Radon Levels in Boise & Treasure Valley: What Idaho Homeowners Need to Know

What Is Radon and Why Should Boise Homeowners Care?

Radon is a colorless, odorless, tasteless radioactive gas that forms naturally from the decay of uranium in soil and rock. According to the U.S. Environmental Protection Agency and the American Lung Association, radon is:

• The #1 cause of lung cancer among non-smokers in the United States
• The second leading cause of lung cancer overall, responsible for an estimated 21,000 deaths annually
• Impossible to detect without testing—you cannot see, smell, or taste it
• Found in homes across all 50 states, but especially prevalent in Idaho due to our geology

The U.S. Surgeon General has issued a national health advisory recommending that all homes be tested for radon.

Radon Levels by County in the Treasure Valley

The EPA created a Map of Radon Zones to help identify areas with elevated radon potential. Here's what the data shows for our area:

Ada County (Boise, Meridian, Eagle, Garden City, Kuna, Star)

• EPA Zone: Zone 2 (Moderate Potential)
• Average Indoor Level: 6.5 pCi/L
• Percent of Homes Above 4.0 pCi/L: 38%
• In Some Boise Zip Codes: 36% of homes test high

Canyon County (Nampa, Caldwell, Middleton)

• EPA Zone: Zone 1 (HIGHEST Potential)
• Average Indoor Level: 6.7 pCi/L
• Percent of Homes Above 4.0 pCi/L: 39%
• Risk Level: Highest radon potential in Idaho

Important: Even if you live in a Zone 2 or Zone 3 area, your specific home can still have dangerous radon levels. The only way to know is to test your home for radon.

Why Idaho Has Such High Radon Levels

Several geological and environmental factors combine to make Idaho a radon hotspot:

• Granite and Volcanic Rock: The Boise Foothills and much of the valley floor contain uranium-bearing granite and volcanic deposits that naturally produce radon gas.
• Dry, Porous Soil: Idaho's arid climate means our soil is often dry and porous, allowing radon to migrate easily from the ground into homes.
• Tight, Energy-Efficient Homes: Modern homes are sealed tightly for energy efficiency, which can trap radon inside at higher concentrations.
• Basements and Crawl Spaces: Radon enters through cracks in concrete floors, sump pits, gaps around pipes, and construction joints. Homes with below-grade spaces have higher exposure risk.

How Radon Enters Your Home

Radon gas seeps into homes through multiple entry points:

• Cracks in concrete slab floors
• Gaps around service pipes (plumbing, electrical)
• Sump pump openings and floor drains
• Construction joints where walls meet floors
• Crawl space vents and exposed dirt floors
• Well water in some cases

This is why our crawl space encapsulation services can significantly improve indoor air quality—sealing the crawl space reduces radon infiltration.

Understanding Radon Measurements

Radon is measured in picocuries per liter of air (pCi/L). Here's what the numbers mean:

• Below 2.0 pCi/L: Low risk. No action typically required.
• 2.0 – 4.0 pCi/L: Consider mitigation. WHO recommends action at 2.7 pCi/L.
• 4.0 pCi/L or Higher: EPA recommends taking action to reduce radon levels.
• Above 8.0 pCi/L: High priority. Equivalent radiation exposure to smoking 1 pack of cigarettes per day.

The Connection Between Radon and Lung Cancer

When you breathe radon gas, radioactive particles can become trapped in your lungs. Over time, these particles damage lung tissue and can lead to lung cancer. According to the American Cancer Society:

• Radon exposure causes approximately 21,000 lung cancer deaths per year in the U.S.
• The risk increases with higher radon levels and longer exposure time
• Smokers exposed to radon have an even higher risk—the combination is especially dangerous
• Lung cancer from radon exposure can take 5-25 years to develop

Who Should Test for Radon in the Treasure Valley?

The short answer: Everyone. The EPA, Idaho Department of Health and Welfare, and American Lung Association all recommend testing every home—regardless of age, construction type, or location.

You should especially test if:

• You live in Ada or Canyon County (high-risk areas)
• You have a basement or crawl space
• You've never tested your home before
• You're buying or selling a home
• You've made major renovations that changed your home's ventilation
• It's been more than 2 years since your last test

Learn More

The Idaho Department of Health and Welfare provides excellent resources including free or low-cost test kits for Idaho residents.

Ready to test? Learn about our radon testing and mitigation services.