Radon Levels By State

Last updated November 24, 2024

Average Radon Level
Top
Last
Average Radon Level (pCi/L)
1.AlaskaAlaska10.7
2.South DakotaSouth Dakota9.6
3.PennsylvaniaPennsylvania8.6
4.OhioOhio7.8
5.WashingtonWashington7.5
6.MontanaMontana7.4
7.KentuckyKentucky7.4
8.IdahoIdaho7.3
9.ColoradoColorado6.8
10.IowaIowa6.1
11.West VirginiaWest Virginia6.1
12.North DakotaNorth Dakota6.0
13.MaineMaine5.9
14.WisconsinWisconsin5.7
15.New HampshireNew Hampshire5.6
16.MarylandMaryland5.4
17.IllinoisIllinois5.3
18.NebraskaNebraska5.2
19.WyomingWyoming5.0
20.KansasKansas4.9
21.TennesseeTennessee4.8
22.IndianaIndiana4.7
23.MinnesotaMinnesota4.6
24.New JerseyNew Jersey4.4
25.UtahUtah4.4
26.MissouriMissouri4.3
27.Rhode IslandRhode Island4.3
28.New YorkNew York4.2
29.North CarolinaNorth Carolina4.0
30.AlabamaAlabama3.9
31.MassachusettsMassachusetts3.9
32.New MexicoNew Mexico3.9
33.VermontVermont3.7
34.VirginiaVirginia3.6
35.MichiganMichigan3.5
36.ConnecticutConnecticut3.4
37.NevadaNevada3.4
38.OregonOregon3.1
39.ArkansasArkansas2.5
40.OklahomaOklahoma2.5
41.DelawareDelaware2.4
42.South CarolinaSouth Carolina2.4
43.CaliforniaCalifornia2.3
44.GeorgiaGeorgia2.3
45.TexasTexas2.1
46.ArizonaArizona1.9
47.FloridaFlorida1.8
48.MississippiMississippi1.2
49.LouisianaLouisiana1.1

Tracking Radon Across States

Radon, a stealthy and naturally occurring radioactive gas, is prevalent across the United States, silently contributing to a significant share of lung cancer cases nationwide. With no smell, taste, or color, it quietly infiltrates our homes, originating from the decay of uranium in soil, rock, and water. Prolonged exposure to this silent menace has long-term health implications, making it essential to evaluate and monitor average radon levels in every state.

The U.S. Environmental Protection Agency (EPA) recommends taking action if radon levels exceed 4 pCi/L in homes. To provide a comprehensive overview of radon distribution in the U.S, we've collated data from various states, ranking each according to their average radon level in picocuries per liter (pCi/L), a measure of radioactivity.

  • Alaska leads the list as the state with the highest average radon level of 10.7 pCi/L, significantly above the EPA's recommended action level. Following Alaska, South Dakota and Pennsylvania also report alarmingly high radon levels of 9.6 and 8.6 pCi/L, respectively.
  • Interestingly, the top ten states with the highest radon levels are a combination of both coastal and inland states, debunking any presumptions of geographical favoritism.
  • On the flip side, Louisiana records the lowest average radon level of 1.1 pCi/L, followed by Mississippi and Florida. It's noteworthy that the three states with the lowest radon levels are all in the Southern U.S.
  • From the middle to the lower end of the spectrum, average radon levels remain fairly consistent, hovering around the 4 pCi/L mark. This concentration range includes states like North Carolina, Nevada, and Oregon.

States with the Highest Radon Levels

When evaluating the states with the highest average radon levels, Alaska grabs the top spot, with an average of 10.7 pCi/L. In the second position, we have South Dakota, exhibiting a high average radon level of 9.6 pCi/L. Next comes Pennsylvania, with a radon level of 8.6 pCi/L.Following closely, Ohio secures the fourth position with an average radon level of 7.8 pCi/L outperforming the fifth spot, Washington, which sees a 7.5 pCi/L radon level. Montana and Kentucky both present a joint average of 7.4 pCi/L of radon, posing significant health risks to their residents.

Idaho's radon level is not far behind, standing at 7.3 pCi/L and surpassing Colorado's level of 6.8 pCi/L. Lastly, Iowa closes our top ten list, having an average radon level of 6.1 pCi/L which, although lower, still is above the EPA's recommended radon action level.

