Florida Private Well Water Risk: Arsenic & Nitrate
These figures are USGS statistical estimates for private (domestic) wells in Florida. 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%
of the private-well population is modeled above the 10 mg/L nitrate limit
~548
people on wells estimated above the limit
~1,910,000
total residents on private wells statewide
Source: USGS machine-learning nitrate model, Ransom et al. (2022), domestic-well depth zone.
Arsenic
Across Florida, an estimated ~50,923 people rely on private wells with modeled arsenic above the 10 µg/L EPA limit. The highest modeled exposure is in Palm Beach County (~3,454 people).
Counties with the highest modeled arsenic exposure
| County | Est. well residents over arsenic limit | 90% range |
|---|---|---|
| Palm Beach County | ~3,454 | 2,241–5,381 |
| Osceola County | ~3,272 | 2,108–5,002 |
| Lee County | ~2,748 | 1,761–4,239 |
| St. Lucie County | ~2,426 | 1,711–3,442 |
| Clay County | ~2,142 | 1,373–3,273 |
| Putnam County | ~2,088 | 1,324–3,266 |
| DeSoto County | ~1,944 | 1,223–3,014 |
| Orange County | ~1,743 | 1,117–2,720 |
| Okeechobee County | ~1,677 | 1,116–2,464 |
| Nassau County | ~1,604 | 1,084–2,360 |
| Baker County | ~1,600 | 1,063–2,383 |
| Polk County | ~1,485 | 920–2,379 |
| Marion County | ~1,196 | 756–1,929 |
| Hendry County | ~1,163 | 746–1,774 |
| Collier County | ~1,138 | 715–1,803 |
| Columbia County | ~1,131 | 729–1,736 |
| Bradford County | ~1,119 | 739–1,686 |
| Charlotte County | ~1,110 | 700–1,730 |
| Duval County | ~1,086 | 728–1,601 |
| St. Johns County | ~985 | 652–1,479 |
| Brevard County | ~938 | 654–1,346 |
| Union County | ~903 | 599–1,347 |
| Lake County | ~885 | 533–1,475 |
| Bay County | ~854 | 559–1,291 |
| Pasco County | ~826 | 519–1,315 |
| Alachua County | ~819 | 515–1,289 |
| Martin County | ~808 | 532–1,226 |
| Highlands County | ~767 | 487–1,203 |
| Hillsborough County | ~717 | 444–1,139 |
| Indian River County | ~640 | 449–919 |
| Hardee County | ~595 | 372–941 |
| Volusia County | ~565 | 372–863 |
| Glades County | ~479 | 306–732 |
| Leon County | ~461 | 286–747 |
| Wakulla County | ~389 | 248–613 |
| Jackson County | ~380 | 255–573 |
| Suwannee County | ~373 | 243–576 |
| Calhoun County | ~363 | 238–553 |
| Citrus County | ~325 | 213–492 |
| Sumter County | ~307 | 203–471 |
| Sarasota County | ~303 | 189–476 |
| Washington County | ~291 | 190–448 |
| Gadsden County | ~230 | 149–356 |
| Flagler County | ~229 | 156–334 |
| Levy County | ~220 | 139–350 |
| Jefferson County | ~215 | 137–338 |
| Seminole County | ~204 | 126–320 |
| Madison County | ~202 | 130–312 |
| Liberty County | ~191 | 128–283 |
| Holmes County | ~153 | 109–217 |
| Gilchrist County | ~149 | 100–225 |
| Hamilton County | ~148 | 95–226 |
| Hernando County | ~124 | 81–189 |
| Manatee County | ~108 | 67–173 |
13 additional Florida 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 Florida
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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