From NPR:
New data from a public health registry that tracks the health effects of 9/11 suggest that as many as 70,000 people may have developed post-traumatic stress disorder as a result of the terrorist attacks.
The estimate, released Wednesday by New York City's Department of Health, is based on an analysis of the health of 71,437 people who enrolled in the World Trade Center Health Registry. They agreed to be tracked for up to 20 years after the Sept. 11, 2001, attacks, and the study was based on answers they volunteered about their health two and three years after the attack.
Of the estimated 400,000 people believed to have been heavily exposed to pollution from the disaster, data suggests that 35,000 to 70,000 people developed PTSD and 3,800 to 12,600 may have developed asthma, city health officials said.
They include rescue and recovery workers, lower Manhattan residents, area workers, commuters and passers-by.
