USA States Ranked by Indoor Radon Levels
Measured averages from Airthings devices across USA. Action level: 4 pCi/L — the threshold at which remediation is recommended.
Iowa has the highest average indoor radon in USA at 2.6 pCi/L, based on Airthings device measurements across 50 states.
Updated October 19, 2026
Highest
2.6pCi/L
Iowa
USA average
1.8pCi/L
across all states
Above action level
0/ 50
states
| # | Location | Avg level | vs action level |
|---|---|---|---|
| 1 | Iowa | 2.6 pCi/L | 0.6× under |
| 2 | South Dakota | 2.5 pCi/L | 0.6× under |
| 3 | Wyoming | 2.5 pCi/L | 0.6× under |
| 4 | Nebraska | 2.5 pCi/L | 0.6× under |
| 5 | Idaho | 2.5 pCi/L | 0.6× under |
| 6 | New Mexico | 2.5 pCi/L | 0.6× under |
| 7 | West Virginia | 2.4 pCi/L | 0.6× under |
| 8 | North Dakota | 2.4 pCi/L | 0.6× under |
| 9 | New Hampshire | 2.4 pCi/L | 0.6× under |
| 10 | Kentucky | 2.3 pCi/L | 0.6× under |
| 11 | Colorado | 2.3 pCi/L | 0.6× under |
| 12 | Indiana | 2.3 pCi/L | 0.6× under |
| 13 | Tennessee | 2.3 pCi/L | 0.6× under |
| 14 | Ohio | 2.2 pCi/L | 0.5× under |
| 15 | Pennsylvania | 2.2 pCi/L | 0.5× under |
| 16 | Alabama | 2.1 pCi/L | 0.5× under |
| 17 | Kansas | 2.1 pCi/L | 0.5× under |
| 18 | Vermont | 2.0 pCi/L | 0.5× under |
| 19 | Maine | 2.0 pCi/L | 0.5× under |
| 20 | Montana | 2.0 pCi/L | 0.5× under |
| 21 | South Carolina | 2.0 pCi/L | 0.5× under |
| 22 | Rhode Island | 1.9 pCi/L | 0.5× under |
| 23 | Utah | 1.9 pCi/L | 0.5× under |
| 24 | North Carolina | 1.9 pCi/L | 0.5× under |
| 25 | Delaware | 1.9 pCi/L | 0.5× under |
| 26 | Minnesota | 1.8 pCi/L | 0.5× under |
| 27 | Georgia | 1.8 pCi/L | 0.5× under |
| 28 | Florida | 1.8 pCi/L | 0.5× under |
| 29 | Wisconsin | 1.8 pCi/L | 0.4× under |
| 30 | Missouri | 1.8 pCi/L | 0.4× under |
| 31 | Illinois | 1.7 pCi/L | 0.4× under |
| 32 | Michigan | 1.7 pCi/L | 0.4× under |
| 33 | Maryland | 1.6 pCi/L | 0.4× under |
| 34 | Alaska | 1.6 pCi/L | 0.4× under |
| 35 | Connecticut | 1.6 pCi/L | 0.4× under |
| 36 | Arizona | 1.5 pCi/L | 0.4× under |
| 37 | Virginia | 1.5 pCi/L | 0.4× under |
| 38 | Massachusetts | 1.5 pCi/L | 0.4× under |
| 39 | New York | 1.4 pCi/L | 0.4× under |
| 40 | New Jersey | 1.4 pCi/L | 0.4× under |
| 41 | Oregon | 1.4 pCi/L | 0.3× under |
| 42 | Nevada | 1.3 pCi/L | 0.3× under |
| 43 | Arkansas | 1.3 pCi/L | 0.3× under |
| 44 | Oklahoma | 1.3 pCi/L | 0.3× under |
| 45 | California | 1.1 pCi/L | 0.3× under |
| 46 | Texas | 1.1 pCi/L | 0.3× under |
| 47 | Washington | 1.0 pCi/L | 0.3× under |
| 48 | Mississippi | 0.9 pCi/L | 0.2× under |
| 49 | Hawaii | 0.8 pCi/L | 0.2× under |
| 50 | Louisiana | 0.6 pCi/L | 0.1× under |