Radon in Well Water: Health Risks, Testing & Treatment

Radon is an invisible, odorless radioactive gas that can dissolve in groundwater and enter your home through your well. While less publicized than airborne radon, waterborne radon poses real health risks — and it's more common in certain parts of San Diego County than you might think.

What Is Radon?

Radon is a naturally occurring radioactive gas produced when uranium in soil and rock breaks down. It's part of the normal decay chain of uranium, which exists in varying concentrations throughout Earth's crust.

The gas dissolves easily in cold water. When groundwater flows through rock containing uranium, it picks up radon along the way. Deep wells drilled into granite or other uranium-bearing formations are most likely to have elevated radon levels.

How Radon Gets Into Your Home

Radon in well water enters your home two ways:

1. Directly through water: You can ingest radon by drinking contaminated water
2. Released into air: When water is used for showers, laundry, or dishwashing, radon escapes into your indoor air

The air exposure is actually the bigger concern. The EPA estimates that 10,000 pCi/L (picocuries per liter) of radon in water contributes about 1 pCi/L to indoor air levels. Since the EPA action level for indoor air is 4 pCi/L, high waterborne radon can significantly impact your home's air quality.

Health Risks of Radon in Water

Lung Cancer

Radon's primary health risk is lung cancer. When radon escapes from water into your home's air, you breathe in radioactive particles that can damage lung tissue. Radon is the second leading cause of lung cancer in the United States, behind smoking.

The risk increases with:

• Higher radon concentrations
• Longer exposure duration
• More time spent indoors
• Smoking (radon + smoking risks multiply, not just add)

Stomach Cancer

Drinking radon-contaminated water may increase stomach cancer risk, though this link is less established than the lung cancer connection. The stomach lining receives direct radiation exposure from ingested radon.

Who's Most at Risk?

• Smokers and former smokers: Dramatically higher lung cancer risk from radon exposure
• Children: Higher respiration rates mean more exposure; longer lifetime for cancer to develop
• Home workers: More hours spent breathing indoor air
• People with lung conditions: Already compromised respiratory systems

Radon Levels in San Diego County

High-Risk Areas

Radon levels correlate with geology. In San Diego County, the highest risk areas have granite and other uranium-bearing rock:

• Julian and surrounding mountains: Granite bedrock common
• Palomar Mountain: Deep wells in crystalline rock
• Parts of Fallbrook: Varied geology with some granite formations
• Pine Valley: Mountain geology similar to Julian
• Descanso: Located in granitic terrain

Lower-Risk Areas

Coastal and valley areas typically have lower radon potential:

• Ramona: Mixed geology, generally lower uranium content
• Valley Center: Alluvial soils less radon-prone
• Coastal communities: Sedimentary formations have minimal uranium

However: Local geology varies significantly. The only way to know your well's radon level is to test it.

Radon Testing for Well Water

When to Test

Consider radon testing if:

• Your well is in a granite or metamorphic rock area
• You're buying a home with a well (especially in mountain communities)
• Your indoor air tested high for radon
• You've never tested your well water
• Neighbors have found elevated radon

How Testing Works

Radon water testing requires special handling because radon escapes quickly from water when exposed to air:

1. Sample collection: Water is collected in special vials that prevent radon escape
2. Timing matters: Samples must reach the lab within 24-48 hours
3. Lab analysis: Liquid scintillation counting measures radon concentration
4. Results: Reported in picocuries per liter (pCi/L)

Testing Cost

Radon water testing typically costs $40-100. This is a specialized test not included in standard water quality panels. Make sure your lab is certified for radon analysis.

Understanding Results

Note: These are guidelines. Any radon exposure carries some risk. The EPA's proposed Maximum Contaminant Level for radon in water is 300 pCi/L for systems without air mitigation programs.

Radon Treatment Options

Aeration Systems

How it works: Water is sprayed or agitated in a tank, allowing radon gas to escape. The gas is then vented outside your home.

Effectiveness: 95-99% radon removal

Pros:

• Most effective treatment method
• Removes radon completely from water
• No filter replacement needed
• Also removes other dissolved gases (hydrogen sulfide)

Cons:

• Higher upfront cost ($3,000-6,000 installed)
• Requires electricity to operate
• Needs proper venting to outside
• Regular maintenance needed (cleaning, pump checks)

Granular Activated Carbon (GAC) Filters

How it works: Water passes through activated carbon that absorbs radon. The radon decays while trapped in the carbon.

Effectiveness: 85-95% removal (with proper sizing and maintenance)

Pros:

• Lower initial cost ($1,000-2,500 installed)
• No venting required
• Also removes other contaminants (chlorine, some organics)
• Simple installation

Cons:

• Carbon beds become radioactive over time
• Requires special disposal procedures
• Filter replacement costs ($200-500 per change)
• Not recommended for very high radon levels (over 10,000 pCi/L)

Point-of-Use vs. Point-of-Entry

Radon treatment should be point-of-entry (whole house), not point-of-use (single faucet). Since radon releases into air during any water use, treating only drinking water doesn't address shower/laundry exposure.

Reducing Radon Exposure

While Awaiting Treatment

If you've discovered elevated radon, you can reduce exposure before installing a treatment system:

• Ventilate during water use: Run bathroom fans, open windows when showering
• Shorter showers: Less radon released into enclosed space
• Cold water for drinking: Hot water releases radon faster; use cold water and let it sit covered
• Overall home ventilation: Fresh air dilutes indoor radon

Test Your Indoor Air Too

If your water has elevated radon, test your home's air. Airborne radon (from soil, not just water) is often a bigger source. Home radon test kits cost $15-40 at hardware stores, or hire a professional for $100-300.

Radon and Real Estate

Buying a Home

If you're purchasing a home with a well in a radon-prone area:

• Request radon water testing as part of your inspection
• Also test indoor air radon
• Factor treatment costs into negotiations if levels are high
• Get radon levels in writing before closing

Selling a Home

California doesn't require radon disclosure, but:

• Buyers often request testing, especially in mountain areas
• Having test results ready shows transparency
• If treatment is installed, document it thoroughly
• Consider proactive testing to avoid surprises during escrow

Frequently Asked Questions