What is Radon?

Radon is a naturally-occurring radioactive gas.  Found everywhere, radon results from the decay of radium, a radioactive element found in most soils.  The radium remains in the ground, but radon gas seeps through the soil and enters buildings.  Radon is colorless, odorless, and tasteless gas that can only be detected by testing.

Radon is denoted by the chemical symbol Rn and has an atomic number of 86.  Radon is a noble gas and is generally chemically non-reactive.  However, radon is radioactive in that there are no stable isotopes.  The most stable isotope, radon-222 (222Rn or Rn-222) has a half-life of 3.8 days (92 hours).  Radon concentration in soil and rock is maintained by the decay of its longer-lived progenitors: radium, uranium, and thorium.

Radon is a dense gas and will percolate upward through the soil. As a gas, radon can easily be inhaled and subsequently undergo radioactive decay while in the lungs.  Radon decay products, like radon's progenitors, are solids and will deposit themselves on surfaces, including in the lungs, as radioactive contaminants. When each atom of radon decays, it emits an alpha particle and a radioactive decay product.  Some of these radon decay products further decay by producing alpha particles.  These alpha particles can damage the living cells in your lungs, causing radon-induced lung cancer. The decay in the lungs of radon the radon decay products or their inhalation can increase the risk of cancer.

Radon concentrations vary from location to location.  Even homes next door to each other can have very different radon concentrations.  The US EPA has created maps showing the potential for high radon concentrations.  Elevated radon gas concentrations have been found in every county in the United States.


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