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Radon Levels in Washington County, Utah

EPA puts Washington County in Zone 2, its middle radon zone, and most reported tests there come back low, though 9.9% of 657 (2023) reached 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    9.9%

    26.2 pts below UT

    Washington
    9.9%
    Utah
    36.1%

    657 tests, 2023

  • Median result

    1.3pCi/L

    Below action level

    Washington
    1.3 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2023

  • Tests reported

    657

    6th of 22 by tests

    Washington
    657
    Salt Lake
    9,658

    Reported to CDC before any fix, 2023

  • EPA radon zone

    Zone 2

    Moderate potential

    1. 1
    2. Zone 2
    3. 3

    1 highest, 3 lowest

    EPA predicts 2 to 4 pCi/L indoors

  • Rank in Utah

    22 of 22

    Lowest quarter

    Washington
    9.9%
    Beaver
    66.7%

    By share, of 22 with 30+ tests

Read a result for Washington County

Starts at Washington County's median, 1.3 pCi/L

1.3pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 1.3 pCi/L

Below 2 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 4 and aboveEPA says fix it

This result is below 2 pCi/L, the level at which EPA says a fix should be considered. Washington County's median reported result, 2023.

Interpret this reading

The data

Washington County, At a glance

Washington County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Washington County is a county: EPA's forecast for it as a whole is an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³). It describes no single address, and homes above EPA's are found in every zone, this one included.

USGS geologic potential: Moderate across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Washington County, 2023

Share of reported tests at or above 4 pCi/L, by year, Washington County
Share of reported tests at or above 4 pCi/L, by year, Washington County
YearShare of reported tests at or above 4 pCi/L
20144.5%
201511.6%
201617.8%
201713.2%
20186.0%
20199.1%
202013.6%
20217.2%
20229.4%
20239.9%

2023: 9.9%. Across these years the share ran from 4.5% to 17.8%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 657 tests reported to CDC for Washington County over 2023, many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.

Measured: CDC tracking data. Figure above: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).

How to read these figures

Washington County, Compared

Washington County radon figures, compared

Calculated by Radon411

Washington County reports fewer high tests than Utah overall. 9.9% of its 657 tests in 2023 were at or above 4 pCi/L. That is 26.2 points below the 36.1% pooled from 29 Utah counties.

Ordered from highest share down, it comes 22nd of 22 Utah counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 33.4%; Washington County sits 23.5 points below it.

Iron County, the one bordering county with a figure for the same period, reported 21.1%. The reported tests do not follow EPA's Zone 2 label for Washington County (predicted average between 2 and 4 pCi/L): 9.9% of them reached 4 pCi/L, fewer than that label suggests.

Half the tests came in under 1.3 pCi/L and half over it; the single highest reached 22.8 pCi/L. The rest split 69.3% under 2 pCi/L and 20.9% from 2 to 4 (Utah: 35.4% and 28.5%). Year by year, 2014 opened at 4.5% and 2023 closed at 9.9% (up 5.4 points), with 2016 the high at 17.8%.

The busiest year on file was 2022, with 924 tests reported; the quietest, 2019, had 22.

Share of reported tests at or above 4 pCi/L by year, Washington County against Utah2014 to 2023, years with 30 or more tests: Washington County 4.5% to 9.9%, the state's pooled share 36.1% in 2023.
Washington CountyUtah, pooled
Share of reported tests at or above 4 pCi/L by year, Washington County against Utah: data table
YearTestsWashington County, at or above 4 pCi/LUtah, pooled
2014444.5%43.4%
20159511.6%42.3%
201613517.8%39.8%
20176813.2%38.2%
2018846.0%36.6%
20205913.6%37.6%
20211527.2%34.2%
20229249.4%37.7%
20236579.9%36.1%
Washington County against Utah, the United States and nearby counties, 2023
AreaTestsAt or above 4 pCi/LMedianDifference from Washington County
Washington County6579.9%1.3 pCi/LThis county
Utah, pooled29 counties, pooled27,42236.1%Not pooled+26.2 points
United States, pooled642 counties, pooled128,74033.4%Not pooled+23.5 points
Beaver Countyhighest in the state4266.7%9.3 pCi/L+56.8 points
Carbon Countylowest in the state6923.2%2.3 pCi/L+13.3 points
Iron County, UTborders it21321.1%2.1 pCi/L+11.2 points
Kane County, UTborders it1915.8%1.8 pCi/L+5.9 points
Where Washington County's reported results fell, 2023, beside Utah and the United States
ResultWashington County testsWashington County shareUtah shareU.S. shareAgainst Utah
Under 2 pCi/L45569.3%35.4%41.4%+33.9 points
2 to 4 pCi/L13720.9%28.5%25.2%−7.6 points
4 pCi/L and above659.9%36.1%33.4%−26.2 points
Washington County ranked among the 22 Utah counties with 30 or more tests, by share at or above 4 pCi/L, 2023
CountyRankTestsAt or above 4 pCi/LMedian
Utah County12 of 227,83340.6%3.2 pCi/L
Duchesne County13 of 228139.5%3.2 pCi/L
Emery County14 of 223938.5%2.7 pCi/L
Salt Lake County15 of 229,65833.1%2.6 pCi/L
Summit County16 of 2241732.6%2.4 pCi/L
Weber County17 of 221,66928.6%2.1 pCi/L
Davis County18 of 223,59428.4%2.4 pCi/L
Grand County19 of 224623.9%1.9 pCi/L
Carbon County20 of 226923.2%2.3 pCi/L
Iron County21 of 2221321.1%2.1 pCi/L
Washington County22 of 226579.9%1.3 pCi/L
Washington County radon tests by year, against Utah's pooled share
YearTestsAt or above 4 pCi/LMedianHighestUtah, pooledChange from the row before
20236579.9%1.3 pCi/L22.8 pCi/L36.1%+0.5 points
20229249.4%1.4 pCi/L17.9 pCi/L37.7%+2.2 points
20211527.2%0.2 pCi/L10.4 pCi/L34.2%−6.4 points
20205913.6%1.3 pCi/L18.0 pCi/L37.6%+4.5 points
2019229.1%1.3 pCi/L5.7 pCi/L37.7%+3.1 points
2018846.0%1.5 pCi/L13.9 pCi/L36.6%−7.2 points
20176813.2%1.3 pCi/L9.5 pCi/L38.2%−4.6 points
201613517.8%1.5 pCi/L24.8 pCi/L39.8%+6.2 points
20159511.6%1.5 pCi/L14.5 pCi/L42.3%+7.1 points
2014444.5%2.0 pCi/L5.9 pCi/L43.4%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period.

