When legendary college football coach Joe Paterno died of lung cancer last month, most of the questions surrounding his legacy had to do with his storied career and involvement in a sex abuse scandal that rocked Penn State University. Very few reports delved into the fact that Paterno, a nonsmoker, died from a disease in which 98 percent of those it afflicts smoked during their lifetime.

Making Paterno's diagnosis even worse was that he suffered from an aggressive form of the cancer – metastatic small-cell carcinoma – only observed in 15 percent of all cases. His family announced his battle with the disease in November 2011, but it is unclear when exactly doctors diagnosed him.

Some news outlets have speculated that Paterno's cancer may be at least partially attributable to radon gas exposure. According to Northville Patch, Paterno lived in a high radon risk area – the Pennsylvania Appalachians.

Exposure to radon gas is the second-leading cause of lung cancer in the United States, behind smoking. Each year, radon gas contributes to the deaths of 21,000 Americans. Because the gas is invisible and odorless, if homeowners have not established radon detectors, they are unlike to know that unhealthy levels of radon have infiltrated their home until lung cancer has already developed.

"Lung cancer doesn't have real symptoms until it's too late and at an incurable stage," Luzerne County pathologist Dr. Mary Pascucci told the Scranton Times-Tribune. "There are no screening tests for lung cancer like we do for breast and prostate cancer, so the problem is that it's found at a very late stage."

The best way for homeowners to avoid exposure to radon gas is to hire a home inspection service to conduct radon testing.