About 1 in 7 , or 13.5 percent of adults who encountered intense dust clouds after the collapse of the World Trade Center on September 11 were later found to have asthma , compared with just 8.4 percent who had no dust cloud exposure , researchers in Atlanta and New York City reported on Tuesday . Among rescue workers , the asthma risk was highest for those who worked on the pile on September 11 . Likewise , among various groups of people connected to the Twin Tower collapse , rescue and recovery workers were more likely to have a diagnosis of asthma ( 12.2 percent ) than passers-by ( 8.4 percent ) . The results are from a survey , conducted from November 2006 through December 2007 , to assess the health status of more than 46,000 adults five to six years after the disaster . Health.com : Bad air day ? Here 's how to survive . That such a horrific event left lasting physical and emotional scars is , perhaps , no great surprise . Among adults with no prior diagnosis of post-traumatic stress disorder ( PTSD ) , 23.8 percent have reported symptoms after September 11 , and the prevalence of symptoms has increased over time , researchers reported in the Journal of the American Medical Association . The mental health effects , which can be debilitating and often chronic , `` seem to be the largest health problem coming out of 9/11 '' says Lorna Thorpe , Ph.D. , the deputy commissioner of the New York City Department of Health and Mental Hygiene Division of Epidemiology and one of the coauthors of the study . `` But immediately after the 9/11 event , I do n't think there was a clear understanding of what the physical impacts would be . '' Health.com : Is your child 's asthma under control ? Take this test . People in the vicinity of the collapse had `` the potential to inhale huge amounts of particulate matter , '' observes Joan Reibman , M.D. , an associate professor of medicine and environmental medicine at the New York University School of Medicine and the director of the school 's Bellevue Asthma Center , who was not involved in the study . `` We think that could act as a real irritant to the airways . '' Some 23 million Americans have asthma , a lung condition that causes airway swelling and inflammation . People with asthma may experience repeated bouts of coughing , wheezing , shortness of breath , and tightness in the chest . Anthony M. Szema , M.D. , an assistant professor of medicine and surgery and the head of the allergy diagnostic unit at SUNY Stony Brook School of Medicine , has studied the effects of the World Trade Center collapse on children living in Manhattan 's Chinatown . His team 's most recent study , accepted for publication in Allergy & Asthma Proceedings , will show that the rate of asthma at the closest elementary school to the World Trade Center ( 29 percent ) is high compared with the rate of asthma in children in the general population . According to the Centers for Disease Control and Prevention ( CDC ) , 9.3 percent of U.S. children have asthma . `` [ The new study ] is entirely congruous with our findings , '' he says . Health.com : As a new mom , I struggled with my daughter 's chronic cough . The CDC 's Robert M. Brackbill , Ph.D. , M.P.H. , led the team of New York City and Columbia University researchers whose study examined the longer-term health impact of exposure to Ground Zero and its varying effect across groups of people . The analysis is based on data from the World Trade Center Health Registry , described as the largest post-disaster-exposure registry in U.S. history . More than 71,000 rescue and recovery workers , lower Manhattan office workers , nearby residents , and passers-by enrolled in the registry . Participants were interviewed from September 2003 through November 2004 to record their exposure to the disaster and document their pre- and post-event health status , and again in 2006-2007 . Health.com : Diabetes plus stress can equal high blood sugar . For each group followed , intense exposure to the dust plume was associated with new asthma diagnoses . Among rescue and recovery workers , for example , the asthma risk was highest for those who worked on the pile on September 11 . The risk diminished with later start dates . However , even downtown office workers and lower Manhattan residents were affected . Among these people , the risk of asthma was highest if there was a heavy coating of dust in their home or office , compared with no such damage . `` It shows that people who had heavy dust exposure in the initial period , that this was a risk to developing asthma but not the only risk , '' says Reibman , who also serves as the director of New York City 's World Trade Center Environmental Health Center , one of three centers dedicated to treating September 11-related conditions . Reibman says the new study is important because , in addition to corroborating previous studies , it should help people with September 11-related asthma realize that their symptoms are real . Health.com : Managing the highs and lows of manic depression . `` I think it helps us understand that there 's a cause for many of these symptoms , '' she says . She encourages people to recognize their symptoms and seek a proper diagnosis and treatment . 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Health survey looked at 46,000 adults five to six years after 9/11 attacks . The study found that the number of people who reported having been diagnosed with a mental illness increased by about 20 percent in those years. 23 million Americans have asthma , which causes airway swelling and inflammation .