We analyzed tap water quality data for hundreds of cities in Montana 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EPA legal limits, many health experts — including the Environmental Working Group — argue that these legal limits are outdated and don't reflect current scientific understanding of safe exposure levels.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
Helena, Montana
Helena has 13 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 Helena water report →Fort Harrison, Montana
Fort Harrison has 13 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 Harrison water report →Billings, Montana
Billings has 13 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 Billings water report →Bridger, Montana
Bridger has 13 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 Bridger water report →Colstrip, Montana
Colstrip has 13 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 Colstrip water report →Manhattan, Montana
Manhattan has 13 contaminants exceeding EWG health guidelines out of 17 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Manhattan water report →Orem, Montana
Orem has 13 contaminants exceeding EWG health guidelines out of 17 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Orem water report →Ryegate, Montana
Ryegate has 13 contaminants exceeding EWG health guidelines out of 17 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Ryegate water report →Huntley, Montana
Huntley has 13 contaminants exceeding EWG health guidelines out of 17 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Huntley water report →Columbus, Montana
Columbus has 13 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 Columbus water report →Yellowtail, Montana
Yellowtail has 13 contaminants exceeding EWG health guidelines out of 15 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Yellowtail water report →Fort Benton, Montana
Fort Benton has 13 contaminants exceeding EWG health guidelines out of 14 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Fort Benton water report →Missoula, Montana
Missoula 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 Missoula water report →Malmstrom Air Force Base, Montana
Malmstrom Air Force Base 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 Malmstrom Air Force Base water report →Great Fall, Montana
Great Fall has 12 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 Great Fall water report →Black Eagle, Montana
Black Eagle has 12 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 Black Eagle water report →El Dorado Hills, Montana
El Dorado Hills has 12 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 El Dorado Hills water report →Hardin, Montana
Hardin 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 Hardin water report →Forsyth, Montana
Forsyth 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 Forsyth water report →Dallas, Montana
Dallas 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 Dallas water report →Miles City, Montana
Miles City 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 Miles City water report →Cutbank, Montana
Cutbank has 12 contaminants exceeding EWG health guidelines out of 15 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Cutbank water report →Roundup, Montana
Roundup has 12 contaminants exceeding EWG health guidelines out of 15 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Roundup water report →Cut Bank, Montana
Cut Bank has 12 contaminants exceeding EWG health guidelines out of 15 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Cut Bank water report →Kevin, Montana
Kevin has 12 contaminants exceeding EWG health guidelines out of 15 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Kevin water report →What We Found: Key Patterns
The most frequently detected contaminants exceeding health guidelines across these cities are Bromodichloromethane, Haloacetic acids (HAA5), Total trihalomethanes (TTHMs). 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, 312 contaminant readings exceed EWG health guidelines, but only 0 exceed EPA legal limits. This gap of 312 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 | Helena | MT | 24 | 13 | 0 | 31,005 |
| 2 | Fort Harrison | MT | 24 | 13 | 0 | 25 |
| 3 | Billings | MT | 23 | 13 | 0 | 114,000 |
| 4 | Bridger | MT | 20 | 13 | 0 | 50 |
| 5 | Colstrip | MT | 19 | 13 | 0 | 2,350 |
| 6 | Manhattan | MT | 17 | 13 | 0 | 1,800 |
| 7 | Orem | MT | 17 | 13 | 0 | 800 |
| 8 | Ryegate | MT | 17 | 13 | 0 | 270 |
| 9 | Huntley | MT | 17 | 13 | 0 | 240 |
| 10 | Columbus | MT | 16 | 13 | 0 | 1,900 |
| 11 | Yellowtail | MT | 15 | 13 | 0 | 40 |
| 12 | Fort Benton | MT | 14 | 13 | 0 | 0 |
| 13 | Missoula | MT | 24 | 12 | 0 | 68,200 |
| 14 | Malmstrom Air Force Base | MT | 24 | 12 | 0 | 0 |
| 15 | Great Fall | MT | 23 | 12 | 0 | 60,000 |
| 16 | Black Eagle | MT | 23 | 12 | 0 | 1,233 |
| 17 | El Dorado Hills | MT | 23 | 12 | 0 | 60 |
| 18 | Hardin | MT | 20 | 12 | 0 | 3,500 |
| 19 | Forsyth | MT | 16 | 12 | 0 | 2,260 |
| 20 | Dallas | MT | 16 | 12 | 0 | 650 |
| 21 | Miles City | MT | 16 | 12 | 0 | 480 |
| 22 | Cutbank | MT | 15 | 12 | 0 | 3,105 |
| 23 | Roundup | MT | 15 | 12 | 0 | 1,900 |
| 24 | Cut Bank | MT | 15 | 12 | 0 | 478 |
| 25 | Kevin | MT | 15 | 12 | 0 | 275 |
Frequently Asked Questions
What city has the worst tap water in Montana?
Based on 2026 data, Helena, MT 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.
