Skip to content
RADON411

Locations and reports

Radon in Phoenix, Arizona

EPA puts Maricopa County, where Phoenix is, in Zone 2, its middle radon zone, and 17.4% of its 2,393 reported radon tests (2008 to 2017, laboratory totals) were at or above 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

    17.4%

    0.6 pts above AZ

    Maricopa
    17.4%
    Arizona
    16.8%

    Maricopa, 2nd of 6 in AZ, 2008 to 2017

  • Median result

    1.6pCi/L

    Below action level

    Maricopa
    1.6 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of Maricopa's tests, 2008 to 2017

  • Nearest county

    8.9%

    Pinal, 63 miles

    Pinal
    8.9%
    Maricopa
    17.4%

    101 tests, 2008 to 2017

  • EPA radon zone

    Zone 2

    Moderate potential

    1. 1
    2. Zone 2
    3. 3

    1 highest, 3 lowest

    Maricopa, where Phoenix is

  • Tests reported

    2,393

    In Maricopa

    Maricopa
    2,393
    Pinal
    101

    Reported to CDC before any fix, 2008 to 2017

Read a result for Phoenix

Starts at Maricopa County's median, 1.6 pCi/L

1.6pCi/L

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

EPA’s reading of 1.6 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. Maricopa County's median reported result, 2008 to 2017.

Interpret this reading

The data

Phoenix, What is published

What is published for Phoenix

Information:

Every figure for Phoenix is a county's

Radon data is published by county, not by city, so for Phoenix it is Maricopa County's: its EPA zone (Zone 2) and the 2,393 tests reported to CDC for 2008 to 2017, laboratory. Only a test tells you about one home.

Phoenix covers 518 square miles of land, all of it in Maricopa County. About 1,665,481 people live there, 3,215 to the square mile.

Phoenix, Counties

The county Phoenix lies in

Measured

Maricopa County's EPA zone and the figures CDC publishes for it, 2008 to 2017, laboratory.

Maricopa CountyZone 2Moderate predicted potential

17.4%
Reported tests at or above 4 pCi/L
1.6 pCi/L
Median reported result
2,393 tests
Tests reported to CDC
None
Yearly figures on file

Maricopa County ranks 2nd of 6 Arizona counties with 30 or more tests for that period, 0.6 points above the 16.8% pooled across Arizona's counties, 18.3 points below the national pool of 35.7%.

Measured from the middle of Phoenix, the nearest counties with a CDC figure for 2008 to 2017, laboratory are Pinal County (63 miles, 8.9% of 101 tests), Yavapai County (76 miles, 16.2% of 265 tests) and Pima County (103 miles, 6.8% of 410 tests). Across the 5 nearest, the share at or above 4 pCi/L runs from 4.1% to 30.0%; the farthest of them, Mohave County, is 175 miles away at 4.1%.

No business in the directory gives Phoenix as its address; the Arizona list covers it. Arizona's other cities with a page of their own: Tucson and Scottsdale.

The counties around Phoenix

By distance from the middle of Phoenix; counties with 30 or more tests.

Nearest counties to Phoenix with 30 or more tests
CountyDistanceTestsAt or above 4 pCi/LMedian
Pinal County63 mi1018.9%0.9 pCi/L
Yavapai County76 mi26516.2%1.6 pCi/L
Pima County103 mi4106.8%1.1 pCi/L
Coconino County157 mi27330.0%2.3 pCi/L
Mohave County175 mi494.1%0.2 pCi/L

Predicted: EPA Map of Radon Zones, by county. Measured: CDC tracking data, by county, 2008 to 2017, laboratory.

Phoenix, Geology

The ground under Phoenix

Predicted

Most of the ground under Phoenix is one class on USGS's geologic map: 99.1% of its land is low radon potential, with 0.9% moderate. 99.1% 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 Phoenix
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 depositsLow899.1%
Transition ZonePrecambrian igneous, metamorphic and sedimentary rocks and Tertiary volcanic rocks.Moderate100.9%

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

Phoenix beside its county and Arizona

Maricopa County as a whole has more moderate-potential ground than Phoenix: 15.9% of the county against 0.9% of the city. Across Arizona 0.1% of the land is rated high; none of Phoenix's is.

Share of land by USGS radon potential: Phoenix, the county it lies in and Arizona
AreaEPA zoneLow potentialModerate potentialHigh potential
PhoenixBy county99.1%0.9%None
Maricopa CountyZone 284.1%15.9%None
Arizona15 counties, pooled by land areaVaries42.8%57.1%0.1%

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

Phoenix, Homes

Homes in Phoenix

Of Phoenix's 642,867 homes, 60% are detached houses, against 64% across Maricopa County; 26% are in buildings of five or more homes. The homes are older than Maricopa County's as a whole: half were built before 1984 (1992 for Maricopa County), and 14% date from before 1960. 57% of occupied homes are lived in by their owner (Maricopa County: 65%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Phoenix, Maricopa County, Arizona, 2019 to 2023
HomesPhoenixMaricopa CountyArizona
Housing units642,8671,850,8623,142,443
Detached houses60%64%64%
In buildings of 5 or more26%20%16%
Mobile homes3%5%10%
Built before 196014%7%8%
Built since 200026%35%35%
Middle year built198419921992
Owner-occupied57%65%67%

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

Local help

Phoenix, Local resources

Local resources for Phoenix

Who to ask in Arizona: its radon program, test kits and professionals.

What it means

Phoenix, Questions

Questions about radon in Phoenix

What radon zone is Phoenix in?

EPA's map puts Maricopa County, and with it Phoenix, in Zone 2, the map's middle class: a predicted county average of 2 to 4 pCi/L.

What are radon levels in Phoenix?

Most tests near Phoenix come back under EPA's action level, but not all: 17.4% of Maricopa County's 2,393 tests for 2008 to 2017 (laboratory totals) were at or above 4 pCi/L. The median reported result was 1.6 pCi/L.

Should I test my home in Phoenix?

Yes. In Maricopa County, about one reported test in 6 reached 4 pCi/L. That is about what Arizona as a whole reports (16.8%), and ranks Maricopa County 2nd of the 6 Arizona counties with 30 or more tests. The number for one house comes only from testing it. How to test a home.

What ground is Phoenix built on, as far as radon goes?

USGS's geologic map puts all of Phoenix on one named area, "Basin and Range/Sonoran Desert", rated low for radon potential, radon index 8.

Is radon higher in the counties around Phoenix?

It depends which way you go. 1 of the 5 nearest counties with a figure report a larger share than Maricopa County's 17.4% and 4 a smaller one: from Mohave County (4.1%, 175 miles off) to Coconino County (30.0%, 157 miles off).

The answers use the published figures of Maricopa County, the county Phoenix lies in.

Explore