Radon Levels By State 2020

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:

  • Arizona
  • Florida
  • District of Columbia
  • Mississippi
  • Louisiana
  • Hawaii

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.

Radon Levels By State 2020

State Average Radon Level (pCi/L) 2020 Pop.
Hawaii01,412,690
Louisiana1.14,645,180
Mississippi1.22,989,260
Florida1.821,993,000
Arizona1.97,378,490
Texas2.129,472,300
California2.339,937,500
Georgia2.310,736,100
Delaware2.4982,895
South Carolina2.45,210,100
Arkansas2.53,039,000
Oklahoma2.53,954,820
Oregon3.14,301,090
Connecticut3.43,563,080
Nevada3.43,139,660
Michigan3.510,045,000
Virginia3.68,626,210
Vermont3.7628,061
Alabama3.94,908,620
Massachusetts3.96,976,600
New Mexico3.92,096,640
North Carolina410,611,900
New York4.219,440,500
Missouri4.36,169,270
Rhode Island4.31,056,160
New Jersey4.48,936,570
Utah4.43,282,120
Minnesota4.65,700,670
Indiana4.76,745,350
Tennessee4.86,897,580
Kansas4.92,910,360
Wyoming5567,025
Nebraska5.21,952,570
Illinois5.312,659,700
Maryland5.46,083,120
New Hampshire5.61,371,250
Wisconsin5.75,851,750
Maine5.91,345,790
North Dakota6761,723
Iowa6.13,179,850
West Virginia6.11,778,070
Colorado6.85,845,530
Idaho7.31,826,160
Kentucky7.44,499,690
Montana7.41,086,760
Washington7.57,797,100
Ohio7.811,747,700
Pennsylvania8.612,820,900
South Dakota9.6903,027
Alaska10.7734,002