1. World Trade Center
Evacuation Study
Epidemiology 256:
Environmental and Occupational Epidemiology
Thursday, May 24, 2012
Robyn R.M. Gershon, MHS, DrPH
Principal Investigator
Funded by ASPH/CDC
CPHP NCDP
Center for Public Health National Center for Disaster
Preparedness PreparednessColumbia
Columbia University University

2. World Trade Center
2

3. Case Study Presentation:
The World Trade Center Evacuation
Study
• Pre-event facts (Case study book chapter)
• Significance
• Human Behaviors in Fire Emergencies
• Basic Organizational and Structural Facts
• WTC Evacuation Study
• Case Study Questions
3

4. Significance
• High rises may experience fires and other disaster
events
• Certain iconic high rises and public assembly
spaces may be likely terrorist targets
• Lessons identified and learned from high rise
disasters, including the WTC disaster in 2001 may
improve preparedness and response to other high
rise events
4

5. Human Behaviors in Emergencies
What is Known:
• People will generally not go towards smoke
• Seek out groups, group size is important
• People move towards and stay with group even if it
is not the best option
• The faster groups form – the faster they evacuate
5

6. Human Behaviors in Emergencies
What is Known:
• Individual and group panic dependent on several
key factors
• Information serves as motivator
• Leadership is especially important in public spaces –
both for shaping group behaviors and for guidance
• Familiarity helps groups to form and minimizes panic
6

7. Basic Organizational and Structural
Facts
7

8. North
WTC
Complex
South
8

9. Typical World Trade Center
Office Floor
9

10. Preparing for Emergencies
• AFTER 1993 BOMBING Port Authority NYNJ
Instituted a new EP Program:
• PLANNING
• ORIENTATION
• EDUCATION
• PUBLIC ADDRESS ANNOUNCEMENTS
• OCCUPANT FIRE SAFETY TEAMS
• TEAM TRAINING
• FIRE DRILLS
• CRITIQUE 10

11. WTC Worker Protection Programs in
Place 9/11
• Codes met and • Port Authority
exceeded NYC fire Program
and other applicable • Floor warden system
building safety codes • Annual fire drills
• PA system
11

12. Design Features of High Rises
• High rise buildings – robust and redundant
• Not usually designed for rapid, full building
evacuation
• Not designed to withstand impact of fuel-laden
large aircraft in use today
• Rescue of occupants located in inaccessible
areas of high rises above the point of impact is
not possible
12

13. WTC, 2001
North Tower Impact South Tower Impact
(Tower 1) (Tower 2)
• 8:46am • 9:02am
• 767, 10K gallons • 767, 10K gallons
• Impact at 94-98th floors • Impact at 79-84th floors
• Collapsed 1 hour and 42 • Collapsed 57 minutes
minutes after impact after impact
13

14. WTC
Disaster,
2001
Impact
Zones of
Planes
14

15. WTC Fatalities, 2001
• 411 first responders
• 147 jetliner crew and passengers
• 1,462 in North Tower (1,355 above impact, 93%)
• 630 in South Tower (619 above impact, >95%)
• 18 bystanders (on the ground)
• 24 location unknown in WTC 1 and WTC 2
• Total deaths: 2,692
• 11% of occupants died, most above point of
impact
15

16. WTC Fatalities, 2001
• Age Range
– Planes: 2 ½ years – 86 years
– Building: 18 years – 79 years
• Post 9/11
– 479 illness/deaths of workers at Ground Zero
or Fresh Kills Landfill
– 149 traumatic deaths
– 33 suicides
16

17. The WTC Evacuation Study*
Objectives
• To identify individual, organizational, and
environmental/structural (building) factors
that affected evacuation and health
outcomes
• To inform policies and practices that support
safe evacuation of high-rise structures
• To inform preparedness for other mass
evacuations
17
*Funded by CDC/NIOSH

18. WTC Evacuation Study:
Overview
Formative Qualitative Questionnaire Data Participatory
Steps Processes & Development Analysis Action Teams
Analyses & Administration
Identification
of Risk
Reduction Strategies
& Recommendations
Preparation Feedback to
of Reports Participants &
Stakeholders
18

