Enrollment and Coverage by Eligibility Group
Estimates of population sizes for each of the eligibility groups and the WTCHR coverage were reported previously.1 Both are displayed in nonmutually exclusive groups in Table 1. The total number of people eligible to enroll in the WTCHR was estimated at 409,492, of whom 71,437 enrolled. Based on these population estimates, WTCHR coverage is 17.4%, ranging from 34% coverage among rescue and recovery workers to 12% among building occupants, passersby, and people in transit in lower Manhattan on the morning of 9/11. Coverage is highest among police (75%), sanitation workers (62%), occupants of undamaged buildings near the WTC site (52%), and occupants of damaged or destroyed buildings (43%).
The largest group of WTCHR enrollees includes people present in lower Manhattan near the WTC site on the morning of 9/11(n = 43,487), including 10,393 occupants of damaged or destroyed buildings, 19,900 occupants of other nearby buildings, and 13,194 passersby or people in transit. The registry’s 30,665 rescue and recovery workers include police, firefighters, emergency medical services workers, construction or engineering personnel, and sanitation workers (n = 14,747) as well as volunteers affiliated with organizations and unaffiliated volunteers (n = 7,389). The registry also includes 14,665 lower Manhattan residents, 2,075 students (pre-K to 12th) and 571 staff from schools in the vicinity of the WTC site.
Twenty-six percent of enrollees met more than one eligibility criterion. The greatest overlap was among building occupants, passersby, and people in transit who were also either workers (n = 7,695) or residents (n = 6,978) or both (n = 795) (Figure 2). Among children, many students in the registry were also residents who were present downtown on the morning of 9/11 (n = 946) or nonresidents but present downtown on the morning of 9/11 (n = 615).
Overall, 30% of enrollees were recruited from lists (list-identified), and 70% were self-identified. The percentage of list-identified enrollees ranged from 14% among students to 37% among workers.
Enrollee Characteristics, Risk Factors, Exposures, and Injuries
Figure 1 displays enrollees’ primary residence on 9/11 by zip code for the New York City region and nationally. On 9/11, enrollees resided in all 50 states in the U.S. and 15 other countries. Nonetheless, almost 90% of enrollees were residents of New York State or New Jersey (Table 2). Most enrollees (65%) were residents of New York City on 9/11, including large numbers of Manhattan and Brooklyn residents. Manhattan resident enrollees were concentrated in four zip codes in lower Manhattan due to the nature of the WTCHR enrollment criteria.
Enrollees were predominantly white non-Hispanic, age 25–64 years, and had reported annual household incomes greater than $50,000. The overall prevalence of current smoking among enrollees (15.8%) was lower than the average prevalence among NYC adults in 2004 (18.3%).39
More than half of all enrollees (51%) reported being caught in the dust and debris cloud that resulted from the collapse of the WTC Towers 1 and 2. Building occupants (71%) and school staff (64%) were most likely to report dust cloud exposure, followed by students (52%), residents (50%), and workers (37%). Enrollee location when first caught in the dust cloud on the morning of 9/11 was successfully geocoded using a combination of available location variables for 24,847 of the 36,452 (68%) registrants who reported being caught in the dust cloud. Most (91%) of the reported locations were in lower Manhattan (Figure 3) and heavily concentrated in the immediate vicinity of the WTC site and eastward. A small proportion of enrollees reported being present in more distant areas of Manhattan as well as in the city’s other four boroughs, where the likelihood of being caught in the dust cloud on the morning of 9/11 was lower.
Approximately half of enrollees reported witnessing people fleeing from the dust cloud (53%) or collapsing buildings (47%). Many witnessed people injured or killed (33%), people falling or jumping from a building (29%), or an airplane hitting a building (29%). Building occupants, passersby, and people in transit, school staff and school students were most likely to have reported witnessing any of these five types of traumatic events (92%, 84%, and 80%, respectively). The prevalence of any type of injury sustained on 9/11 ranged from 4% in students to 15% in workers and 16% in building occupants, passersby, and people in transit in lower Manhattan on the morning of 9/11. The most commonly reported injuries were cuts and sprains or strains. Fewer enrollees reported more severe injuries such as burns, broken bones, and concussions.
