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Skip Navigation LinksPennsylvania Department of Health > My Health > Environmental Health > Environmental Fact Sheets > Radon


What is Radon?
Radon is a naturally occurring radioactive gas that is odorless and tasteless.  It is formed from the radioactive decay of uranium.  Uranium is found in small amounts in most rocks and soil.  It slowly breaks down to other products such as radium, which breaks down to radon. 
Sources of Radon in Indoor Air
Radon may be present in the earth and rock beneath homes and buildings; well water; and building materials. Radon enters homes and buildings primarily through sump holes, floor drains, cracks in foundations and concrete floors.  When trapped indoors, radon can become concentrated to unacceptable levels.
What is the Average Level of Radon in a Home?
Based on a national residential radon survey completed in 1991, the average indoor radon level is about 1.3 picocuries per liter (pCi/L) in the United States.  The average outdoor level is about 0.4 pCi/L.
What are the Health Effects of Exposure to Radon?
There are no immediate symptoms following exposure to radon.
The World Health Organization (WHO), the National Academy of Sciences, the US Department of Health and Human Services and the U.S. Environmental Protection Agency (EPA) have classified radon as a known human carcinogen, because of the wealth of biological and epidemiological evidence and data showing the connection between exposure to radon and lung cancer in humans.
Numerous studies have been conducted by various organizations around the world to examine the relationship of radon exposure and human lung cancer.  The largest was an international study, led by the National Cancer Institute (NCI), which examined the data on 68,000 underground miners who were exposed to a wide range of radon levels.  The study showed that these miners are dying of lung cancer at 5 times the rate expected for the general population.  This study also showed that miners were at risk of getting lung cancer following exposure to radon at concentrations similar to EPA�s action level of 4 pCi/L for lifetime home exposures to radon.  
The National Academy of Sciences (BEIR VI Report) estimates that radon causes about 15,000 to 22,000 lung cancer deaths a year in the United States.  Lung cancer usually occurs 5-25 years after exposure to radon.  Smokers are at higher risk of developing radon-induced lung cancer. 
There is no evidence that other respiratory diseases, such as asthma, are caused by radon exposure and there is no evidence that children are at any greater risk of radon-induced lung cancer than adults.
What can I do to protect my family?
The EPA has set a health-based guideline for radon in air inside homes of 4 pCi/L of air.
PADOH and EPA recommend remediation for homes with airborne radon levels at or above 4 pCi/L of air.
How can you find a Qualified Radon Service Professional in your area?
If you are interested in finding a qualified radon service professional to test or mitigate your home, or you need to purchase a radon measurement device, you should:
Contact your State Radon Contact at telephone number 1-800-23-RADON to determine what are, or whether there are, requirements associated with providing radon measurement and or radon mitigations/reductions in your State.  Some States maintain lists of contractors available in their state or they have proficiency programs or requirements of their own.
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Content Last Modified: 1/16/2009