Radon levels in Arizona: Low
The model predicts a population-weighted basement average of 1.7 pCi/L (model estimate) across Arizona's 15 counties - close to the US average of 1.8 pCi/L. Above-ground floors average 1.0 pCi/L.
Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. How the numbers work.
0 / 15
EPA Zone 1 counties (0%)
15 / 0
Zone 2 / Zone 3 counties
0
counties predicted ≥ 4 pCi/L
0%
of ZIP codes predicted ≥ 4 pCi/L
Test Arizona once anyway - radon varies house to house
The predicted basement average here is 1.7 pCi/L, below the EPA's 2 pCi/L "consider fixing" threshold. That's good news for the area - but the EPA still recommends every home be tested, because foundation cracks, soil pockets and ventilation make one house very different from its neighbor. One inexpensive kit settles it.
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What the data says about radon in Arizona
According to the EPA zone map, 0 of Arizona's 15 counties are EPA Zone 1 (0%), 15 are Zone 2 and 0 are Zone 3. Zone 2 (predicted screening average of 2-4 pCi/L) is the most common designation. Treat the map as a coarse prior: it predates two decades of test data and never replaces a test in your own home.
The 2001-2021 national model predicts a population-weighted basement average of 1.7 pCi/L for Arizona (low range, close to the US average of 1.8). Of the 15 counties with predictions, 0 are predicted at or above 4 pCi/L, 6 in the 2-4 band and 9 below 2. The county range is narrow: from Yuma County at 1.46 to Coconino County at 2.28 pCi/L, a spread of only 0.82.
26.9% of the state's modeled ZIP codes are predicted at or above 2 pCi/L, and 0% at or above the 4 pCi/L action level - below the national shares of 4.2% and 48.7%. No ZIP in the state is predicted above 4 on average - but averages hide individual homes, which is why the EPA still asks everyone to test.
Arizona counties by predicted radon
Sorted highest to lowest predicted basement average (model estimate). 15 counties.
| County | Predicted basement | Upstairs | Grade | EPA zone | ZIPs |
|---|---|---|---|---|---|
| Coconino County | 2.3 pCi/L | 1.8 | Moderate | EPA Zone 2 | 17 |
| Navajo County | 2.3 pCi/L | 1.4 | Moderate | EPA Zone 2 | 17 |
| Gila County | 2.3 pCi/L | 1.5 | Moderate | EPA Zone 2 | 8 |
| Graham County | 2.2 pCi/L | 1.3 | Moderate | EPA Zone 2 | 6 |
| Apache County | 2.1 pCi/L | 1.2 | Moderate | EPA Zone 2 | 14 |
| Yavapai County | 2.1 pCi/L | 1.4 | Moderate | EPA Zone 2 | 25 |
| Greenlee County | 2.0 pCi/L | 1.2 | Low | EPA Zone 2 | 4 |
| Santa Cruz County | 2.0 pCi/L | 1.1 | Low | EPA Zone 2 | 7 |
| Cochise County | 1.9 pCi/L | 1.0 | Low | EPA Zone 2 | 16 |
| Pinal County | 1.7 pCi/L | 0.9 | Low | EPA Zone 2 | 25 |
| Pima County | 1.7 pCi/L | 0.8 | Low | EPA Zone 2 | 40 |
| Mohave County | 1.7 pCi/L | 0.9 | Low | EPA Zone 2 | 18 |
| Maricopa County | 1.7 pCi/L | 0.9 | Low | EPA Zone 2 | 129 |
| La Paz County | 1.7 pCi/L | 0.8 | Low | EPA Zone 2 | 5 |
| Yuma County | 1.5 pCi/L | 0.8 | Low | EPA Zone 2 | 7 |
Radon levels in Arizona cities
The 27 most-populous Arizona places among the 1,000 largest US cities (Census incorporated places and CDPs), by population. City figures are ZIP-land-weighted means of the model's ZIP predictions (model estimate).
