Radon levels by state
Every state ranked by its population-weighted predicted basement radon average (model estimate, 2001-2021), with the EPA zone mix of its counties. Click a state for its county table.
| # | State | Predicted basement avg | Counties ≥ 4 | ZIPs ≥ 4 | Zone 1 / 2 / 3 |
|---|---|---|---|---|---|
| 1 | South Dakota | 3.9 pCi/L | 34 of 66 | 42.1% | 48 / 18 / 0 |
| 2 | Nebraska | 3.6 pCi/L | 42 of 93 | 50.1% | 53 / 24 / 16 |
| 3 | Iowa | 3.5 pCi/L | 50 of 99 | 41% | 99 / 0 / 0 |
| 4 | North Dakota | 3.3 pCi/L | 11 of 53 | 11.7% | 53 / 0 / 0 |
| 5 | Montana | 3.1 pCi/L | 1 of 56 | 1% | 49 / 7 / 0 |
| 6 | Wyoming | 3.0 pCi/L | 1 of 23 | 2.9% | 21 / 2 / 0 |
| 7 | Ohio | 2.8 pCi/L | 14 of 88 | 10.7% | 53 / 35 / 0 |
| 8 | Idaho | 2.6 pCi/L | 2 of 44 | 3.3% | 19 / 20 / 5 |
| 9 | Colorado | 2.6 pCi/L | 3 of 64 | 1.8% | 53 / 11 / 0 |
| 10 | Kansas | 2.6 pCi/L | 25 of 105 | 16.5% | 65 / 40 / 0 |
| 11 | Kentucky | 2.5 pCi/L | 0 of 120 | 0.6% | 30 / 82 / 8 |
| 12 | Minnesota | 2.4 pCi/L | 9 of 87 | 8.6% | 68 / 19 / 0 |
| 13 | West Virginia | 2.4 pCi/L | 0 of 55 | 0.2% | 20 / 29 / 6 |
| 14 | Tennessee | 2.3 pCi/L | 0 of 95 | 0.2% | 39 / 32 / 24 |
| 15 | Indiana | 2.3 pCi/L | 0 of 92 | 0.1% | 57 / 35 / 0 |
| 16 | Pennsylvania | 2.3 pCi/L | 2 of 67 | 2.9% | 49 / 17 / 1 |
| 17 | Utah | 2.3 pCi/L | 0 of 29 | 1.3% | 7 / 22 / 0 |
| 18 | Missouri | 2.2 pCi/L | 1 of 115 | 1.3% | 11 / 97 / 7 |
| 19 | Maine | 2.2 pCi/L | 0 of 16 | 0% | 12 / 4 / 0 |
| 20 | New Mexico | 2.1 pCi/L | 0 of 32 | 0% | 7 / 26 / 0 |
| 21 | New Hampshire | 2.1 pCi/L | 0 of 10 | 0.4% | 1 / 9 / 0 |
| 22 | Wisconsin | 2.0 pCi/L | 0 of 72 | 0.1% | 28 / 44 / 0 |
| 23 | Nevada | 1.9 pCi/L | 0 of 17 | 0% | 9 / 7 / 1 |
| 24 | Illinois | 1.9 pCi/L | 1 of 102 | 0.4% | 56 / 43 / 3 |
| 25 | Georgia | 1.9 pCi/L | 0 of 159 | 0% | 4 / 55 / 100 |
| 26 | Massachusetts | 1.8 pCi/L | 0 of 14 | 0.4% | 3 / 10 / 1 |
| 27 | Alabama | 1.8 pCi/L | 0 of 67 | 0% | 13 / 33 / 21 |
| 28 | Oklahoma | 1.8 pCi/L | 0 of 77 | 0% | 0 / 9 / 68 |
| 29 | Arkansas | 1.8 pCi/L | 0 of 75 | 0% | 0 / 14 / 61 |
| 30 | Arizona | 1.7 pCi/L | 0 of 15 | 0% | 0 / 15 / 0 |
| 31 | Oregon | 1.7 pCi/L | 0 of 36 | 0% | 0 / 21 / 15 |
| 32 | Vermont | 1.7 pCi/L | 0 of 14 | 0% | 0 / 12 / 2 |
| 33 | North Carolina | 1.7 pCi/L | 0 of 100 | 0.3% | 8 / 31 / 61 |
| 34 | Virginia | 1.6 pCi/L | 0 of 112 | 0.1% | 62 / 28 / 43 |
| 35 | South Carolina | 1.6 pCi/L | 0 of 46 | 0% | 1 / 8 / 37 |
| 36 | Michigan | 1.6 pCi/L | 0 of 83 | 0% | 9 / 32 / 42 |
| 37 | Washington | 1.6 pCi/L | 0 of 39 | 0% | 7 / 14 / 18 |
| 38 | Rhode Island | 1.6 pCi/L | 0 of 5 | 0% | 2 / 2 / 1 |
| 39 | Texas | 1.5 pCi/L | 0 of 253 | 0% | 0 / 39 / 215 |
| 40 | Connecticut | 1.5 pCi/L | 0 of 8 | 0% | 4 / 3 / 1 |
| 41 | California | 1.5 pCi/L | 0 of 58 | 0% | 2 / 29 / 27 |
| 42 | Mississippi | 1.5 pCi/L | 0 of 82 | 0% | 0 / 8 / 74 |
| 43 | Louisiana | 1.4 pCi/L | 0 of 64 | 0% | 0 / 0 / 64 |
| 44 | New York | 1.4 pCi/L | 0 of 62 | 0% | 34 / 13 / 15 |
| 45 | Delaware | 1.3 pCi/L | 0 of 3 | 0% | 0 / 1 / 2 |
| 46 | New Jersey | 1.3 pCi/L | 0 of 21 | 0% | 7 / 11 / 3 |
| 47 | Maryland | 1.3 pCi/L | 0 of 24 | 0% | 8 / 9 / 7 |
| 48 | Florida | 1.3 pCi/L | 0 of 67 | 0% | 0 / 9 / 58 |
| 49 | District of Columbia | 1.1 pCi/L | 0 of 1 | 0% | 0 / 0 / 1 |
| - | Alaska | not modeled | - | - | 0 / 5 / 25 |
| - | Hawaii | not modeled | - | - | 0 / 0 / 5 |
49 states have model predictions; Alaska and Hawaii show EPA zones only. Zone counts use current Census county boundaries (see methodology).