Radon and home risks by county
Radon in Arizona
Every county in Arizona is in EPA radon Zone 2 (moderate potential). Radon zones describe an area's potential; EPA recommends testing every home regardless of zone.
Zone 1 counties
0
high radon potential
Zone 2 counties
15
moderate potential
Zone 3 counties
0
low potential
Counties with water violations
15
since 2016; 7 with unresolved ones
Tap water reports for Arizona cities
Find your county by ZIP
Zone 2: moderate potential (15 counties)
| County | Residents | Water systems | Health violations since 2016 | Unresolved |
|---|---|---|---|---|
| Apache County | 64,800 | 18 | 18 | 0 |
| Cochise County | 125,773 | 53 | 66 | 0 |
| Coconino County | 145,161 | 38 | 27 | 0 |
| Gila County | 54,073 | 42 | 29 | 0 |
| Graham County | 40,242 | 7 | 5 | 0 |
| Greenlee County | 9,410 | 7 | 7 | 0 |
| La Paz County | 16,992 | 22 | 40 | 1 |
| Maricopa County | 4,673,096 | 100 | 43 | 1 |
| Mohave County | 226,479 | 59 | 68 | 1 |
| Navajo County | 109,516 | 42 | 20 | 2 |
| Pima County | 1,080,149 | 142 | 26 | 1 |
| Pinal County | 513,862 | 64 | 105 | 1 |
| Santa Cruz County | 50,508 | 17 | 6 | 0 |
| Yavapai County | 252,013 | 106 | 91 | 3 |
| Yuma County | 220,310 | 29 | 146 | 0 |
How to read this table
Water systems counts community systems that list the county in their service area; one system can serve several counties. Health violations are breaches of a legal limit or treatment rule recorded by EPA since January 2016, not paperwork lapses. A violation stays unresolved until the state records it as fixed.
Other states
- California
- Colorado
- Florida
- Idaho
- Illinois
- Iowa
- Michigan
- Minnesota
- New Jersey
- New York
- Ohio
- Pennsylvania
- Texas
- Utah
Sources: EPA Map of Radon Zones, EPA ECHO Safe Drinking Water Act data (2026Q3, published October 2026), US Census Bureau Vintage 2024 estimates. See the methodology.