Radon in Salt Lake County, Utah

What the numbers say

Salt Lake County sits 6.3 points below the Utah median (45.4% of tests over the limit across the state's counties). The median reading among its 10,449 reported tests was 3.1 pCi/L — and the single highest test on record reached 172.9 pCi/L, more than 43× the action level. EPA maps place the county in Radon Zone 2 — moderate predicted potential (2–4 pCi/L average screening levels), which still produces plenty of homes over the limit.

Why: the ground under Salt Lake County

On the Wasatch Front, where alluvial fans of granitic debris shed from the Wasatch Range fill the valleys. The uranium in that crystalline source rock, plus the permeability of coarse basin fill, gives Utah's population centers real radon potential — Utah DEQ testing regularly finds homes above the action level along the Front.

Geology sources: Utah DEQ radon program · USGS WRI 98-4169.

The housing stock factor

The median Salt Lake County home dates to 1986 — decades before radon-resistant new construction entered building codes. With 1,196,523 residents largely housed in that older stock, testing is the only way any individual household knows where it stands.

Salt Lake County in the Utah picture

Ranked nearby in Utah

• Duchesne County — #13, 47.4% of 27 tests over the limit
• Tooele County — #14, 45.4% of 371 tests over the limit
• Wayne County — #15, 40% of 2 tests over the limit
• Kane County — #17, 38.9% of 11 tests over the limit
• Weber County — #18, 36.2% of 870 tests over the limit
• Davis County — #19, 33.7% of 2,100 tests over the limit

(Ranking neighbors — counties adjacent in the Utah test ranking, not necessarily on the map.)

High test? Fixes and real pricing: the Utah mitigation cost guide. Every statistic here traces to the methodology (CDC EPHT (labs), 2008–2017; zones: EPA; year built & population: ACS 5-year).