19. WTC Evacuation Study Model
Worksite Individual and
Compliance and Organizational Initiation Initiation and
Safety Culture Factors Length of Time
Knowledge
Beliefs
(Experience) Attitudes,
Perceptions
of Safety
Climate, Behavioral Evacuation Injuries
Outcomes
Perception of Intentions Behaviors
Risk, Fear,
Instinct (Gut
Subjective Feeling)
Norms Environmental Long
Sensory Enabling Term
Cues Factors Health
Progression
Group
Behaviors Final
Destination
19

20. Major Study Outcomes
1. Length of time to initiate evacuation
2. Length of time to fully evacuate
• Controlling for floor and elevator use
(WTC 1 and 2)
3. Injuries (physical)
4. Long term health impact (physical and
psychological)
20

21. Quantitative Data
Demographics
• Responses: 1767 total
• Of these,1444 (82%) evacuated on 9/11/01
* Demographics (N=1444):
• Gender: 58% male
• Age, mean yrs: 44 yrs
• Age, range: 22-80 yrs
• Tenure, mean: 6 yrs
• Tenure, range: 0-37 yrs
• Marital status: 70% married/partner
• Children: 48%
• Race: 80% Caucasian
• Education: 66% college+
• Employment: 84% private company
• Union membership: 7%
21

22. Quantitative Data
Health Status
• Pre-existing disability or medical condition: 23%
• Including…
• Respiratory: 28%
• Mobility: 28%
• Mental Health: 17%
• Heart Condition: 16%
• General Medicine: 7%
• Sensory Deficit: 6%
• Smoking: 19%
• 29% of those with a disability/medical condition said
their disability affected their ability to walk down large
number of stairs
22

23. Quantitative Data
Knowledge
• Knowledge Related
Emergency Preparedness/Knowledge/Experience (alpha = .77)
to Preparedness
(10 Questions)
140
• Mean 3.4
• Median 3.0 120
• Mode 2.0 100
Frequency
• Range 0-10
80
60
40
20
0
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00
Emergency Preparedness/Knowledge/Experience
Mean = 3.42, Median = 3.00, Mode = 2.00, SD = 2.41
23

24. Quantitative Data
• Building Participants DID NOT KNOW:
89%
73%
70%
59%
51%
26% 25%
24

25. Quantitative Data
Lack of Familiarity with Building
• 56% somewhat familiar
• 22% slightly/not at all familiar
• 50% did NOT know enough about building to
leave on their own
• 27% had evacuated the building at least once
• 16% reluctant to evacuate
25

26. Quantitative Data
Preparedness for Persons with
Disabilities
Disability Preparedness Scale (alpha = 0.76)
Mean = 0.32
Median = 0.00
Mode = 0.00
Range = 0- 4
26

27. Quantitative Data
Preparedness for Persons with Disabilities
28% reported having a person with a disability on
their floor
11% said a plan for evacuation of persons with
disabilities was in place
10% said co-workers were assigned to assist persons
with disabilities
8% said there was special equipment for the
evacuation of persons with disabilities
5% said there was a designated area for persons with
disabilities to gather
27

28. Quantitative Data
Emergency Preparedness
• Workplace Preparedness for Emergencies
(8 questions)
• Mean 2.8
• Median 3.0
• Mode 3.0
• Range 0-8
28

29. WTC Results on
Emergency Preparedness Safety Climate
Emergency Preparedness Safety Climate: 8-items mean 2.83, med 3.0, mode 3.0
Had NEVER exited the building as part of a drill
Reported NO PLANS regarding where to gather after evacuating
NO PLANS for head count
NEVER PROVIDED with evacuation plans
Had participated in fire drills, but of these, ONLY 11% HAD EVER ENTERED A
STAIRWELL
Were NEVER PROVIDED with written fire safety instructions
WERE NOT familiar with who
was in charge 29

30. Outcomes
• Initiation of start time
• Length of time to descend/controlled by floor
and elevator use
• Injuries (physical)
• Long term health impact (physical and
psychological)
30

31. Quantitative Data
Key Time Periods
WTC1 WTC2
range range
• First became aware 8:46-9:20 8:46-9:02
• Made decision to leave 8:46-9:30 8:46-9:30
• Began to leave 8:46-9:30 8:46-9:30
• Reached street level 8:46-10:28 8:46-9:58
8:00 a.m. 8:46 a.m. 8:55 a.m. 9:02 a.m. 9:59 a.m. 10:28 a.m. 11:00 a.m.
Tower 1 Tower 2 Tower 1 (North)
(North) impact (South) impact collapses
Announcement heard Tower 2 (South) 31
in Tower 2 (South) collapses

