Secondary Logo

Journal Logo

Original Articles

Health Effects in New York State Personnel Who Responded to the World Trade Center Disaster

Mauer, Matthew P. DO, MPH; Cummings, Karen R. MPH; Carlson, G Anders PhD

Author Information
Journal of Occupational and Environmental Medicine: November 2007 - Volume 49 - Issue 11 - p 1197-1205
doi: 10.1097/JOM.0b013e318157d31d
  • Free
  • Take the CME Test

Abstract

Learning Objectives

  • Identify the most common respiratory and psychological symptoms reported by the more than 1,400 New York State personnel in this epidemiological study who had worked at the World Trade Center (WTC) site, but who probably were less exposed than many firefighters or police responders.
  • Compare rates of respiratory and psychological symptoms in workers who were—and those who were not—caught in the cloud of toxic dust created when the WTC buildings collapsed.
  • Appraise the results of clinical laboratory tests in this cohort.

The World Trade Center (WTC) disaster on September 11, 2001, led to a response by a variety of individuals, including employees from a number of New York State (NYS) agencies and NYS National Guard personnel. These NYS responders had variable levels of potential exposure dependent on job tasks, time of first response, length of deployment, personal protective equipment use, and work locations. Overall, this population may represent a group with lower levels of exposure in comparison to responders with potentially high levels of exposure such as members of the Fire Department of New York (FDNY)1 and the New York Police Department (NYPD).2

The collapse of the twin towers of the WTC resulted in a massive cloud of dust and debris that spread over a large area of lower Manhattan, as well as fires at the site, which burned out of control for many weeks. Recovery activities also resulted in potential exposures to diesel exhaust from construction equipment, trucks, and other sources. Responders were potentially exposed to construction materials such as gypsum, calcite, and cement or concrete dust as well as metals, volatile organic compounds, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polychlorinated dibenzodioxins, polychlorinated dibenzofurans, glass fibers, and asbestos.3–8 The content and distribution of material was indicative of a complex mixture of building debris and combustion products in the resulting plume.3 The dust has been characterized as caustic and alkaline.9,10 Biomonitoring of some workers has demonstrated increased levels of some compounds, such as polycyclic aromatic hydrocarbons, heptachlorodibenzodioxins, heptachlorodibenzofurans, and some metals.11

Studies have demonstrated a variety of health effects in WTC responders and community residents. Cough, exertional dyspnea, airway hyperreactivity, upper respiratory (UR) symptoms, and gastroesophageal reflux symptoms were reported in FDNY personnel.1,12,13 Cough, dyspnea, wheeze, mild pulmonary function test (PFT) changes, hoarseness, and UR symptoms were reported in NYPD personnel.2 Lower respiratory (LR) and UR symptoms were reported in ironworkers, office workers, and cleanup and recovery workers.14–17 Increased asthma and respiratory symptoms were reported in local residents.18–20 Increased asthma severity was reported in pediatric patients.21 Psychological symptoms, depression, and posttraumatic stress disorder (PTSD) were reported in local residents and workers.22–24

In 2002, NYS employees and NYS National Guard personnel who were directed to respond to the WTC disaster were offered the opportunity to undergo a medical monitoring evaluation. These evaluations included completion of a health and exposure questionnaire, a medical examination, and clinical and laboratory tests. The NYS Department of Health (NYSDOH) Bureau of Occupational Health collected the questionnaire data and results of the medical evaluations from those responders who consented to participate in this WTC study.

Results reported here include a characterization of the study population and any potentially WTC-related health effects they may have experienced. Descriptive data including self-reported symptoms and medical evaluation results are reported, as well as results from comparisons between study participants who reported being caught in the cloud of dust on September 11, 2001, when the WTC buildings collapsed and participants who reported not being caught in the cloud of dust.

Methods

Medical Monitoring Program

In 2002, a medical monitoring evaluation was offered to all NYS employees and NYS National Guard personnel who were directed to respond to the WTC disaster between September 11, 2001, and December 23, 2001, in the secure or exclusion zone (Fig. 1), in the waste stream corridor, or at Fresh Kills Landfill, regardless of whether they had experienced symptoms. The December date was consistent with the date of the official pronouncement that the fires had been extinguished.

