We analyzed tap water quality data for hundreds of cities in Oklahoma 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EPA legal limits, many health experts — including the Environmental Working Group — argue that these legal limits are outdated and don't reflect current scientific understanding of safe exposure levels.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
Edmond, Oklahoma
Edmond has 20 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 Edmond water report →Arcadia, Oklahoma
Arcadia has 20 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 Arcadia water report →Moore, Oklahoma
Moore has 18 contaminants exceeding EWG health guidelines out of 38 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Moore water report →Piedmont, Oklahoma
Piedmont has 18 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 Piedmont water report →Yukon, Oklahoma
Yukon has 18 contaminants exceeding EWG health guidelines out of 30 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Yukon water report →Mustang, Oklahoma
Mustang has 18 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 Mustang water report →Norman, Oklahoma
Norman 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 Norman water report →Stillwater, Oklahoma
Stillwater has 17 contaminants exceeding EWG health guidelines out of 30 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Stillwater water report →Ponca City, Oklahoma
Ponca City has 17 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 Ponca City water report →Bethany, Oklahoma
Bethany has 17 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 Bethany water report →Martha, Oklahoma
Martha has 17 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 Martha water report →El Reno, Oklahoma
El Reno has 16 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 El Reno water report →Newcastle, Oklahoma
Newcastle has 16 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 Newcastle water report →Marlow, Oklahoma
Marlow has 16 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 Marlow water report →Broken Arrow, Oklahoma
Broken Arrow has 16 contaminants exceeding EWG health guidelines out of 27 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Broken Arrow water report →Olustee, Oklahoma
Olustee has 16 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 Olustee water report →Tipton, Oklahoma
Tipton has 16 contaminants exceeding EWG health guidelines out of 23 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Tipton water report →Del City, Oklahoma
Del City has 15 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 Del City water report →Midwest City, Oklahoma
Midwest City has 15 contaminants exceeding EWG health guidelines out of 28 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Midwest City water report →Oklahoma City, Oklahoma
Oklahoma City has 15 contaminants exceeding EWG health guidelines out of 27 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Oklahoma City water report →Altus, Oklahoma
Altus has 15 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 Altus water report →Davidson, Oklahoma
Davidson has 15 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 Davidson water report →Arapaho, Oklahoma
Arapaho has 15 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 Arapaho water report →Lawton, Oklahoma
Lawton has 14 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 Lawton water report →Fort Sill, Oklahoma
Fort Sill has 14 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 Fort Sill water report →What We Found: Key Patterns
The most frequently detected contaminants exceeding health guidelines across these cities are Bromodichloromethane, Chloroform, Dibromochloromethane. 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, 411 contaminant readings exceed EWG health guidelines, but only 4 exceed EPA legal limits. This gap of 407 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 | Edmond | OK | 36 | 20 | 0 | 79,408 |
| 2 | Arcadia | OK | 36 | 20 | 0 | 300 |
| 3 | Moore | OK | 38 | 18 | 0 | 55,083 |
| 4 | Piedmont | OK | 32 | 18 | 0 | 7,542 |
| 5 | Yukon | OK | 30 | 18 | 0 | 22,498 |
| 6 | Mustang | OK | 29 | 18 | 0 | 18,576 |
| 7 | Norman | OK | 36 | 17 | 0 | 100,939 |
| 8 | Stillwater | OK | 30 | 17 | 1 | 53,000 |
| 9 | Ponca City | OK | 25 | 17 | 1 | 27,155 |
| 10 | Bethany | OK | 24 | 17 | 0 | 20,307 |
| 11 | Martha | OK | 24 | 17 | 0 | 205 |
| 12 | El Reno | OK | 29 | 16 | 0 | 16,212 |
| 13 | Newcastle | OK | 29 | 16 | 0 | 7,900 |
| 14 | Marlow | OK | 29 | 16 | 0 | 6,426 |
| 15 | Broken Arrow | OK | 27 | 16 | 1 | 116,330 |
| 16 | Olustee | OK | 24 | 16 | 1 | 607 |
| 17 | Tipton | OK | 23 | 16 | 0 | 916 |
| 18 | Del City | OK | 32 | 15 | 0 | 22,128 |
| 19 | Midwest City | OK | 28 | 15 | 0 | 55,935 |
| 20 | Oklahoma City | OK | 27 | 15 | 0 | 644,000 |
| 21 | Altus | OK | 22 | 15 | 0 | 18,717 |
| 22 | Davidson | OK | 20 | 15 | 0 | 0 |
| 23 | Arapaho | OK | 19 | 15 | 0 | 0 |
| 24 | Lawton | OK | 24 | 14 | 0 | 92,757 |
| 25 | Fort Sill | OK | 24 | 14 | 0 | 23,000 |
Frequently Asked Questions
What city has the worst tap water in Oklahoma?
Based on 2026 data, Edmond, OK 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.
