We analyzed tap water quality data for hundreds of cities in Arizona to identify the 25 with the most contaminants exceeding health guidelines. This ranking is based on 2026 data from the EPA and EWG databases.
While all public water systems must meet EPA legal limits, many health experts — including the Environmental Working Group — argue that these legal limits are outdated and don't reflect current scientific understanding of safe exposure levels. The cities below have the widest gap between what's in their water and what's considered safe by modern health standards.
Rankings at a Glance
Goodyear, Arizona
Goodyear has 18 contaminants exceeding EWG health guidelines out of 34 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Goodyear water report →Avondale, Arizona
Avondale has 17 contaminants exceeding EWG health guidelines out of 36 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Avondale water report →Litchfield Park, Arizona
Litchfield Park has 15 contaminants exceeding EWG health guidelines out of 31 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Litchfield Park water report →Dragoon, Arizona
Dragoon has 15 contaminants exceeding EWG health guidelines out of 25 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Dragoon water report →Peoria, Arizona
Peoria has 13 contaminants exceeding EWG health guidelines out of 29 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Peoria water report →Thatcher, Arizona
Thatcher has 13 contaminants exceeding EWG health guidelines out of 25 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Thatcher water report →Apache Junction, Arizona
Apache Junction has 13 contaminants exceeding EWG health guidelines out of 22 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Apache Junction water report →Payson, Arizona
Payson has 12 contaminants exceeding EWG health guidelines out of 35 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Payson water report →Tempe, Arizona
Tempe has 12 contaminants exceeding EWG health guidelines out of 34 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Tempe water report →Gilbert, Arizona
Gilbert has 12 contaminants exceeding EWG health guidelines out of 33 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Gilbert water report →Tucson, Arizona
Tucson has 12 contaminants exceeding EWG health guidelines out of 32 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Tucson water report →Douglas, Arizona
Douglas has 12 contaminants exceeding EWG health guidelines out of 21 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Douglas water report →Oro Valley, Arizona
Oro Valley has 12 contaminants exceeding EWG health guidelines out of 21 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Oro Valley water report →Pine, Arizona
Pine has 12 contaminants exceeding EWG health guidelines out of 19 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Pine water report →Prescott, Arizona
Prescott has 11 contaminants exceeding EWG health guidelines out of 25 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Prescott water report →Surprise, Arizona
Surprise has 11 contaminants exceeding EWG health guidelines out of 25 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Surprise water report →Green Valley, Arizona
Green Valley has 11 contaminants exceeding EWG health guidelines out of 22 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Green Valley water report →Florence, Arizona
Florence has 11 contaminants exceeding EWG health guidelines out of 21 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Florence water report →Luke AFB, Arizona
Luke AFB has 11 contaminants exceeding EWG health guidelines out of 20 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Luke AFB water report →Mesa, Arizona
Mesa has 10 contaminants exceeding EWG health guidelines out of 33 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Mesa water report →Tolleson, Arizona
Tolleson has 10 contaminants exceeding EWG health guidelines out of 24 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Tolleson water report →Queen Creek, Arizona
Queen Creek has 10 contaminants exceeding EWG health guidelines out of 21 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Queen Creek water report →San Tan Valley, Arizona
San Tan Valley has 10 contaminants exceeding EWG health guidelines out of 21 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full San Tan Valley water report →Flagstaff, Arizona
Flagstaff has 10 contaminants exceeding EWG health guidelines out of 18 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Flagstaff water report →Buckeye, Arizona
Buckeye has 10 contaminants exceeding EWG health guidelines out of 18 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Buckeye water report →What We Found: Key Patterns
The most frequently detected contaminants exceeding health guidelines across these cities are Total trihalomethanes (TTHMs), Nitrate, Arsenic. These appear repeatedly across different water systems and regions.
Water quality varies significantly even within the same state, driven by local geology, agricultural activity, and industrial proximity.
Across all ranked cities, 303 contaminant readings exceed EWG health guidelines, but only 4 exceed EPA legal limits. This gap of 299 highlights how legal standards may not fully protect public health — EPA limits haven't been updated for many contaminants in decades.
Full Rankings Table
| Rank | City | State | Detected | Above Guidelines | Above Legal | People Served |
|---|---|---|---|---|---|---|
| 1 | Goodyear | AZ | 34 | 18 | 0 | 50,001 |
| 2 | Avondale | AZ | 36 | 17 | 0 | 83,001 |
| 3 | Litchfield Park | AZ | 31 | 15 | 1 | 50,770 |
| 4 | Dragoon | AZ | 25 | 15 | 0 | 15,603 |
| 5 | Peoria | AZ | 29 | 13 | 0 | 135,975 |
| 6 | Thatcher | AZ | 25 | 13 | 0 | 20,600 |
| 7 | Apache Junction | AZ | 22 | 13 | 0 | 15,610 |
| 8 | Payson | AZ | 35 | 12 | 2 | 17,682 |
| 9 | Tempe | AZ | 34 | 12 | 1 | 165,000 |
| 10 | Gilbert | AZ | 33 | 12 | 0 | 247,600 |
| 11 | Tucson | AZ | 32 | 12 | 0 | 732,906 |
| 12 | Douglas | AZ | 21 | 12 | 0 | 16,656 |
| 13 | Oro Valley | AZ | 21 | 12 | 0 | 250 |
| 14 | Pine | AZ | 19 | 12 | 0 | 6,284 |
| 15 | Prescott | AZ | 25 | 11 | 0 | 42,217 |
| 16 | Surprise | AZ | 25 | 11 | 0 | 40,007 |
| 17 | Green Valley | AZ | 22 | 11 | 0 | 22,085 |
| 18 | Florence | AZ | 21 | 11 | 0 | 15,900 |
| 19 | Luke AFB | AZ | 20 | 11 | 0 | 1,149 |
| 20 | Mesa | AZ | 33 | 10 | 0 | 466,000 |
| 21 | Tolleson | AZ | 24 | 10 | 0 | 6,680 |
| 22 | Queen Creek | AZ | 21 | 10 | 0 | 94,313 |
| 23 | San Tan Valley | AZ | 21 | 10 | 0 | 87,435 |
| 24 | Flagstaff | AZ | 18 | 10 | 0 | 76,960 |
| 25 | Buckeye | AZ | 18 | 10 | 0 | 15,783 |
Frequently Asked Questions
What city has the worst tap water in Arizona?
Based on 2026 data, Goodyear, AZ has the most contaminants exceeding EWG health guidelines among the cities we analyzed.
How are cities ranked in this report?
Cities are ranked by the number of contaminants exceeding EWG health guidelines. These guidelines are typically stricter than EPA legal limits and reflect current scientific research on safe exposure levels.
Is my tap water safe if my city isn't on this list?
Not necessarily. Even cities not on this list may have contaminants of concern. We recommend checking your specific water quality using our free water scan tool.
What's the best water filter for contaminated water?
A reverse osmosis (RO) system is the most effective for removing the widest range of contaminants. For whole-home protection, a combination of RO for drinking water and a whole-home filter for showers and baths is recommended.
Related Reports
Data sources: Environmental Working Group (EWG) Tap Water Database, U.S. EPA Safe Drinking Water Information System (SDWIS)
Last updated: April 2026
Methodology: Contaminant levels are compared against both EPA legal limits (Maximum Contaminant Levels) and EWG health guidelines, which are often stricter and based on the latest scientific research.
