Huang, Monica J. MPH; Li, Jiehui MBBS, MSc; Liff, Jonathan M. PhD; Cohen, David E. MD; Cone, James MD, MPH
The terrorist attack on the World Trade Center (WTC) in New York City on September 11, 2001 (9/11), claimed nearly 2800 lives and exposed hundreds of thousands of people to horrific events and potentially harmful environmental contaminants from fires and collapsing buildings. The collapse of the WTC towers created an enormous dust and smoke cloud, components of which included construction materials, soot, paint, glass fibers, jet fuel hydrocarbons, plastic, organic compounds, metals, asbestos, silica, and slag wool. Fires at the site burned for months following the disaster, further adding to the airborne contamination.1–3 Chemical analyses of the dust found a basic pH and suggested that indoor dust from the WTC may have retained its alkalinity more than outdoor dust exposed to rain.3,4
Many studies have documented the mental and physical health conditions, such as posttraumatic stress disorder (PTSD), asthma, and lower and upper airway diseases, of people exposed to 9/11.5–9 Other physical health symptoms have also been reported among people exposed to 9/11, including skin rash and other skin symptoms.10,11 Among New York City (NYC) firefighters surveyed 3 weeks after 9/11, 41% reported skin symptoms, including 14% reporting skin rash, with significant dose response associated with arrival time at the WTC site.10 A WTC Health Registry (WTCHR) study found that survivors of collapsed or damaged buildings who were caught in the dust cloud resulting from the collapse of the WTC towers were 70% more likely to report skin rash or irritation than those who were not.11 No studies, however, have examined the association between 9/11-related exposures and skin rash among individuals with a wide range of exposures, taking into account the events of the day itself and continued exposure to contaminants in the days and months following.
Using data from the NYC WTCHR, this study described the distribution of skin rash reported among Lower Manhattan residents and area workers and rescue and recovery workers and volunteers after the 9/11 attacks and examined whether self-reported skin rash at different points in time after 9/11 was associated with 9/11 exposure. Of particular interest was whether exposure to WTC dust, from the dust cloud on the day of the disaster and from continued exposure to dust remaining in damaged homes, office buildings, and at the WTC site, was associated with skin rash or irritation symptoms.
The methods of the wave 1 (W1) and wave 2 (W2) WTCHR surveys have been described elsewhere.5,6 In brief, there were 71,437 people enrolled in the W1 survey between September 2003 and November 2004, about 17% coverage of the estimated eligible exposed population, including rescue and recovery workers, Lower Manhattan residents, area workers, passersby, and students and school staff from the catchment area.5 The W2 survey was conducted from November 2006 through December 2007; 68% of 68,444 adult W1 enrollees participated.6 The present study is based on a subset of 42,025 W2 participants, including 21,280 who were Lower Manhattan residents and/or area workers at enrollment and 20,745 workers and volunteers involved in rescue and recovery activities. Residents or area workers who were also rescue/recovery workers or volunteers were considered rescue/recovery workers for study purposes. We excluded from the analysis participants with unknown or incomplete information about skin rash or age and those who reported post-9/11 skin rash that began before 9/11 or reported skin cancer at W1. We also excluded passersby and students/school staff because information regarding their extended exposure to dust after 9/11 is unavailable.
Both W1 and W2 questionnaires elicited a history of skin rash or irritation symptoms. At W1, we asked, “Since 9/11, have you experienced skin rash or irritation?” and at W2, “Have you experienced skin rash or irritation in the last 30 days?” We categorized enrollees as having “post-9/11 skin rash in W1” if at W1 they reported experiencing these symptoms only starting after 9/11. We categorized enrollees as having “continued report of post-9/11 skin rash in W2” if they met the criteria for “post-9/11 skin rash in W1” and reported having these symptoms in the 30 days prior to W2. Thus, “continued report of post-9/11 skin rash in W2” was a subset of “post-9/11 skin rash in W1.”
