Radon in Utah: radon map by county
EPA's Map of Radon Zones puts 7 of Utah's 29 counties in Zone 1 (predicted average indoor radon above 4 pCi/L), 22 in Zone 2 and 0 in Zone 3. Of 21,450 building tests that radon laboratories reported for 2008 to 2017, 41.9% were at or above EPA's 4 pCi/L action level, against 36.5% nationally (number 13 of 42 states with 1,000+ tests). The highest county share is Box Elder County (64.3% of 338 tests).
Radon by county in Utah
| County | EPA zone | Lab tests | Median | 4+ pCi/L |
|---|---|---|---|---|
| Beaver County | Zone 2 | 3 | 99.9 | 100% |
| Box Elder County | Zone 2 | 338 | 5.8 | 64.3% |
| Cache County | Zone 2 | 1,002 | 4.7 | 56.8% |
| Carbon County | Zone 1 | 52 | 2.7 | 32.3% |
| Daggett County | Zone 2 | 1 | 0.8 | 0% |
| Davis County | Zone 2 | 2,100 | 2.7 | 33.7% |
| Duchesne County | Zone 1 | 27 | 3.9 | 47.4% |
| Emery County | Zone 2 | 1 | 3.4 | 0% |
| Garfield County | Zone 2 | 3 | 6.0 | 100% |
| Grand County | Zone 1 | 39 | 1.4 | 14.8% |
| Iron County | Zone 2 | 84 | 2.3 | 22.4% |
| Juab County | Zone 2 | 31 | 6.2 | 61% |
| Kane County | Zone 2 | 11 | 2.5 | 38.9% |
| Millard County | Zone 2 | 11 | 2.3 | 11.1% |
| Morgan County | Zone 2 | 69 | 4.7 | 60.6% |
| Piute County | Zone 1 | n/a | n/a | n/a |
| Rich County | Zone 2 | 2 | 1.4 | 0% |
| Salt Lake County | Zone 2 | 10,449 | 3.1 | 39.1% |
| San Juan County | Zone 2 | 11 | 5.1 | 66.7% |
| Sanpete County | Zone 1 | 56 | 5.7 | 61.3% |
| Sevier County | Zone 1 | 91 | 4.7 | 54.6% |
| Summit County | Zone 2 | 595 | 2.6 | 33.1% |
| Tooele County | Zone 2 | 371 | 3.5 | 45.4% |
| Uintah County | Zone 1 | 60 | 4.2 | 55.3% |
| Utah County | Zone 2 | 4,620 | 3.8 | 48% |
| Wasatch County | Zone 2 | 373 | 6.0 | 61.7% |
| Washington County | Zone 2 | 178 | 1.8 | 14.8% |
| Wayne County | Zone 2 | 2 | 3.9 | 40% |
| Weber County | Zone 2 | 870 | 2.6 | 36.2% |
Lab tests: buildings tested by radon laboratories, 2008 to 2017; median in pCi/L; “4+ pCi/L” is the share of tests at or above EPA's action level. n/a: no value on file (no tests, or too few to report).
What the zones mean
Zone 1 counties have a predicted average indoor radon screening level above 4 pCi/L, Zone 2 from 2 to 4 pCi/L and Zone 3 below 2 pCi/L. The prediction is from 1993 indoor measurements, geology, aerial radioactivity, soils and foundation types. EPA: “This map should not be used to determine if individual homes need to be tested.” EPA recommends fixing a home at 4 pCi/L or more and considering a fix between 2 and 4 pCi/L, because there is no known safe level of exposure.
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Radon in Utah: questions
What radon zone is Utah?
EPA's 1993 map does not give states one zone; it zones each county. In Utah, 7 counties are Zone 1, 22 Zone 2 and 0 Zone 3. EPA says the map "should not be used to determine if individual homes need to be tested".
Which Utah counties have the highest radon levels?
By the share of laboratory tests at or above 4 pCi/L for 2008 to 2017 (counties with 20 or more tests): Box Elder County 64.3% (median 5.8 pCi/L, 338 tests); Wasatch County 61.7% (median 6.0 pCi/L, 373 tests); Sanpete County 61.3% (median 5.7 pCi/L, 56 tests); Juab County 61% (median 6.2 pCi/L, 31 tests); Morgan County 60.6% (median 4.7 pCi/L, 69 tests).
How common is high radon in Utah?
41.9% of the 21,450 tests in the laboratory data for Utah (2008 to 2017) were at or above 4 pCi/L; the national share was 36.5%. Buildings are tested by choice, often because of a sale or a concern, so the share describes the tests on file, not every home.
Does Utah publish its own radon test data?
Utah's radon program reports county test results; the latest year with county results is 2023, shown on each county page.
Should I test for radon in Utah?
Yes. EPA recommends testing every home no matter where it is, fixing it at 4 pCi/L or more and considering a fix between 2 and 4 pCi/L, because there is no known safe level of radon exposure.
States bordering Utah
Other free hazard lookups
- Radon by county and ZIP codeEPA radon zone and the radon test results on file for any county, ZIP code or address.
- Fault lines near an addressUSGS-mapped earthquake faults within 5 miles, their age and slip rate, and the USGS seismic hazard value.
- Power lines near an addressHigh-voltage transmission lines within 1 mile from federal maps, with voltage and distance.
- Flood zone lookupThe FEMA flood zone mapped at any US address. Not an official flood zone determination.
- Superfund sites near an addressThe nearest EPA Superfund (NPL) sites and their status.
All of these, plus wetlands, FEMA hazard ratings and the federal contamination lists, are in the Environmental Records Report for any US address ($29).
Superfund sites in Utah · Radon map of every state
Data compiled 2026-10-20. County-level screening information, not a radon measurement of any building.