The destruction of the World Trade Center (WTC) in New York City on
11 September 2001 resulted in the pulverization of two 107-story buildings
and the massive release of combustion products from jet fuel and burning
structures. An initial cloud of dust and smoke enveloped the area in
all directions. Subsequent wind-blown plumes dispersed dust and smoke
throughout lower Manhattan and Brooklyn. Fires in the 16-acre site continued
for more than 3 months after the event, with the prolonged release of
combustion products. Analyses of the settled dusts have revealed cement,
glass, and particulate matter, including gypsum, calcium carbonate, cement
dust, and glass fibers. The dusts were alkaline, with a pH ranging from
9.3 to 11.5 (Lioy et al. 2002; McGee et al. 2003; Service 2003). Metals,
including chromium, iron, magnesium, manganese, aluminum, barium, titanium,
and lead, were also detected (Lioy et al. 2002). Particles were also
noted to contain polycyclic aromatic hydrocarbons, polychlorinated biphenyls,
and organochlorine pesticides (Lioy et al. 2002; Offenberg et al. 2003).
Although often considered a financial district, lower Manhattan contains
a large residential community with approximately 58,000 residents living
south of Canal Street. The residential communities encompass many socioeconomic
levels and residents of diverse race/ethnicity. Housing stock consists
of large housing complexes containing thousands of residential units
as well as smaller residential buildings. Some residents in the immediate
area surrounding the former WTC [Ground Zero (GZ)] were immediately evacuated;
however, many remained in their apartments. Residents who were evacuated
returned to their apartments over the ensuing weeks to months. Dusts
from the collapse settled on streets, playgrounds, cars, and buildings.
Dusts entered apartments through open windows, building cracks, and ventilation
systems. Removal of these dusts in individual apartments was accomplished
in a variety of ways; some residents used professional cleaners, whereas
many performed the operation themselves. No consistent cleanup operation
was offered to the residential community until 1 year after the event.
Adverse respiratory health effects from exposures to WTC dusts are
being reported. Firefighters exposed to materials generated during the
collapse of the WTC have developed cough and bronchial hyperresponsiveness
(Banauch et al. 2003; Prezant et al. 2002). A preliminary telephone survey
of a small sample of residents in Manhattan also suggested the presence
of respiratory health effects 8 weeks after the event (Fagan et al. 2002).
To examine whether the destruction of the WTC resulted in adverse respiratory
health effects in the residential community, we developed a collaborative
effort between the New York State Department of Health, New York University
School of Medicine/Bellevue Hospital, and numerous community health programs
and local community organizations. The overall study was designed to
test the hypotheses that the rates and severity of new and previously
existing respiratory diseases increased among residents after 11 September
2001 in the community surrounding GZ compared with a control community.
We now report results of the first part of the study, which was designed
to test the hypothesis that the destruction of the WTC increased the
incidence of persistent new-onset respiratory symptoms and airflow obstruction
in previously normal residents in the surrounding community. Additional
studies will address upper respiratory symptoms, exacerbations of preexisting
asthma, and medical care utilization.
Study participants. Because of the unforeseen nature
of the event, the study was necessarily designed as a hybrid cross-sectional
and retrospective cohort study of residents in an exposed area and a
control area and was approved by institutional review boards of the New
York State Department of Health and New York University. All participants
gave their written consent. Community residents, advocacy groups,
local community boards, local tenant organizations, local medical organizations,
and clinics all actively participated in the design and implementation
of the study. Residents in buildings within a 1-mile radius from the
former WTC were considered to be in the exposed area. Building complexes
in the exposed area were identified in each direction of GZ. Residents
in buildings located > 4.8 miles north of the WTC in Manhattan were
considered to live in the control area. Areas south, east, and west of
the WTC that were affected by the plume were excluded from selection
as a control area. Building complexes in both the exposed area and the
control area were identified by type of housing unit (e.g., low- or high-income
rental, cooperative, condominium, or federally funded housing complex)
to obtain a distribution of socioeconomic levels in the survey. Building
complexes with similar characteristics were identified for the exposed
area and the control area. Residual socioeconomic differences among the
study areas were controlled for during analysis. We oversampled the population
in the exposed area to obtain a large and representative population.
