What We Know from the Research
Office Workers and Passersby:
More than 61% of Registry enrollees (43,000 people) were office workers, passersby or in transit south of Chambers Street on 9/11. The majority lived in New York City (71%), were male (53%) non-Hispanic white (59%) and non-smokers (59%). Forty-eight percent (48%) were between 25 and 44 years of age, with the largest percentage (33%) earning between $75,000 and $150,000 in 2003-2004.1
Among this group, 92% said they experienced trauma on 9/11, 71% were caught in the dust cloud and 16% suffered an injury, such as a cut, sprain or strain.1 In addition, 5 to 6 years after 9/11:
- About 8.4% of office workers and 8.6% of passersby developed new-onset asthma 5 to 6 years after the attacks. Intense dust cloud exposure and experiencing heavy dust in the office were major contributors for both groups and office workers, respectively.
- Passersby had the highest rate of probable PTSD (23.2%) of any group, including rescue and recovery workers and residents. They were also more likely to have chronic post-traumatic stress symptoms, which means they had symptoms in 2003-2004 and 2006-2007.
- Probable PTSD was more likely to be resolved for office workers than for other eligibility groups in the Registry; the prevalence declined from 19.1% in 2003-2004 to 16.9% in 2006-2007.2
In a study of 750 New York City office workers, most reported they were in good or excellent health 2 years after 9/11. Those directly exposed or who had offices closer to the World Trade Center (south of Canal Street) were more likely to report headaches or cough.3
Researchers found an association between chronic WTC exposures and lower respiratory symptoms in a case control study of nearly 800 Lower Manhattan residents and area workers in the WTC Health Registry up to 6 years after 9/11. Area workers reporting lower respiratory symptoms were 3 to 6 times more likely than area workers without symptoms to recall that the surfaces in their workplaces were covered in dust following the WTC collapse; area workers who recalled a thicker layer of dust were at greater risk, suggesting a dose/response relationship.11
Among residents, office workers and passers-by enrolled in the WTC Health 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 one condition.12
In a longitudinal study of nearly 1,000 office workers, residents and clean-up workers who sought care for respiratory illness at the World Trade Center Environmental Health Center between 2005 and 2011, and who were symptom-free prior to 9/11, researchers found improvements in lung function overall among treated patients who were not heavy smokers. However, lung function among office workers, who had the highest likelihood of dust cloud exposure, improved the least.13
A WTC Health Registry analysis of verified cancer diagnoses among 33,928 adult enrollees NOT involved in rescue and recovery work, including Lower Manhattan office workers, students and passersby, found no increase in cancer rates compared to non-exposed New York State residents during the period studied (2003-2008).14
A study of nearly 400 office workers in the vicinity of the World Trade Center, including 65 survivors of the collapsed buildings, suggests little evidence of increased alcohol consumption or alcohol use disorders three years after 9/11. Researchers examined both self-reported alcohol consumption and problems prior to the attacks and found few cases of new alcohol disorders or alcohol relapse.15
Nearly 8,500 adults who survived collapsed or damaged buildings in lower Manhattan on 9/11—including 3,690 evacuated from the World Trade Center—enrolled in the WTC Health Registry Among this group,:4
- Most began evacuating when the first plane hit the north tower. However, many survivors from surrounding damaged or destroyed buildings did not start evacuating until after the second plane hit.
- 62% were caught in the dust cloud.
- 64% experienced at least 3 potentially psychologically traumatizing events (seeing an airplane hit either one of the WTC towers, a building collapse, people running away, someone who was injured or killed, or people falling or jumping from the WTC towers).
- Injuries were common (44%), but few survivors reported injuries that required extensive treatment. The most common were cuts and sprains or strains.
- Building type and time of evacuation were associated with injuries on September 11, 2001 and reported symptoms; building type (collapsed versus damaged) also was associated with mental distress.
Researchers at the WTC Health Registry estimate that 15% of 3,271 civilians who evacuated either of the WTC towers on 9/11 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 were among the exposures that increased their risk for PTSD.9
To search for 2003/2004 baseline survey data, visit the Health Department's interactive health data tool.