Washington County, Geology

The ground under Washington County

Predicted

Most of the ground under Washington County is one class on USGS's geologic map: 99.7% of its land is moderate radon potential, with 0.3% low. The map puts 68.7% of Washington County in the area it calls Colorado Plateau and 28.6% in Basin and Range, with one smaller area beside them. USGS gives the first a radon index of 9 and the second 11, both in the moderate band (9 to 11).

USGS's geologic areas under Washington County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Colorado PlateauPaleozoic and Mesozoic sandstone, shale, limestone.Moderate968.7%
Basin and RangeQuaternary sedimentary and igneous rocks.Moderate1128.6%
Colorado PlateauPaleozoic sadstone, shale, and limestones, some Precambrian gneiss, metasedimentary rocks, granites.Moderate92.0%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Washington County beside the ground around it

Across Utah 32.8% of the land is rated high; none of Washington County's is. Of the 4 counties that border it, 3 have more high-potential ground, Iron County the most at 36.3%.

Share of land by USGS radon potential: Washington County, the 4 counties bordering it and Utah
AreaEPA zoneLow potentialModerate potentialHigh potential
Washington CountyZone 20.3%99.7%None
Iron CountyZone 2None63.7%36.3%
Lincoln County, NVZone 19.2%63.7%27.1%
Kane CountyZone 2None96.3%3.7%
Mohave County, AZZone 256.5%43.5%None
Utah29 counties, pooled by land areaVariesNone67.2%32.8%

The map rates the ground, not the air in any home.

Local help

Washington County, Local resources

Radon testing and mitigation in Washington County

What Utah's program says
Phone
(801) 536-0091
Disclosure when a home is sold or rented
Utah requires that sellers disclose "Hazardous Conditions: Are there any hazardous conditions on the Property such as Radon gas in house or well?"

What it means

Washington County, Questions

Questions about radon in Washington County

Are radon levels high in Washington County?

In 2023, 9.9% of the radon tests reported to CDC for Washington County, Utah were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.3 pCi/L. Of 22 Utah counties with 30 or more tests for the same period, 21 reported a higher share; pooled, the state comes to 36.1%.

Which counties border Washington County?

Washington County borders 4 counties: Iron County, UT, Lincoln County, NV, Kane County, UT and Mohave County, AZ.

Products

Washington County, Products

Testing a home in Washington County

In Washington County, 9.9% of 657 tests reported to CDC in 2023 reached 4 pCi/L, against 36.1% pooled across Utah. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Washington County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Washington County homes, compared

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Washington County, Bordering counties

Counties bordering Washington County

Calculated by Radon411

Washington County, Cities and towns

Cities and towns in Washington County

Washington County is growing: the Census Bureau puts it at 213,670 residents on July 1, 2025, up 17.4% from 182,002 in 2020. That works out to 88 people per square mile of land. St. George alone is home to 108,713 of them, 50.9% of the total. Together its 15 incorporated places hold 96.3% of those residents; the other 3.7% live outside any of them. Reported testing is thin here: 657 tests over 2023, or 3.1 for every 1,000 residents (2025 estimate), where Utah as a whole comes to 7.7.

From St. George to Rockville, CDC publishes no figure by town: each reads Washington County's.

The 12 largest cities and towns in Washington County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
St. George108,713+13.2%50.9%
Washington37,107+29.6%17.4%
Hurricane25,745+27.3%12.0%
Ivins11,546+27.2%5.4%
Santa Clara8,722+14.7%4.1%
La Verkin4,515+3.9%2.1%
Enterprise2,445+19.2%1.1%
Toquerville1,999+6.2%0.9%
Hildale1,319+14.6%0.6%
Apple Valley951+10.1%0.4%
Leeds857−0.8%0.4%
Virgin714+6.9%0.3%
  • Springdale
  • New Harmony
  • Rockville

15 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).

Washington County, Homes

Homes in Washington County

Of Washington County's 78,993 homes, 74% are detached houses, against 67% across Utah; 9% are in buildings of five or more homes. Much of Washington County is recent building: 55% of its homes have gone up since 2000 and the middle year built is 2002, against 1991 for Utah. 73% of occupied homes are lived in by their owner (Utah: 71%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Washington County, Utah, 2019 to 2023
HomesWashington CountyUtah
Housing units78,9931,193,082
Detached houses74%67%
In buildings of 5 or more9%16%
Mobile homes4%3%
Built before 19603%16%
Built since 200055%37%
Middle year built20021991
Owner-occupied73%71%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.