Fig. 1.
Fig. 1.:
The secure or exclusion zone around the World Trade Center (WTC) disaster site, as defined for eligibility in the New York State WTC medical monitoring program.

The NYS Department of Civil Service Employee Health Service (EHS) provided medical evaluations from May 2002 through November 2003. Medical evaluations were conducted at EHS clinic sites and two contracted NYSDOH Occupational Health Clinic Network sites, covering regions throughout NYS. The evaluations involved reviewing the completed health and exposure questionnaire, obtaining a patient history, conducting a physical examination, collecting blood samples for clinical and laboratory tests, performing a PFT and, if deemed necessary by the examining physician, completing a standard chest radiograph. On completing each individual medical evaluation, the examining physician dictated a summary narrative regarding the evaluation and provided their opinion regarding whether the patient was experiencing any health symptoms related to their potential WTC exposures. As appropriate, recommendations were made for additional clinical evaluation.

Study Design

The epidemiological study, which was approved by the NYSDOH Institutional Review Board, involved collecting the completed, self-administered health and exposure questionnaires and data from the medical evaluations, including clinical laboratory test results, physical examination results, PFT results, and physician diagnosis information for medical monitoring program participants who granted their consent. The health and exposure questionnaire collected information on demographics, exposure history, locations and times worked at WTC sites, WTC-related job tasks, WTC-related personal protective equipment use, health symptoms, and diagnoses. Clinical laboratory tests included an SMA–20 (sequential multi–channel analysis with computer–20) and a complete blood count. PFT results included the forced expiratory volume in 1 second (FEV1), the forced vital capacity (FVC), the FEV1/FVC ratio (FEV1/FVC %), and the forced expiratory flow during the middle half of the FVC (FEF25–75), as well as interpretations regarding whether results indicated a normal, obstructive, restrictive, or mixed pattern. In addition, the severity of any abnormalities was recorded.

PFTs were conducted at each individual clinic site by existing clinic staff, using existing spirometers. All clinics were expected to have followed standard established criteria in conducting PFTs. During their evaluation, patients were asked several questions regarding medication use and smoking before the evaluation. In the analysis, PFT results were excluded if the patient had smoked within 2 hours before the evaluation or had used bronchodilator medications before the evaluation.25

Data were analyzed using SAS statistical software (version 8; SAS Institute, Cary, NC). Mean values were expressed with their standard deviation. Contingency tables were constructed to evaluate the relationship between categorical variables, and prevalence ratios (PRs) with their associated 95% confidence intervals (CIs) were calculated. Logistic regression was used to assess outcomes after adjustment for race, education, age, and smoking status. Because of the small numbers of cases for each of the outcomes, each factor was controlled for individually. Results were considered statistically significant when the 95% CI excluded the null.

Results

Study Participants

For the medical monitoring program, a total of 4533 NYS employees and 5269 NYS National Guard personnel were solicited. A total of 1677 (17%) of NYS employees and NYS National Guard personnel expressed interest and were medically evaluated. Of those, over half were examined within 11 months after the WTC disaster. Three quarters were examined within 14 months, and 99% were examined within 19 months. Of those who were medically evaluated, 1423 (85%) agreed to participate in this epidemiological study.

Most study participants were married (n = 1027, 72.2%), white (n = 1178, 82.8%), non-Hispanic (n = 1220, 85.7%), and men (n = 1320, 92.8%). The mean age of the participants was 40 years and the range was 19 to 68 years. Although there were 21 NYS agencies represented, the majority of the participants were from the Division of State Police (n = 635, 44.6%), the NYS National Guard (n = 400, 28.1%), the Department of Transportation (n = 153, 10.8%), and the Department of Environmental Conservation (n = 93, 6.5%). Ninety percent of participants lived outside of the five boroughs of New York City at the time of their evaluation, with only 17 living in Manhattan.

Exposures

Arrival time was based on the time a participant first responded to one of the WTC work areas on a work assignment. Although 1156 (81.2%) participants arrived by the end of the month of September, only one third arrived during the first 2 days, and only 57.3% arrived by September 16. Work assignments at the WTC site peaked between September 17 and September 30. Almost two thirds of the study participants (n = 921, 64.7%) were involved in the response efforts during this time period. In addition, 110 participants reported that they were caught in the cloud of dust on September 11, 2001, when the WTC buildings collapsed. Only 69 of 110 (62.7%) participants arrived on work assignment on September 11. Thus, some participants who reported being caught in the cloud of dust were in the vicinity of the WTC when the buildings collapsed before being assigned to the site as a response worker.

