Iowa well water by county: arsenic and nitrate
Modelled arsenic and nitrate for private-well users in every Iowa county, what to test for, and where to find a certified lab. Private wells aren’t covered by the Safe Drinking Water Act.
All 99 counties
- Linn CountyWell users 24,000Arsenic about 5 in 100Nitrate 0.6 mg/L
- Dubuque CountyWell users 20,000Arsenic about 6 in 100Nitrate 0.6 mg/L
- Johnson CountyWell users 16,300Arsenic about 11 in 100Nitrate 0.4 mg/L
- Pottawattamie CountyWell users 15,900Arsenic about 10 in 100Nitrate 1.7 mg/L
- Black Hawk CountyWell users 12,900Arsenic about 4 in 100Nitrate 0.8 mg/L
- Scott CountyWell users 11,200Arsenic about 15 in 100Nitrate 0.6 mg/L
- Warren CountyWell users 10,700Arsenic about 16 in 100Nitrate 1.7 mg/L
- Clinton CountyWell users 10,600Arsenic about 11 in 100Nitrate 0.9 mg/L
- Muscatine CountyWell users 10,100Arsenic about 8 in 100Nitrate 0.8 mg/L
- Polk CountyWell users 10,000Arsenic about 23 in 100Nitrate 0.3 mg/L
- Benton CountyWell users 8,700Arsenic about 8 in 100Nitrate 0.3 mg/L
- Delaware CountyWell users 8,500Arsenic about 8 in 100Nitrate 0.8 mg/L
- Clayton CountyWell users 8,200Arsenic about 7 in 100Nitrate 0.6 mg/L
- Buchanan CountyWell users 8,200Arsenic about 5 in 100Nitrate 0.4 mg/L
- Lee CountyWell users 8,100Arsenic about 10 in 100Nitrate 0.3 mg/L
- Winneshiek CountyWell users 8,100Arsenic about 4 in 100Nitrate 0.7 mg/L
- Jones CountyWell users 8,000Arsenic about 10 in 100Nitrate 1.1 mg/L
- Dallas CountyWell users 8,000Arsenic about 21 in 100Nitrate 0.8 mg/L
- Woodbury CountyWell users 7,900Arsenic about 22 in 100Nitrate 1.6 mg/L
- Des Moines CountyWell users 7,500Arsenic about 9 in 100Nitrate 0.1 mg/L
- Jackson CountyWell users 7,500Arsenic about 7 in 100Nitrate 1.0 mg/L
- Bremer CountyWell users 7,400Arsenic about 6 in 100Nitrate 1.0 mg/L
- Story CountyWell users 7,400Arsenic about 35 in 100Nitrate 0.1 mg/L
- Washington CountyWell users 7,000Arsenic about 10 in 100Nitrate 0.1 mg/L
- Plymouth CountyWell users 6,900Arsenic about 12 in 100Nitrate 2.6 mg/L
- Madison CountyWell users 6,800Arsenic about 8 in 100Nitrate 1.7 mg/L
- Fayette CountyWell users 6,800Arsenic about 2 in 100Nitrate 0.6 mg/L
- Allamakee CountyWell users 6,500Arsenic about 6 in 100Nitrate 0.6 mg/L
- Cedar CountyWell users 6,400Arsenic about 10 in 100Nitrate 0.7 mg/L
- Webster CountyWell users 6,000Arsenic about 11 in 100Nitrate 0.0 mg/L
- Butler CountyWell users 5,900Arsenic about 4 in 100Nitrate 0.6 mg/L
- Cerro Gordo CountyWell users 5,600Arsenic about 6 in 100Nitrate 0.2 mg/L
- Harrison CountyWell users 5,600Arsenic about 9 in 100Nitrate 1.1 mg/L
- Mills CountyWell users 5,400Arsenic about 7 in 100Nitrate 1.4 mg/L
- Iowa CountyWell users 5,200Arsenic about 13 in 100Nitrate 0.2 mg/L
- Boone CountyWell users 5,200Arsenic about 11 in 100Nitrate 0.1 mg/L
- Kossuth CountyWell users 5,100Arsenic about 32 in 100Nitrate 0.0 mg/L
- Tama CountyWell users 5,100Arsenic about 10 in 100Nitrate 0.5 mg/L
- Henry CountyWell users 5,000Arsenic about 10 in 100Nitrate 0.1 mg/L
- Chickasaw CountyWell users 4,900Arsenic about 9 in 100Nitrate 0.2 mg/L
- Mitchell CountyWell users 4,800Arsenic about 4 in 100Nitrate 0.4 mg/L
- Louisa CountyWell users 4,800Arsenic about 6 in 100Nitrate 0.4 mg/L
- Floyd CountyWell users 4,800Arsenic about 5 in 100Nitrate 0.3 mg/L
- Hardin CountyWell users 4,500Arsenic about 12 in 100Nitrate 0.2 mg/L
- Jasper CountyWell users 4,400Arsenic about 16 in 100Nitrate 0.6 mg/L
