By Gabe Semenza Radon is the second-leading cause of lung cancer in the United states, behind only smoking. Children are especially susceptible. It kills an estimated 21,000 people per year. Apparently, Olympic athletes aren't immune either. According to a news story published this week, Rachael Malmberg, a former U.S. Women's Olympic hockey team member, fell ill with stage 4 lung cancer, which she blames on dangerous levels of radon in her home. According to the story: The 3