As many as 70,000 people in New York may have developed post-traumatic stress disorder because of the Sept. 11 attacks, according to a report by the city's health department.

The report, which appears in Wednesday's Journal of Urban Health, looked at health effects among 71,437 people who registered in the World Trade Center Health Registry and agreed to be tracked for up to 20 years after the attacks on Sept. 11, 2001, that killed nearly 3,000 people.

On Sept. 11, two hijacked planes crashed into the World Trade Center in New York City, one crashed at the Pentagon in Arlington, Va., and a fourth went down in a field in Shanksville, Pa.

Health officials acknowledged it is difficult to pinpoint how many people became ill as a result of the attacks. They said that of the slightly more than 400,000 people who were heavily exposed to the disaster, the latest data suggests:

  • 35,000 to 70,000 people developed PTSD.
  • 3,800 to 12,600 people may have developed asthma.

"The consensus among physicians is that when it comes to physical health, the vast majority of people felt symptoms in the first year," said Lorna Thorpe, deputy commissioner for epidemiology at the New York City Health Department.

"A small proportion of people, however, developed symptoms years later."

In some cases, it was difficult to tell whether symptoms were related to the attacks or existing conditions, she added.

Half of those surveyed said they were in the dust cloud left by the collapsing towers, 70 per cent witnessed a traumatic sight — such as a plane hitting a tower or falling bodies — and 13 per cent were injured that day.

Rescue and recovery workers were not the only people affected, said Dr. Mark Farfel, director of the registry.

"Living and working near the WTC site also put people at risk of health problems," Farfel said.

Ailments both physical, psychological

Two to three years after the disaster, psychological trauma and new respiratory problems were still elevated, according to the report.

The rate of PTSD was highest among those injured (35 per cent), low-income (31 per cent) and Hispanic (30 per cent) respondents. Asthma rates were highest (six per cent) among people who worked on the debris pile.

The city's health department and the federal Centers for Disease Control's Agency for Toxic Substances and Disease Registry conducted the study.

The sample includes an estimated 17 per cent of those exposed to the disaster as rescue and recovery workers, residents of the area, commuters or passersby.

New York City offers free physical and mental health care to eligible people affected by the attacks.

With files from the Associated Press