In addition, at the time that this study was developed and implemented,
this was the only study of health effects of local residents, and we
thought that the detection of individuals in this study might provide
the only opportunity for identification of residents for follow-up studies
of health effects. We used the ratio of 9:1 (exposed:control area) while
recruiting study participants. The exposed area included 49 buildings
in lower Manhattan composed of approximately 9,200 households. The control
area included approximately 1,000 households.
Study procedure. A self-administered questionnaire
to identify asthma or asthmalike symptoms was developed from previously
validated questionnaires (Abramson et al. 1991; Asher et al. 1995; Burney
et al. 1989; Ravault and Kauffmann 2001). Questions were modified to
delineate reference times in relation to 11 September 2001, to identify
the onset of symptoms, and to determine whether symptoms were present
within the 4-week period of responding to the questionnaire. Additional
questions were included to obtain demographic information as well as
to identify the presence of the resident in the apartment during the
time of interest and any preceding or subsequent medical problems and
medications. Questionnaires were available in Spanish and traditional
Chinese.
The study was publicized at community board meetings, tenant meetings,
local health fairs, building luncheons, and meetings. Notices of the
study were included in local newspapers and building newsletters. Postings
were also placed in buildings and streets. Outreach workers were situated
in buildings at the time of delivery of the questionnaires to help distribute
questionnaires and respond to questions.
Questionnaires were distributed to all defined buildings 12 ± 4
months after the collapse of the WTC. Questionnaires were initially distributed
via bulk mail. However, it became apparent that the federal postal service
was not functioning in many of the areas near GZ in a consistent manner
and that many of the questionnaires had not been delivered. Subsequently,
in areas with questionable mail delivery, questionnaires were hand delivered
to every apartment or, when entry was denied, to every building lobby.
A first-class mailing of the questionnaire was then repeated, and all
apartments were sent reminder postcards. Up to four residents (two adults,
two oldest children) in each apartment were asked to complete the questionnaire.
Because of a concern about potential selection bias in our response,
two buildings of similar housing stock were targeted in the exposed area
and in the control area for more intensive outreach. Residents of these
buildings received a third copy of the packets, and outreach workers
remained in these buildings for additional days and evenings to respond
to questions and reinforce participation in the study. These targeted
buildings represented 440 households in the exposed area and 240 in the
control area. These targeted buildings with higher response rates were
used to provide an estimate of selection bias compared with the remaining
study sites.
Case definitions. “Previously normal” residents
were considered to be those who did not have a physician diagnosis of
asthma, chronic obstructive pulmonary disease, or emphysema before 11
September 2001.
Previously normal residents with new-onset symptoms were considered
those who answered positively to any of the questions pertaining to respiratory
symptoms of cough, shortness of breath (SOB), or wheeze or were using
oral or inhaled medications for asthma at any time after 11 September
2001. Previously normal residents with persistent new-onset symptoms
were defined as participants with symptoms that began after 11 September
2001 and who had a frequency of symptoms more than twice each week or
medication use within 4 weeks of responding to the questionnaire.
Screening spirometry. Participants who were previously
normal and had persistent new-onset symptoms were invited to perform
a scheduled screening spirometry at a local community site. Participants
were excluded for analysis if they were < 6 years of age because of
the potential for technical difficulties. Participants > 65 years
of age or with a history of cardiovascular disease were excluded for
safety reasons, because the studies were performed in the field. Participants
with a current or > 5 pack-year history of cigarette use, who lived
in the control area but worked in the exposed area, who returned to the
residence after January 2002, or who refused to be recontacted were also
excluded.
