Radon zones in Washington
| Adams County | Washington | 2 |
| Asotin County | Washington | 2 |
| Benton County | Washington | 2 |
| Chelan County | Washington | 3 |
| Clallam County | Washington | 3 |
| Clark County | Washington | 1 |
| Columbia County | Washington | 2 |
| Cowlitz County | Washington | 3 |
| Douglas County | Washington | 2 |
| Ferry County | Washington | 1 |
| Franklin County | Washington | 2 |
| Garfield County | Washington | 2 |
| Grant County | Washington | 2 |
| Grays Harbor County | Washington | 3 |
| Island County | Washington | 3 |
| Jefferson County | Washington | 3 |
| King County | Washington | 3 |
| Kitsap County | Washington | 3 |
| Kittitas County | Washington | 2 |
| Klickitat County | Washington | 2 |
| Lewis County | Washington | 3 |
| Lincoln County | Washington | 2 |
| Mason County | Washington | 3 |
| Okanogan County | Washington | 1 |
| Pacific County | Washington | 3 |
| Pend Oreille County | Washington | 1 |
| Pierce County | Washington | 3 |
| San Juan County | Washington | 3 |
| Skagit County | Washington | 3 |
| Skamania County | Washington | 1 |
| Snohomish County | Washington | 3 |
| Spokane County | Washington | 1 |
| Stevens County | Washington | 1 |
| Thurston County | Washington | 3 |
| Walla Walla County | Washington | 2 |
| Whatcom County | Washington | 3 |
| Whitman County | Washington | 2 |
| Yakima County | Washington | 2 |
Sources
- Washington: EPA Map of Radon Zones, US Environmental Protection Agency, checked 1 November 2026
- EPA Map of Radon Zones, US Environmental Protection Agency, checked 1 November 2026
- Washington: EPA Map of Radon Zones, US Environmental Protection Agency, checked 1 November 2026
- EPA Map of Radon Zones, US Environmental Protection Agency, checked 1 November 2026
- Washington: EPA Map of Radon Zones, US Environmental Protection Agency, checked 1 November 2026
- EPA Map of Radon Zones, US Environmental Protection Agency, checked 1 November 2026
- Washington: EPA Map of Radon Zones, US Environmental Protection Agency, checked 1 November 2026
- EPA Map of Radon Zones, US Environmental Protection Agency, checked 1 November 2026
- Washington: EPA Map of Radon Zones, US Environmental Protection Agency, checked 1 November 2026
- EPA Map of Radon Zones, US Environmental Protection Agency, checked 1 November 2026
- Washington: EPA Map of Radon Zones, US Environmental Protection Agency, checked 1 November 2026
- EPA Map of Radon Zones, US Environmental Protection Agency, checked 1 November 2026
"Secondary" marks a source used only because the official page could not be read.