Were you looking for information about Radon? Radion is a common misspelling of radon.
Radon is an odorless, tasteless, and colorless radioactive gas that is released from the normal decay of uranium in rocks and soil. It is present in nearly all air and breathed in every day, but usually at low levels. The gas usually exists at low levels outdoors, but in areas without adequate ventilation (such as underground mines), radon can accumulate to levels that substantially increase the risk of lung cancer.
(Click Radon for more information on radon, including where it comes from, what long-term exposure can do to you, and how to measure radon levels in the home.)