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  By the NYC Health Commissioner
  9/11-Affected People
  Healthcare Professionals


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Wave 2 Survey (5-6 years after 9/11)

Major Findings

The Registry published numerous findings based on data collected from its second major survey in 2006 and 2007.

Among the 50,000 study participants, probable post-traumatic stress disorder (PTSD) and new asthma were two of the most commonly reported conditions 5 to 6 years after 9/11. People caught in the dust cloud on 9/11 had the highest risk for developing these conditions according to findings . published in the Journal of the American Medical Association in 2009:

Post-Traumatic Stress Disorder (PTSD)

  • 19% reported new post-traumatic stress symptoms 5 to 6 years later, an increase from 14% in 2003 and 2004.
  • More than half (52%) who reported post-traumatic stress symptoms said they did not receive treatment in the previous year.
  • · The rate of PTSD was highest among low-income (32%) and Hispanic enrollees (31%), and those passing by on 9/11 (23%), including commuters and tourists.


  • 10% reported they had developed new asthma, with most diagnosed in the first 16 months after 9/11. The number reporting new onset of asthma symptoms was not elevated 5 to 6 years after 9/11. The rate of new asthma was highest (12%) among rescue and recovery workers who worked on the debris pile on 9/11.
  • The findings also suggest that people who found a heavy layer of dust when they returned to their homes or offices were at a higher risk for developing new asthma.

Wave 2 and Other Findings

Injury as a result of the 2001 terrorist attack on the World Trade Center, including, for instance, broken bones or burns, increased the risk of chronic disease 5-6 years after 9/11, according to a study of more than 14,000 enrollees who reported no previous diagnosis of heart disease, respiratory disease, diabetes or cancer. Enrollees who reported more than one injury—a group of nearly 2,000 people—were twice as likely to also report respiratory illness as those who were not injured. Enrollees with multiple injuries and probable posttraumatic stress disorder (PTSD) were three times more likely to report heart disease than those with no injuries and no PTSD. (American Journal of Epidemiology, 2014).

Researchers linked data for 46,346 Registry enrollees living in New York State to a state hospital-discharge reporting system that records medical diagnoses. They found 1,151 heart disease (including hardening of the arteries and heart attack) and 284 stroke-related hospitalizations occurring in 2003-2010. Male rescue/recovery workers with high levels of WTC exposure were at 82% higher risk for heart disease hospitalization compared to those with low levels of exposure; women who had posttraumatic stress disorder (PTSD) symptoms when they enrolled in the Registry faced a 32% higher risk compared to women without PTSD symptoms. Men with PTSD at enrollment were at a 53% higher risk of hospitalization due to stroke compared with men without PTSD. (Journal of the American Heart Association 2013).

A longitudinal study of 21,000 responders found that nearly 10% had both lower respiratory symptoms and likely posttraumatic stress disorder 5 to 6 years after 9/11. This combination, or comorbidity, was associated with more severe illness than responders with only respiratory symptoms, disability and poor quality of life (American Journal of Industrial Medicine 2013).

A longitudinal study that examined the course of PTSD among nearly 3,000 police officers for more than 6 years after 9/11 found that social integration reduced symptoms, even among those who were highly exposed (Anxiety, Stress & Coping 2013).

Respiratory symptoms were associated with WTC exposures in younger children and with behavior problems in adolescents measured 6-7 years after 9/11. Other risks for respiratory illness included race/ethnicity and living in low-income households. (Journal of Asthma 2013).

High levels of unmet mental health needs and poor mental health days were reported by adult enrollees with PTSD symptoms 5-6 years after 9/11, even among those who also reported being diagnosed with a mental health condition (Social Science & Medicine 2013).

