In this report we describe disaster-related exposures and physical and respiratory health reported on an initial interview survey among 3,184 children enrolled in the WTCHR. Children < 5 years of age at the time of interview had a higher than expected prevalence of reported asthma after 9/11, and new diagnosis of asthma in all age groups was significantly associated with exposure to the dust cloud on 9/11. The OR for the association was increased when we restricted the outcome to those with dust cloud exposure plus eye irritation. More than half of the children had new or worsened respiratory symptoms at some time after 9/11, but the importance of this is not yet known because duration and severity of these symptoms were not determined on the initial interviews. Few children (3%) sustained direct injuries on 9/11.
The high proportion of children with new or worsened respiratory symptoms parallels findings reported for adults who lived or worked in lower Manhattan in the fall of 2001 (Brackbill et al. 2006
; Lin et al. 2005
; Reibman et al. 2005
). Follow-up of the children is needed to determine severity and duration of the symptoms reported. In adults, many symptoms abated when the smoke and dust cleared after December 2001 (Reibman et al. 2005
More severe pulmonary injury has been reported in workers who had close and intense exposure to dust and burning debris (Banauch et al. 2003
; Landrigan et al. 2004
; Skloot et al. 2004
; Wheeler et al. 2007
). Although few residents and school children had such intense exposures, nearly half of our cohort had a report of dust cloud exposure, and this was associated with new asthma diagnosis. The dust cloud was a quickly expanding mass of debris that included, among other toxics, large amounts of alkaline pulverized cement, a mucous membrane irritant. We did not find an association of new asthma diagnosis with length of time spent in lower Manhattan from 9/11 to 20 December 2001, when air pollution continued because of disaster-related fires and cleanup activities that contributed to airborne particulates. However, we cannot rule out the role of these exposures, because our estimate of time in lower Manhattan was crude, and we lacked precise information on characteristics of the children’s homes and schools (e.g., were windows open and facing truck routes, were effective filters installed).
Others have reported exacerbation of previously diagnosed asthma among adults and children in New York City after 9/11 (Fagan et al. 2002
; Szema et al. 2004
; Wagner et al. 2005
). Fagan et al. (2002)
reported that among 13% of Manhattan adults with asthma interviewed by telephone 5–9 weeks after 9/11, 27% reported an exacerbation. Two studies reported post-9/11 asthma exacerbations among children with previously diagnosed asthma (Szema et al. 2004
; Wagner et al. 2005
). Szema et al. (2004)
used data from one clinic in Manhattan’s Chinatown to compare children who lived within 5 miles of the WTC site with children who lived farther away. Children living < 5 miles from the WTC site showed a larger increase in clinic visits for asthma after 9/11, but use of rescue inhaler was greater in children at a distance. The study was limited by small sample size and use of residence distance from the WTC site as a proxy for actual exposure (Matte and Mostashari 2004
). The study did not determine whether additional asthma-related care was obtained elsewhere; thus, data may be missing, especially for the “controls,” who lived farther away. Wagner et al. (2005)
examined adults and children with known asthma receiving Medicaid-managed care, using data from a mail survey and medical record review conducted in mid-2002. Overall, 21.7% of 16,629 eligible individuals 5–56 years of age responded to the survey, with lower response (19%) among parents of children 5–17 years of age. Although they noted increased asthma exacerbation among persons living near the WTC, data were not provided specifically for children included in that group (Wagner et al. 2005
). None of these studies reported on new diagnosis of asthma after 9/11.
Both environmental and psychological factors can trigger asthma and wheezing (Eder et al. 2006
; Wright et al. 1998
). Our analysis found no association between reported stress and new-onset asthma; however, the WTCHR had very limited psychological data on children, and these initial WTCHR interviews were done 2–3 years after the event, measuring psychological stress at the time of interview, not at the time of the onset of asthma.
In our cohort, the baseline age-specific prevalence of asthma before 9/11 was comparable with published data for the United States and the Northeast United States, but at the time of interview, 2–3 years after 9/11, it was higher in the youngest group, children 2–4 years of age (Centers for Disease Control and Prevention 2003
). Childhood asthma normally manifests during the first 5 years of life, often after exacerbation from an environmental irritant, allergen, or infection (Eder et al. 2006
; Peden 2003
; Pope 2000
; Wong et al. 2004
). It is possible that the intense exposures on 9/11 and during the ensuing months caused exacerbations in some children with a predisposition to asthma, resulting in increased detection and diagnosis at earlier ages than might otherwise have occurred. Consideration must also be given to the fact that children and infants are among the most susceptible to many air pollutants, in part because children’s lung development continues to adulthood (Kim 2004
). Eighty percent of alveoli are formed postnatally, and ongoing lung growth and development continues through age 18 (Gauderman et al. 2004
; Kim 2004
). Although chronic exposure to air pollution has been associated with decreased pulmonary function at age 18 (Gauderman et al. 2004
), no such data are available on short-term or disaster-related exposures (Gauderman et al. 2004
; Kim 2004
). The effect of outdoor air pollution on new development of asthma is not clear (Beasley et al. 2003
; Kim 2004
). In one prospective study, the risk of developing asthma was related to pollution only in children with high ozone exposure combined with vigorous exercise (McConnell et al. 2002
Only long-term follow-up of the children enrolled in the WTCHR will determine whether they have a sustained increase in asthma prevalence. For example, if the higher rate in very young children is attributable to de novo disease, then the increased prevalence will continue as this cohort ages. On the other hand, if the higher rate is attributable to earlier exacerbation and diagnosis in children with a predisposition for asthma, the prevalence will level off to the overall population-wide prevalence rates at older ages.
