Californians are required to disclose the radon level in their home, if known, before transferring it to a new owner. Nevadans are not. In both states, renters are particularly vulnerable. "There are no regulations to protect renters from radon in Nevada," said Susan Howe, radon education program director for the University of Nevada Cooperative Extension. "There are no regulations dealing with radon in Nevada, period. There are no laws to protect people when they buy or build homes."

More than two decades after U.S. regulators first issued guidelines on radon infiltration into homes and buildings, the World Health Organization reports that the radon threat to human health is much more serious than previously known.

By the time 11-year-old Chandler Nash Elliott hung himself in his father's home, the state of Nevada had a nearly two-inch-thick case file full of abuse and neglect allegations that almost spanned the boy's lifetime.