How Much Radon Exposure Is Dangerous?

Radon is a naturally occurring gas that rises from the soil, and it's completely invisible, odorless, and tasteless. You won't know it’s there by sight or smell, but long-term exposure to elevated radon levels can quietly lead to serious health risks, especially in enclosed spaces like basements or crawl spaces. This page answers a question that many homeowners in our area never think to ask until it’s too late: how much radon is dangerous?

What Levels Are Considered Dangerous?

The Environmental Protection Agency (EPA) has set a recommended action level of 4.0 picocuries per liter (pCi/L) for indoor radon levels. At or above this threshold, corrective action is strongly advised. However, many health experts warn that even radon levels between 2.0 and 4.0 pCi/L can carry risk, especially with prolonged exposure.

Radon becomes dangerous because of its cumulative effect on your lungs. The gas breaks down into radioactive particles that, when inhaled over time, can damage lung tissue and increase the likelihood of developing lung cancer. Radon exposure is the second leading cause of lung cancer in the United States, after smoking.

Short-Term vs. Long-Term Exposure

Brief exposure to elevated radon levels isn’t likely to cause immediate harm, but the danger builds over time. Living in a home with high radon for months or years, especially if you sleep or work in a basement, greatly increases the risk of developing long-term health issues. The problem is, you don’t feel radon building up. There are no symptoms, no irritation, no signs to alert you.

That’s why consistent testing and early action are critical. A home that tests “safe” one year may show elevated levels the next due to changes in ventilation, foundation shifts, or seasonal variations in soil moisture.

Who Is Most at Risk?

Some people face greater risks than others when exposed to radon, even at lower levels. These include:

• Smokers or former smokers who already have damaged lung tissue
  
• Young children whose developing lungs are more sensitive
  
• Elderly adults who have longer cumulative exposure and often spend more time indoors
  
• Anyone with chronic respiratory conditions, like asthma or COPD
  

For these groups, radon levels below 4.0 pCi/L can still be dangerous. Knowing who lives in your home, and how much time they spend in lower levels can help you evaluate your overall risk.

You Can’t See the Problem? That’s What Makes It Dangerous

Unlike a water leak or a foundation crack, radon exposure doesn’t give you visible warnings. You won’t notice a smell, a sound, or a physical clue. Many homeowners assume their house is safe because it looks dry or structurally sound, but radon can enter through tiny gaps in the foundation, porous concrete, or even well water in some areas.

Even homes without basements can test high. Radon gas moves upward from the soil and accumulates in any enclosed space with poor ventilation. The only way to know how much radon is present is to test for it directly.

How to Know If You're at Risk

Every home should be tested for radon, especially in areas where elevated levels are common. You can’t rely on appearance, smell, or even recent renovations to tell you whether radon is present. The gas moves up from the soil and can enter through the tiniest openings in a foundation, crawl space, or slab. Even airtight homes with no visible cracks can accumulate radon to unsafe levels.

Certain parts of the country are more vulnerable than others. In Pennsylvania, most counties are classified as Zone 1, meaning homes are very likely to exceed the EPA’s action level of 4.0 pCi/L. Tennessee faces similar challenges, with an estimated 40% of homes testing above safe thresholds. In Maryland, the statewide average indoor radon level is 5.4 pCi/L, already beyond what’s considered safe for long-term exposure.

Protecting Your Home and Health

If your home does have elevated radon levels, mitigation systems can be installed to vent the gas safely outside. These systems are affordable, discreet, and highly effective when installed properly. More importantly, they provide peace of mind, protecting not just your home, but the people inside it.

The cost of mitigation is far less than the potential cost of delayed action. Lung cancer caused by radon exposure is preventable, but only if you know the risk is there.

Get a Radon Mitigation Estimate

If your home has elevated radon levels, taking action now can protect your family’s long-term health. At '58 Foundations & Waterproofing, we offer professional radon mitigation solutions to safely reduce radon levels and restore peace of mind. Contact us today to request a free estimate and learn how we can help make your home a healthier, safer place to live.