1. The Numbers Behind the Risk
According to the EPA, radon is responsible for approximately 21,000 lung cancer deaths in the United States every year. That estimate comes from the National Academy of Sciences' Biological Effects of Ionizing Radiation (BEIR VI) report, which remains the most comprehensive analysis of radon-related cancer risk.
To put that number in perspective, the EPA estimates that secondhand smoke causes about 7,300 lung cancer deaths per year. That means radon kills roughly three times as many people annually as secondhand smoke. Motor vehicle crashes kill about 40,000 people per year, so radon is responsible for more than half as many deaths as car accidents.
The Surgeon General has issued a national health advisory about radon, warning that it is the second leading cause of lung cancer in the United States. The World Health Organization (WHO) has classified radon as a Group 1 carcinogen, the highest classification, meaning there is sufficient evidence that radon causes cancer in humans.
Despite these numbers, radon awareness remains relatively low. The EPA estimates that about 1 in 15 homes in the United States has radon levels at or above the recommended action level of 4 pCi/L. In some areas, including parts of Georgia, the percentage is even higher. Radon risks for children are especially concerning since their developing lungs and faster breathing rates make them more susceptible to damage.
2. How Radon Causes Lung Cancer
Radon itself is a noble gas, meaning it does not react chemically with your body. The danger comes from what happens when radon decays. As radon gas breaks down, it produces short-lived radioactive particles called radon progeny (also known as radon daughters). These include polonium-218 and polonium-214, which are alpha emitters.
When you breathe air containing radon, some of these radioactive decay products attach to tiny particles in the air and are deposited in your lungs. Once there, the alpha particles they emit can damage the DNA in lung tissue cells. Over time, this repeated damage can lead to mutations that cause cells to grow uncontrollably, which is the definition of cancer.
Alpha particles are relatively heavy and do not penetrate skin. They are not a risk from outside the body. But when alpha-emitting particles are deposited directly on lung tissue from inhaled air, they deliver concentrated radiation to the cells they contact. This is why radon is specifically a lung cancer risk and not a risk for other types of cancer.
No Immediate Symptoms
Radon exposure does not cause immediate symptoms like coughing, headaches, or difficulty breathing. The damage is cumulative and occurs over years of exposure. By the time lung cancer develops, the exposure has been happening for a long time. This is why professional radon testing is so important. You cannot feel, smell, or see radon, and you will not know you are being exposed without a test.
3. Who Is at Risk?
Everyone who is exposed to elevated radon levels is at risk. However, some groups face higher risk than others.
Smokers and former smokers
The combination of smoking and radon exposure creates a synergistic risk. According to the EPA, a smoker exposed to radon has a lung cancer risk roughly 10 times higher than a non-smoker at the same radon level. The combined risk is greater than the sum of the individual risks.
Non-smokers
Radon is the number one cause of lung cancer among people who have never smoked. About 2,900 of the estimated 21,000 annual radon-related lung cancer deaths occur in people who never smoked. This is a significant risk that affects people who might otherwise consider themselves low-risk for lung cancer.
Children
Children may be more vulnerable to radon because their lungs are still developing, they breathe faster than adults (inhaling more radon per pound of body weight), and they have more years ahead of them during which cancer could develop. The EPA considers children to be at increased risk.
People who spend more time at home
Since radon exposure is cumulative, people who spend more time at home are exposed to more radon. This includes remote workers, retirees, stay-at-home parents, and anyone who spends significant time in the lower levels of their home where radon tends to concentrate.
4. What the EPA and WHO Say
The EPA has established an action level of 4 pCi/L for indoor radon. If your home tests at or above this level, the EPA recommends installing a radon mitigation system. The EPA also notes that there is no known safe level of radon exposure and encourages homeowners to consider mitigation even at levels between 2 and 4 pCi/L.
The World Health Organization takes a more aggressive position. The WHO recommends an action level of 2.7 pCi/L (100 Bq/m3), and states that national action levels should not exceed 8.1 pCi/L (300 Bq/m3). The WHO's lower recommendation reflects the growing scientific evidence that risk exists at levels below the EPA's 4 pCi/L threshold.
Both organizations agree on the fundamental science: radon causes lung cancer, and the risk increases with higher exposure levels and longer exposure duration. The relationship between radon exposure and lung cancer risk is well-established through decades of epidemiological research, including studies of uranium miners and residential populations.
The Good News
Unlike many cancer risks, radon exposure is something you can measure and control. Testing is simple and affordable, and radon solutions for homeowners are highly effective, reducing levels by 90% to 99% in most homes. Radon-related lung cancer is one of the most preventable forms of cancer, but only if you know your levels and take action when they are elevated. For a complete breakdown of risk by radon level, see our radon and lung cancer risk guide.
5. Radon Risk in Georgia
Georgia has a mixed radon risk profile. The northern part of the state, including the Atlanta metropolitan area, sits on Piedmont and Blue Ridge geological formations that contain granite and gneiss bedrock. These rock types are higher in naturally occurring uranium, which produces radon as it decays.
Several north Georgia counties fall in EPA Zone 1 (highest predicted radon potential), and many more fall in Zone 2 (moderate potential). However, the EPA is careful to note that elevated radon levels have been found in homes in every zone, including Zone 3 areas. The zone map predicts average potential, not individual home levels.
In the Atlanta metro area, radon testing has consistently found homes above the EPA action level. The only way to know your specific home's radon level is to test it. Two homes on the same street can have very different radon levels because of differences in soil composition, foundation type, and home construction.
Georgia does not require radon testing for home sales or new construction at the state level, but radon testing is increasingly common during real estate transactions, particularly in north Georgia counties where awareness is growing. Learn the difference between testing methods in our short-term vs. long-term testing comparison.
6. What You Can Do About It
The single most important step is testing your home. Radon testing is inexpensive (professional tests typically cost $125 to $250 in the Atlanta area) and takes about 48 hours. Until you test, you simply do not know what your exposure level is.
If Your Levels Are Below 4 pCi/L
Your home passes the EPA's action threshold. Retest every 2 years, or sooner if you make significant changes to your home (renovations, HVAC modifications, foundation work). Consider mitigation if levels are between 2 and 4 pCi/L, especially if you have smokers or children in the home.
If Your Levels Are At or Above 4 pCi/L
The EPA recommends installing a mitigation system. A professional radon mitigation system typically costs $1,200 to $2,500 and can reduce radon levels by 90% to 99%. Most systems are installed in a single day. After installation, a follow-up test confirms the system is working effectively.
Radon mitigation is one of the most cost-effective health interventions available. For a one-time investment of $1,200 to $2,500 plus minimal ongoing electricity costs, you can virtually eliminate a significant cancer risk for your entire family. There are very few health problems where the solution is this affordable and this effective.
