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How does radon cause lung cancer?

By Radon411 Editorial TeamUpdated How we research

Short answer

Radon decays into radioactive particles that, when breathed in, are deposited on the cells lining the airways, where their radiation can damage DNA and lead to lung cancer over many years. Radon is the second leading cause of lung cancer in the United States, and smoking greatly raises the risk.

Next step: a test is the only way to know your home's level. How to test your home

Radon escapes from the ground into the air, where it decays into radon progeny, solid radioactive particles with short half-lives that can attach to dust. Breathed in, they are deposited on the cells lining the airways, and as they break down further they release small bursts of energy, including alpha particles, that can damage lung tissue and DNA.

The risk depends mostly on how much radon is in your home, how much time you spend there, and whether you smoke or have ever smoked. EPA estimates radon causes about 21,000 lung cancer deaths a year in the United States, about 2,900 of them among people who never smoked.

It takes many years for lung cancer to develop, and most people have no symptoms until it is advanced. Not everyone exposed to elevated radon will develop lung cancer, and reducing radon in your home always helps reduce the risk.

What to do next: test your home, fix a high level, and if you smoke, stop. If you are concerned about your health, talk to a doctor and mention your radon result.

From radon gas to lung damage, step by step

Radon itself is a gas you breathe in and out. The harm comes from what it turns into. Radon escapes from the ground into the air, where it decays and produces further radioactive particles, and those particles are what reach the lining of the lungs.

How radon leads to lung cancer
StageWhat happens
Decay in the airRadon decays quickly into radon progeny, radioactive atoms with short half-lives
Particles formThe progeny are solid particles that can attach to dust and other particles and move with the air
Breathing inThe particles can get trapped in the lungs and are deposited on the cells lining the airways
RadiationAs they break down further, they release small bursts of energy; some decays expel high-energy alpha particles
DamageThat energy can damage lung tissue and DNA and, over a lifetime, lead to lung cancer

The alpha particles are the main source of health concern. Many scientists believe that the alpha radiation dose from long-term exposure to elevated levels of radon progeny in air increases the chance of getting lung cancer.

How large the risk is

Radon is the second leading cause of lung cancer in the United States; only smoking causes more lung cancer deaths. EPA estimates that radon is responsible for about 21,000 lung cancer deaths every year, about 2,900 of them among people who have never smoked, and that it is the number one cause of lung cancer among non-smokers.

Bar chart of EPA's radon risk estimates for people who smoked and people who never smoked: out of 1,000 people exposed over a lifetime, about how many could get lung cancer at 20, 10, 8, 4, 2, 1.3 and 0.4 pCi/L, from about 260 smokers at 20 pCi/L to about 3 at 0.4 pCi/L, with EPA's advice at each level.
Read this figure as text

EPA estimate, lifetime exposure

  • Out of 1,000 people who smoked
  • Out of 1,000 people who never smoked
About how many people out of 1,000 exposed over a lifetime could get lung cancer, by radon level
Radon levelCould get lung cancer, per 1,000What to do
20 pCi/L740 Bq/m³Smoked: About 260Never smoked: About 36Fix your home
10 pCi/L370 Bq/m³Smoked: About 150Never smoked: About 18Fix your home
8 pCi/L300 Bq/m³Smoked: About 120Never smoked: About 15Fix your home
4 pCi/L150 Bq/m³Smoked: About 62Never smoked: About 7Fix your home
2 pCi/L75 Bq/m³Smoked: About 32Never smoked: About 4Consider fixing between 2 and 4 pCi/L
1.3 pCi/L50 Bq/m³Smoked: About 20Never smoked: About 2Average indoor radon level
0.4 pCi/L15 Bq/m³Smoked: About 3Never smoked: No figure givenAverage outdoor radon level
  • Smoked: If you are a former smoker, your risk may be lower.
  • Never smoked: If you are a former smoker, your risk may be higher.
  • Reducing radon levels below 2 pCi/L (75 Bq/m3) is difficult.
  • Lifetime risk of lung cancer deaths, as EPA estimates it.
Out of 1,000 people exposed over a lifetime, about how many could get lung cancer at each radon level, for people who smoked and people who never smoked.

