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Radon Levels in Pima County, Arizona

EPA puts Pima County in Zone 2, its middle radon zone, and most reported tests there come back low, though 6.8% of 410 (2008 to 2017, laboratory totals) reached 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

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  • Share at 4+ pCi/L

    6.8%

    10.0 pts below AZ

    Pima
    6.8%
    Arizona
    16.8%

    410 tests, 2008 to 2017

  • Median result

    1.1pCi/L

    Below action level

    Pima
    1.1 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    410

    2nd of 6 by tests

    Pima
    410
    Maricopa
    2,393

    Reported to CDC before any fix, 2008 to 2017

  • 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 Arizona

    5 of 6

    Middle half

    Pima
    6.8%
    Coconino
    30.0%

    By share, of 6 with 30+ tests

Read a result for Pima County

Starts at Pima County's median, 1.1 pCi/L

1.1pCi/L

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

EPA’s reading of 1.1 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. Pima County's median reported result, 2008 to 2017.

Interpret this reading

The data

Pima County, At a glance

Pima County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Pima 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: Low across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Pima County, 2008 to 2017, laboratory

Reported results by concentration band, Pima County, 2008 to 2017, laboratory
Under 2 pCi/L: 78%2 to 4 pCi/L: 15%4 pCi/L and above: 7%

Of 410 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Pima County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L32178.3%
2 to 4 pCi/L6114.9%
4 pCi/L and above286.8%
What these figures count

These are the 410 tests reported to CDC for Pima County over 2008 to 2017 (laboratory totals), 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: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).

How to read these figures

Pima County, Compared

Pima County radon figures, compared

Calculated by Radon411

Pima County reports fewer high tests than Arizona overall. 6.8% of its 410 tests over the 2008 to 2017 laboratory totals were at or above 4 pCi/L. That is 10.0 points below the 16.8% pooled from 13 Arizona counties.

Ordered from highest share down, it comes 5th of 6 Arizona counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 35.7%; Pima County sits 28.9 points below it.

Next door, the shares run from 8.9% in Pinal County to 17.4% in Maricopa County. The reported tests do not follow EPA's Zone 2 label for Pima County (predicted average between 2 and 4 pCi/L): 6.8% of them reached 4 pCi/L, fewer than that label suggests.

Half the tests came in under 1.1 pCi/L and half over it; the single highest reached 21.7 pCi/L. The rest split 78.3% under 2 pCi/L and 14.9% from 2 to 4 (Arizona: 60.1% and 23.2%).

CDC's ten-year totals for Pima County went from 336 tests (2005 to 2014) to 410 (2008 to 2017), the share going from 5.7% to 6.8%.

Pima County against Arizona, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Pima County
Pima County4106.8%1.1 pCi/LThis county
Arizona, pooled13 counties, pooled3,58916.8%Not pooled+10.0 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+28.9 points
Coconino Countyhighest in the state27330.0%2.3 pCi/L+23.2 points
Mohave Countylowest in the state494.1%0.2 pCi/L−2.7 points
Graham County, AZborders it1136.4%3.0 pCi/L+29.6 points
Cochise County, AZborders it2626.9%2.8 pCi/L+20.1 points
Maricopa County, AZborders it2,39317.4%1.6 pCi/L+10.6 points
Pinal County, AZborders it1018.9%0.9 pCi/L+2.1 points
Santa Cruz County, AZborders it60.0%1.7 pCi/L−6.8 points
Yuma County, AZborders it180.0%0.6 pCi/L−6.8 points
Where Pima County's reported results fell, 2008 to 2017, laboratory, beside Arizona and the United States
ResultPima County testsPima County shareArizona shareU.S. shareAgainst Arizona
Under 2 pCi/L32178.3%60.1%39.6%+18.2 points
2 to 4 pCi/L6114.9%23.2%24.7%−8.3 points
4 pCi/L and above286.8%16.8%35.7%−10.0 points
Pima County ranked among the 6 Arizona counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Coconino County1 of 627330.0%2.3 pCi/L
Maricopa County2 of 62,39317.4%1.6 pCi/L
Yavapai County3 of 626516.2%1.6 pCi/L
Pinal County4 of 61018.9%0.9 pCi/L
Pima County5 of 64106.8%1.1 pCi/L
Mohave County6 of 6494.1%0.2 pCi/L
Pima County ten-year laboratory totals, against Arizona's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestArizona, pooledChange from the row before
2008 to 20174106.8%1.1 pCi/L21.7 pCi/L16.8%+0.5 points
2007 to 20163956.3%1.1 pCi/L21.7 pCi/L16.5%−0.3 points
2006 to 20153806.6%1.1 pCi/L21.7 pCi/L17.6%+0.9 points
2005 to 20143365.7%1.1 pCi/L21.7 pCi/L17.4%First on file

