How much radon is in your county?
Real radon test results for US counties, from state health programs and the CDC. Every figure shows its source, period and number of tests. We never fill gaps with estimates.
Or choose a state.
2,662counties with test data
47states covered
5,302,702radon tests on record
Radon across the US
Laboratory test results reported to the CDC, so every state is measured the same way.
- Under 10%
- 10–20%
- 20–30%
- 30–40%
- 40% or more
- No data
Data table
| State | Tests ≥ 4 pCi/L | Lab tests | Counties |
|---|---|---|---|
| North Dakota | 59% | 6,607 | 53 |
| Nebraska | 59% | 42,782 | 93 |
| South Dakota | 58% | 6,275 | 62 |
| Iowa | 58% | 95,245 | 99 |
| Ohio | 52% | 98,840 | 88 |
| Colorado | 47% | 96,367 | 63 |
| Wisconsin | 47% | 68,104 | 72 |
| Montana | 46% | 9,893 | 51 |
| Wyoming | 44% | 7,638 | 23 |
| Kentucky | 44% | 28,793 | 120 |
| Minnesota | 43% | 130,912 | 87 |
| Illinois | 43% | 108,909 | 102 |
| Utah | 42% | 28,342 | 28 |
| Pennsylvania | 42% | 203,045 | 67 |
| Idaho | 42% | 12,961 | 44 |
| Indiana | 39% | 43,148 | 92 |
| Maine | 38% | 11,825 | 16 |
| West Virginia | 38% | 10,061 | 55 |
| New Hampshire | 35% | 15,608 | 10 |
| Tennessee | 33% | 31,066 | 95 |
| Missouri | 31% | 58,525 | 115 |
| Virginia | 30% | 53,199 | 131 |
| New Mexico | 28% | 3,721 | 29 |
| Michigan | 27% | 114,407 | 83 |
| Connecticut | 26% | 25,572 | 8 |
| Washington | 26% | 8,201 | 39 |
| Oregon | 25% | 23,951 | 34 |
| Georgia | 25% | 30,152 | 129 |
| New York | 25% | 97,145 | 62 |
| Maryland | 24% | 47,941 | 24 |
| Massachusetts | 24% | 234,152 | 14 |
| Rhode Island | 24% | 37,874 | 5 |
| Arkansas | 23% | 668 | 58 |
| Nevada | 23% | 10,930 | 16 |
| Florida | 23% | 53,794 | 62 |
| North Carolina | 23% | 73,139 | 99 |
| Alabama | 22% | 12,569 | 65 |
| Vermont | 22% | 10,600 | 14 |
| South Carolina | 19% | 26,481 | 46 |
| Alaska | 18% | 830 | 9 |
| Arizona | 17% | 3,589 | 13 |
| Delaware | 17% | 12,214 | 3 |
| Oklahoma | 13% | 814 | 52 |
| California | 10% | 9,415 | 56 |
| Texas | 10% | 4,615 | 138 |
| District of Columbia | 9% | 2,126 | 1 |
| Louisiana | 2% | 499 | 36 |
States with their own test data
Results published by state health and environment agencies, loaded county by county.
All states
States marked CDC data show laboratory test results from the CDC Tracking Network (2008–2017).
- AlabamaCDC data
- AlaskaCDC data
- ArizonaCDC data
- ArkansasCDC data
- CaliforniaCDC data
- ColoradoState data
- ConnecticutCDC data
- DelawareCDC data
- District of ColumbiaCDC data
- FloridaCDC data
- GeorgiaCDC data
- HawaiiNo data yet
- IdahoCDC data
- IllinoisCDC data
- IndianaCDC data
- IowaState data
- KansasNo data yet
- KentuckyCDC data
- LouisianaCDC data
- MaineCDC data
- MarylandCDC data
- MassachusettsCDC data
- MichiganState data
- MinnesotaState data
- MississippiNo data yet
- MissouriCDC data
- MontanaCDC data
- NebraskaCDC data
- NevadaCDC data
- New HampshireCDC data
- New JerseyNo data yet
- New MexicoCDC data
- New YorkCDC data
- North CarolinaCDC data
- North DakotaCDC data
- OhioCDC data
- OklahomaCDC data
- OregonCDC data
- PennsylvaniaState data
- Rhode IslandCDC data
- South CarolinaCDC data
- South DakotaCDC data
- TennesseeCDC data
- TexasCDC data
- UtahCDC data
- VermontCDC data
- VirginiaCDC data
- WashingtonState data
- West VirginiaCDC data
- WisconsinState data
- WyomingCDC data
How we get our data
Collect public results
We load radon test results published by state programs and the CDC Tracking Network.
Validate every county
County codes, value ranges and test counts are checked before anything replaces live data.
Show the source
Each figure names its source, period and sample size, and is spot-checked against the source.