Participants could have worked at multiple locations. Almost two thirds (n = 894, 62.8%) of the participants spent at least some time on the pile or adjacent to the pile. “Adjacent to the pile” was defined as within one block of the WTC rubble. Of the 650 (45.7%) participants spending time outside of the secure area (within five blocks of the secure area), 499 (76.8%) spent time in at least one of the other locations as well. Information on the time of arrival and location worked at the WTC site was unknown for 82 participants.

Participants were engaged in a multitude of tasks and could have performed more than one task. The most common tasks were security (n = 776, 54.5%), traffic control (n = 464, 32.6%), and supervising (n = 274, 19.3%). There were 192 (13.4%) participants who indicated that they participated in the rescue and recovery effort (ie, bucket brigade, hand digging, or search and rescue).

Respirator Use

Almost two thirds of the participants (n = 897, 63.0%) used some type of respiratory protection at least part of the time during their work at the WTC site (Table 1). Participants could have used more than one type of respiratory protection during their duties at the WTC site. The two most common types of respiratory protection used were a one-strap dust mask (n = 401, 28.2%) and a two-strap dust mask (n = 332, 23.3%). A respirator (cartridge, powered air purifying respirator, self–contained breathing apparatus, unknown type) was used by less than one third of the participants (n = 426, 29.9%) at least part of the time. Participants were more likely to use some type of respiratory protection during the week after the WTC collapse, after which usage began to decline. Use of disposable dust masks decreased over time and use of respirators increased temporarily during the month of September. It should be noted that reported respiratory protection use does not account for whether participants were properly fit-tested or whether they used respiratory protection appropriately.

TABLE 1
TABLE 1:
Self-Reported Respiratory Protection Used by New York State WTC Responders

Self-Reported Symptoms

The prevalence of self-reported new or worsening symptoms since September 11, 2001, is shown in Table 2. Nearly half of the participants reported at least one new or worsening LR symptom (n = 674, 47.4%) or UR symptom (n = 606, 42.6%). The most common symptom reported was dry cough, occurring in 30.5% of the participants. Only 250 (17.6%) participants reported being treated for respiratory symptoms before the medical monitoring program. Of these, 57 (22.8%) reported that those symptoms did not improve posttreatment.

TABLE 2
TABLE 2:
Prevalence of Self-Reported New or Worsening Symptoms Since September 11, 2001, in New York State WTC Responders

Nearly one third of the participants reported experiencing new or worsening psychological symptoms after September 11, 2001. The most common psychological symptoms were sleep problems (n = 233, 16.4%), excessive fatigue (n = 233, 16.4%), and feeling excessively irritable (n = 178, 12.5%). Only 39 (2.7%) participants reported being treated for psychological symptoms.

PRs were calculated to compare reported symptoms among participants who reported being caught in the cloud of dust on September 11, 2001, when the WTC buildings collapsed and those who did not report being caught in the cloud of dust (Table 2). Unadjusted data are presented because PRs and CIs were similar after adjusting for race, education, age, and smoking status. As only five women reported being caught in the cloud of dust, we did not adjust for gender. The categories of LR symptoms (PR 1.23, CI 1.03 to 1.46) and UR symptoms (PR 1.29, CI 1.08 to 1.55) were more likely to be reported by participants caught in the cloud of dust. This was also true for a number of specific symptoms in these two categories. Psychological symptoms, collectively, did not vary significantly among the two comparison groups. Nevertheless, participants caught in the cloud of dust were more likely than participants not caught in the cloud of dust to report some specific psychological symptoms, including feeling jumpy or easily startled (PR 2.40, CI 1.42 to 4.05), concentration problems (PR 1.85, CI 1.20 to 2.85), emotional numbness (PR 1.83, CI 1.16 to 2.90), flashbacks (PR 1.76, CI 1.10 to 2.83), and difficulty remembering things (PR 1.59, CI 1.02 to 2.46).