- Grundy CountyWell users 4,200Arsenic about 15 in 100Nitrate 0.2 mg/L
- Marion CountyWell users 4,000Arsenic about 12 in 100Nitrate 0.9 mg/L
- Keokuk CountyWell users 4,000Arsenic about 12 in 100Nitrate 0.3 mg/L
- Franklin CountyWell users 3,900Arsenic about 26 in 100Nitrate 0.1 mg/L
- Marshall CountyWell users 3,600Arsenic about 23 in 100Nitrate 0.3 mg/L
- Hamilton CountyWell users 3,600Arsenic about 12 in 100Nitrate 0.0 mg/L
- Buena Vista CountyWell users 3,600Arsenic about 36 in 100Nitrate 0.3 mg/L
- Hancock CountyWell users 3,500Arsenic about 11 in 100Nitrate 0.1 mg/L
- Crawford CountyWell users 3,500Arsenic about 4 in 100Nitrate 5.2 mg/L
- Jefferson CountyWell users 3,500Arsenic about 13 in 100Nitrate 0.9 mg/L
- Howard CountyWell users 3,400Arsenic about 6 in 100Nitrate 0.5 mg/L
- Sioux CountyWell users 3,300Arsenic about 26 in 100Nitrate 1.9 mg/L
- Guthrie CountyWell users 3,300Arsenic about 8 in 100Nitrate 1.4 mg/L
- Winnebago CountyWell users 3,100Arsenic about 16 in 100Nitrate 0.0 mg/L
- Carroll CountyWell users 3,100Arsenic about 10 in 100Nitrate 0.9 mg/L
- Worth CountyWell users 3,100Arsenic about 6 in 100Nitrate 0.1 mg/L
- Shelby CountyWell users 3,000Arsenic about 5 in 100Nitrate 3.0 mg/L
- Sac CountyWell users 3,000Arsenic about 27 in 100Nitrate 1.1 mg/L
- Monona CountyWell users 3,000Arsenic about 12 in 100Nitrate 2.2 mg/L
- Clarke CountyWell users 2,800Arsenic about 12 in 100Nitrate 1.6 mg/L
- Cass CountyWell users 2,800Arsenic about 8 in 100Nitrate 1.3 mg/L
- Mahaska CountyWell users 2,800Arsenic about 7 in 100Nitrate 0.2 mg/L
- Dickinson CountyWell users 2,800Arsenic about 34 in 100Nitrate 0.3 mg/L
- Wright CountyWell users 2,700Arsenic about 11 in 100Nitrate 0.0 mg/L
- Wapello CountyWell users 2,600Arsenic about 13 in 100Nitrate 0.4 mg/L
- Greene CountyWell users 2,500Arsenic about 9 in 100Nitrate 0.1 mg/L
- Adair CountyWell users 2,400Arsenic about 6 in 100Nitrate 2.3 mg/L
- Palo Alto CountyWell users 2,300Arsenic about 34 in 100Nitrate 0.1 mg/L
- Lyon CountyWell users 2,300Arsenic about 38 in 100Nitrate 2.4 mg/L
- Humboldt CountyWell users 2,300Arsenic about 13 in 100Nitrate 0.0 mg/L
- Fremont CountyWell users 2,200Arsenic about 9 in 100Nitrate 2.3 mg/L
- Montgomery CountyWell users 2,200Arsenic about 6 in 100Nitrate 1.7 mg/L
- Pocahontas CountyWell users 2,200Arsenic about 17 in 100Nitrate 0.0 mg/L
- Poweshiek CountyWell users 2,200Arsenic about 17 in 100Nitrate 0.3 mg/L
- Ida CountyWell users 2,200Arsenic about 8 in 100Nitrate 3.7 mg/L
- Calhoun CountyWell users 2,200Arsenic about 16 in 100Nitrate 0.0 mg/L
- Audubon CountyWell users 2,100Arsenic about 10 in 100Nitrate 3.4 mg/L
- Emmet CountyWell users 1,900Arsenic about 33 in 100Nitrate 0.0 mg/L
- Cherokee CountyWell users 1,900Arsenic about 30 in 100Nitrate 2.7 mg/L
- Union CountyWell users 1,900Arsenic about 7 in 100Nitrate 1.5 mg/L
- Decatur CountyWell users 1,900Arsenic about 7 in 100Nitrate 1.5 mg/L
- Taylor CountyWell users 1,800Arsenic about 4 in 100Nitrate 1.8 mg/L
- Ringgold CountyWell users 1,700Arsenic about 5 in 100Nitrate 2.3 mg/L
- Page CountyWell users 1,700Arsenic about 6 in 100Nitrate 3.9 mg/L
- Adams CountyWell users 1,700Arsenic about 7 in 100Nitrate 1.1 mg/L
- O'Brien CountyWell users 1,500Arsenic about 33 in 100Nitrate 1.3 mg/L
- Osceola CountyWell users 1,500Arsenic about 33 in 100Nitrate 0.7 mg/L
- Clay CountyWell users 1,400Arsenic about 62 in 100Nitrate 0.4 mg/L