At W1, we asked enrollees whether they were caught in the dust and debris cloud that resulted from the collapse of the WTC towers and, if so, to identify their location when caught in the dust cloud. In the W2 survey, we asked enrollees for more detail about their dust cloud experiences, including whether they could not see more than a few feet in front of them, had trouble walking, had to find shelter, were covered head to toe with dust, or could not hear anything. We categorized dust cloud exposure as “intense” if participants reported being in the dust cloud at baseline and answered yes to any of the W2 follow-up questions. We defined “some” exposure as reporting being in the dust cloud and reporting a geocodable location in Lower Manhattan, as described previously.5,6
Other 9/11-related dust exposure included the extent of home or workplace damage (none, damage without heavy layer of dust, or a heavy layer of dust). For rescue/recovery workers, we asked about the number of days worked at the WTC site as a proxy for their dust exposure in the days following 9/11.
Cumulative incidence was used to measure the incidence of post-9/11 skin rash reported in W1, continued report of skin rash in W2, and skin rash reported at W2 only. We used unconditional logistic regression to discern the association between the exposures and skin rash when controlling for survey characteristics, demographic factors, and comorbid conditions. Given that probable PTSD was highly associated with the 9/11 attack and its aftermath,6,12 and given that PTSD or stress has been previously found to be associated with skin problems,13–15 somatization symptoms,16,17 and physical health status,18,19 we examined the association of 9/11-related exposure with skin rash only among those who were free from history of and coexisting PTSD and nonspecific psychological distress at both W1 and W2 in the multivariate analysis. A history of PTSD was defined as any self-report of ever having been diagnosed with PTSD prior to 9/11 or having probable PTSD (scoring 44 or higher on the 9/11 stressor-specific PTSD checklist) at W1, W2, or both. We defined nonspecific psychological distress as a score of more than 5 on the Kessler 6-item scale.20 We assessed the goodness of fit of the final model using the Hosmer-Lemeshow method.21
We used SAS version 9.2 (SAS Institute Inc, Cary, NC) for all analyses. This study was approved by the institutional review board of the New York City Department of Health and Mental Hygiene. All participants gave verbal consent to participate in the two surveys and subsequent research analyses.
A total of 42,025 adult WTCHR participants who completed the W1 and W2 surveys and met the inclusion criteria were included in this study, including 21,280 Lower Manhattan residents and area workers and 20,745 rescue/recovery workers and volunteers. The Lower Manhattan residents and area workers consisted of 4666 residents, 15,072 area workers, and 1542 participants who both lived and worked in the area. The cumulative incidence of post-9/11 skin rash at W1 and W2 by demographics and by exposures are listed in Tables 1 and 2, respectively.
In Table 1, 12% of residents and area workers reported skin rash or irritation beginning after 9/11, 6% reported skin rash after 9/11 that was also reported at W2, and 16% reported skin rash symptoms at W2 only. Cumulative incidence of reported skin rash was similar among rescue and recovery workers. Residents and area workers with post-9/11 skin rash reported at W1 and those who also reported skin rash at W2 were more likely to be older and female, though this was not observed among rescue/recovery workers. In both residents/area workers and rescue/recovery workers, current smokers were more likely to report post-9/11 skin rash at W1 and report skin rash at W2, whereas non-Hispanic whites were less likely to do so. For skin rash reported only at W2, cumulative incidence among resident and area worker enrollees did not vary significantly by sociodemographics, though race/ethnicity and smoking trends continued to appear for rescue/recovery workers.
As indicated in Table 2, incidence of post-9/11 skin rash reported at W1 was 82% higher among Lower Manhattan residents and area workers with intense dust cloud exposure on 9/11 (15.8% vs 8.7%) and 91% higher among those with home damage (22.0% vs 11.5%) than among those with no exposure to dust cloud or no home damage, respectively. Similar comparisons were seen among rescue and recovery workers. Incidence of post-9/11 rash reported at W1 was 70% higher among rescue/recovery workers with intense dust cloud exposure (17.7% vs 10.4%) and 91% higher among those who worked more than 90 days at the WTC site (18.3% vs 9.6%) than among those with no exposure to the dust cloud or 1 to 7 days at the WTC site, respectively. In contrast, cumulative incidence of skin rash reported only in W2 differed little by 9/11 dust cloud exposure, merely 18% and 16% higher for residents/area workers and rescue/recovery workers, respectively, when comparing those with higher levels of 9/11 exposure to those with a lower level of exposure.
