Why Every Home Buyer In Lake Tahoe Needs a Radon Test

By Carson Long, Incline Village Realtor | Mizak Mountain Luxury Team | COMPASS | Incline Village’s #1 Team in 2025

There is a health risk hiding in a significant number of Lake Tahoe homes that most buyers never think to test for, most sellers never disclose, and most real estate agents never bring up. It has no smell. No color. No taste. You cannot see it or feel it. And according to the EPA, it is the leading cause of lung cancer among non-smokers in the United States.

It’s radon. And the Lake Tahoe Basin is one of the highest-risk areas in California and Nevada for elevated indoor radon levels.

This is not a fringe concern or an overstated risk. The California Geological Survey published a formal radon potential study specifically for the Lake Tahoe area, and the findings are significant: approximately 40% of California homes around Lake Tahoe test at or above the EPA’s recommended action level of 4 picocuries per liter (pCi/L). In the El Dorado County portion of the basin, that number climbs to approximately 55%. One home in the study measured radon levels more than 20 times the EPA action threshold.

On the Nevada side, a University of Nevada Cooperative Extension study found that nearly 60% of homes in Stateline, Glenbrook, and Zephyr Cove tested at elevated levels. The California Geological Survey’s newer interactive radon map — more precise than the outdated county-level EPA maps that many real estate agents still reference — classifies the Tahoe area as a “High” radon risk zone, not the “Moderate” designation that older maps incorrectly assign based on county-wide averages.

If you are buying a home in the Tahoe Basin and you have not ordered a radon test, you need to understand what you may be walking into.

WHY LAKE TAHOE HAS AN ELEVATED RADON PROBLEM

Radon is not a man-made problem. It is a geological one. Radon gas is produced naturally as uranium and thorium decay underground. Every region has some level of radon potential — but the geology beneath Lake Tahoe creates conditions that are particularly favorable for elevated radon generation and accumulation.

The Sierra Nevada is fundamentally a granitic mountain range. The granite and granodiorite bedrock that forms the foundation of the entire basin contains naturally elevated concentrations of uranium. As that uranium decays, it produces radium, which in turn produces radon gas. The Carson Range — the ridge of mountains directly east of Lake Tahoe that includes Incline Village and the Nevada side of the basin — contains uraniferous sediments that have been documented by U.S. Geological Survey researchers, with uranium concentrations in some Holocene valley-fill sediments approaching extraordinarily high levels.

Outdoors, radon disperses harmlessly into the atmosphere. The problem occurs when radon seeps into enclosed structures through crawl spaces, foundation cracks, slab penetrations, and gaps around utility penetrations. Once inside, particularly in homes with tight construction, lower levels, or basements, radon can accumulate to concentrations that represent a serious long-term health risk.

The risk is not evenly distributed — it varies house by house depending on the home’s specific construction, foundation type, the soil immediately beneath the structure, and how well-sealed or ventilated the lower levels are. This is exactly why testing every individual property is essential. Your neighbor’s test result tells you very little about your own.

WHAT THE EPA SAYS AND WHAT THE NUMBERS MEAN

The EPA recommends that all homes be tested for radon regardless of geographic location, and recommends taking action to reduce radon in any home where the average annual level is 4.0 pCi/L or higher. The average indoor radon level in American homes is approximately 1.3 pCi/L. Outdoor air typically measures around 0.4 pCi/L.

To put the risk in concrete terms: the EPA estimates that radon causes approximately 21,000 lung cancer deaths in the United States every year. Of those, about 2,900 occur in people who have never smoked. The agency classifies radon as a Class A carcinogen — the same category as asbestos and benzene. It is the second leading cause of lung cancer after smoking, and the number one cause among non-smokers.

At 4 pCi/L — the action threshold — the EPA estimates a risk level roughly comparable to smoking half a pack of cigarettes per day, or having 200 chest X-rays per year. At 8 pCi/L, the risk doubles. At 20 pCi/L — a level that has been recorded in Lake Tahoe homes — the risk is severe.

These are not speculative numbers. They are based on decades of epidemiological research and are the foundation of the EPA’s national radon policy.

WHO IS MOST AT RISK: YEAR-ROUND RESIDENTS VS. VACATION HOME BUYERS

The health risk from radon is cumulative and based on long-term exposure. For buyers purchasing a second home or vacation property they occupy a few weeks per year, the personal health risk from radon is lower — though not zero, and still worth knowing and addressing.

For buyers purchasing a primary residence at Lake Tahoe — which describes an increasing percentage of Incline Village buyers who are making the full relocation from California — the stakes are considerably higher. You are making a long-term commitment to sleeping, living, and breathing the air in this home year-round. If that home has elevated radon levels and you don’t test, you won’t know until it has already become a prolonged exposure. Radon-induced lung cancer typically develops after years of elevated exposure, not months.

