In the largest study so far of post-9/11 health problems, almost 70 percent of workers who helped with the cleanup of the World Trade Center site suffered new or worsened respiratory symptoms, researchers at Mount Sinai Medical Center found. The study found that people who worked on the cleanup had pulmonary abnormalities of twice the rate in the comparable United States population and that the abnormalities persisted for many months and, in some cases, years after exposure.
See "Many 9/11 Workers Have Lung Issues, Report Says", Maria Newman, The New York Times, September 4, 2006