Spirometry was performed in the field by trained personnel with a Micro
Direct (Lewiston, ME) portable spirometer that complied with American
Thoracic Society specifications. Studies with three measurements within
5% of each other were considered acceptable. Participants on medications
were asked to withhold use of medications for at least 4 hr. Values of
forced expiratory volume in 1 sec (FEV1), forced vital capacity
(FVC), FEV1/FVC, and flows at mid lung volumes (FEF25-75)
were obtained. Analyses were performed using normal predicted values
from Hankinson et al. (1999). Because studies were being performed in
the community, bronchodilator responses were not assessed.
Airway hyperresponsiveness. Previously normal participants
were invited to perform a methacholine challenge test (MCT) as a monitor
of bronchial hyperresponsiveness. Participants < 55 years of age with
an FEV1 ≥ 70% predicted and either persistent new-onset
symptoms or absence of symptoms were invited to undergo an MCT at the
New York University/Bellevue Hospital pulmonary function laboratory.
Spirometry was performed to confirm baseline values. MCT was performed
using the 2-min tidal breathing protocol with methacholine delivered
via a nebulizer up to a maximal dose of 8 mg/mL (Crapo et al. 2000).
A test was considered positive if the subject had a ≥ 20% drop
in FEV1.
Statistical methods. We calculated the overall response
rate on the basis of the number of households responding in the exposed
area and control area because of the variation in the number of individuals
residing in each household. An undetermined number of residents permanently
moved out of the exposed area after the event. Packets that were returned
unopened were therefore considered to have come from vacant households
and were considered vacant for this calculation. The rates for each health
outcome were calculated as the number of participants with a specific
outcome, divided by the number of eligible participants. We computed
cumulative incidence ratios (IRs) comparing the exposed area and control
area and used 95% confidence intervals (CIs) to estimate the precision
of the cumulative IR. We used unconditional logistic regression analysis
to compute adjusted odds ratios (ORs) while controlling for potential
confounders, including age, sex, education, race, and smoking. Because
respiratory diseases are not rare events, ORs from logistic regression
tended to persistently overestimate cumulative IRs. Therefore, the crude
IRs with 95% CI are presented in result tables, and adjusted OR as well
as CIs were used only to examine if the results were still statistically
significant after controlling for confounders.
The demographic characteristics between the participants in the exposed
area and control areas were compared using the t-test of continuous
variables (e.g., age) or the chi-square test for categorical variables
(e.g., sex). For the analysis of the spirometry data, means ± SDs
are presented. The t-test was used to compare the mean in the
exposed area with the mean in the control area.
Study participants. A total of 9,168 survey packages
were sent to households in the exposed area and 962 to households in
the control area. Responses were obtained from 2,520 households
in the exposed area (22.3%) and 295 in the control area (23.3%). Household
responses were greater in the targeted buildings, with 205 of 440 households
responding from the exposed area (43.8%) and 99 of 240 (41.2%) households
responding from the control area.
A total of 3,196 individual responses were returned for analysis; 384
respondents were excluded from analysis because they did not reside in
the residence on 11 September 2001, they returned to the residence after
1 January 2002, the residence was in the control area but the respondent
worked in the exposed area, or the questionnaire was answered for a person
born after 11 September 2001. Of the 2,812 responses that were therefore
used for analyses, 2,520 were returned from residents in the exposed
area, and 292 from residents in the control area (see Figure 1).
![Figure 1](fig1sm.gif)
Figure 1. Study cohort classifications. Previously normal residents
were considered to be those who did not have a physician diagnosis
of asthma, chronic obstructive pulmonary disease, or emphysema before
11 September 2001.
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Table 1
![Table 1](tab1sm.gif)
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Table 2
![Table 2](table2sm.gif)
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Table 3
![Table 3](tab3sm.gif)
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Table 4
![Table 4](tab4sm.gif)
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Table 5
![Table 4](tab5sm.gif)
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The demographic characteristics of the 2,812 remaining respondents
are shown in Table 1. In both the exposed area and the control area,
there were more women respondents than men respondents. Although most
respondents were between 35 and 64 years of age, there was a higher
response rate from older participants in the control area. A wide distribution
of income levels was detected in both the exposed area and control
area;
however, more respondents from the exposed area earned < $25,000
compared with those in the control area. More respondents in the control
area
were Caucasian, whereas more respondents in the exposed area were of
Asian or Hispanic/Latino descent. These differences reflect differences
in the underlying populations according to the 2000 U.S. Census (U.S.
