New York City firemen and emergency personnel exposed to dust from the collapse of the World Trade Center buildings experienced a decrease in lung function capability equal to 12 years of age-related decline, reports a new study published by the American Thoracic Society.

Researchers compared lung function data compiled by the New York City Fire Department for more than 12,000 of its firefighters and emergency personnel for the four years before the attacks and one year after. All of those included in the study were directly exposed to toxins surrounding Ground Zero after the towers collapsed, arriving either before the collapse or in the days immediately following.

More than 14 percent (1,660) of the rescue workers experienced early high-intensity exposure to the dust by arriving the morning of 9/11 and by being present during the collapse of the twin towers, the authors said. Nearly 68 percent (8,185) had intermediate-intensity exposure by arriving two days following the collapse. Roughly 16 percent (1,921) had low-intensity exposure by arriving at the site on or after the third day.

The investigators said that rescue workers who had exposure to early and intermediate arrival-based periods had significantly more frequent and more severe respiratory symptoms than did the group that arrived later. Researchers also noted that the initial lack of adequate respiratory protective equipment decreased any protective impact it would have been able to provide.