What Every Homeowner Should Know About Radon Exposure

Every homeowner should know that radon is an invisible, odorless radioactive gas that causes about 21,000 lung cancer deaths in the United States each year, according to the U.S. Environmental Protection Agency (EPA). It is the second leading cause of lung cancer after smoking and the number one cause of lung cancer among people who do not smoke. Radon seeps into homes through cracks in the foundation, gaps around pipes, and openings in floors and walls. The only way to know if your home has dangerous radon levels is to test for it. This article covers how radon gets into your home, the health risks, Missouri-specific radon data, how testing works, and what to do if your levels are too high.

What Is Radon and Why Should Homeowners Worry About It?

Radon is a naturally occurring radioactive gas that forms when uranium in soil, rock, and water breaks down. It rises through the ground and can enter buildings through foundation cracks, sump pumps, construction joints, and gaps around service pipes. According to the CDC, radon gas decays into radioactive particles that can get trapped in your lungs when you breathe. Over time, these particles damage lung tissue and increase the risk of lung cancer.

Homeowners should worry about radon because it has no color, no smell, and no taste. You cannot detect it without testing. According to the EPA, nearly 1 in 15 homes in the United States has a radon level at or above the recommended action level of 4 picocuries per liter (pCi/L). The National Cancer Institute estimates that 15,000 to 22,000 lung cancer deaths each year in the United States are related to radon exposure. This article is written by Alan Redburn, CPI, a Certified Professional Inspector who provides radon testing services across the Mid-Missouri region.

How Does Radon Get Into Your Home?

Radon gets into your home through the ground beneath and around the foundation. The gas moves upward through the soil and enters through cracks in basement floors and walls, gaps around pipes and wires, construction joints, crawl spaces, sump pump openings, and porous concrete block walls. According to the EPA, any home can have a radon problem, including new and old homes, well-sealed and drafty homes, and homes with or without basements.

Once radon enters a building, it can accumulate to dangerous levels in areas with poor ventilation. Basements and lower floors are usually the highest-risk areas because they are closest to the soil. In Mid-Missouri, many homes have basements or crawl spaces that create direct pathways for radon to enter. Homes in Cuba, Rolla, and Jefferson City are built on soil and rock formations that naturally contain uranium, which is the starting material for radon gas.

Even homes that sit right next to each other can have very different radon levels. Soil composition, foundation type, and construction methods all play a role. The Missouri Department of Health and Senior Services (MDHSS) notes that radon is present in every county in Missouri. This means no home is automatically safe, and testing is the only reliable way to know your level.

What Are the Health Risks of Radon Exposure?

The health risks of radon exposure are serious and well documented. Radon is classified as a known human carcinogen by the International Agency for Research on Cancer (IARC), the National Toxicology Program (NTP), and the EPA. According to the EPA, radon causes approximately 21,000 lung cancer deaths in the United States each year. The U.S. Surgeon General has called radon the second leading cause of lung cancer in the country.

The risk is significantly higher for people who smoke. According to data from the EPA, the lifetime risk of lung cancer death from radon at 4 pCi/L is about 62 per 1,000 for smokers compared to about 7 per 1,000 for people who have never smoked. Memorial Sloan Kettering Cancer Center reports that radon increases lung cancer risk 8 to 9 times higher in smokers than in nonsmokers due to the combined effect of radon and tobacco smoke on lung tissue.

According to StatPearls published by the National Institutes of Health, 9% to 13% of all lung cancer cases in the United States are believed to be caused by radon exposure. The World Health Organization estimates that 3% to 15% of all lung cancer worldwide is due to radon. There are no short-term symptoms from radon exposure. The damage builds up over years of breathing in radioactive particles, which is why regular testing is so important.

What Radon Level Is Dangerous in a Home?

A radon level of 4 pCi/L or higher is considered dangerous in a home and requires action, according to the EPA. The EPA also recommends that homeowners consider taking steps to reduce radon when levels are between 2 and 4 pCi/L. The average indoor radon level in the United States is about 1.3 pCi/L, and the average outdoor level is about 0.4 pCi/L, according to the EPA.

The World Health Organization recommends a lower action level of 2.7 pCi/L (100 Bq/m3). There is no known safe level of radon exposure. Even levels below 4 pCi/L carry some risk, though the risk increases with higher concentrations and longer exposure times. The EPA has stated that lowering radon levels in all homes above the action level could reduce lung cancer deaths by 2% to 4%, or about 5,000 lives per year, according to the National Cancer Institute.