States with the Highest Radon Levels:

  1. Alaska - 10.7 pCi/L
  2. South Dakota - 9.6 pCi/L
  3. Pennsylvania - 8.6 pCi/L
  4. Ohio - 7.8 pCi/L
  5. Washington - 7.5 pCi/L
  6. Montana - 7.4 pCi/L
  7. Kentucky - 7.4 pCi/L
  8. Idaho - 7.3 pCi/L
  9. Colorado - 6.8 pCi/L
  10. Iowa - 6.1 pCi/L

By Region

Alabama

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Ranked in U.S.

#30

Alaska

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Ranked in U.S.

#1

Arizona

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Ranked in U.S.

#46

Arkansas

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Ranked in U.S.

#39

California

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Ranked in U.S.

#43

Colorado

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Ranked in U.S.

#9

Connecticut

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Ranked in U.S.

#36

Delaware

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Ranked in U.S.

#41

Florida

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Ranked in U.S.

#47

Georgia

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Ranked in U.S.

#44

Idaho

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Ranked in U.S.

#8

Illinois

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Ranked in U.S.

#17

Indiana

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Ranked in U.S.

#22

Iowa

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Ranked in U.S.

#10

Kansas

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Ranked in U.S.

#20

Kentucky

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Ranked in U.S.

#7

Louisiana

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Ranked in U.S.

#49

Maine

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Ranked in U.S.

#13

Maryland

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Ranked in U.S.

#16

Massachusetts

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Ranked in U.S.

#31

Michigan

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Ranked in U.S.

#35

Minnesota

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Ranked in U.S.

#23

Mississippi

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Ranked in U.S.

#48

Missouri

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Ranked in U.S.

#26

Montana

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Ranked in U.S.

#6

Nebraska

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Ranked in U.S.

#18

Nevada

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Ranked in U.S.

#37

New Hampshire

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Ranked in U.S.

#15

New Jersey

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Ranked in U.S.

#24

New Mexico

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Ranked in U.S.

#32

New York

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Ranked in U.S.

#28

North Carolina

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Ranked in U.S.

#29

North Dakota

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Ranked in U.S.

#12

Ohio

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Ranked in U.S.

#4

Oklahoma

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Ranked in U.S.

#40

Oregon

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Ranked in U.S.

#38

Pennsylvania

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Ranked in U.S.

#3

Rhode Island

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Ranked in U.S.

#27

South Carolina

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Ranked in U.S.

#42

South Dakota

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Ranked in U.S.

#2

Tennessee

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Ranked in U.S.

#21

Texas

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Ranked in U.S.

#45

Utah

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Ranked in U.S.

#25

Vermont

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Ranked in U.S.

#33

Virginia

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Ranked in U.S.

#34

Washington

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Ranked in U.S.

#5

West Virginia

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Ranked in U.S.

#11

Wisconsin

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Ranked in U.S.

#14

Wyoming

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Ranked in U.S.

#19

Table

Region ↕Average Radon Level↕
Alabama iconAlabama3.9
Alaska iconAlaska10.7
Arizona iconArizona1.9
Arkansas iconArkansas2.5
California iconCalifornia2.3
Colorado iconColorado6.8
Connecticut iconConnecticut3.4
Delaware iconDelaware2.4
Florida iconFlorida1.8
Georgia iconGeorgia2.3
Idaho iconIdaho7.3
Illinois iconIllinois5.3
Indiana iconIndiana4.7
Iowa iconIowa6.1
Kansas iconKansas4.9
Kentucky iconKentucky7.4
Louisiana iconLouisiana1.1
Maine iconMaine5.9
Maryland iconMaryland5.4
Massachusetts iconMassachusetts3.9
Michigan iconMichigan3.5
Minnesota iconMinnesota4.6
Mississippi iconMississippi1.2
Missouri iconMissouri4.3
Montana iconMontana7.4
Nebraska iconNebraska5.2
Nevada iconNevada3.4
New Hampshire iconNew Hampshire5.6
New Jersey iconNew Jersey4.4
New Mexico iconNew Mexico3.9
New York iconNew York4.2
North Carolina iconNorth Carolina4.0
North Dakota iconNorth Dakota6.0
Ohio iconOhio7.8
Oklahoma iconOklahoma2.5
Oregon iconOregon3.1
Pennsylvania iconPennsylvania8.6
Rhode Island iconRhode Island4.3
South Carolina iconSouth Carolina2.4
South Dakota iconSouth Dakota9.6
Tennessee iconTennessee4.8
Texas iconTexas2.1
Utah iconUtah4.4
Vermont iconVermont3.7
Virginia iconVirginia3.6
Washington iconWashington7.5
West Virginia iconWest Virginia6.1
Wisconsin iconWisconsin5.7
Wyoming iconWyoming5.0
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