32. Study Outcomes
Length of Time to Initiate*
Evacuation
(N=1444)
Mean Minimum Maximum
WTC 1 6 minutes 1 minute 44 minutes
WTC 2 6 minutes 1 minute 44 minutes
* Start of Evacuation - First Awareness
32

33. Delaying Activities
Once they decided to leave, but BEFORE they
began to…
• Gathering items (40%)
• Seeking out friends/co-workers (33%)
• Searching for any others (26%)
• Making phone calls (18%)
• Shutting down/PC-related (8%)
• Waiting for direction (7%)
• Gathering safety equipment (5%)
• Changing shoes (3%)
• Trying to obtain permission to leave (1%)
33

34. Factors Significantly* Associated
with Initiation
Individual
- Age (O.R. = 1.4) - Management
- Delaying activities (O.R. = 3.1) - Military/first responders
- Disabilities/medical conditions - Participation in drills
- Hesitating (O.R. = 3.7) - Poor knowledge
- Injuries (O.R. = 1.4) - Sensory input
- Looking for groups (O.R. = 1.5) - Smoking
* p< .05 OR = Odds Ratio 34

35. Quantitative Data
Sources of Communication
• Obtained info from:
– Face-to-face communications (42%)
– PA announcement (12%)
– Telephone (7%)
– Cell phone (7%)
– Television (7%)
– Radio (4%)
– Blackberry (4%)
– Computer (2%)
35

36. Factors Significantly* Associated with
Initiation
Organizational
- Difficulty locating exits (O.R. = 2.0)
- Lack of leaders
- Emergency preparedness safety climate ↑
- (O.R. = 3.3); (WTC 1)
- (O.R. = 2.4); (WTC 2)
Structural/Environmental
- Poor signage (O.R. = 3.3)
- PA Announcement (Tower 2)
* p< .05 36

37. Quantitative Data
Outcomes: Length of Time to Descend
WTC 1
Mean: 42 minutes Rate*: 59 Seconds/floor
Range:1-96 minutes
WTC 2
Mean: 27 minutes Rate*: 31 Seconds/floor
Range: 0-70 minutes
* Controlling for floor/elevator use
37

38. Significant* Factors Associated with
Length of Time
Individual
• Disability/medical condition (O.R. = 1.7)
• Injuries (O.R. = 1.9)
• Seriousness (O.R. = 1.8)
• Stopping (O.R. = 3.3.)
Organizational
Emergency preparedness safety climate ↑ (O.R. = 2.3)
Structural
• Any adverse environmental condition (O.R. = 4.6)
• Any damage (O.R. = 2.3)
• Multiple sources of communication
• Overcrowding on stairs or in lobbies (O.R. = 2.2)
38
*p < .05

39. Quantitative Data
Outcomes: Injuries/Long Term Health
• Physical Injuries: 37% (n=530)
• Surface Trauma 12% (n=172)
• Inhalation Injury 11% (n=164)
• Orthopedic Injury 7% (n=104)
• Eye injury 4% (n=60)
• General Trauma 4% (n=51)
• Psychological Injuries: 25% (n=357)
• Severity:
• 63% sought medical care
• 7% were hospitalized
39

40. Significant* Factors Associated with
Injuries
• Disability/Medical condition (O.R. = 2.0)
• Fear for employment (O.R. = 4.9)
• Female gender (O.R. = 1.9)
• Lack of familiarity (O.R. = 2.7)
• Less participation in drills
• Not feeling personally responsible for own safety
• Physical capability was low (O.R. = 2.8)
• Starting from higher floor
• Stopping
• Supervisor would not approve (O.R. = 6.4)
• Unsure of stairs
*p < .05 40

41. Significant* Factors Associated with
Injuries
• Any environmental condition
• Any structural damage
• Difficulty in following stairway route
• Inadequate training
• Lack of emergency preparedness
• Making phone calls
• Multiple sources of communication
• Problem with shoes (O.R. = 2.6)
*p < .05 41

42. Study Outcomes
Long Term Injury Patterns
• 221 persons (15.4%) of the evacuees reported at least one long-
term injury related to evacuation of the WTC on 9/11 (some
reported more than one condition).
• Long-term mental health problems were most common.
Condition n
Mental Health 132
Respiratory 61
Orthopedic 30
Medical 18
Cardiac 5
Vision / Hearing 5
42