Census Bureau 2000) and were considered potential confounders. As such,
they were controlled for in multivariate analyses.
Respiratory symptoms in residents. A previous diagnosis
of respiratory disease was identified in 417 (16.6%) and 41 (13.9%) of
the residents in the exposed area and the control area, respectively.
These residents were not considered previously normal and were excluded
from subsequent analysis. Thus, information from 2,103 participants in
the exposed area and 251 participants in the control area was available
for analysis.
As shown in Table 2, more than twice as many previously normal residents
in the exposed area complained of respiratory symptoms at some time after
the collapse of the WTC compared with residents in the control area.
Cough was the most common symptom and was noted in three times as many
participants in the exposed area as in the control area. Four times as
many residents in the exposed area complained of wheeze compared with
residents in the control area. Approximately three times as many residents
in the exposed area complained of SOB. The difference in these symptoms
in the residents in the exposed area remained significant even after
adjusting for age, sex, education, smoking, and race.
To assess whether respiratory symptoms were persistent, previously
normal participants were asked about the presence and frequency of individual
symptoms within the 4 weeks preceding the survey. Symptoms were considered
persistent if they occurred with a frequency of at least twice each week.
As shown in Table 3, symptoms had resolved in many of the residents by
the 4 weeks preceding the survey. However, almost three times the number
of residents in the exposed area continued to have any persistent respiratory
symptom compared with residents in the control area. The predominant
symptom remained cough. Persistent wheezing was reported in 10.5% of
participants in the exposed area compared with 1.6% in the control area.
Similar results were noted for the targeted population that received
intensive outreach and had a greater response rate (43.8 and 41.2% response
rate for exposed area and control area, respectively) compared with the
total study population. Respondents from the targeted exposed area had
a greater risk of new-onset respiratory symptom (IR, 3.05; 95% CI, 2.12-4.39)
and persistent respiratory symptoms (IR, 4.63; 95% CI, 2.50-8.57) compared
with residents in the targeted control area. Persistent daytime SOB was
reported in 13.7%, and wheezing was reported in 13.7% of these previously
normal residents.
We assessed the severity of the reported persistent symptoms, as defined
by the frequency of each individual symptom, in previously normal participants
with persistent new-onset symptoms. This analysis is shown in Table 4.
Almost 24% of participants with a persistent symptom complained of cough
on a daily basis. Daily wheezing was described by 17.5% of the residents
in the exposed area who had a persistent symptom. Using frequency of
symptoms to characterize severity of asthma according to the Global Initiative
for Asthma guidelines (National Heart, Lung, and Blood Institute 2002),
this symptom frequency would be compatible with at least moderate persistent
asthma.
Screening spirometry in residents. Three hundred sixteen
participants were eligible and agreed to screening spirometry in the
field. Many residents did not respond to repeated attempts at telephone
scheduling, failed to come to the scheduled appointments, or could not
complete a successful study. Spirometry was successfully completed in
117 (37%) of the eligible residents. No differences were detected between
residents with symptoms in the exposed area compared with asymptomatic
residents in any parameter of airflow, including FEV1, FVC,
FEV1/FVC, and FEF25-75 (Table 5). We failed to
observe a difference in the number of individuals with an FEV1 or
FEV1/FVC below the lower limit of normal in the individuals
in the exposed area with new-onset persistent symptoms and asymptomatic
individuals, or between individuals in the control area. Of participants
with persistent symptoms in the exposed area, 20.8% had used a controller
medication (inhaled corticosteroid, long-acting ß-agonist, theophylline
compound, leukotriene modifier) in the 4 weeks before spirometry, compared
with none of the participants in the asymptomatic groups. Of participants
with persistent symptoms in the exposed area, 16.7% had used a short-acting ß-adrenergic
agonist inhaler for asthma, compared with 1.5% in the asymptomatic exposed
group and none in the control residents.
