Radon guide
What radon does to your health
The health danger agencies warn about with radon is lung cancer, and it takes years to appear. EPA and the Surgeon General's office estimate that radon is behind more than 21,000 lung cancer deaths in the United States each year, second only to smoking and the top cause among people who have never smoked.
How does radon cause lung cancer?
Radon breaks down into radioactive particles. When you breathe them in, some get trapped in your lungs; as they break down further they give off small bursts of energy that can damage lung tissue. Over a lifetime, that damage can lead to cancer, though not everyone exposed to high levels develops it. Radon is a gas you inhale, so the risk is to the lungs; EPA also notes that swallowing radon in well water carries a much smaller stomach cancer risk than breathing it.
Are there symptoms of radon exposure?
There is no warning sign to watch for: radon has no smell or color, and nothing tells you that you are breathing it. Lung cancer itself usually develops over many years, and most people notice nothing until the disease is advanced, when it is harder to treat. That is why health agencies tell everyone to test rather than wait for signs.
How risk rises with the level
EPA's lifetime estimate: out of 1,000 people living with each level, how many could get lung cancer from radon.
Source: EPA Assessment of Risks from Radon in Homes, as published in EPA's citizen and home buyer guides. Average US home: 1.3 pCi/L.
Why do smokers face so much more risk?
At every level in EPA's table, the estimate for smokers is several times the estimate for people who never smoked; at 4 pCi/L it is 62 against 7. The two exposures compound each other. Quitting lowers the risk, and EPA notes that former smokers fall somewhere between the two groups.
Who else is more exposed?
People who spend most of their day on a home's lowest floor, where radon tends to collect. CDC also lists burning wood or coal indoors, which adds particles to the air. For children, CDC says there is not enough data to show a higher cancer risk than for adults, though they may take in a larger dose at the same level because they breathe faster and their lungs are smaller.
Can you live in a house with high radon?
Many people do without knowing it; nearly 1 in 15 US homes is estimated to be at or above 4 pCi/L. The risk builds with years of exposure, so the answer is to test and, if the level is high, install a system that brings it down. A mitigation system typically gets a house down to 2 pCi/L or lower. Read how to test and how mitigation works.
This page explains public health estimates. It is not medical advice. If you are worried about lung cancer, talk to a doctor.
Sources: CDC, Radon and Your Health (June 2026); EPA, A Citizen's Guide to Radon (2016); EPA, Home Buyer's and Seller's Guide to Radon (2024). Updated October 2026.