According to a study by the American Medical Association, firefighters who responded to the World Trade Center were nearly 20 percent more likely to develop cancer than firefighters who were not at the site. The toxic dust and debris at the site contained more than 2,500 contaminants.

During the first seven years following 9/11, 263 of the firefighters were diagnosed with cancer, which is more than in the general population of same-aged men and more than in firefighters who were not at the site. Other illnesses included asthma, chronic sinus infection, depression, anxiety, panic attacks and post-tramatic stress disorder.Cancers attributed to breathing in those toxins didn't show up immediately after exposure, the study found. Leukemia didn't occur in the firefighters for five or six years; tumors, not for ten to 20 years. As a result of this study, and many more similar studies, legislators decided to extend the "look-back" period from 300 to 600 months.A study conducted jointly by the US Fire Administration and the National Institute of Occupational Safety and Health looked at the health of career firefighters in San Francisco, Chicago and Philadelphia. Health information was gathered from 29,993 career firefighters who worked from 1950 to 2009.The study found that compared to the general population, the firefighters had higher rates of cancers of the respiratory, digestive and urinary systems. The rate of mesothelioma (a cancer attributed to exposure to asbestos) was two times higher than the national rate.However, the study did not address other lifestyle factors, such as smoking, diet and alcohol consumption. In addtion, few women and minorities were part of the study.According to the National Fire Incident Reporting System, firefighting-related injuries average about 70,070 annually and the majority of those injuries (87%) are sustained at structure fires. One-fourth of those injuries are categorized as "over-exertion."