Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Iowa County, Iowa
EPA puts Iowa County in Zone 1, its highest radon zone, and high results are common there: 59.2% of the 519 radon tests reported to CDC (2008 to 2017, laboratory totals) came back at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
59.2%
0.7 pts above IA
- Iowa
- 59.2%
- Iowa
- 58.5%
519 tests, 2008 to 2017
Median result
5.1pCi/L
Action level reached
- Iowa
- 5.1 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
519
45th of 99 by tests
- Iowa
- 519
- Polk
- 10,945
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in Iowa
68 of 99
Middle half
- Iowa
- 59.2%
- Sioux
- 84.2%
By share, of 99 with 30+ tests
Read a result for Iowa County
Starts at Iowa County's median, 5.1 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 5.1 pCi/L
At or above 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. Iowa County's median reported result, 2008 to 2017.
The data
Iowa County, At a glance
Iowa County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Iowa County in
USGS geologic potential: High across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Iowa County, 2008 to 2017, laboratory
Under 2 pCi/L: 19%2 to 4 pCi/L: 22%4 pCi/L and above: 59%
Of 519 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 99 | 19.1% |
| 2 to 4 pCi/L | 113 | 21.8% |
| 4 pCi/L and above | 307 | 59.2% |
What these figures count
These are the 519 tests reported to CDC for Iowa County over 2008 to 2017 (laboratory totals), many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.
Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).
Iowa County, Compared
Iowa County radon figures, compared
Calculated by Radon411More than half: 59.2% of the 519 radon tests reported to CDC for Iowa County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 68th of 99 Iowa counties with 30 or more tests for the same period. That is 0.7 points above the 58.5% pooled from 99 Iowa counties.
The median result, 5.1 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 158.3 pCi/L. The rest split 19.1% under 2 pCi/L and 21.8% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 59.2% share point the same way here.
4 of its 7 bordering counties with figures ran higher, led by Poweshiek County at 70.6%; Linn County reported 39.7%. Statewide for the same period, Sioux County reported the highest share (84.2%) and Decatur County the lowest (25.9%).
CDC's ten-year totals for Iowa County went from 380 tests (2005 to 2014) to 519 (2008 to 2017), the share going from 60.0% to 59.2%.
Nationally, every county with a figure for the same period pools to 35.7%; Iowa County sits 23.5 points above it. CDC also counts 51 tests taken after mitigation in Iowa County for the same period: tests in homes where a fix was already in.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Iowa County, Geology
The ground under Iowa County
PredictedUSGS's geologic map puts all of Iowa County's mapped land in one class: high radon potential. 95.7% of it lies in the area the map calls Loess-Covered Drift Plains, to which USGS gives a radon index of 13, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Loess-Covered Drift Plains | Pre-Illinoian and Illinoian glacial deposits, and loess. | High | 13 | 95.7% |
| Iowan Surface | Pre-Illinoian glaical deposits and loess. | High | 12 | 4.3% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Iowa County beside the ground around it
On high-potential ground Iowa County is close to Iowa as a whole: 100% of its land against 98.8%. Of the 7 counties that border it, none has as large a share of high-potential ground; Benton County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Iowa County, Local resources
Radon testing and mitigation in Iowa County
- Iowa HHS Radon ProgramIowa HHS Radon Program, run by Iowa Department of Health and Human Services, licenses or certifies radon professionals, offers free or discounted test kits and states the rule for disclosing radon when a home is sold, and answers questions about testing and mitigation in Iowa.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
You can reach the Hotline by calling 1-800-383-5992 to order low-cost radon test kits and find answers to your radon questions.
- Compare kits
- Professionals in Iowa185 professionals are listed in Iowa.
What Iowa's program says
- Phone
- (515) 281-4928
- Licensing of radon professionals
Iowa’s radon program approves applications for persons who wish to become certified to perform radon testing or credentialed to perform mitigation and laboratories that provide radon testing devices and analytical services.
- Disclosure when a home is sold or rented
However, per Iowa Code chapters 543B.9 and 543B.18 and Iowa Administrative Code 193E Chapter 14 administered by the Iowa Real Estate Commission, a seller must disclose any known tests for the presence of radon and if yes, provide the date of last report and the result(s).
What it means
Iowa County, Questions
Questions about radon in Iowa County
Are radon levels high in Iowa County?
