A study of 5,000 rescue workers published in April 2010 by Dr. David J. Prezant – the chief medical officer for the Office of Medical Affairs at the New York City Fire Department – found that all the workers studied had impaired lung functions, with an average impairment of 10 percent. The study found that firefighters who arrived on the Sept. 11 morning had the worst impairments, which presented themselves within the first year after the attack, with little or no improvements in the ensuing six years. Thirty to 40% of workers were reporting persistent symptoms and 1000 of the group studied were on "permanent respiratory disability". Dr. Prezant noted that medication given to the victims can ease but not cure the symptoms. Dr. Byron Thomashow, medical director of the Center for Chest Disease and Respiratory Failure at New York – Presbyterian/Columbia hospital, said that "The drop-off in lung function initially is really quite significant and doesn't get better. That's not what we've generally come to expect in people with fire and smoke exposure. They usually recover."
