radon(redirected from 222Rn)
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Colorless, odorless gas that occurs naturally due to the breakdown of minerals in the earth. It tends to become trapped in our modern, nearly air-tight homes. Since there has been some correlation between radon and lung cancer, the EPA recommends levels no higher than 4 picocuries per liter (pCi/L), although generally acceptable levels are in the range of 4 to 8 pCi/L. The EPA Web site at www.epa.gov has information on testing for radon and reducing it.