1 Center for Environmental Health, New York State Department of Health, Troy, NY
2 Department of Medicine, Division of Pulmonary and Critical Care Medicine, New York University School of Medicine, New York, NY
3 Department of Epidemiology and Biostatistics, School of Public Health, University at Albany, State University of New York, Renssalaer, NY
Correspondence to Dr. Shao Lin, Bureau of Environmental and Occupational Epidemiology, New York State Department of Health, 547 River Street, Room 200, Troy, NY 12180 (e-mail: sxl05{at}health.state.ny.us).
Received for publication July 23, 2004. Accepted for publication October 29, 2004.
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ABSTRACT |
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asthma; environmental pollution; New York City; respiratory tract diseases; terrorism
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INTRODUCTION |
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One of the immediate public health concerns was the effect of this intensive exposure to these air pollutants on the health of local residents. Analyses of settled dust samples collected 56 days after the disaster indicated that 14 percent by weight were particles that can be inhaled deeply into the lungs (3) and are associated with respiratory diseases. Adverse health effects could have arisen from both acute high-level exposures and prolonged low-level exposures. Moreover, it is unknown whether the adverse respiratory effects, if they existed, were transient or persistent. Studies of asthmatic Lower Manhattan residents found worse symptoms and increases in medical care utilization and asthma medication prescriptions after 9/11 (4
, 5
). To our knowledge, these studies of persons with asthma are the only published studies of the respiratory health of residents near the site of the former WTC ("Ground Zero"). The pollution from the WTC disaster may have also caused new disease among previously healthy residents of New York City. Additionally, local residents complained about upper respiratory and other symptoms consistent with exposure to irritants. Since there are large residential communities around Ground Zero, the potential for respiratory health effects from exposure to these agents deserves investigation.
The goals of the present study included 1) determining whether there was an increase in the incidence of new-onset and persistent upper and lower respiratory symptoms in residents living near Ground Zero as compared with residents of a control area and 2) investigating whether there was an increase in symptom exacerbation among asthmatic residents living near Ground Zero as compared with a control area. Additionally, subgroups of residents with new-onset persistent symptoms and asymptomatic persons were identified and followed for assessment of chronic respiratory health effects, including symptom persistence and physiologic abnormalities as measured by spirometry. In this paper, we discuss the results pertaining to upper respiratory symptoms.
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MATERIALS AND METHODS |
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The area defined as the affected area is located within 1.5 km of the former WTC site and includes 49 buildings in Lower Manhattan with approximately 9,200 households. A control area was used for comparison, because the health histories of residents living near the WTC prior to 9/11 were not available and respiratory diseases usually have a strong seasonal component. The prevailing wind direction was considered in selecting the control area. Therefore, areas south, east, and west of the WTC that were impacted by the plume, including Brooklyn, New Jersey, and Staten Island, were excluded from the control area. Efforts were made to identify control buildings in census blocks with similar characteristics as the affected area. The control area consisted of approximately 1,000 households in five Upper Manhattan apartment buildings more than 9 km from the WTC site. To obtain a large, representative sample in the affected area, we oversampled the population of the affected area at a 9:1 ratio (affected area:control area). Figure 1 shows the study areas and the prevailing wind directions at John F. Kennedy International Airport for September 1130, 2001.
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Study materials and procedures
A study packet containing a cover letter, consent forms, questionnaires, and a stamped, addressed envelope was mailed to all apartments in the study buildings. The study packets also contained information about Project Liberty (a federally sponsored program providing free crisis counseling services to those affected by the WTC disaster) for persons who experienced anxiety while reviewing the materials. To accommodate the needs of the large populations of non-English speakers in the study areas, translations of the study materials were available for Spanish- and Chinese-speaking residents.
The questionnaires included a household questionnaire and four individual questionnaires. An adult resident was asked to complete the household questionnaire by providing information on the age, gender, and asthma status of all household members. The household questionnaire also asked about the condition of the apartment immediately after 9/11, the duration and frequency of odors or dust in the apartment, and any cleaning, sampling, or inspections that were performed.