Over the 2008 to 2017 laboratory totals, 59.2% of the radon tests reported to CDC for Iowa County, Iowa were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.1 pCi/L. Of 99 Iowa counties with 30 or more tests for the same period, 67 reported a higher share; pooled, the state comes to 58.5%.
Which counties border Iowa County?
Iowa County borders 7 counties: Johnson County, Poweshiek County, Keokuk County, Benton County, Washington County, Tama County and Linn County.
Products
Iowa County, Products
Testing a home in Iowa County
In Iowa County, 59.2% of 519 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 58.5% pooled across Iowa. In Zone 1 the year-round level in Iowa County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.
Test kits and monitors3
See every kit and monitor
Monitor
Corentium Home 2 battery digital radon monitor
- C-NRPP 2024/25: Not included
- Battery
- Bluetooth
- Screen, app
Method: Alpha spectrometry
Readings: Every 60 minutes
Short-term kit
Air Chek Short-Term radon test kit you hang, lab fee included
- Lab fee included
In home: 72 to 168 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Iowa County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Iowa County
Explore
Iowa County, Bordering counties
Counties bordering Iowa County
Calculated by Radon411- Radon levels in Poweshiek CountyEPA zone 1
70.6%at or above 4 pCi/L
Median 7.2 pCi/L · 419 tests · 11.4 points above Iowa County
- Radon levels in Tama CountyEPA zone 1
67.9%at or above 4 pCi/L
Median 7.0 pCi/L · 333 tests · 8.7 points above Iowa County
- Radon levels in Benton CountyEPA zone 1
62.1%at or above 4 pCi/L
Median 5.6 pCi/L · 696 tests · 2.9 points above Iowa County
- Radon levels in Keokuk CountyEPA zone 1
60.3%at or above 4 pCi/L
Median 5.2 pCi/L · 214 tests · 1.1 points above Iowa County
- Radon levels in Washington CountyEPA zone 1
54.9%at or above 4 pCi/L
Median 4.6 pCi/L · 1,186 tests · 4.3 points below Iowa County
- Radon levels in Johnson CountyEPA zone 1
41.6%at or above 4 pCi/L
Median 3.2 pCi/L · 7,321 tests · 17.6 points below Iowa County
- Radon levels in Linn CountyEPA zone 1
39.7%at or above 4 pCi/L
Median 3.0 pCi/L · 9,395 tests · 19.5 points below Iowa County
Iowa County, Cities and towns
Cities and towns in Iowa County
About 16,504 people live in Iowa County by the Census Bureau's estimate for July 1, 2025, 161 fewer than in 2020 (−1.0%). That works out to 28 people per square mile of land. Its largest town, Williamsburg, has 3,408 residents, 20.6% of the total. CDC's 519 reported tests for 2008 to 2017 work out to 31.4 per 1,000 residents (2025 estimate), close to Iowa's 29.4.
From Williamsburg to Millersburg, CDC publishes no figure by town: each reads Iowa County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Williamsburg | 3,408 | +1.6% | 20.6% |
| Marengo | 2,425 | −0.5% | 14.7% |
| North Englishextends beyond Iowa County | 1,041 | −2.3% | Counted whole |
| Victorextends beyond Iowa County | 855 | −2.2% | Counted whole |
| Ladora | 223 | −2.6% | 1.4% |
| Parnell | 191 | −1.5% | 1.2% |
| Millersburg | 137 | Level | 0.8% |
7 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025). A place that extends beyond Iowa County is counted whole, so it has no share.
Iowa County, Homes
Homes in Iowa County
Iowa County is a place of houses on their own lots: 78% of its 7,355 homes are detached single-family houses, against 72% across Iowa. Half of its homes were built before 1971, close to Iowa's 1971: 40% date from before 1960 and 20% from 2000 or later. Owners live in 76% of the occupied homes (Iowa: 72%), so for most households a test and a fix are their own to order.
| Homes | Iowa County | Iowa |
|---|---|---|
| Housing units | 7,355 | 1,427,175 |
| Detached houses | 78% | 72% |
| In buildings of 5 or more | 6% | 14% |
| Mobile homes | 4% | 3% |
| Built before 1960 | 40% | 39% |
| Built since 2000 | 20% | 21% |
| Middle year built | 1971 | 1971 |
| Owner-occupied | 76% | 72% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.