Arsenic in Idaho well water
In Idaho, 18% of 8,340 tested private well samples exceeded the EPA limit for arsenic (10 ug/L).
Arsenic occurs naturally in New England bedrock and dissolves into well water. Long-term exposure raises the risk of bladder, lung and skin cancers, and is linked to heart disease and lower IQ in children. It has no taste or smell, so testing is the only way to know.
Check your arsenic number
Type the value from your lab report. It is compared to the EPA limit, the same way the full interpretation does it.
Getting it fixed
Book a free in-home water test with a licensed local company, or see the treatment guide for what removes arsenic.
By county, from individual samples
Public monitoring samples against the EPA limit (10 ug/L); counties with at least 30 samples.
| County | Samples | Detected | Above EPA limit | Median | Highest |
|---|---|---|---|---|---|
| Owyhee | 234 | 88% | 60% | 13.6 | 140 ug/L |
| Washington | 120 | 93% | 53% | 11 | 950 ug/L |
| Twin Falls | 582 | 95% | 49% | 10 | 107 ug/L |
| Canyon | 1,140 | 92% | 40% | 7.05 | 150 ug/L |
| Payette | 378 | 91% | 39% | 8.1 | 56 ug/L |
| Gem | 183 | 77% | 23% | 5 | 58 ug/L |
| Minidoka | 134 | 94% | 21% | 4 | 43 ug/L |
| Elmore | 272 | 87% | 17% | 3 | 54 ug/L |
| Ada | 673 | 88% | 16% | 3.8 | 39 ug/L |
| Boise | 91 | 74% | 15% | 1 | 97 ug/L |
| Jefferson | 190 | 77% | 11% | 2 | 110 ug/L |
| Bonner | 340 | 58% | 10% | 0.6 | 23.9 ug/L |
| Bear Lake | 100 | 61% | 9% | 0.6 | 85 ug/L |
| Boundary | 102 | 34% | 9% | 0 | 25 ug/L |
| Bannock | 314 | 72% | 8% | 2 | 50.5 ug/L |
- Bruneau CCD, Owyhee County100% of 36
- Wilder CCD, Canyon County93% of 122
- Filer CCD, Twin Falls County78% of 83
- Parma CCD, Canyon County78% of 136
- Huston CCD, Canyon County75% of 75
- Fruitland CCD, Payette County74% of 112
- Twin Falls CCD, Twin Falls County64% of 92
- Weiser CCD, Washington County60% of 105
- Buhl CCD, Twin Falls County60% of 114
- Grand View CCD, Owyhee County58% of 72
- Homedale CCD, Owyhee County58% of 38
- Heyburn CCD, Minidoka County57% of 37
- Glenns Ferry CCD, Elmore County56% of 59
- West Salmon Falls CCD, Twin Falls County51% of 47
- Notus CCD, Canyon County49% of 75
- Sweet CCD, Gem County48% of 31
- Hollister CCD, Twin Falls County48% of 135
- Marsing CCD, Owyhee County48% of 50
- Murphy CCD, Owyhee County45% of 38
- Caldwell CCD, Canyon County37% of 93
Sources
- Individual samples from the USGS Water Quality Portal and state monitoring, summarized per geography. arsenic counts and shares are listed on each county and town page with their sources.