In households with more than four persons, two adult residents and the two oldest residents under age 18 years were asked to complete the individual questionnaire. For children younger than age 12, a parent or legal guardian completed the questionnaire. The individual questionnaire was primarily designed to estimate the prevalence and incidence of asthma and respiratory symptoms. This questionnaire was derived from the International Union Against Tuberculosis and Lung Diseases questionnaire and the International Study of Asthma and Allergies in Childhood questionnaire, both of which have been validated and used in epidemiologic studies to detect symptoms associated with asthma and bronchial hyperresponsiveness (69
).
For questions about upper and lower respiratory symptoms and irritation symptoms, the resident was asked whether the problem had occurred in the past 12 months, whether it started after 9/11, whether it worsened after 9/11, and, depending on the type of symptom, either the average frequency or the perceived severity of the symptom during the past 4 weeks. Additional questions assessed unplanned medical visits (outpatient visits, emergency department visits, and hospitalizations), physician diagnoses of asthma and other respiratory disorders, use of asthma medication, and respiratory functional status. The questionnaire also included questions related to sociodemographic factors, smoking history, temporary residence changes after 9/11, and employment location. After receipt of a completed questionnaire, a Metro Card with a value of $6 was mailed to the participant to acknowledge participation.
The study packets were initially distributed 1 year after 9/11 (±4 months) via bulk mail. Because of inconsistencies in the handling of this material, additional deliveries were made to each residence by hand. Where access could not be gained to make hand deliveries, the packets were left in building lobbies. Finally, in addition to the bulk mailing, a first-class mailing of the packets was made to all households, followed by a reminder postcard. After distribution of the packets, field-workers spent time in the buildings to encourage participation, provide additional copies of the study materials, and answer questions. The days and times of these outreach activities were varied to maximize the numbers and types of persons encountered. Posters advertising the study were placed in and around the buildings. Further publicity about the study was generated through notices in local newspapers and building newsletters, as well as by staff in attendance at meetings of community boards and tenant organizations and local health fairs. To estimate potential selection bias, we selected one building in the affected area (440 apartments) and two buildings in the control area (240 apartments) to receive additional outreach. These intensive outreach activities included additional mailings, advertisements, and time spent in the buildings by field-workers.
Outcome definitions
Health outcomes were defined on the basis of reported respiratory symptoms, unplanned medical visits, physician diagnoses, medication use, respiratory functional limitation, and the time period in which symptoms occurred. "New-onset" symptoms were defined as upper respiratory symptoms that began after 9/11. A "persistent new-onset" symptom was a new-onset symptom that had bothered the respondent "some" or "a lot" in the 4 weeks prior to completing the survey.
Statistical analysis
Because of variations in the number of persons residing in each apartment and the lack of information about the number of persons in nonresponding households, the response rate was calculated using the number of responding households as a numerator. Packets that were returned marked "vacant" were omitted from this calculation.
The demographic characteristics of participants in the affected and control areas were compared using the 2 test. For new-onset respiratory health outcomes, we computed cumulative incidence by dividing the number of participants with a new-onset outcome after 9/11 by the total number of participants. However, the denominators for unplanned medical visits, new diagnoses of asthma, and medication use were based on the subgroup of participants who were "previously healthy" (i.e., free of a physician's diagnosis of asthma, emphysema, chronic obstructive pulmonary disease, and chronic bronchitis prior to 9/11). Cumulative incidence ratios (CIRs) comparing the affected and control areas were computed, and 95 percent confidence intervals were used to estimate the precision of the CIRs. For respiratory functional status (before and after 9/11), prevalence rates (the number of persons in a disease status category divided by the total number of participants in each area) and prevalence ratios and their 95 percent confidence intervals were computed. Finally, the
2 test was used to compare data for the self-described breathing statements.
Unconditional logistic regression analysis was used to compute adjusted odds ratios while controlling for potential confounders, including age, gender, education, race, and smoking. Education was used as a surrogate for socioeconomic status, because information about education was more complete (11 percent missing data) than information for income (25.3 percent missing data), and education and income were highly correlated. Because respiratory diseases are not rare events, adjusted odds ratios from logistic regression tend to consistently overestimate the CIRs. Therefore, the crude CIRs and 95 percent confidence intervals are presented in the tables, and adjusted results were used only to determine whether the results were still statistically significant after controlling for confounders.
