The most dangerous part of firefighting may not be the danger of being burned in a fire. It’s cancer. Cancer caused 61 percent of the professional firefighter line-of-duty deaths from January 1, 2002, to December 31, 2016, according to the International Association of Fire Fighters (IAFF). That is more than any other single cause. In 2016 alone, cancer caused 70 percent of the line-of-duty deaths of professional firefighters. It’s no mystery why the cancer risk has increased. “In today’s modern society – in buildings that our people go into every day – everything is now made out of chemicals,” Professional Firefighters of Arizona President Bryan Jeffries told a state legislative committee last year.