Radon (Rn) is a noble gas produced by the radioactive decay of radium, found in uranium ores, phosphate rock, and a number of common minerals (1). It is an invisible, odorless, and tasteless gas that seeps up through the ground and diffuses into the air (3). Because it is inert, radon itself does not pose a hazard. However, it undergoes radioactive decay producing a series of short-lived progeny, often called daughters, that can emit alpha, beta, or gamma particles and are electrically charged, readily attaching to air-borne particles (1). Alpha particles can travel only a short distance and cannot go through your skin. Beta particles can penetrate your skin, but they cannot go all the way through your body(2). Gamma radiation, however, can go all the way through your body (2).

The primary source of exposure to radon is indoor or household air. Many houses and buildings have been constructed right on top of radon emitting rocks. Radon daughters are often attached to dust, and you are exposed to them primarily through breathing (2). They are present in nearly all air. However, background levels of radon in outdoor air are generally quite low, about 0.003 to 2.6 picocuries of radon per liter of air (2). In indoor locations, such as homes, schools, or office buildings, levels of radon and daughters are generally higher than outdoor levels (2). Cracks in the foundation or basement of your home may allow increased amounts of radon to move into your home. In some areas of the country the amount of uranium and radium in rock types, such as phosphate rock or granite, is high. In these areas radon levels in outdoor air will generally be higher (2).

The radiation released during the process of decay passes into lung tissue and causes lung damage. There is very limited information on whether radon gas can penetrate the skin, but some radon may be able to pass through the skin when you bathe in water containing radon (2). Long-term exposure to radon and radon daughters in air increases your chances of getting lung cancer. When exposures are high, noncancer diseases such as thickening of certain tissues of the lungs may occur. This usually occurs within a few days or weeks after exposure to radon. Cancer due to radon exposure takes several years before effects become apparent (2). This is known from studies of workers exposed to radon in mines, primarily uranium miners, and from tests on laboratory animals (2). It is not known if radon causes health effects other than to the lung.

The following are some very informative external links that pertain to Radon:

EXTOXNET FAQS IndoorAir Pollution Home


1. Godish, T. Indoor Air Pollution Control. Lewis Publishers. Chelsea, MI. 1989.

2. Radon, ASTDR Public Health Statement, December 1990. URL: http://faraday.ee.latrobe.edu.au/~khorsell/radiation/statements/radon.html

3. Questions and Answers about Radon and Cancer, National Cancer Institute. June 1996. URL: http://imsdd.meb.uni-bonn.de/cancernet/600352.htm

This Page prepared by B.T. Johnson, November 1997 UCD EXTOXNET FAQ Team.