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Arsenic in Iowa well water, by county

By the Tested Water teamLab data from the USGS and EPA Water Quality Portal, 2001 to 2019Updated November 8, 2026

Arsenic is widespread, over the limit in 15% or more of tested wells, in 15 of the 69 Iowa counties with 10 or more tested wells. A county's share tells you how likely a problem is nearby. Only a test of your own well tells you what's in it.

Find an arsenic test See every county

How Iowa compares with the rest of the country

Across Iowa, about 1 in 14 tested wells had arsenic over the EPA limit of 10 µg/L (104 of 1,432). Across all tested wells in the US it's about 1 in 9. That's less often than in the country as a whole. Counties still differ, so check yours below.

Why it matters: Drinking it for years raises the risk of skin, bladder and lung cancer.

Arsenic dissolves out of certain rocks and old sediments, so it can be high even where nobody has polluted anything.

Arsenic in tested wells, county by county

Share of each county's tested wells with at least one result over the EPA limit of 10 µg/L. Counties need 10 or more tested wells to be listed. Widespread means 15% or more, worth checking 5 to 15%, rare under 5%.

CountyWells testedWells over the limitLevel
Greene County 12
75% 9 of 12
 Widespread
Emmet County 11
55% 6 of 11
 Widespread
Shelby County 13
54% 7 of 13
 Widespread
Palo Alto County 16
44% 7 of 16
 Widespread
Humboldt County 15
33% 5 of 15
 Widespread
Cass County 15
27% 4 of 15
 Widespread
Wright County 16
25% 4 of 16
 Widespread
Scott County 17
24% 4 of 17
 Widespread
Montgomery County 13
23% 3 of 13
 Widespread
Buena Vista County 21
19% 4 of 21
 Widespread
Hancock County 17
18% 3 of 17
 Widespread
O'Brien County 17
18% 3 of 17
 Widespread
Guthrie County 19
16% 3 of 19
 Widespread
Dallas County 46
15% 7 of 46
 Widespread
Monona County 20
15% 3 of 20
 Widespread
Hamilton County 29
14% 4 of 29
 Worth checking
Mills County 23
13% 3 of 23
 Worth checking
Hardin County 25
12% 3 of 25
 Worth checking
Pottawattamie County 26
12% 3 of 26
 Worth checking
Story County 27
11% 3 of 27
 Worth checking
Carroll County 31
10% 3 of 31
 Worth checking
Kossuth County 12
8% 1 of 12
 Worth checking
Woodbury County 37
8% 3 of 37
 Worth checking
Linn County 44
5% 2 of 44
 Rare
Webster County 31
3% 1 of 31
 Rare
Muscatine County 30
0% 0 of 30
 Rare
Benton County 29
0% 0 of 29
 Rare
Cherokee County 27
0% 0 of 27
 Rare
Jasper County 27
0% 0 of 27
 Rare
Butler County 25
0% 0 of 25
 Rare
Clayton County 25
0% 0 of 25
 Rare
Winneshiek County 25
0% 0 of 25
 Rare
Sioux County 24
0% 0 of 24
 Rare
Black Hawk County 23
0% 0 of 23
 Rare
Clinton County 23
0% 0 of 23
 Rare
Jackson County 23
0% 0 of 23
 Rare
Johnson County 22
0% 0 of 22
 Rare
Tama County 22
0% 0 of 22
 Rare
Plymouth County 21
0% 0 of 21
 Rare
Buchanan County 19
0% 0 of 19
 Rare
Dubuque County 19
0% 0 of 19
 Rare
Harrison County 19
0% 0 of 19
 Rare
Marshall County 19
0% 0 of 19
 Rare
Louisa County 18
0% 0 of 18
 Rare
Sac County 17
0% 0 of 17
 Rare
Audubon County 16
0% 0 of 16
 Rare
Crawford County 16
0% 0 of 16
 Rare
Fayette County 16
0% 0 of 16
 Rare
Washington County 16
0% 0 of 16
 Rare
Fremont County 15
0% 0 of 15
 Rare
Iowa County 15
0% 0 of 15
 Rare
Keokuk County 15
0% 0 of 15
 Rare
Floyd County 13
0% 0 of 13
 Rare
Grundy County 13
0% 0 of 13
 Rare
Mitchell County 13
0% 0 of 13
 Rare
Polk County 13
0% 0 of 13
 Rare
Chickasaw County 12
0% 0 of 12
 Rare
Lyon County 12
0% 0 of 12
 Rare
Marion County 12
0% 0 of 12
 Rare
Allamakee County 11
0% 0 of 11
 Rare
Boone County 11
0% 0 of 11
 Rare
Delaware County 11
0% 0 of 11
 Rare
Franklin County 11
0% 0 of 11
 Rare
Howard County 11
0% 0 of 11
 Rare
Ida County 11
0% 0 of 11
 Rare
Worth County 11
0% 0 of 11
 Rare
Henry County 10
0% 0 of 10
 Rare
Jones County 10
0% 0 of 10
 Rare
Page County 10
0% 0 of 10
 Rare

21 more Iowa counties have 1 to 9 tested wells for arsenic, too few to rate.

Download this table (CSV) · Free to reuse under CC BY 4.0

Where to get your well tested for arsenic in Iowa

1

Free state testing

Iowa tests private wells for bacteria, nitrate, arsenic and manganese for free through participating county health offices. Check which tests it includes before you count on it for arsenic.

Iowa's private well page
2

A lab Iowa certifies

Ask for arsenic by name. Results from a certified lab count for a home sale or a loan.

Labs certified by Iowa
3

A mail-in kit

Fill the bottles at your kitchen tap and mail them back. We mark the kits that include arsenic.

Compare kits

Keep reading about wells in Iowa

Questions people ask about arsenic in Iowa

Is there arsenic in Iowa well water?

Arsenic is widespread, over the limit in 15% or more of tested wells, in 15 of the 69 Iowa counties with 10 or more tested wells. Across Iowa, about 1 in 14 tested wells had arsenic over the EPA limit of 10 µg/L (104 of 1,432). Across all tested wells in the US it's about 1 in 9. That's less often than in the country as a whole. Counties still differ, so check yours below.

Where can I get my well tested for arsenic in Iowa?

Iowa tests private wells for bacteria, nitrate, arsenic and manganese for free through participating county health offices. If that doesn't cover you, use a lab certified by Iowa for drinking water, or a mail-in kit that includes arsenic from a certified lab.

See Iowa's list of certified labs, or compare mail-in kits.

Where these numbers come from

  • Lab tests: Water Quality Portal (USGS and EPA), well samples since 2000. A well counts as over if any of its tests was over the EPA limit of 10 µg/L. Wells tested for studies and monitoring, not a random sample of homes.
  • Likely overstated: our own check of who tested the wells, when and where. How we check.
  • State programs and links: Iowa Department of Natural Resources.