Fifteen years after 9/11, illnesses compound for first responders

Tens of thousands of people who worked at ground zero are still coping with the long-term health effects from the worst terrorist attack in U.S. history. 15 years after the attack, doctors and researchers continue to study the connection between the toxins at the site and physical ailments, along with complications from mental health issues like post-traumatic stress disorder. NewsHour Weekend Special Correspondent Karla Murthy reports.