We also found associations between new asthma diagnosis and ethnicity. White and Asian children had lower asthma prevalence than did black and Hispanic children, both before and after 9/11, although after 9/11, Asian and Hispanic children had the highest rates of new asthma diagnosis: 8% for each, compared with 4.4% for whites. Descriptive studies of asthma prevalence have shown high variability among subsets of Hispanics and Asians in the United States, including higher rates in some Hispanics and lower rates in Asian children (Davis et al. 2006
; Lara et al. 2006
). Asthma is thought to be influenced by many factors, including physical and social environment, genetics, and health-seeking patterns (Eder et al. 2006
; Hunninghake et al. 2006
). Information on pre-9/11 environmental influences for the WTCHR cohort is not available, but these influences likely play a role in the differences we observed.
It is also possible that ethnic differences in health care access and location of care influenced asthma diagnosis. Prior studies have shown that children are more likely to receive asthma diagnoses in emergency department settings than in primary care offices (Akinbami et al. 2005
). Health-seeking behaviors differ by ethnicity; for example, rates of emergency department use and hospitalization differ by age and race (Grant et al. 1999
). The WTCHR did not collect data on where and how the children were diagnosed, and it is likely that children of different ethnicities were receiving pediatric care in different settings. Black and Hispanic children also had much higher prevalence of increased or worsened wheezing after 9/11, suggesting possible missed opportunities for diagnosing asthma in these children.
Information on children’s respiratory health from the WTCHR interviews provides important baseline measures for a cohort that will be followed prospectively. However, these data have several limitations.
The voluntary nature of enrollment creates potential for bias. Parents who were especially worried, or whose children had been ill, may have been more likely to enroll in the WTCHR; for example, parents of children newly diagnosed with asthma might have been concerned that disaster-related exposures were the cause and might have been motivated to enroll these children. However, this cannot account for the strong association with dust cloud exposure, found in all ages, and with an even stronger association for those who reported both dust cloud exposure and eye irritation.
Reporting bias may have been introduced by using parent proxies for child interviews, although some data suggest good correlation between adolescents and parents on survey questions asking about prior diagnosis of asthma (Hedman et al. 2005
; Magzamen et al. 2005
Recall bias may influence responses 2–3 years after an event, although work after other disasters suggests that during such remarkable life episodes, memory is acute and well preserved (Bradburn et al. 1987
). It is not known whether this applies to parents reporting for their children.
The WTCHR interview collected information on a variety of new or worsened physical health symptoms after 9/11, but not on how soon after 9/11 those symptoms first occurred or on their duration or severity. We did not determine asthma-related impairment. Physical symptoms and diagnoses were self-reported, not confirmed with medical record review or medical evaluation. Nonetheless, the question “Have you ever been told by a doctor or other health professional that you [your child] had asthma?” is considered reliable in surveys to study the epidemiology of asthma (Centers for Disease Control and Prevention 2003
; Eder et al. 2006
; Lara et al. 2006
; Magzamen et al. 2005
). This standardized question allows comparison with other surveys. Further study of the WTCHR cohort will require more detailed questions about frequency and severity of symptoms, and diagnostic tests.
The survey did not collect information on co-factors for asthma, including allergic status of the children and exposure to environmental tobacco smoke. Smoking histories, collected on children who were 12–17 years of age on 9/11, may be underreported by both parents as well as teens ≥ 18 years of age who answered their own interviews. We included smoking in the multivariable analysis of factors associated with new asthma diagnosis, but numbers reporting smoking were very small.
We were not able to adjust our analysis for cases where multiple children were enrolled from single households; instead, we gave each child equal weight in the analysis. Further, we did not collect data on the number of children from any household who were not enrolled.
Finally, our data on intensity of exposures to the dust cloud and time spent in lower Manhattan are limited because of the deliberate nature of the initial interview as a screening tool, to identify broad categories of exposure.
The strength of the WTCHR data is 2-fold. Despite the voluntary nature of enrollment, the registry constitutes the largest sample of child subjects exposed to the events of 9/11. The collection of exposure data allows for stratification of risk and enables examination of outcomes by exposure (e.g., presence in the dust and debris cloud or not, distance of school or home from WTC site). For some exposures, data are available to examine dose effect. Exposure registries do not routinely collect concurrent data from deliberately sampled unexposed persons, because no clearly stated hypothesis or defined outcome suggests what characteristics the comparison group should have (Goldhaber et al. 1983
; NYCDOHMH and ATSDR 2004
The WTCHR, with a large number of enrollees across all ages 0–17 years, and sub-populations who experienced a range of exposures, is a unique and essential tool for understanding the long-term health effects of the 9/11 attacks on exposed children and youths. The vulnerability of children makes it important to follow them to observe both short- and long-term respiratory and other effects. The fact that the event was discrete in time provides an opportunity to follow the course of healing of respiratory and psychological trauma. Ongoing follow-up of this cohort will elucidate recovery and sequelae of respiratory and toxic exposures in children.