District of Columbia Lead-Safe and Healthy Homes Hub

Health Topics Radon


How does Radon Get Into the Home?

Radon is an invisible and odorless gas that is one of the leading causes of lung cancer. It comes from the natural breakdown of soil, rock, and water and gets into the air we breathe.

1. Cracks in solid floors
2. Construction joints
3. Cracks in walls
4. Gaps in suspended floors
5. Gaps around service pipes
6. Cavities inside walls

Radon gas typically accumulates the most in the lower levels of a structure but can spread depending on the circulation of air in a home and many other factors.

What are some Health Risks of Radon?

Radon gas decays into radioactive particles, which can get trapped in the lungs when you breathe. As these particles continue to break down, they can release small bursts of energy, which can damage lung tissue and lead to lung cancer. Radon is the number one cause of lung cancer in non-smokers. Stop smoking and lower your radon level to reduce your lung cancer risk.

The combination of smoking and radon exposure can greatly increase your chances of developing lung cancer.

Like other environmental pollutants, there is some uncertainty about the magnitude of radon health risks. However, we know more about radon risks than risks from most other cancer-causing substances. This is because estimates of radon risks are based on studies of cancer in humans (underground miners).

Smoking combined with radon is an especially serious health risk. Children have been reported to have greater risk than adults of certain types of cancer from radiation, but there are currently no conclusive data on whether children are at greater risk than adults from radon.

Your chances of getting lung cancer from radon depend mostly on:

• How much radon is in your home
• The amount of time you spend in your home
• Whether you are a smoker or have ever smoked

Testing for Radon

There is no known safe level of radon,so there is always some risk. But the risk can be reduced by lowering the radon level in your home.Testing is the only way to know if there is radon in your home. Radon is heavier than air, so it is usually found in higher concentrations in lower levels of buildings. The EPA and the Surgeon General recommend testing all homes below the third floor of a house or building for radon. You can test your own home because it is easy, inexpensive, and only takes a few minutes. You can also test for radon in the home by hiring a qualified tester.

U.S. EPA recommends seeking more than one estimate for any radon-related work, asking for references, and contacting some of those references to ask if they are satisfied with the contractor’s work.

How to Lower the Radon Levels in Your Home

There are several proven methods to reduce radon in your home, but the one primarily used is a vent pipe system and fan, which pulls radon from beneath the house and vents it to the outside. This system, known as a soil suction radon reduction system, does not require major changes to your home.

Sealing foundation cracks and other openings makes this kind of system more effective. Similar systems can also be installed in houses with crawl spaces.

One or more suction pipes are inserted through the floor slab into the crushed rock or soil underneath. They also may be inserted below the concrete slab from outside the home. The number and location of suction pipes that are needed depends on how easily air can move in the crushed rock or soil under the slab and on the strength of the radon source. Often, only a single suction point is needed.

Your home type will affect the kind of radon reduction system that will work best. Homes are generally categorized according to their foundation design.

For example: basement; slab-on-grade, concrete poured at ground level; or crawlspace, a shallow unfinished space under the first floor. Some homes have more than one foundation design feature. For instance, it is common to have a basement under part of the home and to have a slab-on-grade or crawlspace under the rest of the home. In these situations a combination of radon reduction techniques may be needed to reduce radon levels.

Radon contractors can use other methods that may also work in your home. The right system depends on the design of your home and other factors.


A special message from the District’s expert on Radon

Other Resources

For more information about Radon, please visit:

1. DC Radon [link]

2. EPA [link]

Radon Hotlines

1-800-SOS-RADON (1-800-767-7236)* National Radon Hotline Purchase radon test kits by phone.

1-800-55RADON (1-800-557-2366)*
National Radon Helpline Get live help for your radon questions.

National Radon Fix-It Line For general information on fixing or reducing the radon level in your home.

Safe Drinking Water Hotline, operated under contract to EPA. For information on testing, treatment, radon in water, and drinking water standards.