All participants were invited to undergo an MCT according to eligibility
criteria defined in “Materials and Methods.” MCT was performed
in 24 volunteer participants, including those with persistent new-onset
respiratory symptoms (n = 12), asymptomatic participants from
the exposed area (n = 6), and asymptomatic participants from outside
the exposed area (n = 6). No significant difference was noted
in baseline spirometry between these groups (data not shown). Many (6
of 12) participants with persistent new-onset symptoms had a positive
MCT compared with asymptomatic participants (p < 0.05). None
of the asymptomatic participants in either group had a positive MCT.
The World Trade Center Residents’ Respiratory Health Study was
initiated in response to questions by residents in the surrounding community
of the disaster site about the respiratory health risk for residents
and was designed to study upper and lower respiratory tract symptoms,
physician diagnoses, unplanned medical visits, and physical condition
of the apartments after the collapse of the WTC. We now report on the
presence and persistence of new respiratory health issues in residents
near GZ. The study was completed 16 months after the destruction of the
WTC. Our study suggested an increased incident rate of new-onset respiratory
symptoms in residents near GZ compared with residents in a control area.
Although these symptoms resolved in many residents, an increased incident
rate of persistent new-onset respiratory symptoms was also detected compared
with a control group. These data suggest that exposure to dust and fumes
from the destruction of the WTC was associated with new-onset respiratory
symptoms that persisted in a subset of residents.
The predominant respiratory symptom detected in symptomatic residents
consisted of cough, with some participants also experiencing dyspnea
and wheezing. These symptoms are consistent with those identified in
the rescue workers and responder populations such as the firefighters
and ironworkers (Feldman et al. 2004). They fit some but not all criteria
for reactive airways dysfunction (RADS) (Alberts and do Pico 1996; Bardana
1999; Brooks et al. 1985). We cannot document the exposure level of the
residents to the dusts and fumes, and although some of these residents
may have had high-level exposure from the initial dust cloud, others
may have only experienced lower-level exposure from settled dust and
persistent fires. Descriptions of irritant-induced asthma have included
cases with a history of repeated low-intensity exposures, in which the
symptoms have a more delayed expression, and this pattern may be more
consistent with the potential exposure history and symptoms of many of
the residents in this study (Brooks 1998; Kipen et al. 1994). The persistence
of symptoms identified in some of the study participants is also consistent
with irritant-induced asthma, in which symptoms can persist for years
(Chang-Yeung et al. 1994; Demeter et al. 2001). The persistence of symptoms
is also consistent with the findings recently described in firefighters
exposed to WTC dusts (Banauch et al. 2003).
Only a subset of residents with potential exposure experienced the
onset and persistence of respiratory symptoms. The characteristics of
this susceptible group are unclear. The variation in response may be
due to differences in the intensity or duration of exposure to the WTC
dusts in the population with persistent symptoms compared with those
without. Alternatively, irritant-induced asthma has been described to
be more common in participants with preexisting allergic or atopic disorders
(Brooks et al. 1998). We did not specifically explore whether participants
with persistent symptoms had preexisting atopic disorders in this study.
The possibility exists that psychological stress might play a role
in the reported symptoms, because post-traumatic stress disorder has
been reported to be associated with asthma and other respiratory diseases
(Fagan et al. 2003). In the present study we could not determine whether
environmental factors, psychological distress, or a combination, contributed
to the increase of respiratory symptoms, because psychological factors
were not examined in this part of the study.
