Oregon has meaningful radon risk, with approximately 30% of Oregon homes estimated to have levels above the EPA action level of 4.0 pCi/L. The state’s geology — including uranium-bearing volcanic rock in the Cascade Range, granitic basement rock in the Klamath Mountains of southwestern Oregon, and sedimentary formations in the Willamette Valley — creates radon potential across significant portions of the state. The Health Authority Radiation Protection Services administers radon program resources for Oregon residents.
EPA Radon Zone Designation
Zone 1 in portions of the Cascade Range and southern Oregon, Zone 2 across much of western Oregon, Zone 1-2 in central and eastern Oregon.
Highest-Radon Areas in Oregon
The Portland metropolitan area (Multnomah, Washington, Clackamas counties) is Zone 2 with meaningful radon risk. Southern Oregon counties overlying Klamath Mountain and Cascade geology — Josephine, Jackson, Klamath, and Lake counties — are Zone 1. Central Oregon counties including Deschutes (Bend area) and Jefferson show elevated levels.
Radon Contractor Requirements in Oregon
NRPP or NRSB national certification. Oregon has no separate state radon licensing statute. The Health Authority Radiation Protection Services maintains radon program resources. Verify contractor credentials at nrpp.info or nrsb.org before engaging any radon professional for measurement or mitigation work.
Radon Disclosure in Oregon
Oregon’s property disclosure law requires sellers to disclose known material defects. Known elevated radon conditions are material information. Radon testing is common in Oregon real estate transactions, particularly in southern Oregon and the Portland metro area.
Testing Resources for Oregon Residents
Contact the Health Authority Radiation Protection Services for the most current list of certified radon professionals, any available test kit programs, and jurisdiction-specific requirements that may have been updated since this page was last reviewed. The national NRPP contractor directory (nrpp.info) is searchable by zip code and provides real-time certification verification.
Frequently Asked Questions
Is the Portland area high in radon?
The Portland metro area (Multnomah, Washington, Clackamas counties) is Zone 2 with meaningful radon risk. Testing is recommended for all Portland metro homes, particularly those with basements.
Does Oregon require radon contractor licensing?
NRPP or NRSB national certification is required. No separate Oregon licensing statute. Verify credentials at nrpp.info or nrsb.org.
What parts of Oregon have the highest radon?
Southern Oregon counties — Josephine, Jackson, Klamath, Lake — overlying Klamath Mountain and Cascade geology have the highest potential. Central Oregon (Deschutes/Bend area) also shows elevated levels. Portland metro is Zone 2 with meaningful risk.
Southern Oregon Radon: Klamath Mountains and Cascades
Southern Oregon has the state’s highest radon concentrations. Josephine County (Grants Pass) and Jackson County (Medford, Ashland) overlie the Klamath Mountains — ancient ocean crust and island arc geology with elevated heavy mineral content including uranium-bearing formations. Douglas County (Roseburg) is at the transition between the Klamath Mountains and the Cascades. Klamath County (Klamath Falls) and Lake County in south-central Oregon also show significant radon levels from volcanic and basement rock geology. Southern Oregon homebuyers should treat radon testing as mandatory.
Portland Metro and Willamette Valley Radon
The Portland metropolitan area — Multnomah, Washington, Clackamas, and Clark (Washington state) counties — is Zone 2 with moderate radon risk. The Willamette Valley’s primarily sedimentary geology creates lower radon conditions than southern Oregon or the Cascade foothills, but Zone 2 still represents meaningful risk. Washington County (Beaverton, Hillsboro) shows slightly higher levels than downtown Portland due to proximity to Tualatin Mountains geology. Clackamas County (Lake Oswego, Oregon City) at the valley edge shows Zone 1 to Zone 2 transition. Hood River County (Columbia Gorge area) and The Dalles (Wasco County) show elevated levels from Columbia River Basalt formations.
Oregon Testing Resources
The Oregon Health Authority (OHA) Radiation Protection Services administers the state radon program. OHA provides certified contractor information, county-level radon survey data, and educational materials. Oregon participates in EPA’s SIRG program. Contact OHA for the current certified contractor list and test kit guidance. The Oregon Geological Survey has published radon potential maps providing sub-county geological risk information for homeowners seeking more precise local context.
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