The risk rises with exposure: the risk of lung cancer increases proportionally with increasing radon exposure, by about 16 percent per 100 of long-term average concentration, in WHO's estimate. Worldwide, WHO estimates radon causes between 3 and 14 percent of all lung cancers in a country, depending on its average radon level and how many people smoke.

Radon and smoking

Radon and cigarette smoke work together. Lung cancer risk is higher for smokers because of the synergistic effects of radon and smoking, and smokers are estimated to be 25 times more at risk from radon than non-smokers. Radon still causes lung cancer in people who have never smoked.

Lifetime lung cancer risk at about 1.3 pCi/L, the average indoor radon level
PersonChance of lung cancer
Never smokedAbout 2 in 1,000
SmokerAbout 20 in 1,000

Two steps lower the risk: stop smoking, and lower your radon level. See how radon affects human health.

Why it takes years

Lung cancer from radon is not a quick reaction. It takes many years for lung cancer to develop, and the time between exposure and the onset of the disease may be many years. Not everyone exposed to elevated levels of radon will develop lung cancer.

What your chance of lung cancer from radon depends on
FactorWhy
How much radon is in your homeThe risk rises with the level
How much time you spend in your homeExposure adds up over time
Whether you smoke or have ever smokedRadon and smoking act together

The evidence comes from both high and ordinary levels. An increased rate of lung cancer was first seen in uranium miners exposed to very high concentrations, and studies in Europe, North America and China have confirmed that even the lower concentrations commonly found in homes pose health risks.

Symptoms and medical tests

Radon gives no warning. Most people don't have symptoms until lung cancer is advanced, when it is harder to treat. Nor can a doctor measure past radon exposure in a routine way.

What medical tests can and cannot show about radon
QuestionAnswer
Can routine medical testing find radon in the body?No. Radon in human tissues is not detectable by routine medical testing
Can any test find its decay products?Some radon progeny can be detected in urine and in lung and bone tissue
Do those tests show how much radon you breathed?No. They cannot tell how much radon you were exposed to
How is exposure estimated?By measuring radon levels in the air

That is why testing is the only way to know if you and your family are at risk from radon. See what are the symptoms of radon in your home.

Lowering the risk

Reducing radon inside your home will always help reduce your risk of lung cancer, and you will reduce your risk when you reduce radon levels, even after living with an elevated level for a long time. The risk from breathing radon in air is much larger than the risk of stomach cancer from swallowing water with radon in it, so the air in your home comes first.

Questions about radon and lung cancer

How does radon cause lung cancer?

Radon decays into radioactive particles that, when breathed in, are deposited on the cells lining the airways. The radiation they give off can damage DNA and lung tissue and, over time, lead to lung cancer.

How much radon exposure causes lung cancer?

The risk rises with exposure: it increases proportionally with increasing radon exposure. Not everyone exposed to elevated levels will develop lung cancer.

How long does it take radon to cause lung cancer?

Many years. The time between exposure and the onset of the disease may be many years.

Can non-smokers get lung cancer from radon?

Yes. EPA estimates radon is the number one cause of lung cancer among non-smokers, with about 2,900 deaths a year among people who never smoked.

Does radon cause other cancers?

Lung cancer is the cancer radon is known for. The risk of stomach cancer from swallowing water with radon in it is much smaller than the lung cancer risk from breathing radon in air.

Are children more at risk from radon?

There is not enough data to show whether children have a higher risk of lung cancer from radon than adults.

Can a doctor test me for radon exposure?

Not with routine tests. Some decay products can be detected in urine and tissue, but those tests cannot tell how much radon you were exposed to.

Learn

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