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RESULTS |
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Although we attempted to make the residents of affected and control areas demographically comparable, differences remained. The affected area had distributions of age and household income that were significantly different from those of the comparison area (table 1). In paired 2 tests, there were significantly higher proportions of Hispanics, Asians, and residents with less education (i.e., not high school graduates) but lower proportions of African Americans and Caucasians from the affected area as compared with the control area. In general, these demographic differences are similar to differences in the underlying populations according to 2000 US Census data. Since low socioeconomic status is associated with asthma, these variables were considered potential confounders and were controlled for in the multivariate analyses.
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DISCUSSION |
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Among previously healthy residents in the affected area, we found a 73 percent increase in unplanned medical visits and a 189 percent increase in new medication use for respiratory problems after 9/11. Moreover, there was a 144 percent increase in the use of respiratory medication in the past 4 weeks, including use of fast-relief and controller medicines, among previously healthy affected-area residents. Additionally, the self-described respiratory functional status of affected-area residents was impacted more than that of control-area residents. Shortness of breath with varying levels of exertion was significantly higher in affected-area residents than in the controls. Self-reported descriptions of breathing during the past 4 weeks also indicated significantly higher levels of breathing trouble in the affected area. Szema et al. (5) found that visits to a health clinic for asthma and prescriptions for asthma medication both increased among pediatric asthma patients after 9/11. All of these findings suggest that residents near Ground Zero experienced a significant increase in respiratory diseases related to the WTC disaster and that these symptoms were still persistent in a significant portion of the residents after 1 year.
Our study was one of the earliest of the few studies to estimate the incidence of respiratory disease among residents of Lower Manhattan after 9/11. Both Fagan et al. (4) and Szema et al. (5
) studied residents of Lower Manhattan; however, their populations were restricted to persons with asthma. Although residents near Ground Zero were probably not exposed to air pollution levels as high as those of the firefighters involved in WTC rescue, recovery, and clean-up activities, we have shown that residents of the affected area did report significantly more upper respiratory symptoms than residents of the control area.
Ambient air quality after 9/11
The New York City Department of Health and Mental Hygiene (12) measured the levels and composition of outdoor and indoor surface and airborne dust from November 4 to December 11, 2001, in residential areas near Ground Zero and in a comparison area. That study found a greater percentage of synthetic vitreous fibers, asbestos, quartz, calcite, portlandite, and gypsum in settled dust in Lower Manhattan than in the comparison area. The Environmental Protection Agency collected dust samples at various locations in the immediate vicinity of the WTC site 12 days after 9/11 (2
). The WTC samples of particulate matter less than 2.5 µm in diameter were alkaline and composed primarily of calcium-based compounds such as calcium sulfate (gypsum) and calcium carbonate (calcite). Gypsum and calcite can irritate the mucus membranes of the eyes, nose, throat, and upper airways (13
), and calcium carbonate dust can cause coughing, sneezing, and nasal irritation (14
).
Although smoke or debris might have contributed to the increase in adverse respiratory health outcomes in this study, psychological stress might also have played an important role in these effects (15). In the current study, we could not determine whether environmental factors, psychological distress, or both contributed to the increase in respiratory symptoms, since psychological factors were not examined.
Strengths and limitations
This study is an important first step in identifying the acute and chronic respiratory health impact of the WTC disaster. Of the few studies that have investigated respiratory health among residents of Lower Manhattan after 9/11, it is one of the largest. This study responded to local residents by examining specific symptoms of concern to the community. The design and analysis used in this study allowed for the control for seasonal and socioeconomic confounding effects. In addition, the use of a cohort design allowed for examination of multiple health outcomes.
Although intensive outreach activities were implemented as described in Materials and Methods, we obtained low response rates. This may have been due to the emotional aftermath of the disasterresidents might not have been willing to answer questions that would provoke an emotional reaction. In addition, at the time of this study, the residents of Lower Manhattan were inundated with forms from government agencies and other organizations. The amount of information requested during this time was probably overwhelming. In addition, residents may have thought they had already completed a questionnaire when in fact they had not. New York City also has a history of lower response rates. The 2000 Census only recorded a final response rate of 55 percent in New York City, despite intense advertising and door-to-door follow-up. More importantly, a significant number of residents moved out of the affected area after 9/11. For this reason, if the denominator for calculating the household response rate was overestimated (despite attempts to identify vacant households), the actual response rate would have been underestimated.
