Children exposed to the dust cloud following the September 11 collapse of the twin towers were found to be twice as likely to be diagnosed with asthma as those not exposed to the dust cloud, a survey released today shows.

New York City’s Department of Health and Mental Hygiene released a survey on post – 9/11 effects on children, based on a World Trade Center health registry, which comprises data on about 71,000 individuals.

Wednesday’s survey is based on data from about 3,100 children under 18 years of age at the time of the World Trade Center catastrophe, who lived or went to school south of Canal Street or were south of Chambers Street on 9/11, reports the New York Times.

Among its findings, the survey shows that children under age 5 exposed to the dust cloud created by the collapsing twin towers were more likely than the average child to be diagnosed with asthma in the two to three years after the event.

These figures are substantially lower than those found in rescue workers, who were 12 times as likely to be diagnosed as the general population.

Half of the 3,100 children enrolled in the WTC Health Registry developed at least one new or worsened respiratory symptom, like a cough, in the few years after 9/11, the survey found. Overall, about 6 percent of the enrolled children were newly diagnosed with asthma.

The survey also looked at the mental health of enrolled children and found no evidence of increased rates of post-traumatic stress disorder. About 3 percent had symptoms suggestive of PTSD in the years after 9/11, about the same level of children in the general population. Children who were caught in the dust cloud experienced higher levels of stress than those who were not exposed, it was found.

Additional research is needed to clarify those findings, the Department has said, as the information is self-reported. The World Trade Center Health Registry initial survey was conducted in 2003 and 2004.