Participants caught in the cloud of dust were more likely to report several other symptoms, including acid stomach or heartburn (PR 1.60, CI 1.08 to 2.37), eye irritation or burning (PR 1.67, CI 1.29 to 2.17), headache (PR 1.73, CI 1.27 to 2.36), and skin irritation, burning, or rash (PR 1.70, CI 1.02 to 2.82).

Self-Reported Physician Diagnosis Since September 11, 2001

A diagnosis was considered new if the condition had not been diagnosed in the participant before September 11, 2001. New diagnoses included respiratory conditions (upper or lower) in 81 (5.7%) participants, psychological conditions in 70 (4.9%) participants, gastrointestinal conditions in 53 (3.7%) participants, and musculoskeletal conditions in 51 (3.6%) participants.

Participants caught in the cloud of dust were more likely to report a physician diagnosis of a psychological condition than participants not caught in the cloud of dust (PR 2.59, CI 1.44 to 4.64).

Medical Monitoring Evaluation

Physical examinations revealed few abnormalities. The two most common physical examination abnormalities reported were rash (n = 38, 2.7%) and nasal irritation or inflammation (n = 30, 2.1%).

Physician diagnosis categories for potentially WTC-related conditions are shown in Table 3. A diagnosis was considered potentially WTC-related if the physician designated the relatedness as yes or unknown. New-onset or exacerbated asthma was the most common LR diagnosis; rhinitis was the most common UR diagnosis; and PTSD and depression were the two most common psychological diagnoses.

TABLE 3
TABLE 3:
Physician Diagnosis Categories for Potentially WTC-Related Conditions—From Medical Monitoring Evaluations of New York State WTC Responders

The mean spirometric values for all parameters (FVC, FEV1, FEV1/FVC%, FEF25–75) were within the normal range (Table 4). There were 182 (14.4%) participants who exhibited abnormal spirometry (Table 5). An obstructive pattern was noted in 133 (10.5%) participants, with severity reported as mild in 106 (8.4%), and moderate in six (0.5%). Severity was not reported for 21 participants with an obstructive pattern. There were 47 (3.7%) participants with a restrictive pattern, with severity reported as mild in 41 (3.2%), moderate in two, and severe in three. Two participants had a mixed pattern with moderate severity.

TABLE 4
TABLE 4:
Pulmonary Function Test Results for New York State WTC Responders
TABLE 5
TABLE 5:
Interpretation of Pulmonary Function Test Results for New York State WTC Responders

Clinical laboratory test results were reviewed and analyzed. Results from the SMA-20 and complete blood count, which include tests of renal function, liver function, white blood cell count, red blood cell count, and hemoglobin, among others, did not reveal any significant abnormalities in this cohort.

Discussion

The results of this study contribute additional evidence to the growing body of literature indicating that some WTC responders did experience health effects related to their exposures. The majority of our participants spent at least some period of time in the immediate vicinity of the debris pile at the WTC site; however, only one third were deployed in the first 2 days. In other WTC studies,1,2,14,16,26 the vast majority of evaluated responders arrived on-site by September 15, whereas almost half of this study’s cohort arrived on-site after September 16. In addition, this study’s cohort includes participants who first arrived on-site anytime before December 23, 2001. Thus, it is likely that this population experienced lower overall levels of exposure than other cohorts such as FDNY and NYPD first-responders did.

The types of respiratory symptoms reported in this study are similar to those reported in other WTC studies. The prevalence of most respiratory symptoms seemed to be similar to or lower than what has been reported for other cohorts of responders.1,2,16 This also suggests that this population of responders experienced lower levels of exposure than other responders who were present during or shortly after the collapse of the towers. Furthermore, the comparison between participants who reported being caught in the cloud of dust after the collapse and those who reported not being caught in the cloud of dust suggests that both LR and UR symptoms, as well as headache, eye irritation, symptoms of acid stomach or heartburn, and skin irritation are associated with being present when the buildings collapsed.

