Radon in Missouri: radon map by county

EPA's Map of Radon Zones puts 11 of Missouri's 115 counties in Zone 1 (predicted average indoor radon above 4 pCi/L), 97 in Zone 2 and 7 in Zone 3. Of 42,913 building tests that radon laboratories reported for 2008 to 2017, 30.7% were at or above EPA's 4 pCi/L action level, against 36.5% nationally (number 22 of 42 states with 1,000+ tests). The highest county share is Atchison County (69.9% of 75 tests).

counties in Zone 1 (above 4 pCi/L predicted)

counties in Zone 2 (2 to 4)

counties in Zone 3 (below 2)

30.7%

of 42,913 lab tests at or above 4 pCi/L

Radon by county in Missouri

EPA radon zone and radon test results for each county in Missouri
County	EPA zone	Lab tests	Median	4+ pCi/L
Adair County	Zone 2	82	1.8	27.2%
Andrew County	Zone 1	110	4.9	60.8%
Atchison County	Zone 1	75	5.6	69.9%
Audrain County	Zone 2	116	2.5	29.9%
Barry County	Zone 2	44	3.1	41.8%
Barton County	Zone 2	21	1.4	16.7%
Bates County	Zone 2	13	1.5	26.1%
Benton County	Zone 2	44	2.0	30.6%
Bollinger County	Zone 2	4	1.4	0%
Boone County	Zone 2	4,290	1.9	21.7%
Buchanan County	Zone 1	420	4.2	52.9%
Butler County	Zone 3	21	1.9	21.2%
Caldwell County	Zone 2	16	1.5	6.3%
Callaway County	Zone 2	164	1.7	27.1%
Camden County	Zone 2	625	2.2	22.9%
Cape Girardeau County	Zone 2	220	2.8	35.2%
Carroll County	Zone 2	17	2.7	33.3%
Carter County	Zone 2	4	2.8	25%
Cass County	Zone 1	705	3.5	45.5%
Cedar County	Zone 2	19	1.3	5%
Chariton County	Zone 2	15	1.7	13.3%
Christian County	Zone 2	317	1.9	31.7%
Clark County	Zone 2	12	2.2	29.4%
Clay County	Zone 1	2,794	3.1	39.2%
Clinton County	Zone 1	94	2.8	38.1%
Cole County	Zone 2	633	2.1	24.6%
Cooper County	Zone 2	76	2.6	41.1%
Crawford County	Zone 2	26	1.5	14.7%
Dade County	Zone 2	7	1.3	0%
Dallas County	Zone 2	21	1.4	14.8%
Daviess County	Zone 2	26	2.0	26.7%
DeKalb County	Zone 2	30	2.3	24.2%
Dent County	Zone 2	10	3.0	35.7%
Douglas County	Zone 2	1	1.2	0%
Dunklin County	Zone 3	15	1.3	6.3%
Franklin County	Zone 2	602	2.6	33.2%
Gasconade County	Zone 2	40	2.3	31.8%
Gentry County	Zone 2	20	3.5	41.7%
Greene County	Zone 2	1,053	2.5	32.7%
Grundy County	Zone 2	23	2.8	37%
Harrison County	Zone 2	19	1.9	29.2%
Henry County	Zone 2	64	3.4	38.3%
Hickory County	Zone 2	7	2.0	0%
Holt County	Zone 1	21	4.9	62.1%
Howard County	Zone 2	49	3.5	43.5%
Howell County	Zone 2	98	3.5	45.7%
Iron County	Zone 1	11	3.5	50%
Jackson County	Zone 1	4,936	3.1	41.3%
Jasper County	Zone 2	198	2.0	29.1%
Jefferson County	Zone 2	1,765	3.1	41.6%
Johnson County	Zone 2	204	1.9	25.8%
Knox County	Zone 2	8	1.9	0%
Laclede County	Zone 2	35	2.3	37%
Lafayette County	Zone 2	146	3.5	46.7%
Lawrence County	Zone 2	62	1.8	27.1%
Lewis County	Zone 2	56	2.6	32.4%
Lincoln County	Zone 2	333	2.2	33.6%
Linn County	Zone 2	33	1.8	18.9%
Livingston County	Zone 2	44	2.1	22.4%
Macon County	Zone 2	34	1.7	19.4%
Madison County	Zone 2	17	3.5	39.1%
Maries County	Zone 2	20	1.8	14.3%
Marion County	Zone 2	224	3.2	41.8%
McDonald County	Zone 2	17	1.9	21.1%
Mercer County	Zone 2	7	1.7	27.3%
Miller County	Zone 2	126	1.9	16.9%
Mississippi County	Zone 3	4	0.1	0%
Moniteau County	Zone 2	56	2.2	25%
Monroe County	Zone 2	27	1.5	23.3%
Montgomery County	Zone 2	34	1.6	12.8%
Morgan County	Zone 2	106	2.2	21.1%
New Madrid County	Zone 3	9	1.4	11.1%
Newton County	Zone 2	134	2.5	31.1%
Nodaway County	Zone 1	173	2.7	34.2%
Oregon County	Zone 2	3	2.0	33.3%
Osage County	Zone 2	42	1.5	15.4%
Ozark County	Zone 2	4	4.7	50%
Pemiscot County	Zone 3	5	0.8	0%
Perry County	Zone 2	65	3.2	37.8%
Pettis County	Zone 2	93	2.8	37.9%
Phelps County	Zone 2	168	1.5	14.7%
Pike County	Zone 2	29	2.9	40%
Platte County	Zone 1	1,355	3.0	37.8%
Polk County	Zone 2	54	1.6	11.5%
Pulaski County	Zone 2	78	1.3	18.7%
Putnam County	Zone 2	7	1.8	33.3%
Ralls County	Zone 2	36	2.7	32.6%
Randolph County	Zone 2	55	1.8	17.2%
Ray County	Zone 2	82	2.5	38.9%
Reynolds County	Zone 2	3	2.2	33.3%
Ripley County	Zone 2	4	3.0	30%
Saline County	Zone 2	37	3.7	49.1%
Schuyler County	Zone 2	7	1.0	9.1%
Scotland County	Zone 2	12	1.4	16.7%
Scott County	Zone 3	43	2.2	29.4%
Shannon County	Zone 2	5	1.3	26.3%
Shelby County	Zone 2	22	1.7	24.1%
St. Charles County	Zone 2	4,713	2.2	26.5%
St. Clair County	Zone 2	13	1.5	7.7%
St. Francois County	Zone 2	114	2.9	41.1%
St. Louis city	Zone 2	1,074	1.9	16.9%
St. Louis County	Zone 2	12,151	2.3	26.3%
Ste. Genevieve County	Zone 2	57	2.5	31.1%
Stoddard County	Zone 3	20	1.1	12%
Stone County	Zone 2	108	2.9	41.6%
Sullivan County	Zone 2	5	1.4	33.3%
Taney County	Zone 2	122	3.0	37%
Texas County	Zone 2	48	1.3	19.3%
Vernon County	Zone 2	29	0.9	8.8%
Warren County	Zone 2	204	2.7	36.8%
Washington County	Zone 2	28	1.5	26.3%
Wayne County	Zone 2	9	1.9	23.5%
Webster County	Zone 2	83	1.6	20.4%
Worth County	Zone 2	10	1.5	9.1%
Wright County	Zone 2	14	2.7	27.8%