| City | Population | Predicted basement | Upstairs | Grade | ZIPs ≥ 4 |
|---|---|---|---|---|---|
| Phoenix | 1,650,070 | 1.7 pCi/L | 0.9 | Low | 0% |
| Tucson | 547,239 | 1.7 pCi/L | 0.8 | Low | 0% |
| Mesa | 511,648 | 1.7 pCi/L | 0.9 | Low | 0% |
| Chandler | 280,167 | 1.6 pCi/L | 1.0 | Low | 0% |
| Gilbert | 275,411 | 1.7 pCi/L | 1.1 | Low | 0% |
| Glendale | 253,855 | 1.7 pCi/L | 0.9 | Low | 0% |
| Scottsdale | 244,394 | 1.8 pCi/L | 1.8 | Low | 0% |
| Peoria | 198,750 | 1.8 pCi/L | 1.2 | Low | 0% |
| Tempe | 189,834 | 1.6 pCi/L | 0.8 | Low | 0% |
| Surprise | 158,285 | 1.9 pCi/L | 1.1 | Low | 0% |
| Goodyear | 111,805 | 1.8 pCi/L | 1.1 | Low | 0% |
| Buckeye | 108,909 | 1.8 pCi/L | 1.0 | Low | 0% |
| Yuma | 100,858 | 1.6 pCi/L | 0.9 | Low | 0% |
| Avondale | 93,545 | 1.7 pCi/L | 1.0 | Low | 0% |
| San Tan Valley | 81,321 | 1.7 pCi/L | 1.0 | Low | 0% |
| Flagstaff | 76,586 | 2.4 pCi/L | 2.2 | Moderate | 0% |
| Queen Creek | 76,570 | 1.7 pCi/L | 0.9 | Low | 0% |
| Maricopa | 71,022 | 1.8 pCi/L | 1.1 | Low | 0% |
| Casas Adobes | 66,795 | 1.8 pCi/L | 0.9 | Low | 0% |
| Casa Grande | 63,743 | 1.9 pCi/L | 0.9 | Low | 0% |
| Lake Havasu City | 59,257 | 1.8 pCi/L | 0.9 | Low | 0% |
| Marana | 58,430 | 1.8 pCi/L | 1.0 | Low | 0% |
| Catalina Foothills | 50,796 | 1.7 pCi/L | 1.0 | Low | 0% |
| Prescott Valley | 50,045 | 2.1 pCi/L | 1.4 | Moderate | 0% |
| Oro Valley | 48,311 | 1.8 pCi/L | 1.1 | Low | 0% |
| Prescott | 47,757 | 2.1 pCi/L | 1.5 | Moderate | 0% |
| Sierra Vista | 44,431 | 1.9 pCi/L | 0.9 | Low | 0% |
Highest-radon ZIP codes in Arizona
The 10 Arizona ZIP codes with the highest predicted basement average (model estimate), out of 338 modeled. A ZIP average is still an area figure - neighboring homes routinely test several pCi/L apart.
| ZIP | County | Predicted basement | Upstairs | Grade |
|---|---|---|---|---|
| 85929 | Navajo County | 2.5 pCi/L | 1.7 | Moderate |
| 85938 | Apache County | 2.5 pCi/L | 1.7 | Moderate |
| 85935 | Navajo County | 2.5 pCi/L | 1.7 | Moderate |
| 86001 | Coconino County | 2.5 pCi/L | 2.4 | Moderate |
| 85542 | Graham County | 2.5 pCi/L | 1.3 | Moderate |
| 86046 | Coconino County | 2.5 pCi/L | 1.8 | Moderate |
| 85933 | Navajo County | 2.4 pCi/L | 1.5 | Moderate |
| 85941 | Gila County | 2.4 pCi/L | 1.7 | Moderate |
| 86510 | Navajo County | 2.4 pCi/L | 1.4 | Moderate |
| 85901 | Navajo County | 2.4 pCi/L | 1.6 | Moderate |
Arizona radon questions
- Is radon high in Arizona?
- Arizona's population-weighted predicted basement average is 1.7 pCi/L, close to the US average of 1.8. 0 of its 15 modeled counties are predicted at or above the EPA action level of 4 pCi/L, 6 are in the 2-4 "consider fixing" range and 9 are below 2. 0% of Arizona ZIP codes are predicted at 4 or higher.
- Which Arizona county has the highest radon?
- Coconino County has the highest predicted basement average in Arizona at 2.3 pCi/L (EPA Zone 2). The lowest is Yuma County at 1.5 pCi/L. These are area figures; individual homes in any county can test far higher.
- How many EPA Zone 1 counties are in Arizona?
- 0 of Arizona's 15 counties (0%) are EPA Zone 1 (highest potential), 15 are Zone 2 and 0 are Zone 3. The EPA zone map dates from 1993; the predicted values on this page come from a 2001-2021 model built on millions of actual tests, so the two can disagree for a given county.
- Should I test for radon in Arizona?
- Yes. Even though Arizona's predicted average is below 2 pCi/L, the EPA recommends every home be tested - radon varies house to house, and 26.9% of Arizona ZIP codes are still predicted at 2 pCi/L or higher.
Arizona radon program
Arizona's radon program page is at www.azdhs.gov; it lists testing and certified-mitigator guidance for the state. The EPA also keeps a directory of every state radon contact: EPA state radon contacts page. Then read how to test and what mitigation costs.