Almost one quarter of participants who were treated for post-September 11 respiratory symptoms before their participation in the medical monitoring program reported that those symptoms did not improve posttreatment. This suggests that some respiratory conditions were persistent, which has been suggested in other WTC studies.13,16

Collectively, self-reported psychological symptoms were not associated with being caught in the cloud of dust; however, such an association was suggested for several specific symptoms, including “concentration problems,” “emotional numbness,” “flashbacks,” and “feeling jumpy or easily startled.” Each of these symptoms has been described in PTSD.27 Although we did not attempt to define PTSD in study participants, these findings are consistent with results reported by Galea et al, who reported an association between PTSD and directly witnessing the events of September 11, 2001.22 Tapp et al also reported that workers in the dust cloud at the time of the WTC collapse had a greater risk of PTSD symptoms compared with those not exposed to the dust cloud.26 Furthermore, participants caught in the cloud of dust were more likely to report that a physician had diagnosed them with a psychological condition. This also suggests that those responders present at the time of the building collapses experienced a greater psychological impact.

The results of this analysis suggest that exposure to the complex mixture of dust and smoke from the WTC site, particularly at the time when the buildings collapsed, resulted in an array of health effects. With regard to psychological effects, witnessing the disaster and its aftermath impacted some members of this cohort. The associations between some health effects and being caught in the cloud of dust on September 11, 2001, when the WTC buildings collapsed suggest that time of arrival was a critical factor in the development of health effects, as has been suggested by other studies.1,2,26

In the medical monitoring program, WTC-related medical or psychological conditions were diagnosed in a relatively low percentage of participants. In addition, physical examination results revealed only a small percentage of participants with each of the reported abnormalities. As medical evaluations may have occurred as late as November 2003, more than 2 years after the WTC disaster, it is possible that some health effects experienced post-September 11 may not have persisted long enough to be observed or diagnosed during the medical evaluations. Nevertheless, it is also possible that this population experienced fewer observable health effects than other WTC cohorts.

PFT results revealed abnormalities in only a small percentage of this cohort, suggesting that this population experienced less lung disease than other WTC cohorts. Nevertheless, these results must be interpreted with caution as they represent spirometry conducted at only a single point in time for each participant. Challenge testing or postbronchodilator testing might have revealed additional participants with airway hyperreactivity.

Less than two thirds of participants reported using some type of respiratory protection at least part of the time, and the most commonly used device was the one-strap dust mask. This type of mask is not recommended for respiratory protection.28 The use of disposable dust masks did decrease over time. Concurrently, during the first month after the disaster, use of respirators gradually increased. Presumably, some responders started using more appropriate respiratory protection as the month progressed. Suboptimal respirator use was an issue with other responder groups as well. Among a cohort of firefighters,12 45% of those present during the collapse reported not wearing a respirator. Of those arriving later that day, 35% wore no respirator. The most common respiratory protection used among this cohort on the first day was a disposable paint or dust mask. Even during the second week of the disaster, only 57% of firefighters were using a more protective, half-face elastomeric respirator, with only 53% of those using them reporting that they did so during most of their work time.12

By late September 2001, the overall use of any respiratory protection in our study cohort began to decline. The reasons for this are unclear. This may relate to perceptions about exposures in the areas around the WTC site. It may be hypothesized that some responders who arrived on-site later than first responders did not perceive a need to wear respiratory protection, or to wear such protection regularly, because of changing conditions in and around the WTC site. In addition, some of the responders in this cohort likely worked in more peripheral areas where the need for respiratory protection may not have been a significant issue in later time periods.

A primary limitation of this study is the potential for selection bias. Participation in the medical monitoring program was low. There are a number of possible reasons for this, including the elapsed time between potential exposures and the medical monitoring program. It is also possible that many of these responders had low perceived levels of exposure, so they may have been less likely to participate. In addition, many NYS National Guard personnel were called to duty in Iraq during the time period when the medical monitoring program was available. Those responders who chose to participate in the medical monitoring program and this study may have been more likely to have experienced health effects or may have been more highly exposed. Alternatively, individuals with illness of greater severity may have sought treatment before the start of the medical monitoring program and thus may have been less likely to participate.

