Indiana Private Well Water Risk: Arsenic & Nitrate
These figures are USGS statistical estimates for private (domestic) wells in Indiana. They describe the area's modeled risk — not any single well.
This is a modeled probability for the area, not a measurement of your well. USGS statistical models estimate how many private wells in this area are likely to exceed the federal limit — they cannot tell you what is in your water. Two neighbors can have very different results. The only way to know your well is to test it.
Nitrate
0.1%
of the private-well population is modeled above the 10 mg/L nitrate limit
~711
people on wells estimated above the limit
~1,410,000
total residents on private wells statewide
Source: USGS machine-learning nitrate model, Ransom et al. (2022), domestic-well depth zone.
Arsenic
Across Indiana, an estimated ~150,861 people rely on private wells with modeled arsenic above the 10 µg/L EPA limit. The highest modeled exposure is in Kosciusko County (~8,677 people).
Counties with the highest modeled arsenic exposure
| County | Est. well residents over arsenic limit | 90% range |
|---|---|---|
| Kosciusko County | ~8,677 | 6,307–11,702 |
| Allen County | ~7,595 | 5,986–9,573 |
| Madison County | ~6,936 | 5,517–8,622 |
| DeKalb County | ~5,996 | 4,541–7,536 |
| Boone County | ~5,896 | 4,407–7,572 |
| Tippecanoe County | ~5,755 | 4,305–7,520 |
| Jasper County | ~5,552 | 4,328–7,033 |
| St. Joseph County | ~5,356 | 4,096–7,061 |
| Whitley County | ~5,182 | 3,954–6,583 |
| Noble County | ~5,162 | 3,721–6,965 |
| Hancock County | ~5,017 | 3,996–6,279 |
| Hendricks County | ~4,777 | 3,696–6,128 |
| Hamilton County | ~4,107 | 3,367–5,051 |
| Delaware County | ~4,068 | 3,136–5,235 |
| Porter County | ~3,977 | 2,944–5,372 |
| Starke County | ~3,737 | 2,727–5,002 |
| Wells County | ~3,196 | 2,347–4,253 |
| Marshall County | ~3,160 | 2,251–4,360 |
| Lake County | ~3,001 | 2,241–3,983 |
| Adams County | ~2,987 | 2,201–4,015 |
| LaPorte County | ~2,805 | 2,092–3,726 |
| Elkhart County | ~2,680 | 2,088–3,488 |
| Shelby County | ~2,592 | 2,076–3,236 |
| Carroll County | ~2,531 | 1,973–3,190 |
| White County | ~2,288 | 1,771–2,897 |
| Grant County | ~2,231 | 1,574–3,117 |
| Howard County | ~2,158 | 1,657–2,941 |
| Clinton County | ~2,156 | 1,635–2,780 |
| Tipton County | ~1,910 | 1,442–2,520 |
| Jay County | ~1,899 | 1,385–2,543 |
| Huntington County | ~1,869 | 1,407–2,451 |
| Miami County | ~1,722 | 1,379–2,202 |
| Pulaski County | ~1,690 | 1,319–2,146 |
| Marion County | ~1,662 | 1,238–2,236 |
| Steuben County | ~1,509 | 1,194–1,909 |
| LaGrange County | ~1,457 | 1,159–1,832 |
| Henry County | ~1,400 | 1,147–1,706 |
| Montgomery County | ~1,325 | 1,047–1,670 |
| Wabash County | ~1,325 | 1,061–1,654 |
| Johnson County | ~1,224 | 956–1,569 |
| Randolph County | ~938 | 737–1,189 |
| Morgan County | ~851 | 698–1,042 |
| Rush County | ~814 | 661–1,007 |
| Newton County | ~799 | 614–1,090 |
| Bartholomew County | ~724 | 517–1,017 |
| Vigo County | ~647 | 529–791 |
| Fountain County | ~623 | 505–763 |
| Cass County | ~599 | 489–816 |
| Warren County | ~533 | 424–667 |
| Wayne County | ~518 | 427–632 |
| Blackford County | ~512 | 361–715 |
| Decatur County | ~477 | 390–584 |
| Fulton County | ~469 | 366–698 |
| Jackson County | ~348 | 256–476 |
| Clay County | ~321 | 258–398 |
| Putnam County | ~298 | 242–366 |
| Parke County | ~271 | 219–336 |
| Posey County | ~259 | 202–335 |
| Owen County | ~245 | 196–307 |
| Daviess County | ~214 | 174–263 |
| Benton County | ~209 | 162–267 |
| Vanderburgh County | ~151 | 115–199 |
| Jennings County | ~133 | 95–189 |
| Fayette County | ~131 | 109–159 |
| Franklin County | ~118 | 96–146 |
| Vermillion County | ~116 | 95–144 |
| Ripley County | ~100 | 81–123 |
25 additional Indiana counties have lower modeled arsenic exposure (fewer than 100 estimated well residents over the limit).
Source: USGS domestic-well arsenic model, Lombard et al. (2021); county population product (2017).
Treating arsenic in Indiana
Arsenic is not removed by carbon pitchers or faucet filters. Reverse osmosis is the treatment that brings it below the federal limit at your tap.
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