Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Greene County, Illinois
EPA puts Greene County in Zone 1, its highest radon zone, and only 12 radon tests from it are on file with CDC (2017). Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Highest bordering
64.5%
Morgan County
- Morgan
- 64.5%
- Macoupin
- 34.8%
4 of 6 neighbours have 30+ tests, 2008 to 2017
Nearest county
38.9%
Jersey County, 19 miles
- Jersey
- 38.9%
- Illinois
- 43.1%
Share at 4+ pCi/L, 90 tests, 2008 to 2017
Ground above low
100.0%
0.9 pts above Illinois
- Greene
- 100.0%
- Illinois
- 99.1%
Share of land USGS rates moderate or high potential
Tests reported
26
Too few for a share
- Greene
- 26
- Needed
- 30
2007 to 2016, laboratory
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Read a result for Greene County
Starts at EPA's action level
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.0 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.
The data
Greene County, At a glance
Greene County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Greene 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 Greene County, 2017
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 50.0% |
| 2015 | 25.0% |
| 2017 | 0.0% |
2017: 0.0%. Across these years the share ran from 0.0% to 50.0%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
Only 12 tests were reported to CDC for Greene County over 2017, and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor this house.
Measured: CDC tracking data. Figure above: 2017. Measured data period: 2005 to 2017 (every CDC figure on file).
Greene County, Compared
Greene County radon figures, compared
Calculated by Radon411CDC's largest figure for Greene County rests on 26 tests over the 2007 to 2016 laboratory totals, 13 of them at or above 4 pCi/L, so each test moves its share by 3.8 points and no rank or comparison is drawn from it. Results reached as high as 23.1 pCi/L, with a middle value of 3.9 pCi/L.
Of the counties bordering it, 4 have a figure over the 2008 to 2017 laboratory totals: Morgan County reported the largest share at or above 4 pCi/L, 64.5%, and Macoupin County the smallest, 34.8%, with Pike County at 46.3% and Jersey County at 38.9% between. Farther out, Cass County (43 miles away) at 38.5%, Madison County (45 miles away) at 37.4% and Brown County (46 miles away) at 37.8% have figures too. Pooled across 102 Illinois counties, 43.1% of reported tests reached that level; across every county in the country with a figure, 35.7%.
Statewide for the same period, Stark County reported the highest share (80.5%) and Williamson County the lowest (13.3%). EPA's 1993 map puts Greene County in Zone 1, the map's highest label: a predicted county average above 4 pCi/L. USGS geology rates 100% of the county's land high radon potential.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Greene County, Geology
The ground under Greene County
PredictedUSGS's geologic map puts all of Greene County's mapped land in one class: high radon potential. All of it lies in the area the map calls Galesburg Plain, 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 |
|---|---|---|---|---|
| Galesburg Plain | Illinoian glacial deposits and loess over Paleozoic sedimentary rocks. | High | 13 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Greene County beside the ground around it
Greene County has more high-potential ground than Illinois as a whole: 100% of its land against 64.5%. Of the 6 counties that border it, none has as large a share of high-potential ground; Morgan County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Greene County, Local resources
Radon testing and mitigation in Greene County
- IEMA-OHS Radon ProgramIEMA-OHS Radon Program, run by Illinois Emergency Management Agency and Office of Homeland Security, licenses or certifies radon professionals and states the rule for disclosing radon when a home is sold, and answers questions about testing and mitigation in Illinois.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsAsk the program whether it has free or discounted kits, or compare kits you can buy.
- Compare kits
- Professionals in Illinois339 professionals are listed in Illinois.
What Illinois's program says
- Phone
- (800) 325-1245
- Licensing of radon professionals
The Agency also licenses and regulates the individuals who provide radon measurement and mitigation to the public.
- Disclosure when a home is sold or rented
Illinois Radon Awareness Act - This is the legislation that requires the seller to provide to the buyer of any interest in residential real property the IEMA-OHS pamphlet entitled "Radon Testing Guidelines for Real Estate Transactions" and the Illinois Disclosure of Information on Radon Hazards.
What it means
Greene County, Questions
Questions about radon in Greene County
Are radon levels high in Greene County?