The period of time between participants’ exposures and their medical evaluations could have resulted in poor recall of pertinent information. Those participants who reported being caught in the cloud of dust may have been more likely to recall symptoms and other aspects of their health and exposure history, because of the intense nature of their experience. In addition, because the questionnaire asked about symptoms experienced “since September 11, 2001,” it is possible that more symptoms could be reported by participants evaluated later in the medical monitoring program because of the increased period of time during which symptoms may have been experienced. Nevertheless, our analysis provided no indication that the rate of symptoms reported increased or decreased significantly as a function of time from May 2002 through November 2003.

Health symptoms were grouped into symptom categories for the analysis. It is possible that some symptoms described by participants might have been misclassified by symptom category, because of the ambiguous nature of the symptom or because some symptoms could have multiple causes. For instance, dry and productive cough were included as LR symptoms, but they could potentially be caused by postnasal drip, an UR condition, or by reflux, a gastrointestinal condition. Symptoms we categorized as psychological, such as sleep problems and excessive fatigue, could have resulted from other causes such as sleep-disordered breathing from respiratory conditions or sleep apnea worsened by upper airway inflammation. We assigned symptoms to specific categories based on what we believed to be the most likely explanations.

This project was primarily conducted as a service to provide medical monitoring evaluations to NYS personnel directed to respond to the WTC disaster. Medical examinations were conducted by a number of clinicians in several different clinics. Thus, it is possible that interobserver variation affected reports of physical examination findings, diagnoses, and PFT interpretations. To minimize this possibility, before the initial examinations, all involved health care providers were invited to participate in a conference call with the director of EHS and the principal investigator to discuss the medical monitoring program and other WTC-related issues. In addition, written informational materials were distributed to providers in an effort to encourage uniformity of the medical evaluation process. All clinics involved in the medical monitoring program had prior experience in occupational health.

Conclusions

The results from this study suggest that some NYS employees and NYS National Guard personnel who were directed to respond to the WTC disaster experienced new or worsening health effects because of their exposures, including UR, LR, and psychological symptoms. This cohort of responders generally reported fewer symptoms than most other more highly exposed responder cohorts. In addition, a number of health effects, including respiratory symptoms and symptoms suggestive of PTSD, were associated with having been caught in the cloud of dust on September 11, 2001, when the WTC buildings collapsed. This suggests that being present when the buildings collapsed was associated with health effects among responders.

Acknowledgment

The authors thank Dr Richard Ciulla and the staff of the NYS Department of Civil Service Employee Health Service for coordination of the medical monitoring program and collection of the medical evaluation data. They also thank the NYS Governor’s Office of Employee Relations and the NYS Division of Military and Naval Affairs for their coordination of the solicitations of eligible NYS employees and National Guard personnel for the medical monitoring program.

Supported by a Grant U1Q/CCU221159-04 from the Centers for Disease Control and Prevention (CDC).

