We analyzed tap water quality data for hundreds of cities in Maryland 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EPA legal limits, many health experts — including the Environmental Working Group — argue that these legal limits are outdated and don't reflect current scientific understanding of safe exposure levels.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
Westminster, Maryland
Westminster 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 Westminster water report →Aberdeen, Maryland
Aberdeen has 14 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 Aberdeen water report →Hopewell, Maryland
Hopewell has 14 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 Hopewell water report →La Plata, Maryland
La Plata has 12 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 La Plata water report →Silver Spring, Maryland
Silver Spring has 12 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 Silver Spring water report →Sharptown, Maryland
Sharptown has 12 contaminants exceeding EWG health guidelines out of 16 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Sharptown water report →Bel Air, Maryland
Bel Air has 11 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 Bel Air water report →Hampstead, Maryland
Hampstead has 11 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 Hampstead water report →Elkton, Maryland
Elkton 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 Elkton water report →Taneytown, Maryland
Taneytown has 11 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 Taneytown water report →Baltimore, Maryland
Baltimore 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 Baltimore water report →Salisbury, Maryland
Salisbury 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 Salisbury water report →Tysons, Maryland
Tysons 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 Tysons water report →Frederick, Maryland
Frederick has 10 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 Frederick water report →Rockville, Maryland
Rockville has 9 contaminants exceeding EWG health guidelines out of 22 total detected, placing it among the most concerning water supplies analyzed.
See full Rockville water report →Hagerstown, Maryland
Hagerstown has 9 contaminants exceeding EWG health guidelines out of 19 total detected, placing it among the most concerning water supplies analyzed.
See full Hagerstown water report →Smithsburg, Maryland
Smithsburg has 9 contaminants exceeding EWG health guidelines out of 19 total detected, placing it among the most concerning water supplies analyzed.
See full Smithsburg water report →Williamsport, Maryland
Williamsport has 9 contaminants exceeding EWG health guidelines out of 19 total detected, placing it among the most concerning water supplies analyzed.
See full Williamsport water report →Funkstown, Maryland
Funkstown has 9 contaminants exceeding EWG health guidelines out of 19 total detected, placing it among the most concerning water supplies analyzed.
See full Funkstown water report →Lavale, Maryland
Lavale has 9 contaminants exceeding EWG health guidelines out of 17 total detected, placing it among the most concerning water supplies analyzed.
See full Lavale water report →Manchester, Maryland
Manchester has 9 contaminants exceeding EWG health guidelines out of 17 total detected, placing it among the most concerning water supplies analyzed.
See full Manchester water report →California, Maryland
California has 9 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full California water report →Havre De Grace, Maryland
Havre De Grace has 9 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Havre De Grace water report →Woodsboro, Maryland
Woodsboro has 9 contaminants exceeding EWG health guidelines out of 14 total detected, placing it among the most concerning water supplies analyzed.
See full Woodsboro water report →Oakland, Maryland
Oakland has 9 contaminants exceeding EWG health guidelines out of 13 total detected, placing it among the most concerning water supplies analyzed.
See full Oakland water report →What We Found: Key Patterns
The most frequently detected contaminants exceeding health guidelines across these cities are Total trihalomethanes (TTHMs), Haloacetic acids (HAA5), Nitrate and nitrite. 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, 264 contaminant readings exceed EWG health guidelines, but only 2 exceed EPA legal limits. This gap of 262 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 | Westminster | MD | 25 | 17 | 0 | 35,256 |
| 2 | Aberdeen | MD | 29 | 14 | 0 | 16,200 |
| 3 | Hopewell | MD | 27 | 14 | 0 | 13,200 |
| 4 | La Plata | MD | 24 | 12 | 0 | 91,260 |
| 5 | Silver Spring | MD | 20 | 12 | 0 | 1,900,000 |
| 6 | Sharptown | MD | 16 | 12 | 0 | 625 |
| 7 | Bel Air | MD | 23 | 11 | 0 | 104,567 |
| 8 | Hampstead | MD | 23 | 11 | 0 | 0 |
| 9 | Elkton | MD | 20 | 11 | 1 | 15,625 |
| 10 | Taneytown | MD | 19 | 11 | 0 | 6,750 |
| 11 | Baltimore | MD | 21 | 10 | 0 | 1,600,000 |
| 12 | Salisbury | MD | 21 | 10 | 1 | 30,343 |
| 13 | Tysons | MD | 21 | 10 | 0 | 378 |
| 14 | Frederick | MD | 19 | 10 | 0 | 54,000 |
| 15 | Rockville | MD | 22 | 9 | 0 | 52,000 |
| 16 | Hagerstown | MD | 19 | 9 | 0 | 92,200 |
| 17 | Smithsburg | MD | 19 | 9 | 0 | 2,500 |
| 18 | Williamsport | MD | 19 | 9 | 0 | 2,400 |
| 19 | Funkstown | MD | 19 | 9 | 0 | 1,300 |
| 20 | Lavale | MD | 17 | 9 | 0 | 5,500 |
| 21 | Manchester | MD | 17 | 9 | 0 | 4,954 |
| 22 | California | MD | 16 | 9 | 0 | 43,030 |
| 23 | Havre De Grace | MD | 16 | 9 | 0 | 14,000 |
| 24 | Woodsboro | MD | 14 | 9 | 0 | 846 |
| 25 | Oakland | MD | 13 | 9 | 0 | 1,850 |
Frequently Asked Questions
What city has the worst tap water in Maryland?
Based on 2026 data, Westminster, MD 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.
