Researchers tracking Sept. 11 responders who became ill after working at the World Trade Center site found many had lung problems years later in a study the authors said proves persistent illness in people exposed to toxic dust caused by the twin towers' collapse.
The study by the Mount Sinai Medical Center's medical monitoring program examined more than 3,000 responders between 2004 and 2007, repeating exams conducted between the middle of 2002 and 2004.
Slightly more than 24 percent of the patients had abnormal lung function, the study found. In the earlier examinations, about 28 percent of the patients had similar results.
"We know people we are following are still sick. It's confirming what we've been seeing clinically," said Dr. Jacqueline M. Moline, who treats ailing responders and co-authored the study.
Experts have struggled since the 2001 attacks to find standards to define post-Sept. 11 illness and the time it would take to develop. The city's medical examiner recently added to the official victims' list a man who died in October of cancer and lung disease, citing his exposure to the dust cloud that enveloped the city when the 110-story towers collapsed.
Mount Sinai's program has treated more than 26,000 people who were at the site or worked there in the days after Sept. 11. The study's authors noted that participants asked to be enrolled in the program and may have more health problems than others who were exposed but didn't enroll.
But Norman H. Edelman, chief medical officer of the American Lung Association, said the study is "probably an important finding" of long-term post-Sept. 11 illness.
"The most reasonable explanation is that there's a subset of people who for whatever reason were more sensitive to the stuff that was inhaled," Edelman said.
The researchers tracked 3,160 people who took followup exams between September 2004 and December 2007; all had previous exams at least 18 months earlier.
The study appears in Thursday's editions of CHEST, a journal published by the American College of Chest Physicians.