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 Lee County, Illinois
EPA puts Lee County in Zone 1, its highest radon zone, and high results are common there: 43.8% of the 219 radon tests reported to CDC (2017) 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
43.8%
10.1 pts above IL
- Lee
- 43.8%
- Illinois
- 33.7%
219 tests, 2017
Median result
3.3pCi/L
Below action level
- Lee
- 3.3 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2017
Tests reported
219
39th of 70 by tests
- Lee
- 219
- Cook
- 26,937
Reported to CDC before any fix, 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 Illinois
35 of 70
Middle half
- Lee
- 43.8%
- Stark
- 69.2%
By share, of 70 with 30+ tests
Read a result for Lee County
Starts at Lee County's median, 3.3 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 3.3 pCi/L
Between 2 and 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Lee County's median reported result, 2017.
The data
Lee County, At a glance
Lee County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Lee 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 Lee County, 2017
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 42.6% |
| 2015 | 51.9% |
| 2016 | 100.0% |
| 2017 | 43.8% |
2017: 43.8%. Across these years the share ran from 42.6% to 100.0%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 219 tests reported to CDC for Lee County over 2017, 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: 2017. Measured data period: 2005 to 2017 (every CDC figure on file).
Lee County, Compared
Lee County radon figures, compared
Calculated by Radon411In Lee County, about 4 in 10 reported tests in 2017 (96 of 219) were at or above EPA's action level. Against the national pool of 31.7%, the gap is 12.1 points higher. Across 93 Illinois counties pooled together, 33.7% of tests reached that level, so Lee County runs 10.1 points above its state.
Of 5 neighbours with a figure, 3 reported a larger share at or above 4 pCi/L and 2 a smaller one; the spread is 41.1% (DeKalb County) to 58.6% (Bureau County). By share, Lee County is 35th of 70 Illinois counties with 30 or more tests for the same period.
Year by year, 2014 opened at 42.6% and 2017 closed at 43.8% (about level), with 2015 the high at 51.9%. Half the tests came in under 3.3 pCi/L and half over it; the single highest reached 48.8 pCi/L. Below the action level, 69 tests (31.5%) came in under 2 pCi/L, against 37.7% statewide, and 54 tests (24.7%) fell between 2 and 4, against 28.6% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 43.8% share point the same way here. USGS geology rates 100% of the county's land high radon potential.
The busiest year on file was 2014, with 303 tests reported; the quietest, 2016, had 6.
Lee CountyIllinois, pooled
43.8% % of tests33.7% % of tests
| Year | Tests | Lee County, at or above 4 pCi/L | Illinois, pooled |
|---|---|---|---|
| 2014 | 303 | 42.6% | 37.8% |
| 2015 | 237 | 51.9% | 36.6% |
| 2017 | 219 | 43.8% | 33.7% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Lee County, Geology
The ground under Lee County
PredictedUSGS's geologic map puts all of Lee County's mapped land in one class: high radon potential. The map puts 67.2% of Lee County in the area it calls Galesburg Plain and 32.8% in Bloomington Ridged Plain. USGS gives both 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 | 67.2% |
| Bloomington Ridged Plain | Wisconsinan glacial deposits and loess over Paleozoic sedimentary rocks. | High | 13 | 32.8% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Lee County beside the ground around it
Lee County has more high-potential ground than Illinois as a whole: 100% of its land against 64.5%. Of the 5 counties that border it, none has as large a share of high-potential ground; DeKalb County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Lee County, Local resources
Radon testing and mitigation in Lee County
Listed radon businesses with an address in Lee 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.
Listed radon professionals by town: Dixon
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
Lee County, Questions
Questions about radon in Lee County
Are radon levels high in Lee County?
In 2017, 43.8% of the radon tests reported to CDC for Lee County, Illinois were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.3 pCi/L. Of 70 Illinois counties with 30 or more tests for the same period, 34 reported a higher share; pooled, the state comes to 33.7%.
