Radon is a metallic element with the atomic number 86 and the symbol Rn. On the periodic table of elements, it is found in Group 18 and in Period 6 to the right of astatine. Radon is one of the Noble gases, also called the inert gases, along with helium, neon, argon, krypton, and xenon. Its name comes from a variation on another element, radium.
Radon, at one time called thoron, is highly radioactive, with a short half-life. It has twenty known isotopes, only three of which occur in nature, and various isotopes were discovered by different scientists. Although Ernest Rutherford discovered Radon-220, the discovery of radon-222 by Friedrich Ernst Dorn in Halle, Germany in 1900 is counted by some as its official discovery. Dorn called it radium emanation, and that name, as well as the symbol Em, are occasionally used.
Radon has a limited number of uses. It is, for example, used as a neutron source and has a role in predicting earthquakes. But radon’s main use is in radiotherapy treatment for cancer. This is ironic, because radon is the second leading cause of lung cancer, as well as causing lung tissue damage that can progress to pulmonary fibrosis and emphysema.
How are people exposed to radon? Found in the Earth’s crust worldwide, and specifically in all fifty of the United States, radon seeps into buildings, particularly those built on granite. The entrance pathways include through the water supply, through openings surrounding sump pumps and drains, through gaps and cracks in the foundation, floors, and walls, and through construction joints, among others. Developments in construction techniques help to keep radon out of newly built homes, and are easier and cheaper to employ than the alternative of mitigating radon after it’s entered a home.
Estimates say that almost 1 in 15 homes in the United States have higher radon levels than the Environmental Protection Agency recommends. Unfortunately, regional and local tests, even on neighboring houses, do not reveal a building’s risk, but on the other hand, radon tests for buildings are cheap and simple, and the Environmental Protection Agency recommends that everyone conduct such a test or have it conducted.
Short-term and long-term tests are available, with short-term testing lasting 2–90 days, and long-term testing taking longer than that. Tests can be done by the homeowner or a qualified tester can be hired. The Environmental Protection Agency maintains a list of qualified testers.