The Registry’s first cancer analysis found no cancer rate increases in people directly exposed to the WTC disaster overall, but it did find small increases in rates of three types of cancer—prostate cancer, thyroid cancer and multiple myeloma—among rescue and recovery workers in 2007-2008 compared to non-exposed New York State residents during the same period. Researchers analyzed verified cancer diagnoses among 55,778 adult Registry enrollees who resided in New York State at the time of their enrollment (Journal of the American Medical Association 2012)

In Registry focus groups with both responders and survivors, participants reported barriers that prevented them from accessing 9/11 services: lack of visibility and accessibility of 9/11 health programs; fear of stigma related to receiving mental health care; unfamiliarity with 9/11-related health conditions; and few referrals from primary care providers (BMC Public Health 2012).

Among residents, office workers and passers-by enrolled in the Registry who reported either lower respiratory symptoms or probable posttraumatic stress disorder, more than 25% said they had both conditions 5-6 years after 9/11. Also, enrollees who had both conditions were much more likely to report 14 days of activity lost in the 30 days before being surveyed compared to enrollees with only 1 condition (American Journal of Public Health 2012).

Researchers found independent associations between acute and chronic WTC exposures, and lower respiratory symptoms up to 6 years after 9/11 in a case control study of nearly 800 Lower Manhattan residents and area workers in the WTC Health Registry. For example, the risk for lower respiratory symptoms increased both with the severity of dust cloud (acute) exposure and the thickness of dust in the home or workplace (chronic exposure) (American Journal of Public Health 2012).

6% of 42,025 Registry adult enrollees reported skin rash for the first time after 9/11 in 2003-2004, and again in 2006-2007. Among enrollees without PTSD or other psychological distress, increased risk for early skin rash was associated with intense dust cloud exposure, damage to the home or workplace, and working at least 31 days at the WTC site (Journal of Occupational and Environmental Medicine 2012).

A longitudinal study of nearly 3,000 police responders found that PTSD prevalence doubled from 7.8% in 2003/2004 to 16.5% in 2006/2007. Female police were significantly more likely than male police to report PTSD symptoms in the first survey, but this gender difference disappeared by the second survey. PTSD risk factors included post-9/11 unemployment and disability (American Journal of Industrial Medicine 2011).

An exploratory study found that 2 to 6 years following the 9/11 disaster, measures of dust exposure, injury and PTSD were each associated with an elevated risk of non-fatal heart disease among adult enrollees (Preventive Medicine 2011).

Many adults directly exposed to the WTC attacks developed lasting heartburn, indigestion, acid reflux and other symptoms of gastroesophageal disease or GERD (American Journal of Gastroenterology 2011).

 Lower Manhattan residents and area workers with persistent respiratory symptoms were more likely to have abnormal lung function than those without these symptoms 7 to 8 years after 9/11 according to an in-depth study using Wave 2 data (American Journal of Respiratory Critical Care Medicine 2011).

 Rescue and recovery workers who worked on the debris pile on 9/11 were at increased risk for sarcoidosis (Journal of Occupational and Environmental Medicine 2011).

 Rescue and recovery workers who wore respirators on 9/11 were less likely to report respiratory problems 5 to 6 years after 9/11 than those who went without adequate respiratory protection (American Journal of Industrial Medicine 2011).

 Volunteers not affiliated with an organization were more highly exposed to the WTC disaster than volunteers affiliated with recognized organizations and were at greater risk for developing physical and mental health conditions after 9/11, including asthma and PTSD symptoms (Preventive Medicine 2011).

Initial findings from an ongoing mortality study indicate that the mortality rate among enrollees living in New York City upon Registry enrollment was significantly lower than in the general population during 2003-2009. Non-rescue/recovery workers who were more highly exposed to the WTC disaster may be at an increased mortality risk, especially cardiac-related, in comparison to those less exposed (The Lancet 2011).

Wave 1 Survey (2 – 3 years after 9/11)

Major Findings

Based on data collected in 2003 and 2004 from more than 71,000 people who enrolled in the WTC Health Registry by completing a baseline survey, the Registry described multiple short-term health effects associated with WTC exposure.