More than 7,400 adult residents (61%) reported that they evacuated their homes on or after 9/11 (Table 3). Of those who evacuated, 9% returned as early as September 13th, 2001. Most (92%) returned to their homes by the time of the interview. More than 24,000 enrollees reported that they had evacuated their workplace on 9/11, with almost 70% of these evacuees returning to their workplace by the time of the interview. On average, workplace evacuees returned to lower Manhattan sooner than residents.
Respiratory and Mental Health Outcomes
Overall, 67% of adult enrollees reported any new or worsening respiratory symptom (persistent cough, shortness of breath, wheezing, throat irritation, or sinus irritation) after 9/11 (Table 3). The prevalence of new symptoms ranged from 32% for sinus irritation to 38% for shortness of breath; worsening symptoms were less frequently reported, ranging from 1.6% for persistent cough to 14% for sinus irritation (data not shown). Nearly 3% (n = 1,967) of adult enrollees reported newly diagnosed asthma after 9/11. Overall, 16% of adult enrollees screened positive for current PTSD and 8% for serious psychological distress (SPD).
Demographic variables, smoking status, and source of interview were generally significantly associated with each of the respiratory and mental health outcomes (Table 3). Adult enrollees who were female, non-White, self-identified, or had lower incomes tended to have higher prevalence of a new or worsening respiratory symptom, newly diagnosed asthma, probable PTSD, and SPD.
Event experiences on 9/11 such as being in the dust cloud, witnessing a traumatic event, and sustaining an injury were also significantly associated with a higher likelihood of having either respiratory or mental health adverse outcomes. Each event experience was associated with an approximately twofold or greater increase in the prevalence of psychological distress and probable PTSD. Most strikingly, enrollees who sustained injuries were nearly three times more likely to develop probable PTSD than those who did not (35% vs. 13%).
Associations were also noted between 9/11 experiences and respiratory outcomes (Table 3). Of all enrollees, rescue and recovery workers and volunteers had the highest percentage of reported newly diagnosed asthma and the second highest percentage of respiratory symptoms. Location of rescue and recovery work, in particular, working on the WTC pile itself, was an important predictor of respiratory health outcomes, as was working on the pile on 9/11. Enrollees who worked on the WTC pile on 9/11 were more than twice as likely to have reported newly diagnosed asthma after 9/11 as those who did not (6.3% vs. 2.7%). Location of work was also associated with adverse mental health outcomes (Table 3).
Among eligibility groups, the prevalence of probable PTSD was highest among building occupants, passersby, and people in transit in lower Manhattan on the morning of 9/11 (19%), followed by residents (16%). Evacuation status and time returning home or to work were associated with both adverse respiratory and mental health outcomes. Residents and building occupants who did not evacuate their home or workplace were more likely than those who evacuated to report newly diagnosed asthma. Among evacuees, asthma was also more commonly reported by residents who returned home within the first week (by September 19th) than those who returned later (3.3% vs 2.4%, p = 0.046). Evacuees who had not returned to live or work in lower Manhattan had the highest prevalence of probable current PTSD, significantly higher than enrollees who had not evacuated their home or workplace and those who had returned to their home or workplace by the time of the interview.
Estimated Burden of Health Problems among Adults
Estimates of the total number of adults with symptoms or newly diagnosed illness after the attacks are shown in Table 4. Using data from the WTCHR, we estimate that among the previously estimated eligible population of 409,492 persons, between 124,800 and 232,200 exposed people experienced new or worsening respiratory symptoms after 9/11, 3,800–12,600 had newly diagnosed asthma by 2 to 3 years after the event, 34,600–70,200 developed probable PTSD, and 9,700–20,000 people experienced SPD.
Children’s Respiratory and Mental Health Outcomes
Of the 3,184 enrollees under age 18 years on 9/11, most (69%) were residents of lower Manhattan. Nearly half (45%) of these children were caught in the dust cloud on 9/11, half (50%) had personally witnessed disturbing events, and 53% had at least one new or worsening respiratory symptom after 9/11. Eye irritation or eye injury was reported for 22% of children; other injuries on 9/11 were reported for 3% (including sprains, lacerations, burns, broken bones, or concussions). For 180 children (5.7%), asthma was newly diagnosed after 9/11. Three percent of children met criteria for possible posttraumatic stress at interview. Dust cloud exposure was associated with newly diagnosed asthma.40 Posttraumatic stress symptoms were associated with dust cloud exposure and with witnessing disturbing events.