Radon Levels By State 2019

Radon is a naturally occurring radioactive gas that is odorless, tasteless and colorless. It is formed by the natural radioactive decay of uranium in rock, soil, and water.

Radon is the second-leading cause of lung cancer, costing the United States over $2 billion per year in both direct and indirect health care costs. Radon has no immediate symptoms that will alert someone of its presence and it takes years of exposure before any problems become apparent.

According to the US EPA, nearly 1in 3 homes checked in seven states had radon levels over the recommended action level for radon exposure of 4 pCi/L. The pCi in “pCi/L” is a picocurie, which is one-trillionth of a curie and is the measure of the rate of radioactive decay of radon. At 4 pCi/L, there will be approximately 12,672 disintegrations in one liter of air during a 24-hour period.

According to Air Chek, Inc., 31 states have radon exposure above 4 pCi/L. In general, these states are in the northern half of the United States. Only five states and the District of Columbia are considered to have low radon levels. Those states are:

Hawaii has the lowest radon levels of all 50 states with an average level of 0 pCi/L. The uranium content of Hawaiian rocks is low and most rocks near the surface are porous, allowing for air infiltration to dilute radon.

The ten states with the highest levels of radon are:

  1. Alaska
  2. South Dakota
  3. Pennsylvania
  4. Ohio
  5. Washington
  6. Montana
  7. Kentucky
  8. Idaho
  9. Colorado
  10. West Virginia

Alaska has the highest radon levels of 10.7 pCi/L. Homeowners in Alaska are encouraged to test for radon every two years.

Below is a table with each state’s average levels of radon.

State Average Radon Level (pCi/L) 2019 Pop.
Hawaii01,416,589
Louisiana1.14,652,581
Mississippi1.22,987,895
District of Columbia1.6711,571
Florida1.821,646,155
Arizona1.97,275,070
Texas2.129,087,070
California2.339,747,267
Georgia2.310,627,767
Delaware2.4975,033
South Carolina2.45,147,111
Arkansas2.53,026,412
Oklahoma2.53,948,950
Oregon3.14,245,901
Connecticut3.43,567,871
Nevada3.43,087,025
Michigan3.510,020,472
Virginia3.68,571,946
Vermont3.7627,180
Alabama3.94,898,246
Massachusetts3.96,939,373
New Mexico3.92,096,034
North Carolina410,497,741
New York4.219,491,339
Missouri4.36,147,861
Rhode Island4.31,056,738
New Jersey4.48,922,547
Utah4.43,221,610
Minnesota4.65,655,925
Indiana4.76,718,616
Tennessee4.86,833,793
Kansas4.92,910,931
Wyoming5572,381
Nebraska5.21,940,919
Illinois5.312,700,381
Maryland5.46,062,917
New Hampshire5.61,363,852
Wisconsin5.75,832,661
Maine5.91,342,097
North Dakota6760,900
Iowa6.13,167,997
West Virginia6.11,791,951
Colorado6.85,770,545
Idaho7.31,790,182
Kentucky7.44,484,047
Montana7.41,074,532
Washington7.57,666,343
Ohio7.811,718,568
Pennsylvania8.612,813,969
South Dakota9.6892,631
Alaska10.7735,720