Researchers analyzed lung function changes in 206 WTC responders from the ESU. Since all ESU officers are required to take an annual lung function tests, the researchers, led by Dr. Eli J. Kleinman, supervising chief surgeon of the New York Police Department, had a unique opportunity to study possible changes in the years after exposure to the WTC site. Also, unlike firefighters, the ESU officers didn't have a history of repeated exposure to respiratory hazards.
While some of the officers showed lower lung function at follow-up tests in 2002 and 2007, most of the officers had no change in lung function beyond the expected age-related declines. Some 5 percent of the officers did have reductions consistent with mild lung dysfunction.
Not surprisingly, decreased lung function was more likely for officers with respiratory symptoms, those who were present when the towers collapsed and those who worked long hours at the WTC site. Smokers had greater declines in lung function, as did the small number of officers who didn't wear respiratory protective devices while working at the WTC site. These findings led researchers to call for the use of effective personal protective equipment and limited duty hours for responders exposed to hazardous conditions.