Radon · Washington
Radon in Washington
Radon (EPA Radon Zones) data for ZIP codes in Washington. Pick a ZIP below to dive into the radon summary.
Last verified 2026-06-10 · methodology
What lands here
Pages show the county zone, what the classification means for home testing recommendations, and state-level supplementary data where available.
Source & refresh
EPA Radon Zones. Refreshed static 1993 baseline plus state-level supplementary updates. Primary source →
Washington top concern
Wildfire (eastern), Cascadia seismic, coastal flood
Washington's wildfire risk concentrates in eastern WA + the Cascades. Cascadia subduction zone shapes long-term seismic risk. Puget Sound coastal flood zones face Risk Rating 2.0 pressure. Seattle has documented LCRR lead-service-line obligations.
See Washington state page for the full state-level rollup across all 12 dimensions.
Read more on radon
Editorial deep-dives explaining the source data, its limits, and how to read it.
EPA Radon Zones — what 1, 2, and 3 mean and when you should test
EPA classifies every US county into Zone 1 (high), Zone 2 (moderate), or Zone 3 (low) for radon. Plain-English guide to the classifications and at-home testing.
EPA SDWIS — how to read drinking-water violations and what they actually mean
Plain-English guide to EPA SDWIS drinking-water violations: health-based vs. monitoring vs. reporting violations, MCLs, and what triggers a public notice.
Radon and real estate — what disclosure laws and home tests actually require
What home sellers must disclose about radon by state, when home tests are required, and how to interpret radon-mitigation systems if a home you're buying has one.
Radon disclosure during real-estate transactions — state-by-state
Whether sellers must disclose known radon results varies by state. Quick map of mandatory-disclosure states + what to ask for during inspection.
11 Washington ZIPs
ZIP 98101
Seattle, WA
Radon →
ZIP 98109
Seattle (Queen Anne), WA
Radon →
ZIP 98033
Kirkland, WA
Radon →
ZIP 99201
Spokane, WA
Radon →
ZIP 98225
Bellingham, WA
Radon →
ZIP 98115
Seattle (Wallingford), WA
Radon →
ZIP 98662
Vancouver (WA), WA
Radon →
ZIP 98052
Redmond (WA), WA
Radon →
ZIP 98039
Medina (WA), WA
Radon →
ZIP 98004
Bellevue (WA), WA
Radon →
ZIP 98112
Seattle (Capitol Hill), WA
Radon →