Two studies of birth records among people indirectly exposed to 9/11 through media coverage yielded different findings:
- A study of birth and fetal death records between 1996 and 2002 found that fewer males were born in the months after 9/11 because there was a higher miscarriage rate for women carrying boys during this period. The lower male birth rate during this period was attributed to the indirect trauma experienced by pregnant women around 9/11. 5
- A study of U.S. Department of Defense birth records of infants whose mothers were exposed to the stress of 9/11 during pregnancy in 2000 and 2001, found no change in the ratio of male to female births or increased risk of adverse infant health outcomes, including birth defects, pre-term birth and growth deficiencies in utero and in infancy.6
Some studies suggest that those indirectly exposed to 9/11 may also suffer moderate levels of trauma. For example:
- Among a sample of California college students screened for mental health conditions before and after 9/11, 44% of women and 32% of men had at least one symptom of posttraumatic stress disorder (PTSD) six to 17 days after 9/11.7
- A study of 143 Canadian students two years after 9/11 found a correlation between watching coverage of the attacks and two main symptoms of PTSD: re-experiencing the event and hyper arousal.8
Research published soon after 9/11 reported elevated rates of PTSD among the US population ranging from 4.3% to 17%. However, data from a national epidemiologic survey conducted from 2004 to 2005 and including nearly 35,000 people suggests that indirect experience of 9/11, such as witnessing the attack on television, had the lowest risk of PTSD, 1.3%, of 32 traumatic events listed. Other events included sexual assault as an adult or child (PTSD risk 40.2%), being stalked (PTSD risk 19.5%) and experiencing a natural disaster (PTSD risk 5.1%).10
- Farfel M, DiGrande L, Brackbill R, et al. An Overview of 9/11 Experiences and Respiratory and Mental Health Conditions among World Trade Center Health Registry Enrollees. Journal of Urban Health: Bulletin of the New York Academy of Medicine. 2008; 85(6): 880-909.
- Brackbill RM, Hadler JL, Ekenga CC, et al. Asthma and Posttraumatic Stress Symptoms 5 to 6 Years Following Exposure to the WTC Terrorist Attack . Journal of the American Medical Association 2009; 302(5):502-516.
- Osinubi OY, Gandhi SK, Ohman-Strickland P, et al. Organizational Factors and Office Workers' Health after the World Trade Center Terrorist Attacks: Long-Term Physical Symptoms, Psychological Distress, and Work Productivity. Journal of Occupational and Environmental Medicine. 2008. 50(2):112-125.
- Brackbill RM, Thorpe LE, DiGrande L, et al. Surveillance for World Trade Center disaster health effects among survivors of collapsed and damaged buildings . Morbidity and Mortality Weekly Report Surveillance Summary. 2006. 55;1-18.
- Bruckner TA, Catalano R & Ahern J. Male Fetal Loss in the U.S. Following the Terrorist Attacks of September 11, 2001. BMC Public Health 2010; 10:273.
- Endara SM, Ryan MA, Sevick CJ et al. Does Acute Maternal Stress in Pregnancy Affect Infant Health Outcomes? Examination of a Large Cohort of Infants Born after the Terrorist Attacks of September 11, 2001. BMC Public Health. 2009; 9:252.
- Matt GE & Vazquez C. Anxiety, Depressed Mood, Self-Esteem, and Traumatic Stress Symptoms among Distant Witnesses of the 9/11 Terrorist Attacks: Transitory Responses and Psychological Resilience. The Spanish Journal of Psychology 2008;11(2):503-515.
- Collimore KC, McCabe RE, Carleton RN & Asmundson GJ. Media Exposure and Dimensions of Anxiety Sensitivity: Differential Associations with PTSD Symptom Clustersz. Journal of Anxiety Disorders 2008; 22:1021-1028.
- DiGrande L, Neria Y, Brackbill RM et al. Long-term Post-traumatic Stress Symptoms Among 3,271 Civilian Survivors of the September 11, 2001, Terrorist Attacks on the World Trade Center. American Journal of Epidemiology. 2011;173(3):271-81.
- Breslau N, Bohnert KM and Koenen KC. The 9/11 Terrorist Attack and Post-traumatic Stress Disorder Revisited. The Journal of Nervous and Mental Disease. 2010;198(8):539-543.
- Maslow CB, Friedman SM, Pillai PS et al. Chronic and Acute Exposures to the World Trade Center Disaster and Lower Respiratory Symptoms: Area Residents and Workers. American Journal of Public Health. 2012 Apr 19. [Epub ahead of print]
- Nair HP, Ekenga CC, Cone JE et al. Co-occurring Lower Respiratory Symptoms and Posttraumatic Stress Disorder 5 to 6 Years After the World Trade Center Terrorist Attack. American Journal of Public Health. 2012 Aug 16. [Epub ahead of print]
- Liu M, Qian M, Cheng Q et al. Longitudinal Spirometry Among Patients in a Treatment Program for Community Members With World Trade Center-Related Illness. Journal of Occupational & Environmental Medicine. 2012 Apr 19. [Epub ahead of print]
- Li J, Cone JE, Kahn AR et al. Association between World Trade Center Exposure and Excess Cancer Risk. Journal of the American Medical Association. 2012 Dec 19;308(23):2479-88.
- North CS, Adinoff B, Pollio DE et al. Alcohol Use Disorders and Drinking among Survivors of the 9/11 Attacks on the World Trade Center in New York City. Comprehensive Psychiatry. 2013 May 1. pii: S0010-440X(13)00087-4. doi: 10.1016/j.comppsych.2013.03.027. [Epub ahead of print]