In 2017, 0.0% of the radon tests reported to CDC for Greene County, Illinois were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.7 pCi/L. Of the counties bordering it, 4 have a figure over the 2008 to 2017 laboratory totals: Morgan County reported the largest share at or above 4 pCi/L, 64.5%, and Macoupin County the smallest, 34.8%, with Pike County at 46.3% and Jersey County at 38.9% between.
Which counties border Greene County?
Greene County borders 6 counties: Jersey County, Calhoun County, Scott County, Morgan County, Macoupin County and Pike County.
Products
Greene County, Products
Testing a home in Greene County
No CDC figure names Greene County; the nearest county with one, Jersey County (19 miles away), reported 38.9% of its tests at or above 4 pCi/L over the 2008 to 2017 laboratory totals, the only reading nearby until a test of this home. In Zone 1 the year-round level in Greene 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
View Plus radon and air quality monitor
- C-NRPP 2024/25: Approved
- Battery
- Wi-Fi, Bluetooth
- Screen, app
Method: Alpha spectrometry
Short-term kit
PicoCan short-term charcoal canister radon test
- Lab fee included
Method: Charcoal
In home: 48 to 96 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Greene County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Greene County
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Greene County, Bordering counties
Counties bordering Greene County
Calculated by Radon411- Radon levels in Calhoun CountyEPA zone 1
66.7%at or above 4 pCi/L
Median 4.5 pCi/L · 6 tests
- Radon levels in Morgan CountyEPA zone 1
64.5%at or above 4 pCi/L
Median 5.8 pCi/L · 169 tests
- Radon levels in Scott CountyEPA zone 1
50.0%at or above 4 pCi/L
Median 4.4 pCi/L · 12 tests
- Radon levels in Pike CountyEPA zone 1
46.3%at or above 4 pCi/L
Median 3.8 pCi/L · 108 tests
- Radon levels in Jersey CountyEPA zone 1
38.9%at or above 4 pCi/L
Median 3.2 pCi/L · 90 tests
- Radon levels in Macoupin CountyEPA zone 2
34.8%at or above 4 pCi/L
Median 2.7 pCi/L · 187 tests
Greene County, Cities and towns
Cities and towns in Greene County
Greene County has been losing residents: from 11,924 in 2020 to 11,313 on July 1, 2025, a fall of 5.1% by the Census Bureau's estimates. That works out to 21 people per square mile of land. Its largest town, Carrollton, has 2,349 residents, 20.8% of the total. Together its 9 incorporated places hold 68.5% of those residents; the other 31.5% live outside any of them. Reported testing is thin here: 26 tests over 2007 to 2016, or 2.3 for every 1,000 residents (2025 estimate), where Illinois as a whole comes to 8.3.
From Carrollton to Wilmington, CDC publishes no figure by town: each reads Greene County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Carrollton | 2,349 | −5.1% | 20.8% |
| White Hall | 2,159 | −5.0% | 19.1% |
| Roodhouse | 1,484 | −5.1% | 13.1% |
| Greenfield | 997 | −5.2% | 8.8% |
| Kane | 274 | −5.5% | 2.4% |
| Rockbridge | 170 | −5.0% | 1.5% |
| Eldred | 141 | −5.4% | 1.2% |
| Hillview | 91 | −4.2% | 0.8% |
| Wilmington | 86 | −5.5% | 0.8% |
9 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).
Greene County, Homes
Homes in Greene County
Greene County is a place of houses on their own lots: 84% of its 5,801 homes are detached single-family houses, against 58% across Illinois. The homes are older than Illinois' as a whole: half were built before 1956 (1970 for Illinois), and 53% date from before 1960. Owners live in 77% of the occupied homes (Illinois: 67%), so for most households a test and a fix are their own to order.
| Homes | Greene County | Illinois |
|---|---|---|
| Housing units | 5,801 | 5,443,501 |
| Detached houses | 84% | 58% |
| In buildings of 5 or more | 1% | 22% |
| Mobile homes | 10% | 2% |
| Built before 1960 | 53% | 38% |
| Built since 2000 | 8% | 16% |
| Middle year built | 1956 | 1970 |
| Owner-occupied | 77% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.