43. Lessons Learned
From Evacuees
• Staying calm (“Behaving”)
• Instincts
• Mutual support
• Leadership (group)
• Directions/encouragement of first responders/NY/NJ
Port Authority
• Integrity and condition of stairwells
• General lack of massive overcrowding on stairwells
43

44. Lessons Learned from the WTC
Evacuation Study
• Human behaviors in this high rise fire were as predicted
– Design features that support these behaviors will be
most effective
• Training and drilling improve competency
– These should be mandatory
• EP safety climate was associated with reduced
evacuation times, injuries and long term mental health
problems.
– EP Best practices should be implemented in all high
rise work settings
44

45. Most Important Lesson Learned
• EMERGENCY PREPAREDNESS=RESILIENCY
45

46. Regulatory Risk Reduction Strategies
1. NYC high-rise fire safety codes: Emergency Action Plan §6-02
– EAP must specify the procedures for:
• Sheltering in-place
• In-building relocation
• Partial evacuation
• Full evacuation
– Pre-planning for persons with disabilities
2. Designation and certification of an Emergency Action Plan Director
(EAPD) §9-08
– EAPD has the authority to implement this in the absence of
lawful authorities (i.e., they become the incident commander)
46

47. Lessons Learned…and Implemented
• 2002: OSHA Compliance Document- Emergency Action Plans
• 2003: Society for Fire Protection Engineers Guide: Human
Behavior in Fires
• 2005: NIOSH: Emergency Preparedness for Businesses
• 2005: FEMA Emergency Management Guide for Businesses
• 2007: NFPA Std on Disaster/Emergency Preparedness
Management
• 2007: NFPA 101 Life Safety Code
• GAPS: ARE HIGH RISE BUSINESS OCCUPANCIES
COMPLYING?? Public Assembly Places???
47

48. Tribute in Lights
48

49. Freedom Tower 9/11/11
49

50. Robyn R.M. Gershon
Department of Epidemiology and Biostatistics
Philip R. Lee Institute for Health Policy Studies
School of Medicine, University of California, San Francisco
Robyn.Gershon@ucsf.edu
415-476-1890 50

51. References
• Sherman MF, Peyrot M, Magda LA, Gershon RRM. Modeling pre-evacuation delay by evacuees in World
Trade Center Towers 1 and 2 on September 11th, 2001: A revisit using regression analysis. Fire Safety
Journal. 2011; 46(7) 414-424.
• Gershon RRM, Magda LA, Riley HEM, Sherman MR. The World Trade Center evacuation study: factors
associated with initiation and length of time for evacuation. Fire and Materials. February 2011.
doi:10.1002/fam.1080.
• Gill KB*, Gershon RRM. Disaster mental health training programs in NYC following September 11, 2001.
Disasters. 2010;34(3). doi:10.1111/j.1467-7717.2010.01159.x
• Gershon RRM, Rubin MS, Qureshi KA, Canton AN, Matzner FJ. Participatory action research methodology
in disaster research: results from the World Trade Center evacuation study. Disaster Medicine and Public
Health Preparedness. 2008; 2(3):142-149.
• Qureshi KA, Gershon RRM, Smailes E, Raveis V, Murphy B, Matzner F, Fleischman A. A roadmap for the
protection of disaster research participants: findings from the WTC evacuation study. Prehospital and
Disaster Medicine. 2007; 22(6):484-49.
• Gershon RRM, Qureshi KA, Rubin MS, Raveis VH. Factors associated with high-rise evacuation:
qualitative results from the World Trade Center Evacuation study. Prehosp Disaster Med. 2007; 22(3):165-
173.
• Gershon RRM, Gemson DH, Qureshi K*, McCollum MC. Terrorism preparedness training for occupational
health professionals. J Occup Environ Med. 2004;46(12):1204-1209.
• Nandi A, Galea S, Tracey M, Ahern J*, Resnick H, Gershon RRM, Vlahov D. The effects of job loss,
unemployment, work stress, and work satisfaction on the persistence of probable PTSD: results from a
cohort study of New York City metropolitan area residents one year after the September 11 attacks. J
Occup Environ Med. 2004;46(10):1057-1064.
• Gershon RRM, Hogan E, Qureshi KA*, Doll L. Preliminary results from the World Trade Center evacuation
study-New York City, 2003. Morb Mortal Wkly Rep. 2004; 53(35):815-816. 51