Despite our original hypothesis, we were unable to detect a significant
difference in airflow parameters measured by screening spirometry performed
in the field between residents with persistent new-onset respiratory
symptoms and asymptomatic or control residents. We did not have preexisting
medical information available to us for the population of study, and
as a result, we performed between-subject comparisons. The possibility
exists that our statistical power was not great enough to detect small
differences in airflow measurements between the two populations. The
symptoms detected in the exposed population may also be due to changes
in the small airways or to an increase in bronchial hyperresponsiveness,
both of which can be missed with routine screening spirometry. In addition,
many participants in the group with persistent symptoms in the exposed
area were using a controller medication at the time of the study. Use
of these medications may have improved their lung function. The findings
are, however, consistent with those described in firefighters exposed
to WTC dusts in which no significant differences in spirometry values
were detected between participants with high and low exposure, suggesting
that these parameters are insensitive for between-subject comparisons
in these exposed populations (Prezant et al. 2002). MCT performed in
a small pilot study of participants suggested that the symptoms of some
of these residents might be explained by the presence of bronchial hyperresponsiveness,
a finding that would be consistent with the data reported for firefighters
(Prezant et al. 2002).
The predominant compounds detected in the settled dusts collected 1
and 2 days after the WTC explosion included calcium sulfate (gypsum)
and calcium carbonate (calcite) (Lioy et al. 2002; McGee et al. 2003;
Service 2003). The aqueous extracts were extremely alkaline (Lioy et
al. 2002). These particle characteristics are associated with mucus membrane
irritation and thus have the potential to elicit airway symptoms consistent
with those detected in this study (Stellman 1998). Biologic plausibility
for health effects from WTC dusts is supported by in vitro and in
vitro studies. Primary human lung cells (alveolar macrophages
and epithelial cells) reveal an increase in inflammatory cytokines, interleukins
8 and 6, in response to WTC dusts (Payne et al. 2004). Animal studies,
using WTC-derived fine particulate matter, demonstrate that very high
doses elicit pulmonary inflammation and hyperresponsiveness (Gavett et
al. 2003). Although lower doses of these particles did not induce inflammation
or hyperresponsiveness, the effects of chronic exposures were not tested
in these studies.
Despite the large sample size of this study, there are some potential
limitations to the study. In contrast to the firefighters, in whom a
baseline health and pulmonary function profile was well established and
documented before 11 September 2001, no consistent information was available
about the health of the residents in the surrounding GZ community before
11 September 2001. Many of these residents were considered normal before
that date and thus do not have documented respiratory health information
preceding 11 September 2001. We therefore used self-reported health information.
The possibility of reporting bias or differential recall by persons in
the different study areas exists. To minimize this possibility, questions
about health problems that should be unrelated to WTC events were also
included in the questionnaire. The similar rate of problems such as disability
affecting physical activity in the two areas (14.2 and 13%, respectively)
suggested the absence of significant reporting bias due to residence
area. Participants responding affirmatively about every symptom may have
been affected by recall bias. Ten of the respondents answered in this
way; however, minimal changes were observed when these individuals were
excluded from the analysis. We also obtained information about unplanned
medical visits in the months after the WTC collapse, events that may
be more memorable than symptoms. Unplanned medical visits for respiratory
problems were significantly increased in the affected area (14.7%) over
the control area (8.4%) [cumulative incidence ratio (CIR), 1.76; 95%
CI, 1.15-2.68)] after controlling for potential confounders. A significantly
higher proportion of affected area residents started using respiratory
medication after 11 September 2001 (17.9%) compared with controls (6.2%)
(CIR, 2.88; 95% CI, 1.75-4.75). We also compared the proportion of respondents
reporting a specific respiratory symptom and unplanned medical visits
in both areas. We found that the proportions were similar in the affected
and control areas for most symptoms. If there had been overreporting
in the affected area, the proportion of individuals reporting a specific
symptom who also had unplanned medical visits should have been lower
in the affected area than in the control area.