Lab tests: buildings tested by radon laboratories, 2008 to 2017; median in pCi/L; “4+ pCi/L” is the share of tests at or above EPA's action level. n/a: no value on file (no tests, or too few to report).

What the zones mean

Zone 1 counties have a predicted average indoor radon screening level above 4 pCi/L, Zone 2 from 2 to 4 pCi/L and Zone 3 below 2 pCi/L. The prediction is from 1993 indoor measurements, geology, aerial radioactivity, soils and foundation types. EPA: “This map should not be used to determine if individual homes need to be tested.” EPA recommends fixing a home at 4 pCi/L or more and considering a fix between 2 and 4 pCi/L, because there is no known safe level of exposure.

Radon in Missouri: questions

What radon zone is Missouri?

EPA's 1993 map does not give states one zone; it zones each county. In Missouri, 11 counties are Zone 1, 97 Zone 2 and 7 Zone 3. EPA says the map "should not be used to determine if individual homes need to be tested".

Which Missouri counties have the highest radon levels?

By the share of laboratory tests at or above 4 pCi/L for 2008 to 2017 (counties with 20 or more tests): Atchison County 69.9% (median 5.6 pCi/L, 75 tests); Holt County 62.1% (median 4.9 pCi/L, 21 tests); Andrew County 60.8% (median 4.9 pCi/L, 110 tests); Buchanan County 52.9% (median 4.2 pCi/L, 420 tests); Saline County 49.1% (median 3.7 pCi/L, 37 tests).

How common is high radon in Missouri?

30.7% of the 42,913 tests in the laboratory data for Missouri (2008 to 2017) were at or above 4 pCi/L; the national share was 36.5%. Buildings are tested by choice, often because of a sale or a concern, so the share describes the tests on file, not every home.

Does Missouri publish its own radon test data?

Missouri's radon program reports county test results; the latest year with county results is 2023, shown on each county page.

Should I test for radon in Missouri?

Yes. EPA recommends testing every home no matter where it is, fixing it at 4 pCi/L or more and considering a fix between 2 and 4 pCi/L, because there is no known safe level of radon exposure.

States bordering Missouri

Radon in Arkansas (0 of 75 in Zone 1)Radon in Illinois (56 of 102 in Zone 1)Radon in Iowa (99 of 99 in Zone 1)Radon in Kansas (65 of 105 in Zone 1)Radon in Kentucky (30 of 120 in Zone 1)Radon in Nebraska (53 of 93 in Zone 1)Radon in Oklahoma (0 of 77 in Zone 1)Radon in Tennessee (39 of 95 in Zone 1)

Other free hazard lookups

All of these, plus wetlands, FEMA hazard ratings and the federal contamination lists, are in the Environmental Records Report for any US address ($29).

Superfund sites in Missouri · Radon map of every state

Data compiled 2026-10-20. County-level screening information, not a radon measurement of any building.