Which counties border Lee County?
Lee County borders 5 counties: Ogle County, Bureau County, DeKalb County, Whiteside County and LaSalle County.
Products
Lee County, Products
Testing a home in Lee County
In Lee County, 43.8% of 219 tests reported to CDC in 2017 reached 4 pCi/L, against 33.7% pooled across Illinois. In Zone 1 the year-round level in Lee 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
MonitorX-Sense
XR0B-SR battery digital radon monitor with an alarm
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Alpha spectrometry
First reading: Within 24 hours
Short-term kit
RA400 short-term liquid scintillation radon test kit, lab fee included
- Lab fee included
Method: Liquid scintillation
In home: 48 to 96 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Lee County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Lee County
Explore
Lee County, Bordering counties
Counties bordering Lee County
Calculated by Radon411- Radon levels in Bureau CountyEPA zone 1
58.6%at or above 4 pCi/L
Median 5.1 pCi/L · 333 tests · 14.8 points above Lee County
- Radon levels in Ogle CountyEPA zone 1
52.4%at or above 4 pCi/L
Median 4.1 pCi/L · 636 tests · 8.6 points above Lee County
- Radon levels in LaSalle CountyEPA zone 1
45.8%at or above 4 pCi/L
Median 3.6 pCi/L · 1,002 tests · 2.0 points above Lee County
- Radon levels in Whiteside CountyEPA zone 1
43.1%at or above 4 pCi/L
Median 3.3 pCi/L · 696 tests · 0.7 points below Lee County
- Radon levels in DeKalb CountyEPA zone 1
41.1%at or above 4 pCi/L
Median 3.3 pCi/L · 1,707 tests · 2.7 points below Lee County
Lee County, Cities and towns
Cities and towns in Lee County
About 32,914 people live in Lee County by the Census Bureau's estimate for July 1, 2025, 1,149 fewer than in 2020 (−3.4%). That works out to 45 people per square mile of land. Its largest town, Dixon, has 14,582 residents, 44.3% of the total. Reported testing is thin here: 219 tests over 2017, or 6.7 for every 1,000 residents (2025 estimate), where Illinois as a whole comes to 10.9.
From Dixon to Harmon, CDC publishes no figure by town: each reads Lee County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Dixon | 14,582 | −5.0% | 44.3% |
| Rochelleextends beyond Lee County | 9,498 | +0.3% | Counted whole |
| Amboy | 2,206 | −2.8% | 6.7% |
| Ashton | 929 | −3.3% | 2.8% |
| Franklin Grove | 868 | −3.0% | 2.6% |
| Paw Paw | 798 | −3.3% | 2.4% |
| Sublette | 371 | −1.9% | 1.1% |
| Leeextends beyond Lee County | 300 | −2.3% | Counted whole |
| Compton | 264 | −2.2% | 0.8% |
| Steward | 222 | −2.2% | 0.7% |
| West Brooklyn | 128 | −2.3% | 0.4% |
| Nelson | 127 | −2.3% | 0.4% |
- Harmon
13 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. “(part)” marks a place that extends into another county. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025). A place that extends beyond Lee County is counted whole, so it has no share.
Lee County, Homes
Homes in Lee County
Lee County is a place of houses on their own lots: 78% of its 14,993 homes are detached single-family houses, against 58% across Illinois. The homes are older than Illinois' as a whole: half were built before 1962 (1970 for Illinois), and 48% date from before 1960. 73% of occupied homes are lived in by their owner (Illinois: 67%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Lee County | Illinois |
|---|---|---|
| Housing units | 14,993 | 5,443,501 |
| Detached houses | 78% | 58% |
| In buildings of 5 or more | 8% | 22% |
| Mobile homes | 6% | 2% |
| Built before 1960 | 48% | 38% |
| Built since 2000 | 11% | 16% |
| Middle year built | 1962 | 1970 |
| Owner-occupied | 73% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.