Despite the active involvement of the community in the design and implementation
of this study, the response rate in both the exposed area and control
area was low. Several possible explanations can be suggested for this
low response rate. First, although we used many means to deliver the
questionnaires, the absence of reliable mail in many of the exposed areas
may have reduced our ability to reliably distribute the surveys. Moreover,
because of the well-documented emotional aftermath of the event, many
residents may have been unwilling to answer questions that may have provoked
sensitive emotions even 1 year after the event. In addition, at the time
of the study, residents were also receiving forms from many other agencies.
Both confusion over which studies were being completed, and study fatigue
may have occurred. Finally, we were unable to determine a true response
rate because a significant number of residents permanently moved out
of the exposed area after 11 September 2001. In some buildings, residents
estimated that > 50% of the occupants had moved from the buildings.
We were unable to obtain a listing of residents in the area before and
after the event, and for this reason, the denominator for calculating
the household response rate may have been an overestimate, resulting
in an underestimate of the actual response rate. Furthermore, low response
rates are common for studies performed in New York City; the 2000 Census
recorded only a final response rate in New York City of 55% despite intense
advertising and door-to-door follow-up (U.S. Census Bureau 2000).
The potential for selection bias exists in this self-administered survey,
and it is possible that residents with new-onset respiratory symptoms
may have been more likely to participate in this study compared with
those without symptoms. Several procedures were used during the study
in an attempt to minimize this potential problem. The importance of participation
for residents with and without breathing problems was stressed in all
announcements of the study. In addition, a target population that received
intensive outreach was studied in both the exposed area and the control
area. This target population, which had a higher response rate compared
with the study population as a whole, demonstrated an even greater increase
in persistent symptoms in residents in the exposed area compared with
the control area, with an increase in individual symptoms ranging from
14 to 63% in the target population. Had there been a significant selection
bias or an overestimation of the association, analysis of the target
population should have demonstrated a weaker exposure-disease association
compared with the control population. In contrast, analysis of symptoms
in the target population demonstrated that increases in new-onset symptoms
were consistently and significantly higher in the exposed areas compared
with the control area. This finding suggests that if there were selection
bias, it would be in the opposite direction (i.e., the true association
would be underestimated).
A plume dispersion model is not yet complete by the U.S. Environmental
Protection Agency and thus was not available to us to allow a detailed
exposure assessment. However, we obtained self-report information on
the condition of the individual households as a possible surrogate for
exposure. Many of the apartments that were in close proximity to GZ were
severely damaged by the event. Apartments that surrounded GZ in all directions
were covered in dusts from the initial dispersion. The presence of persistent
new-onset respiratory symptoms was significantly associated with the
presence of physical damage of the apartment, dust on the surfaces, or
a long duration of dust or odors (data not shown). In addition, residents
who were south of Canal Street in lower Manhattan on 11 September 2001
(i.e., in close proximity to the WTC) were at higher risk of developing
persistent new-onset respiratory symptoms compared with residents who
were not in the area on the day of the event.
The possibility of exposure misclassification may also exist. To minimize
this bias, we excluded individuals who had moved out of their residence
for a prolonged period of time or who may have had exposure that was
unrelated to their area of residence. Some residents may have altered
their behavior and spent less time at home in the aftermath of 11 September
2001; however, we would not be able to identify these residents. In addition,
because of wind, it is also possible that the WTC dust plume also affected
residents in the control area.
These data suggest that residents living in the community surrounding
the former WTC experienced a higher rate of adverse respiratory health
effects 1 year after the event compared with a control population. Respiratory
symptoms consisted of cough, dyspnea, and wheeze. Although most of these
symptoms resolved by approximately 12 months after the event, a significant
number of residents continued to have persistent new-onset respiratory
symptoms. Abnormalities in screening spirometry failed to explain the
symptoms in these participants, and additional tests, including tests
for bronchial hyperresponsiveness, may be helpful to further characterize
these symptoms. Biologic plausibility for these complaints is provided
by chemical analysis of the settled dusts and animal studies. Long-term
health effects remain unknown and warrant further investigation and follow-up
of exposed residents.