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

Pima County, Geology

The ground under Pima County

Predicted

USGS's geologic map puts all of Pima County's mapped land in one class: low radon potential. All of it lies in the area the map calls Basin and Range/Sonoran Desert, to which USGS gives a radon index of 8, in the low band (5 to 8).

USGS's geologic areas under Pima County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Basin and Range/Sonoran DesertQuaternary to Tertiary sediments, with uranium-bearing Tertiary volcanic rocks, highly variable volcanic, metamorphic, and sedimentary rocks, and eolian depositsLow8100%

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

Pima County beside the ground around it

Across Arizona 0.1% of the land is rated high; none of Pima County's is. Of the 6 counties that border it, 4 have more moderate-potential ground, Graham County the most at 70.4%.

Share of land by USGS radon potential: Pima County, the 6 counties bordering it and Arizona
AreaEPA zoneLow potentialModerate potentialHigh potential
Pima CountyZone 2100%NoneNone
Santa Cruz CountyZone 2100%NoneNone
Pinal CountyZone 284.9%15.1%None
Cochise CountyZone 299.7%0.3%None
Maricopa CountyZone 284.1%15.9%None
Graham CountyZone 229.6%70.4%None
Yuma CountyZone 299.9%NoneNone
Arizona15 counties, pooled by land areaVaries42.8%57.1%0.1%

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

Local help

Pima County, Local resources

Radon testing and mitigation in Pima County

What it means

Pima County, Questions

Questions about radon in Pima County

Are radon levels high in Pima County?

Over the 2008 to 2017 laboratory totals, 6.8% of the radon tests reported to CDC for Pima County, Arizona were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.1 pCi/L. Of 6 Arizona counties with 30 or more tests for the same period, 4 reported a higher share; pooled, the state comes to 16.8%.

Which counties border Pima County?

Pima County borders 6 counties: Santa Cruz County, Pinal County, Cochise County, Maricopa County, Graham County and Yuma County.

Products

Pima County, Products

Testing a home in Pima County

In Pima County, 6.8% of 410 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 16.8% pooled across Arizona. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Pima County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Pima County homes, compared

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Pima County, Bordering counties

Counties bordering Pima County

Calculated by Radon411

Pima County, Cities and towns

Cities and towns in Pima County

The Census Bureau estimates 1,074,685 residents in Pima County for July 1, 2025, 29,440 more than in 2020 (+2.8%). That works out to 117 people per square mile of land. Tucson alone is home to 548,371 of them, 51.0% of the total. CDC's 410 reported tests for 2008 to 2017 work out to 0.4 per 1,000 residents (2025 estimate), close to Arizona's 0.5.

From Tucson to South Tucson, CDC publishes no figure by town: each reads Pima County's.

The cities and towns in Pima County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Tucson548,371+1.1%51.0%
Maranaextends beyond Pima County65,523+24.5%Counted whole
Oro Valley48,085+1.8%4.5%
Sahuarita37,694+9.7%3.5%
South Tucson4,452−3.6%0.4%

5 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). A place that extends beyond Pima County is counted whole, so it has no share.

Pima County, Homes

Homes in Pima County

Of Pima County's 475,378 homes, 60% are detached houses, against 64% across Arizona; 18% are in buildings of five or more homes. Half of its homes were built before 1986, close to Arizona's 1992: 13% date from before 1960 and 27% from 2000 or later. 65% of occupied homes are lived in by their owner (Arizona: 67%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Pima County, Arizona, 2019 to 2023
HomesPima CountyArizona
Housing units475,3783,142,443
Detached houses60%64%
In buildings of 5 or more18%16%
Mobile homes10%10%
Built before 196013%8%
Built since 200027%35%
Middle year built19861992
Owner-occupied65%67%

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