How High Are Radon Levels in Missouri?

Radon levels in Missouri are higher than the national average. According to Radon.org, the average indoor radon level in Missouri is about 2.6 pCi/L, which is double the national average of 1.3 pCi/L. Data from the Missouri Department of Health and Senior Services residential radon testing program shows that 1 in 3 homes tested in Missouri had radon levels above the EPA action level of 4.0 pCi/L.

According to the EPA’s Map of Radon Zones, Missouri has areas classified as both high and moderate potential for elevated indoor radon. Northern and central Missouri counties, including Boone, Callaway, and Cole, have been identified as higher-risk areas. However, elevated radon levels have been found in every part of the state. Homes in Cuba, St. James, Owensville, and throughout Mid-Missouri sit on geological formations that can produce significant amounts of radon gas.

The MDHSS offers free short-term radon test kits to Missouri residents while supplies last. Testing is the only way to know your home’s radon level, and the department recommends that all homes in Missouri be tested regardless of location or foundation type. Buyers and sellers in the Mid-Missouri real estate market should make radon testing a standard part of every transaction.

How Do You Test Your Home for Radon?

You test your home for radon by placing a testing device in the lowest livable area of the home, typically the basement or ground floor, for a set period of time. There are two main types of radon tests: short-term tests that last 2 to 7 days and long-term tests that last 90 days or more. Short-term tests give a quick snapshot, while long-term tests provide a more accurate picture of your home’s year-round average radon level.

You can purchase a DIY radon test kit from a hardware store or order one online. You place the kit in the proper location, leave it undisturbed for the required time, then mail it to a laboratory for analysis. For the most accurate and reliable results, hire a professional inspector who uses calibrated continuous radon monitors. Professional testing follows EPA and InterNACHI protocols for placement, house conditions, and test duration.

During a real estate transaction, professional radon testing is the standard approach. The test is often scheduled alongside a buyer’s home inspection so results are available during the negotiation period. Radon levels can fluctuate with seasons, weather, and changes to the home, so the EPA recommends retesting every few years or after major renovations, HVAC changes, or structural modifications.

What Should You Do if Your Home Has High Radon?

If your home has high radon, you should hire a certified radon mitigation contractor to install a radon reduction system. The most common method is a sub-slab depressurization system, which draws radon from beneath the foundation and vents it outside through a pipe and fan. According to the Missouri Department of Health and Senior Services, radon mitigation typically costs less than $2,500 for a 2,000-square-foot home. Memorial Sloan Kettering Cancer Center reports that most radon mitigation systems cost between $800 and $1,500.

A properly installed system can reduce indoor radon levels by up to 99%, according to the EPA. After installation, you should retest the home to confirm that levels have dropped below 4 pCi/L. A home re-inspection after mitigation verifies that the system is working correctly. The MDHSS recommends using contractors certified by the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB).

Other steps that can help reduce radon include sealing cracks and gaps in the foundation, increasing ventilation in lower levels of the home, and covering exposed soil in crawl spaces. However, these measures alone are usually not enough to lower radon to safe levels. A professional mitigation system is the most effective long-term solution.

Does Radon Affect Home Sales in Missouri?

Yes, radon affects home sales in Missouri. Radon testing has become a standard part of real estate transactions across the state. Buyers often request radon tests as part of the home inspection process. If levels are elevated, buyers may ask for mitigation before closing, request a price reduction, or negotiate a credit to cover the cost of a mitigation system.

Sellers who test early and address radon before listing their home can avoid delays and build buyer confidence. According to the Porch homebuyer survey, 46% of buyers use inspection results to negotiate a lower price, and buyers save an average of $14,000 through these negotiations. Having a clean radon test or a working mitigation system in place can be a selling point. Sellers in Rolla, Jefferson City, and Cuba who get a pre-listing inspection that includes radon testing put themselves in a stronger position.

Missouri currently has no state regulations requiring radon testing in real estate transactions, but the EPA’s Home Buyer’s and Seller’s Guide to Radon strongly recommends it. The MDHSS also states that sellers should note any radon mitigation systems on the Seller’s Disclosure form. Buyers who skip radon testing take on a hidden risk that could affect their health and their investment.

Can Radon Be a Problem in New Homes?

Yes, radon can be a problem in new homes. New construction is not immune to radon. The gas comes from the soil beneath the home, so the age of the building does not determine whether radon will be present. According to the EPA, radon can enter any home, including newly built ones, through small openings in the foundation. Some new homes are built with radon-resistant features, but these features only reduce the likelihood of elevated levels; they do not eliminate radon entirely.