- Davis CountyWell users 1,200Arsenic about 7 in 100Nitrate 1.6 mg/L
- Van Buren CountyWell users 1,200Arsenic about 7 in 100Nitrate 0.8 mg/L
- Appanoose CountyWell users 1,000Arsenic about 9 in 100Nitrate 1.3 mg/L
- Lucas CountyWell users 990Arsenic about 10 in 100Nitrate 1.9 mg/L
- Wayne CountyWell users 850Arsenic about 14 in 100Nitrate 1.1 mg/L
- Monroe CountyWell users 580Arsenic about 7 in 100Nitrate 1.8 mg/L
Each mark = 1 in 100 well users the model places above 10 µg/L arsenic (scale 0–10)10 mg/L nitrate: the federal limit (MCL) for public systems
- These figures describe the area, not your well. Only a lab test shows what’s in your water.
- CDC says the Well Water Index figures “do not describe risk to individual wells.” (CDC Tracking Network)
- The arsenic model is better at spotting low-arsenic areas than at confirming high ones.
- Well-user counts are 2010 USGS estimates; tract values are averages over each census tract.
- Total coliform bacteriaEvery year
- NitrateEvery year
- Total dissolved solidsEvery year
- pHEvery year
- ArsenicAsk your local health department
EPA: Private Drinking Water Wells · CDC: Guidelines for Testing Well Water
Use a state-certified lab
Iowa Department of Natural Resources lists the laboratories certified to test drinking water in Iowa.
Screening tells you if something is worth a closer look
A lab result is the number you can act on.
As an Amazon Associate, PurityMap earns from qualifying purchases. Affiliate disclosure
Lab-certified results
ETR Labs Basic Water Quality Test Kit
ETR Laboratories
50+ substances, including lead, copper, arsenic, nitrate, hardness and coliform bacteria
- Analyzed by Environmental Testing and Research Laboratories (ETR Labs), Leominster, MA · ISO/IEC 17025:2017, ANAB certificate AT-2638
- Turnaround: 2–4 business days after the lab receives it
What it can't tell you: It does not test PFAS, and not every result on the panel falls under the lab's accredited scope.
Screening: quick check, not lab-grade
Watersafe Drinking Water Test Kit
Silver Lake Research
Lead, bacteria, nitrate, copper, iron, chlorine, hardness and pH
- Turnaround: Minutes; the bacteria test can take up to 48 hours
What it can't tell you: Each test gives a yes/no or a rough range, not a lab number, and it cannot detect PFAS or arsenic.
A mail-in kit’s lab is accredited (ISO/IEC 17025) but may not be certified by your state. For a home sale, a loan, or a health-department follow-up, use a state-certified lab.
Iowa well water
Sources: CDC Well Water Index (2024) · USGS arsenic and nitrate models · USGS domestic well populations · EPA and CDC testing guidance. Data last updated 2026-10-08. All sources →
How many people use private wells in Iowa?
About 501,800 people across 99 Iowa counties, by the USGS 2010 estimate. USGS models place about 58,400 of them in areas where wells are likely to be above the 10 µg/L arsenic limit. These are area estimates, not well results.
Are private wells regulated in Iowa?
The quality and safety of drinking water from private domestic wells are not regulated by the Federal Government under the Safe Drinking Water Act nor by most state governments and laws. (EPA) Testing and treatment are the owner's responsibility.
Where can I get my well tested in Iowa?
Iowa Department of Natural Resources keeps the list of laboratories certified to test drinking water in Iowa. Only use laboratories that are certified to do drinking water testing. (EPA)