What is Radon?
Radon is a gaseous radioactive element having the symbol Rn, the atomic number 86, an atomic weight of 222, a melting point of -71ºC, a boiling point of -62ºC, and (depending on the source, there are between 20 and 25 isotopes of radon – 20 cited in the chemical summary, 25 listed in the table of isotopes); it is an extremely toxic, colorless gas; it can be condensed to a transparent liquid and to an opaque, glowing solid; it is derived from the radioactive decay of radium and is used in cancer treatment, as a tracer in leak detection, and in radiography. (From the word radium, the substance from which it is derived.) Sources: Condensed Chemical Dictionary, and Handbook of Chemistry and Physics, 69th ed., CRC Press, Boca Raton, FL, 1988.
No immediate symptoms. Based on an updated Assessment of Risk for Radon in Homes, radon in indoor air is estimated to cause about 21,000 lung cancer deaths each year in the United States. Smokers are at higher risk of developing Radon-induced lung cancer. Lung cancer is the only health effect which has been definitively linked with radon exposure. Lung cancer would usually occur years (5-25) after exposure. There is no evidence that other respiratory diseases, such as asthma, are caused by radon exposure and there is no evidence that children are at any greater risk of radon induced lung cancer than adults.
What is the Average Level of Radon Found in a Home?
Based on a national residential radon survey completed in 1991, the average indoor radon level is about 1.3 picocuries per liter (pCi/L) in the United States. The average outdoor level is about 0.4 pCi/L.
So, you can see why it comes up often in a real estate transaction. Of course some people are more worried than others and this becomes part of the art of negotiation. During the inspection period (which is usually between 10 days and 2 weeks long) a buyer has the option to have a radon test performed usually by a general home inspector. The cost is somewhere around $100 for the test and it takes 48 hours to perform. If the results of the test come in above 4.0 pCi/L then it is very common for the Buyer to ask for the Seller to mitigate so that the radon level inside the habitable part of the home (not crawlspaces etc.) is below 4.0 pCi/L. The cost for mitigation can vary but in our area the typical cost is between $800 and $900.
What is done to mitigate the radon level in a home?
Most often a 4″ PVC pipe is inserted into a drilled hole in the basement slab. This pipe is routed to the outside of the home and above the roof line. Somewhere along the pipe a fan is installed that will run continuously and will suck the sub-slab air to the outside creating a vacuum. The diverted airstream does not allow radon to seep up through the concrete into the house.
Radon is a fixable problem and it is a good idea to have the test done. I tell my clients that even if they are not concerned about the risk most likely the people who buy the house from them will be.