http://iaq.custhelp.com/cgi-bin/iaq.cfg/php/enduser/std_alp.php?%20p_lva=&p_li=&p_accessibility=0&p_redirect=&p_page=1&p_cv=&p_pv=1.370&p_prods=370
U.S. Environmental Protection Agency
This document answers questions about radon. The document discusses sources of radon, what the health effects from exposure to radon are, what the average level of radon found in a home is, and more.