You canât see it. You canât smell it or even taste it, but radon gas is a deadly intruder in many homes. In fact, one out of every 15 homes in this nation has a high level of radon. Exposure to radon gas is the second leading cause of lung cancer in the United States today. Only smoking causes more lung cancer deaths. Unfortunately, too few Americans know the facts about this danger. While the U.S. Environmental Protection Agency has designated January as a month to call attention to this problem, it is just as deadly during the dog days of summer.