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Spokane Radon Levels

Spokane County sits in EPA Radon Zone 1 and has more radon tests on record than any other Washington county. This page collects the public data, where it comes from, and what it can and can't tell you about a single home.

47.0%
of 18,518 Spokane County tests reported to the state, 1990–2020, at or above 4.0 pCi/L
40.4%
in the latest decade of state data, 2011–2020 (7,151 tests)
79.1%
the highest census-tract share, in ZIP 99212; the lowest is 9.8%, in 99001
5.3
tests per 1,000 housing units in 2018, about twice the rate in Stevens or Ferry County

Look up your area

Enter a zip code in our service area to see the county data and what we know about local geology.

Your result appears here. Area data shows risk for a region; only a test tells you your home's level.

County comparison

CountyEPA zoneTest data
Spokane, WAZone 118,518 tests (WA DOH, 1990–2020); 47.0% ≥ 4.0
Stevens, WAZone 1941 tests (WA DOH, 1990–2020); 45.1% ≥ 4.0
Pend Oreille, WAZone 1284 tests (WA DOH, 1990–2020); 49.3% ≥ 4.0
Kootenai, IDZone 146–70% of tests ≥ 4.0 by ZIP code (IDHW), from Coeur d’Alene 83814 to Athol

Washington counties: Washington Tracking Network, sums of the yearly county results 1990–2020 (Spokane County 8,704 of 18,518 tests at or above 4.0). Zip lookup: census-tract results for all years, matched to zip codes by housing units, so they are approximate. Tests are chosen by homeowners, and the state can't tell whether a test came before or after mitigation. We don't publish figures based on fewer than 20 tests.

Why Spokane's ground produces radon

"In your corner of the state, there's more uranium and radium in the ground than in other places," a Department of Health physicist told the Spokesman-Review in 2009. Four geologic settings shape local readings.

Granite to the north

Washington's uranium deposits are largely tied to granitic and metamorphic rock in the Okanogan Highlands north of Spokane. The same rock forms the sides of the Spokane Valley.

Valley gravel

The Spokane Valley–Rathdrum Prairie floor is glacial outwash reworked by Ice Age floods. Coarse, permeable gravel lets soil gas move easily toward foundations.

Basalt bluffs

Downtown and the South Hill sit on basalt flows. That doesn't mean low radon: census tracts within the South Hill ZIP codes 99203 and 99223 show 26% to 53% of tests at or above 4.0.

West Plains scablands

The largest Missoula floods topped the divide west of Spokane and spilled south toward Cheney, carving the Channeled Scablands.

Where tests run highest

In the state's tract data, 46 of 102 Spokane County census tracts with enough tests are at 50% or higher. The top shares sit in the Spokane Valley and northeast Spokane: 79.1% in one tract in ZIP 99212, and 66% to 68% in 99217.

Spokane radon history

1986Spokane hosts a national radon conference.
1991–92An EPA and state survey measures 449 Spokane County homes on their lowest level: median 4.9 pCi/L, 59% above 4.
1991Washington’s radon construction standards take effect on July 1 in Spokane County and seven other counties, as part of the state’s new indoor air quality code.
1994A county health-district study finds an average of 10.6 pCi/L, reported by the Seattle Times as the state’s highest levels.
2009The Spokesman-Review calls the Spokane region, including Kootenai County, “a hot spot for radon.” SRHD had used test kits sold at cost to map high areas.
2011The Spokesman-Review quotes officials saying 60 percent of Spokane County homes have elevated radon.
2020The Inlander reports that the health district names the Spokane Valley, the Mount Spokane foothills and the High Drive bluff as hot spots.
TodayState data counts 18,518 Spokane County tests from 1990 to 2020; 47% were at or above 4.0 pCi/L, and 40.4% in the 2011–2020 decade.

Winter readings run higher

Heated air rising through a closed house pulls soil gas in at the foundation. The Spokane Regional Clean Air Agency notes radon levels can be highest in winter. Test in the heating season when you can.

Health context

EPA estimates radon causes about 21,000 US lung cancer deaths a year, about 2,900 among people who never smoked, with an uncertainty range of 8,000 to 45,000. Smoking multiplies the risk.

A state physicist told the Spokesman-Review in 2009 there was "no evidence of elevated levels of lung cancer in the Spokane region due to radon." Local numbers show exposure, not local cancer rates.

Sources and method

Washington Tracking Network (Washington State Department of Health): radon test results by county, 1990–2020, and by census tract; housing tested for radon. USGS Open-File Report 93-292-J (1991–92 EPA/State Residential Radon Survey). EPA Map of Radon Zones; WAC 51-51-60101 Table AF101(1). Idaho Department of Health and Welfare: home radon test results by zip code. History: Seattle Times (1994), Spokesman-Review (2009, 2011, 2012), Inlander (2020). USGS SIR 2005-5227 and OF 1953-0199.

EPA caveat: "This map is not intended to determine if a home in a given zone should be tested for radon. Homes with elevated levels of radon have been found in all three zones. All homes should be tested, regardless of zone designation."

Area data is a starting point.

Only a test tells you your home's number.

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