Radon and Lung Cancer: Understanding the Health Risk

March 2, 2026

Radon is the second leading cause of lung cancer in the United States, responsible for approximately 21,000 deaths per year according to the EPA. In Indiana — one of the highest-radon states in the country — this is not an abstract national statistic. Most Indiana homes have radon levels above the U.S. average, and 65 of the state’s 92 counties are EPA Zone 1, meaning predicted average levels exceed the action level of 4 pCi/L.

How Radon Causes Lung Cancer

Radon-222 is a naturally occurring radioactive gas produced by the decay of uranium in soil and rock. It is invisible, odorless, and chemically inert — but radioactive. When radon decays, it produces short-lived radioactive particles called radon progeny (historically called “daughters”) — primarily polonium-218 and polonium-214.

When you breathe air containing radon, these progeny particles attach to the surfaces of your airways and lung tissue. As they decay, they emit alpha particles — high-energy radiation that cannot penetrate skin from the outside, but causes direct cellular damage when emitted inside the lung. This damage to lung cell DNA, accumulated over years, can trigger cancerous mutations.

The critical factors are concentration (measured in picocuries per liter, pCi/L) and duration of exposure. Higher levels and longer exposure = greater total dose = higher cancer risk.

Risk at Different Radon Levels

The EPA publishes lifetime lung cancer risk estimates based on radon exposure levels for both smokers and never-smokers (assuming 70-year lifetime, 70% of time indoors):

The EPA recommends considering mitigation at levels between 2 and 4 pCi/L, and strongly recommends it above 4 pCi/L. There is no known safe threshold — even low levels carry some risk.

Indiana’s Elevated Exposure Risk

Indiana’s geology — primarily glacial till deposits over radon-producing rock formations — means naturally high soil radon concentrations across most of the state. Combined with:

• Long, cold winters requiring homes to be tightly sealed (reducing natural ventilation)
• Predominantly basement construction (where radon accumulates most)
• Older housing stock with less air sealing

…Indiana homeowners face above-average radon exposure compared to most other states.

The EPA estimates 1 in 3 Indiana homes tests above the 4 pCi/L action level. Statewide testing data consistently shows Indiana among the top states for elevated residential radon.

Why the Latency Makes Radon Uniquely Dangerous

Radon-induced lung cancer typically has a latency period of 5–25 years between the exposure and diagnosis. This means:

• People who grew up in high-radon homes decades ago may be experiencing that risk now
• A home test showing 6 pCi/L today represents years of ongoing exposure, not a future risk — it’s a present one
• Mitigation installed today stops the accumulation of future dose but does not undo past exposure

This latency is why public health experts emphasize testing and action rather than waiting for symptoms — there are none until it’s too late.

The Smoker Interaction

The combination of smoking and radon is particularly dangerous because tobacco smoke damages the lung’s natural clearance mechanisms. Normally, the respiratory tract clears foreign particles through mucociliary action. Smoking impairs this system, meaning radon progeny linger in the lung longer, increasing their opportunity to deliver damaging radiation doses.

Radon-related lung cancer in smokers is largely preventable through both smoking cessation and radon mitigation. The combination of both interventions dramatically reduces risk.

Protecting Your Household

The risk from radon is real, measurable, and addressable. Unlike many environmental health risks, radon:

• Can be detected with a simple, inexpensive test
• Can be fixed with a proven mitigation system costing $1,200–$2,000
• Has regulated, licensed professionals in Indiana (IPLA) to ensure quality work

If you haven’t tested your Indiana home, testing is the essential first step. If your level is at or above 4 pCi/L, mitigation with a licensed Indiana contractor reduces the risk dramatically — typically achieving post-mitigation levels below 2 pCi/L, and often below 1 pCi/L.

Find a licensed Indiana radon mitigator on this site — every contractor profile shows their IPLA license number, type, and current status.