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Radon zones in Illinois

The EPA assigns every county in Illinois to one of three radon potential zones. 56 are in Zone 1, the highest category, home to about 27% of the state's residents.

102
Counties
56
Zone 1 counties
Predicted average above 4 pCi/L
43
Zone 2 counties
Predicted average 2-4 pCi/L
3
Zone 3 counties
Predicted average below 2 pCi/L

The map

Radon potential across Illinois

Every county in Illinois, filled by the zone the EPA assigns it. Zones follow geology rather than county lines, so the colour usually changes where the bedrock does, not where the border is.

Zone 1 · 56Zone 2 · 43Zone 3 · 3

Hover a county · click to open it

County by county

All 102 Illinois counties

Zone 1 · > 4 pCi/LZone 2 · 2 - 4 pCi/LZone 3 · < 2 pCi/L
CountyZonePopulationCOPDSmokingLung ca. deaths
Adams County164k8.1%14.4%38.4
Boone County153k7.4%14.1%32.7
Brown County16,2948.0%17.8% -
Bureau County133k8.9%14.8%39.1
Calhoun County14,3177.8%12.9% -
Carroll County116k9.0%15.3%37.8
Cass County113k8.6%15.8%42.2
Champaign County1206k5.6%11.1%29.0
Coles County146k8.2%14.8%43.0
De Witt County115k8.4%15.3%53.6
DeKalb County1100k6.3%12.6%36.9
Douglas County120k8.0%15.1%48.7
Edgar County116k9.8%16.4%42.8
Ford County113k8.7%15.8%54.8
Fulton County133k9.2%16.8%58.5
Greene County112k9.7%17.2%52.1
Grundy County154k6.4%13.3%51.8
Hancock County117k9.0%14.7%41.8
Henderson County16,0889.6%15.1%43.4
Henry County148k7.8%13.8%40.8
Iroquois County126k9.7%16.4%44.5
Jersey County121k7.9%14.0%52.6
Jo Daviess County122k8.6%13.0%30.2
Kane County1515k5.7%11.0%27.8
Kendall County1140k4.7%11.0%30.6
Knox County148k9.4%16.0%48.3
LaSalle County1108k8.2%15.0%47.5
Lee County134k8.4%15.3%43.9
Livingston County135k8.4%15.3%39.1
Logan County128k7.9%15.1%54.6
Macon County1101k8.5%15.0%48.5
Marshall County112k8.9%15.2%41.5
Mason County113k9.4%16.0%65.0
McDonough County127k7.9%13.8%41.3
McLean County1170k5.6%11.2%34.9
Menard County112k7.9%14.1%37.9
Mercer County115k8.6%15.3%54.6
Morgan County132k8.8%15.6%47.1
Moultrie County114k8.6%16.0%42.6
Ogle County151k7.8%14.0%43.0
Peoria County1178k7.5%13.8%43.8
Piatt County117k6.9%12.5%35.4
Pike County114k9.7%16.8%52.5
Putnam County15,5617.8%13.1%42.9
Rock Island County1141k8.1%14.5%36.3
Sangamon County1193k7.3%13.2%37.6
Schuyler County16,7339.8%17.2%39.0
Scott County14,7108.6%15.1%50.3
Stark County15,2188.8%15.1%40.3
Stephenson County143k9.1%15.0%35.2
Tazewell County1130k7.3%13.5%43.4
Vermilion County172k9.7%17.2%60.9
Warren County116k8.2%14.5%47.2
Whiteside County154k8.3%14.6%40.5
Winnebago County1281k8.3%15.5%38.3
Woodford County138k6.8%12.4%33.6
Bond County216k8.0%15.1%43.3
Christian County233k8.6%16.1%53.2
Clark County215k8.3%14.9%44.3
Clay County213k10.3%17.8%56.4
Clinton County237k7.4%14.0%32.7
Cook County25.1M5.7%11.1%28.5
Crawford County218k8.4%15.4%42.7
Cumberland County210k8.1%14.5%33.8
DuPage County2921k5.0%9.5%24.6
Edwards County25,96810.3%17.3%64.2
Effingham County234k7.7%14.1%40.4
Fayette County221k9.2%17.4%55.7
Franklin County237k10.2%17.7%46.6
Gallatin County24,67010.9%17.4%41.1
Hamilton County27,91110.1%17.0%44.6
Hardin County23,56910.5%16.9%56.6
Jackson County252k7.7%13.8%45.8
Jasper County29,1448.1%14.3%34.8
Jefferson County236k8.8%16.1%52.4
Johnson County213k8.9%16.8%36.2
Kankakee County2106k7.9%14.7%43.3
Lake County2709k5.4%10.4%27.7
Lawrence County215k9.2%17.6%47.9
Macoupin County244k9.1%15.9%46.4
Madison County2263k7.2%13.3%45.1
Marion County237k9.5%17.0%56.0
McHenry County2313k5.9%11.5%34.0
Monroe County235k6.2%11.3%32.9
Montgomery County228k8.9%16.1%55.7
Perry County221k9.5%17.4%42.4
Pope County23,7079.9%15.0% -
Randolph County230k8.9%16.3%48.9
Richland County215k8.9%15.5%48.2
Saline County223k9.7%16.7%52.0
Shelby County221k9.0%15.2%42.4
St. Clair County2251k7.2%14.2%40.5
Union County217k10.1%17.1%48.6
Wabash County211k9.4%15.8%43.7
Washington County214k7.8%13.8%33.1
Wayne County216k10.0%17.0%46.4
White County213k11.0%18.1%45.0
Will County2701k5.6%11.6%35.0
Williamson County267k8.2%14.7%51.2
Alexander County34,69512.1%19.6%81.5
Massac County314k9.7%16.6%54.9
Pulaski County34,91111.6%20.0%53.8

Zones from the EPA Map of Radon Zones. COPD and smoking are CDC PLACES model-based estimates of adult prevalence. Lung cancer death rates are age-adjusted deaths per 100,000 per year, 2019-2023, from NCI State Cancer Profiles. A dash means the source does not report a value for that county.

Highest potential

Zone 1 counties in Illinois

These 56 counties have a predicted average indoor radon screening level above the EPA action level. The EPA recommends every home in them be tested.

Other states

Radon zones elsewhere