Radon concentrations are traditionally expressed in picocuries (pCi) per liter, whereby 1 pCi represents the amount of material needed to produce 2.2 radioactive decays per minute. For comparison to epidemiological studies of uranium miners, picocuries are converted into a measure called a Working Level Month (WLM). A WLM is defined as a radon concentration of 100 picocuries per liter of air inhaled for 170 hours. A person breathing the air in a home with a radon level of 4 picocuries per liter (the action level set by EPA) would receive an annual dose equivalent to one WLM.
Fred Cross, a biochemist at Battelle Pacific Northwest Laboratories in Richland, Wash., has performed radon experiments on rats. At high exposures, such as are found in uranium mines, rats develop lung cancers at rates comparable to those found in epidemiological studies of uranium miners.
He has also exposed rats to much lower radon ...
