Arsenic in Wyoming Drinking Water
Ranked by arsenic violation count · Data from EPA SDWIS & UCMR
Arsenic in Wyoming: what the data shows
Wyoming has 38 cities with arsenic-related violations on record. Arsenic contamination is a federal MCL violation at levels above 10 µg/L (10 ppb). The state has 38 cities with at least one arsenic violation. Arsenic enters drinking water primarily through erosion of natural deposits, particularly in western states with arsenite-bearing geology. Industrial sources include mining runoff, glass manufacturing, and semiconductor production. Groundwater systems are significantly more likely to have arsenic issues than surface water systems. Long-term arsenic exposure above the MCL increases the risk of bladder, lung, and skin cancer, as well as cardiovascular disease and diabetes. Reverse osmosis and specialized arsenic-removal media are the most effective point-of-use treatment options.
Cities exceeding 10 µg/L EPA MCL
Arsenic data across Wyoming
Each dot is a city with arsenic violation data. Cities with at least one arsenic-related violation are highlighted. Size reflects population served.
Top 10 cities by arsenic level in Wyoming
Highest Arsenic levels (violations)
All Wyoming cities ranked by arsenic level
| # | City | Level | Level | Violations? | Violations | Grade |
|---|---|---|---|---|---|---|
| 1 | Jackson | 16 violations | Yes | 64 | F | |
| 2 | Marbleton | 16 violations | Yes | 4 | D+ | |
| 3 | Gillette | 10 violations | Yes | 89 | F | |
| 4 | Afton | 8 violations | Yes | 34 | D+ | |
| 5 | Cheyenne | 7 violations | Yes | 36 | F | |
| 6 | Riverton | 7 violations | Yes | 59 | F | |
| 7 | Fort Washakie | 7 violations | Yes | 40 | F | |
| 8 | Newcastle | 6 violations | Yes | 20 | D | |
| 9 | Mills | 5 violations | Yes | 14 | F | |
| 10 | Yellowstone Np | 5 violations | Yes | 13 | D | |
| 11 | Casper | 4 violations | Yes | 22 | F | |
| 12 | Lander | 3 violations | Yes | 3 | B+ | |
| 13 | Torrington | 3 violations | Yes | 63 | F | |
| 14 | Douglas | 3 violations | Yes | 11 | C | |
| 15 | Lyman | 3 violations | Yes | 7 | A- | |
| 16 | Ethete | 3 violations | Yes | 8 | B- | |
| 17 | Dubois | 3 violations | Yes | 2 | C | |
| 18 | Cody | 2 violations | Yes | 3 | B- | |
| 19 | Rawlins | 2 violations | Yes | 7 | C- | |
| 20 | Buffalo | 2 violations | Yes | 19 | B- | |
| 21 | Thayne | 2 violations | Yes | 17 | D | |
| 22 | Lovell | 2 violations | Yes | 4 | B | |
| 23 | Saratoga | 2 violations | Yes | 7 | B | |
| 24 | Burns | 2 violations | Yes | 10 | B- | |
| 25 | Wilson | 2 violations | Yes | 1 | D | |
| 26 | Cokeville | 2 violations | Yes | 8 | D+ | |
| 27 | Laramie | 1 violations | Yes | 6 | C- | |
| 28 | Rock Springs | 1 violations | Yes | 5 | C | |
| 29 | Evanston | 1 violations | Yes | 12 | B+ | |
| 30 | Worland | 1 violations | Yes | 1 | A- | |
| 31 | Thermopolis | 1 violations | Yes | 13 | D | |
| 32 | Wheatland | 1 violations | Yes | 22 | C+ | |
| 33 | Pinedale | 1 violations | Yes | 18 | B+ | |
| 34 | Little America | 1 violations | Yes | 36 | C+ | |
| 35 | Lusk | 1 violations | Yes | 12 | C+ | |
| 36 | Guernsey | 1 violations | Yes | 9 | A- | |
| 37 | Cowley | 1 violations | Yes | 4 | A- | |
| 38 | Farson | 1 violations | Yes | 2 | B- |
Frequently asked questions about arsenic in Wyoming
Is arsenic in Wyoming tap water a concern?
Yes — 38 cities in Wyoming have arsenic-related violations on record. The EPA MCL for arsenic is 10 µg/L. Even at levels below the MCL, long-term arsenic exposure has been linked to cancer and cardiovascular disease.
How can I remove arsenic from my drinking water in Wyoming?
Reverse osmosis (RO) systems are the most effective at removing arsenic, typically reducing it by 90% or more. Specialized arsenic-removal media (such as iron-based adsorption filters) are also highly effective. Standard carbon filters and pitcher filters do NOT effectively remove arsenic. If your water comes from a private well, have it tested for arsenic.
Where does arsenic in Wyoming water come from?
Arsenic enters drinking water primarily through natural erosion of arsenic-bearing rock formations. It is most common in groundwater systems in the western United States, parts of the Midwest, and New England. Industrial sources include mining, smelting, and agricultural pesticide residues. Groundwater sources are far more likely to contain arsenic than surface water.