Buyers building or purchasing new construction homes in Mid-Missouri should still test for radon after the home is completed. A pre-drywall inspection is a good time to verify that radon-resistant features were installed correctly. Even if the builder included a passive radon system, testing after move-in confirms whether additional active mitigation is needed.

How Does Radon Compare to Other Cancer Risks?

Radon causes more deaths than many well-known hazards. According to the EPA’s risk comparison data, radon is responsible for roughly 21,000 lung cancer deaths per year in the United States. By comparison, the National Safety Council reports that drowning causes about 3,900 deaths per year, home fires cause about 2,600 deaths, and drunk driving causes about 13,000 deaths. Radon-related lung cancer kills more Americans each year than drunk driving, yet many homeowners have never tested their homes.

According to Memorial Sloan Kettering Cancer Center, major scientific organizations believe radon contributes to approximately 12% of all lung cancers annually in the United States. The survival rate for lung cancer is among the lowest of all cancers. According to the EPA, between 11% and 15% of people diagnosed with lung cancer will live beyond five years. Testing and mitigation are straightforward, affordable steps that can dramatically reduce this risk for families across Mid-Missouri.

Comparison Table: Radon Levels, Risk, and Recommended Actions

Sources: U.S. Environmental Protection Agency (EPA); World Health Organization (WHO); CDC; Missouri Department of Health and Senior Services (MDHSS).

Frequently Asked Questions

How Often Should You Test Your Home for Radon?

You should test your home for radon at least every two years, according to the EPA. You should also retest after any major renovation, foundation repair, or HVAC system change. If you have a radon mitigation system, test periodically to make sure it is still working properly. Homeowners in Cuba, Missouri and across Mid-Missouri should test more frequently because the region has higher-than-average radon potential.

Does Radon Only Affect Homes With Basements?

No, radon does not only affect homes with basements. Radon can enter any type of home, including those with crawl spaces, slab-on-grade foundations, and even upper floors. According to the EPA, all homes below the third floor should be tested. Homes in Rolla, St. James, and Owensville come in many different styles and foundation types, and all of them are at risk for radon.

Can You Smell or See Radon Gas?

No, you cannot smell or see radon gas. Radon is completely invisible, odorless, and tasteless. According to the CDC, there are no short-term symptoms of radon exposure. The only way to detect radon is through testing. This is why the EPA recommends that every home in the United States be tested, regardless of whether the homeowner notices anything unusual.

Is Radon Testing Required When Buying a Home in Missouri?

No, radon testing is not legally required when buying a home in Missouri. However, both the EPA and the Missouri Department of Health and Senior Services strongly recommend it. Data from the MDHSS shows that 1 in 3 Missouri homes tested above the 4 pCi/L action level. Buyers in Jefferson City, Farmington, and across Mid-Missouri should always include radon testing as part of their buyer’s inspection to protect their family’s health.

How Much Does Radon Testing Cost in Mid-Missouri?

Professional radon testing in Mid-Missouri is affordable and varies depending on the type of test and the provider. Professional testing with a continuous radon monitor typically provides the most accurate results during a real estate transaction. Many inspectors offer radon testing as an add-on to a standard home inspection in Missouri, which can save time and money by combining services.

What Happens if a Seller Refuses to Fix Radon Before Closing?

If a seller refuses to fix radon before closing, the buyer has several options. The buyer can negotiate a price reduction to cover the cost of mitigation after purchase, request a closing credit, or walk away from the transaction if the purchase contract includes an inspection contingency. Mitigation systems typically cost less than $2,500 according to the MDHSS, so most negotiations focus on who pays for the system rather than whether to install one. Learning how to negotiate home inspection repairs helps buyers handle this situation effectively.

Final Thoughts

Radon is a serious health hazard that every homeowner needs to take seriously. It causes an estimated 21,000 lung cancer deaths per year in the United States, and Missouri homes test above the EPA action level at nearly double the national rate. There are no symptoms, no warnings, and no way to detect radon without testing. The good news is that testing is simple, affordable, and effective. If your levels are high, mitigation systems can reduce radon by up to 99% and protect your family for years to come.

If you own a home or are buying one in Cuba, Missouri or anywhere across the Mid-Missouri area, ARC Home Inspections provides professional radon testing with calibrated equipment and clear reporting. Radon tests can be scheduled alongside a full home inspection for the most complete evaluation of your property. Contact ARC Home Inspections today to schedule your radon test and protect the people who matter most.