizona has some of the highest naturally occurring arsenic concentrations in the country. The state's volcanic and hydrothermal geology, particularly in the Basin and Range province, creates widespread arsenic in groundwater. Multiple Arizona public water systems have historically exceeded the 10 ppb MCL, and rural areas relying on private wells or small groundwater systems face elevated risk.
Where does arsenic come from in Arizona's water?
Naturally occurring arsenic in Arizona's volcanic and sedimentary geology is the dominant exposure pathway. The Basin and Range province — which covers most of southern and western Arizona — has documented elevated arsenic in alluvial aquifers filled with volcanic and hydrothermal sediments. The Phoenix metro area draws from both Colorado River water (lower arsenic) and local groundwater (variable arsenic); smaller communities relying solely on local groundwater face higher risk.
What should Arizona residents know?
Arizona has had more public water systems exceed the arsenic MCL than most western states. Communities in rural Maricopa, Pinal, Pima, Yavapai, and Mohave counties relying on local groundwater face the highest risk. Arizona ADEQ actively monitors compliance and has helped many small communities implement treatment. Private well owners throughout Arizona should test, as the state's geology creates arsenic occurrence across a wide area.
Key Facts
| EPA MCL | 10 µg/L (10 ppb) |
| MCLG | Zero |
| Primary source | Volcanic and hydrothermal geology throughout the Basin and Range province |
| State arsenic profile | Among highest naturally occurring arsenic states in the U.S. — many small systems historically exceeded MCL |
| State regulator | Arizona Department of Environmental Quality (ADEQ) |
| Private well risk | Widespread — Arizona geology creates arsenic across a large geographic area |
| Health effects | Bladder, lung, skin cancer; cardiovascular disease; diabetes risk |
| Effective treatment | Reverse osmosis (NSF/ANSI 58) or activated alumina — both well-suited to Arizona's arsenic type |
Why Arsenic Matters in Arizona
Arizona's arsenic problem is among the most significant in the nation due to the state's Basin and Range geology. Volcanic tuff, geothermal deposits, and sedimentary formations across much of the state contain arsenic that leaches into groundwater over geological timescales. Communities in Yavapai County, Mohave County, and rural Maricopa and Pinal counties have frequently exceeded the MCL. Arizona ADEQ has worked with affected communities to implement treatment, but small system financial constraints can delay compliance. Private well users in Arizona should treat arsenic as a primary water quality concern given the state's geology.
Arizona Arsenic Program
Arizona is one of the highest-arsenic states in the country due to volcanic and sedimentary geology throughout the state. ADEQ has maintained an active arsenic compliance program since the 2006 tightening of the federal MCL from 50 ppb to 10 ppb, which forced many small Arizona systems to install treatment. Private wells in rural Arizona — particularly in the Tucson Basin, the Phoenix AMA, and the rural Southeast — are at significant risk and should be tested.
Arizona 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.
City of Tucson
Tucson · 732,906 served
City of Mesa
Mesa · 466,000 served
Town of Gilbert
Gilbert · 247,600 served
City of Chandler
Chandler · 247,328 served
City of Peoria
Peoria · 187,676 served
Arizona Water Co - Pinal Valley
Casa Grande · 134,432 served
Town of Queen Creek
Queen Creek · 95,502 served
Gw Santa Cruz Water Co
Maricopa · 84,000 served
City of Flagstaff
Flagstaff · 76,960 served
Goodyear Water Department
Goodyear · 50,001 served
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
Rural communities in Yavapai County (Prescott Valley area), Mohave County, Pinal County (especially groundwater-dependent areas away from CAP water), and communities throughout the Basin and Range province face elevated arsenic risk. Arizona's significant tribal communities relying on local groundwater should prioritize arsenic testing.
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 Arizona
- 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 Arizona 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 Arizona, 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
Arizona State Overview
All utilities and water quality data
Arizona 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
Arizona Department of Environmental Quality ↗