Among nearly 69,000 adults in the Registry 2 to 3 years after 9/11 (Journal of Urban Health 2008):
  • 67% reported new or worsening respiratory symptoms
  • 3% reported newly diagnosed asthma
  • 16% screened positive for PTSD
  • 8% screened positive for serious psychological distress

More than half (53%) of 3,184 children in the Registry younger than age 18 on 9/11 reported at least one new or worsened respiratory symptom 2-3 years later and 6% reported a new asthma diagnosis. Children under age 5 caught in the dust cloud were at highest risk for new asthma. (Environmental Health Perspectives 2008).

Other Wave 1 Findings

Among 3,271 civilians who evacuated either of the WTC towers on 9/11, 15% had PTSD 2 to 3 years later. Being on a high floor in the towers, initiating evacuation late and working for an employer that sustained fatalities increased the risk for PTSD (American Journal of Epidemiology 2011).

A study compared 2 groups of women who were pregnant between September 11 and December 1, 2001: 500 women in the Registry and 50,000 women who lived at least 5 miles from the WTC site. Although researchers found similar birth weight and gestational age at delivery in two groups, Registry enrollees with probable PTSD were more likely than women without PTSD to deliver premature or underweight babies (Obstetrics & Gynecology 2010).

Nearly 1 in 8 Lower Manhattan residents likely had PTSD 2 to 3 years after 9/11. Demographic factors that increased PTSD risk included older age, female gender, Hispanic ethnicity, low education and income, and divorce. Injury, witnessing horror and dust cloud exposure on 9/11 increased the risk for chronic PTSD (Journal of Traumatic Stress 2008).

PTSD prevalence among nearly 29,000 rescue and recovery workers in the Registry varied significantly by occupation, ranging from 6% for police responders to 21% for unaffiliated volunteers 2 to 3 years after 9/11. Early arrival, the duration of time spent working at the WTC site and performing tasks unrelated to their occupation increased the PTSD risk among workers (American Journal of Psychiatry 2007).

Newly diagnosed asthma was reported by nearly 4% of 26,000 rescue and recovery workers in the Registry 2 to 3 years after 9/11. Earlier arrival and longer duration of work at the site, as well as exposure to the dust cloud and working on the debris pile increased the asthma risk (Environmental Health Perspectives 2007).

If survivors of collapsed and damaged buildings near the World Trade Center were caught in the dust cloud, they were more likely than those not caught in the dust cloud to report any of the following health effects 2 to 3 years after 9/11: injuries, respiratory symptoms, severe headaches, skin rash/irritation, hearing problems or loss, heartburn, diagnosed stroke, self-reported depression, anxiety, or other emotional problem; and current serious psychological distress (Morbidity and Mortality Weekly Report 2006).

Estimated Number Exposed

More than 410,000 people were directly exposed to the WTC disaster, including Statistics in Medicine2007): 

  • More than 91,000 rescue and recovery workers and volunteers
  • More than 57,000 residents south of Canal Street
  • About 15,000 children and staff in schools (pre K-12) south of Canal Street
  • More than 360,000 building occupants, residents and people passing by

Note: About 26% fell into more than 1 group, with the greatest overlap among those in lower Manhattan on  September 11 who  were also a rescue and recovery worker or lived in the area or both.

More Information:
Explanation and Calculation of Outcome Rates PDF Document (Reader Required; Click to Download)
Sample Building and Denominator Estimation PDF Document (Reader Required; Click to Download)


Among the 71,437 people enrolled in the WTC Health Registry (Journal of Urban Health 2008):

  • 70% reported witnessing traumatizing events on 9/11, such as seeing people running away from the dust cloud (53%) or collapsing buildings (47%), seeing people injured or killed (33%) or falling or jumping from the towers (29%) or seeing an airplane hit the towers (29%)
  • More than half (51%) reported being caught in the dust cloud on 9/11
  • 13% suffered an injury
  • 61% of adult residents reported  they evacuated their homes on or after 9/11, with 9% returning as early as 2 days later
  • 83% of building occupants reported they evacuated their workplaces on 9/11 


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