References

1. Prezant DJ, Weiden M, Banauch GI, et al. Cough and bronchial responsiveness in firefighters at the World Trade Center site. N Engl J Med. 2002;347:806–815.
2. Salzman SH, Moosavy FM, Miskoff JA, Friedmann P, Fried G, Rosen MJ. Early respiratory abnormalities in emergency services police officers at the World Trade Center site. J Occup Environ Med. 2004;46:113–122.
3. Lioy PJ, Weisel CP, Millette JR, et al. Characterization of the dust/smoke aerosol that settled east of the World Trade Center (WTC) in lower Manhattan after the collapse of the WTC 11 September 2001. Environ Health Perspect. 2002;110:703–714.
4. Cahill TA, Cliff SS, Perry KD, et al. Analysis of aerosols from the World Trade Center collapse site, New York, October 2 to October 30, 2001. Aerosol Sci Technol. 2004;38:165–183.
5. Centers for Disease Control and Prevention. Occupational exposures to air contaminants at the World Trade Center disaster site—New York, September–October, 2001. Morb Mortal Wkly Rep. 2002;51:453–456.
6. Centers for Disease Control and Prevention. Potential exposures to airborne and settled surface dust in residential areas of lower Manhattan following the collapse of the World Trade Center—New York City, November 4–December 11, 2001. Morb Mortal Wkly Rep. 2003;52:131–136.
7. McGee JK, Chen LC, Cohen MD, et al. Chemical analysis of World Trade Center fine particulate matter for use in toxicologic assessment. Environ Health Perspect. 2003;111:972–980.
8. Offenberg JH, Eisenreich SJ, Gigliotti CL, et al. Persistent organic pollutants in dusts that settled indoors in lower Manhattan after September 11, 2001. J Expo Anal Environ Epidemiol. 2004;14:164–172.
9. Chen LC, Thurston G. World Trade Center cough. Lancet. 2002;360(suppl):s37–s38.
10. Landrigan PJ, Lioy PJ, Thurston G, et al. Health and environmental consequences of the world trade center disaster. Environ Health Perspect. 2004;112:731–739.
11. Edelman P, Osterloh J, Pirkle J, et al. Biomonitoring of chemical exposure among New York City firefighters responding to the World Trade Center fire and collapse. Environ Health Perspect. 2003;111:1906–1911.
12. Feldman DM, Baron SL, Bernard BP, et al. Symptoms, respirator use, and pulmonary function changes among New York City firefighters responding to the World Trade Center disaster. Chest. 2004;125:1256–1264.
13. Banauch GI, Alleyne D, Sanchez R, et al. Persistent hyperreactivity and reactive airway dysfunction in firefighters at the World Trade Center. Am J Respir Crit Care Med. 2003;168:54–62.
14. Skloot G, Goldman M, Fischler D, et al. Respiratory symptoms and physiologic assessment of ironworkers at the World Trade Center disaster site. Chest. 2004;125:1248–1255.
15. Trout D, Nimgade A, Mueller C, Hall R, Earnest GS. Health effects and occupational exposures among office workers near the World Trade Center disaster site. J Occup Environ Med. 2002;44:601–605.
16. Herbert R, Moline J, Skloot G, et al. The World Trade Center disaster and the health of workers: five-year assessment of a unique medical screening program. Environ Health Perspect. 2006;114:1853–1858.
17. Herbstman JB, Frank R, Schwab M, et al. Respiratory effects of inhalation exposure among workers during the clean-up effort at the World Trade Center disaster site. Environ Res. 2005;99:85–92.
18. Centers for Disease Control and Prevention. Self-reported increase in asthma severity after the September 11 attacks on the World Trade Center—Manhattan, New York, 2001. Mortal Wkly Rep. 2002;51:781–784.
19. Reibman J, Lin S, Hwang SA, et al. The World Trade Center residents’ respiratory health study: new onset respiratory symptoms and pulmonary function. Environ Health Perspect. 2005;113:406–411.
20. Lin S, Reibman J, Bowers JA, et al. Upper respiratory symptoms and other health effects among residents living near the World Trade Center site after September 11, 2001. Am J Epidemiol. 2005;162:499–507.
21. Szema AM, Khedkar M, Maloney PF, et al. Clinical deterioration in pediatric asthmatic patients after September 11, 2001. J Allergy Clin Immunol. 2004;113:420–426.
22. Galea S, Ahern J, Resnick H, et al. Psychological sequelae of the September 11 terrorist attacks in New York City. N Engl J Med. 2002;346:982–987.
23. Centers for Disease Control and Prevention. Psychological and emotional effects of the September 11 attacks on the World Trade Center—Connecticut, New Jersey, and New York, 2001. Mortal Wkly Rep. 2002;51:784–786.
24. Bocanegra HT, Brickman E. Mental health impact of the World Trade Center attacks on displaced Chinese workers. J Trauma Stress. 2004;17:55–62.
25. American Thoracic Society. Guidelines for the evaluation of impairment/disability in patients with asthma. Am Rev Respir Dis. 1993;147:1056–1061.
26. Tapp L, Baron S, Bernard B, Driscoll R, Mueller C, Wallingford K. Physical and mental health symptoms among NYC transit workers seven and one-half months after the WTC attacks. Am J Ind Med. 2005;47:475–483.
27. Medline Plus. Post-traumatic stress disorder [Updated 2005]. Available at: www.nlm.nih.gov/medlineplus/ency/article/000925.htm. Accessed July 20, 2007.
28. Centers for Disease Control and Prevention. National Institute for Occupational Safety and Health. University of Kentucky. National Agricultural Safety Database [Updated 2002]. Available at: www.cdc.gov/nasd/docs/d000101-d000200/d000153/lung10.html. Accessed July 20, 2007.
©2007The American College of Occupational and Environmental Medicine