The low response rates, although similar between the two study areas, may have introduced selection bias. That is, residents who experienced symptoms, especially those who lived in the affected area, might have been more likely to participate than those who did not. This could have caused the incidence of new-onset symptoms to be overestimated, particularly in the affected area. To minimize this bias, we emphasized the importance of participation for people with and without breathing problems during recruitment activities. In addition, general terms such as "breathing or lung problems" rather than specific terms like "asthma" were used.
To examine possible selection bias due to low response rates, we compared results for the buildings targeted for increased outreach and the nontargeted buildings. Results from the targeted buildings, in which higher response rates were achieved, are assumed to be more accurate and representative. If there was selection bias, we would expect to find a weaker exposure-disease association in the targeted buildings. Instead, we found that the risk estimates for new-onset and new-onset persistent symptoms were consistently higher in the targeted buildings than in the nontargeted buildings (see appendix table 1). These results suggest that any selection bias was in the opposite direction than we would have expected (i.e., the true association may have been underestimated).
Another potential problem with this study is reporting bias. Affected-area participants may have recalled or reported more symptoms than the controls. To prevent such reporting bias, we asked symptom questions not only qualitatively but also quantitatively, by including questions on specific time frames, severity, and frequency, which are less prone to recall bias. To estimate potential reporting bias, we compared rates of self-reported physical disability (which should not have been related to WTC exposures) between the affected area and the control area. The similar rates in the two areas (14.7 percent and 13.1 percent, respectively) indicate no significant reporting bias due to residence area. A participant responding affirmatively about every symptom may have been affected by recall bias (n = 10). Minimal changes were observed when these persons were excluded from the analysis. We believe recall of unplanned medical visits, including emergency department visits and hospitalizations, is more likely to be accurate than recall of symptoms, since such events are more likely to be memorable, and we solicited information on the reason for and exact month and year of the visit. Among respondents reporting a specific respiratory symptom, we compared the proportions who had unplanned medical visits. We found that the proportions were similar in the affected and control areas for most symptoms. If there was overreporting in the affected area, the proportion of persons reporting a specific symptom who also had unplanned medical visits should have been lower in the affected area than in the control area. Therefore, there is no clear evidence of reporting bias on the basis of our limited assessment. In general, reporting bias can be minimized by using objective indicators (e.g., medical records) rather than self-reported information. In this study, it was not feasible to review medical records. Additionally, an analysis of medical records would probably have underestimated or completely missed the less severe symptoms included in our survey.
One final area of concern is the possibility of exposure misclassification. As described above, we excluded persons with evidence of residential mobility and exposures unrelated to their area of residence in order to minimize this bias. However, an unidentified group of affected-area residents may have altered their behavior, spending less time at home in the aftermath of 9/11. Thus, their actual exposure may have been overestimated. On the other hand, it is also possible that control-area residents were impacted by the WTC plume in unforeseen ways.
Conclusion
This study suggests that residents who lived near Ground Zero on 9/11 reported significantly more upper respiratory and irritation symptoms, unplanned medical visits, and use of respiratory medications and decreased respiratory functional status after 9/11. In a significant portion of the residents, these symptoms persisted 1 year after 9/11. Although we cannot rule out the possibility that selection and reporting bias may have contributed to these increases, chemical analyses of WTC-related pollutants by other researchers support the biologic plausibility of these findings. Further analyses are needed to examine whether increases in reported respiratory disease can be related to differences in exposure and to monitor the potential long-term health effects of the 9/11 disaster in this population.
APPENDIX TABLE 1. Incidence of new-onset and persistent new-onset upper respiratory symptoms after September 11, 2001, among residents of the affected area versus the control area, by level of outreach (targeted areas and nontargeted areas), World Trade Center Health Survey, New York City, 2002
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* CIR, cumulative incidence ratio; CI, confidence interval.
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ACKNOWLEDGMENTS |
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The authors thank Dr. Thomas Matte for his valuable guidance in the design of the study and Heidi Lee, Marcy Lopez, and Koji Park for their outreach work. They also thank the local community boards, tenants' organizations, and downtown New York City health organizations for their cooperation and Dr. Lester Blair of the American Lung Association for his assistance.
The contents of this article are solely the responsibility of the authors and do not necessarily represent the official views of the Centers for Disease Control and Prevention.
Conflict of interest: none declared.
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NOTES |
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References |
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