We analyzed tap water quality data for hundreds of cities in Ohio 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EPA legal limits, many health experts — including the Environmental Working Group — argue that these legal limits are outdated and don't reflect current scientific understanding of safe exposure levels.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
Ironton, Ohio
Ironton has 17 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 Ironton water report →South Lebanon, Ohio
South Lebanon has 17 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 South Lebanon water report →Ashley, Ohio
Ashley has 16 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 Ashley water report →Bexley, Ohio
Bexley has 16 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 Bexley water report →Wilmington, Ohio
Wilmington 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 Wilmington water report →Waterville, Ohio
Waterville 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 Waterville water report →Bowling Green, Ohio
Bowling Green has 16 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 Bowling Green water report →Brookville, Ohio
Brookville has 16 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 Brookville water report →Chagrin Falls, Ohio
Chagrin Falls has 16 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 Chagrin Falls water report →Grand Rapids, Ohio
Grand Rapids has 16 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 Grand Rapids water report →Tontogany, Ohio
Tontogany has 16 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 Tontogany water report →Cincinnati, Ohio
Cincinnati has 16 contaminants exceeding EWG health guidelines out of 26 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Cincinnati water report →Goshen, Ohio
Goshen has 16 contaminants exceeding EWG health guidelines out of 26 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Goshen water report →Marietta, Ohio
Marietta has 16 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 Marietta water report →Ravenna, Ohio
Ravenna has 16 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 Ravenna water report →Lebanon, Ohio
Lebanon 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 Lebanon water report →Milford, Ohio
Milford 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 Milford water report →Rio Grande, Ohio
Rio Grande 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 Rio Grande water report →Beavercreek, Ohio
Beavercreek has 16 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 Beavercreek water report →Gallipolis, Ohio
Gallipolis has 16 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 Gallipolis water report →Celina, Ohio
Celina has 16 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 Celina water report →Jamestown, Ohio
Jamestown has 16 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 Jamestown water report →Bridgeport, Ohio
Bridgeport has 16 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 Bridgeport water report →Phillipsburg, Ohio
Phillipsburg has 16 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 Phillipsburg water report →Delaware, Ohio
Delaware 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 Delaware water report →What We Found: Key Patterns
The most frequently detected contaminants exceeding health guidelines across these cities are Bromodichloromethane, Chloroform, Dibromoacetic acid. 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, 401 contaminant readings exceed EWG health guidelines, but only 11 exceed EPA legal limits. This gap of 390 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 | Ironton | OH | 32 | 17 | 0 | 34,942 |
| 2 | South Lebanon | OH | 27 | 17 | 0 | 6,541 |
| 3 | Ashley | OH | 31 | 16 | 0 | 0 |
| 4 | Bexley | OH | 30 | 16 | 0 | 14,250 |
| 5 | Wilmington | OH | 29 | 16 | 1 | 12,401 |
| 6 | Waterville | OH | 29 | 16 | 0 | 5,715 |
| 7 | Bowling Green | OH | 28 | 16 | 0 | 31,578 |
| 8 | Brookville | OH | 28 | 16 | 0 | 5,923 |
| 9 | Chagrin Falls | OH | 28 | 16 | 0 | 4,991 |
| 10 | Grand Rapids | OH | 28 | 16 | 0 | 1,500 |
| 11 | Tontogany | OH | 28 | 16 | 0 | 671 |
| 12 | Cincinnati | OH | 26 | 16 | 0 | 750,200 |
| 13 | Goshen | OH | 26 | 16 | 1 | 39,508 |
| 14 | Marietta | OH | 25 | 16 | 2 | 18,707 |
| 15 | Ravenna | OH | 25 | 16 | 0 | 16,000 |
| 16 | Lebanon | OH | 24 | 16 | 1 | 39,009 |
| 17 | Milford | OH | 24 | 16 | 1 | 6,700 |
| 18 | Rio Grande | OH | 23 | 16 | 1 | 830 |
| 19 | Beavercreek | OH | 22 | 16 | 0 | 51,229 |
| 20 | Gallipolis | OH | 22 | 16 | 1 | 20,995 |
| 21 | Celina | OH | 22 | 16 | 0 | 11,682 |
| 22 | Jamestown | OH | 21 | 16 | 1 | 32,350 |
| 23 | Bridgeport | OH | 19 | 16 | 0 | 2,830 |
| 24 | Phillipsburg | OH | 19 | 16 | 2 | 490 |
| 25 | Delaware | OH | 31 | 15 | 0 | 150,000 |
Frequently Asked Questions
What city has the worst tap water in Ohio?
Based on 2026 data, Ironton, OH 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.