For families with children, the calculus is even more significant. Children’s developing lungs are more sensitive to radon exposure than adult lungs, and a child who grows up in a home with elevated radon levels has more years of exposure ahead of them than an adult buyer.

HOW A RADON TEST WORKS

A radon test is simple, non-invasive, and inexpensive. During a real estate transaction, the most common method is a short-term passive test using a charcoal canister or electret ion chamber monitor. The device is placed in the lowest livable level of the home — typically a ground-floor room, lower level, or basement — for a minimum of 48 hours with windows and doors kept closed to simulate typical living conditions. The canister is then sent to a certified lab for analysis, and results come back within a few days as a pCi/L reading.

For real estate purposes, a short-term test conducted during the inspection period gives you the information you need to make an informed decision about the property. If results come back below 2.0 pCi/L, the risk is considered low. Between 2.0 and 4.0, the EPA suggests considering mitigation. At 4.0 pCi/L or above, the EPA recommends taking action. Results above 8.0 pCi/L warrant prompt mitigation.

The entire test costs $150 to $300 depending on the testing company and whether you use a professional radon inspector or a certified mail-in kit. In the context of a multi-million dollar real estate purchase, this is one of the least expensive and most consequential tests you can order.

WHAT HAPPENS IF RADON LEVELS ARE HIGH

Elevated radon is not a deal-killer. It is a solvable problem — and a well-established one. Radon mitigation has been performed on hundreds of thousands of American homes and is highly effective when done correctly.

The standard mitigation approach for most Lake Tahoe homes is a sub-slab depressurization system, also called an active soil depressurization (ASD) system. A licensed radon mitigation contractor installs a PVC pipe through the foundation slab or into the crawl space, connected to a continuously running fan that draws radon from beneath the home and exhausts it safely outside before it can enter the living space. These systems typically reduce indoor radon levels by 50% to 99% and are designed to operate indefinitely with minimal maintenance.

The cost of a radon mitigation system in the Lake Tahoe area typically runs $800 to $2,500 depending on the home’s foundation type, size, and the complexity of the installation. In most cases, a well-functioning mitigation system brings elevated homes well below the 2.0 pCi/L level.

During a real estate transaction, a high radon test result gives you documented grounds to request that the seller install a mitigation system prior to closing, or to request a credit toward the cost of installation. This is a completely standard negotiating point in real estate markets where radon testing is common practice.

WHY THIS IS UNDERREPORTED IN TAHOE REAL ESTATE

Here is an uncomfortable truth: radon testing is significantly underutilized in Tahoe real estate transactions compared to markets where radon awareness is higher. Part of this is the “mountain air is clean air” perception that buyers bring to the Tahoe market — which is true for outdoor air but misleading when applied to indoor radon risk. Part of it is that California’s natural hazard disclosure framework has historically used the outdated EPA county-level radon zone maps, which underrepresent the actual risk in the Tahoe basin. And part of it is simply that most real estate agents don’t bring it up because it isn’t legally required and it adds a step to a transaction.

I bring it up with every buyer I represent. The California Geological Survey’s own radon potential map for the Lake Tahoe area, the University of Nevada’s findings on the Nevada side of the basin, and the straightforward math on what a $200 test can reveal about a $2 million asset all point in the same direction. Test the home. Know what you’re buying. Address it if needed.

THE BOTTOM LINE

Radon is the most underappreciated environmental health risk in Lake Tahoe real estate. The basin’s granitic geology creates conditions that produce elevated radon in a meaningful percentage of homes — 40% to 60% in studied areas, depending on location. The EPA classifies it as a Class A carcinogen. It is invisible, odorless, and impossible to detect without a test. And it is entirely fixable when identified.

A $200 radon test is one of the simplest, most important steps you can take when buying a home at Lake Tahoe. If your agent hasn’t mentioned it, mention it yourself. If the seller hasn’t tested, order your own test during the inspection period. And if levels come back elevated, understand that mitigation is straightforward, effective, and a completely reasonable item to negotiate as part of your purchase.

If you have questions about the due diligence process for buying in Incline Village or anywhere on the North Shore, I’m happy to walk you through it.

Carson Long | Mizak Mountain Luxury Team | COMPASS

(775) 298-1270

[email protected]

*The information in this post is for general informational purposes only and does not constitute medical or legal advice. Radon risk varies by property. Always use a certified radon testing professional and consult appropriate health and environmental authorities for guidance specific to your situation.