Tables 3 and 4 show the crude and adjusted associations between exposures, comorbid conditions, and post-9/11 skin rash for Lower Manhattan residents/area workers (Table 3) and rescue/recovery workers and volunteers (Table 4). Among 8921 residents or area workers without PTSD or nonspecific psychological distress, intense dust cloud exposure was significantly associated with reporting post-9/11 skin rash at W1 and continued report of skin rash at W2 (adjusted OR = 1.6, 95% CI = 1.3 to 1.9 for post-9/11 skin rash at W1; adjusted OR = 1.8, 95% CI = 1.3 to 2.5 for continued report of skin rash at W2), after controlling for survey characteristics, demographics, and comorbid conditions including asthma/reactive airways dysfunction syndrome, hay fever, and allergic rhinitis. Damage to the home or workplace with heavy dust was only significantly associated with post-9/11 skin rash at W1 (adjusted OR = 1.8, 95% CI = 1.4 to 2.3) after adjustment for covariates.
Among 8803 rescue/recovery workers without PTSD or nonspecific psychological distress, intense dust cloud exposure and some dust cloud exposure were significantly associated with reporting post-9/11 skin rash at W1 (adjusted OR = 1.6, 95% CI = 1.3 to 1.9 for intense dust cloud; adjusted OR = 1.3, 95% CI = 1.0 to 1.8 for some dust cloud) after controlling for survey characteristics, demographics, and comorbid conditions. Dust cloud exposure was not significantly associated with continued report of post-9/11 skin rash at W2. Working more than 90 days or 31 to 90 days at the WTC site were both significantly associated with reporting post-9/11 skin rash at W1 and continued report of post-9/11 skin rash at W2 (for post-9/11 skin rash at W1: adjusted OR = 1.7, 95% CI = 1.3 to 2.2 for >90 days and adjusted OR = 1.6, 95% CI = 1.3 to 2.1 for 31 to 90 days; for continued report of skin rash at W2: adjusted OR = 1.8, 95% CI = 1.2 to 2.6 for >90 days and adjusted OR = 1.6, 95% CI = 1.1 to 2.3 for 31 to 90 days) after adjusting for covariates.
Skin rash reported at W2 only was not associated with dust cloud exposure, damage to home, or damage to workplace in both bivariate and multivariate analyses for residents and area workers. For rescue/recovery workers, intense dust cloud exposure was significantly associated with skin rash reported at W2 only (adjusted OR = 1.3, 95% CI = 1.1 to 1.5), as was having worked 8 to 30 days at the WTC site (adjusted OR = 1.2, 95% CI = 1.1 to 1.4).
Exposure to dust from the WTC disaster is independently associated with greater self-reported post-9/11 skin rash or irritation at W1, without the influence of probable PTSD and nonspecific psychological distress. Along with dust cloud exposure on 9/11 itself, long-term exposure to dust in the workplace, in the home, and through work at the WTC site was also associated with reporting post-9/11 skin rash at W1, suggesting that post-9/11 skin rash may be related to acute, direct exposures from the disaster itself and cumulative exposure in the days afterward. For residents and area workers, this is supported by earlier WTCHR findings among building survivors showing that those who worked in damaged buildings were more likely to report skin rash than those who evacuated from buildings that had collapsed.11
The effect of 9/11 exposures diminished when we examined continued report of skin rash at W2. Although the dust cloud exposure remained independently significant for residents and area workers, the damage to home and workplace with heavy dust became nonsignificant in multivariate analysis. This suggests that the effect of dust on skin may be time-limited, primarily on the initiation of post-9/11 skin rash. The association of exposure to intense dust cloud with continued report of post-9/11 skin rash reported at W2 may be a reflection of the tendency of skin symptoms to relapse among the most heavily exposed individuals. For rescue/recovery workers, dust cloud exposure became nonsignificant after controlling for covariates, but days worked at the WTC site remained significantly associated with continued report of skin rash at W2. This suggests that for rescue and recovery workers, working at the WTC site may have been a greater source of dust exposure than the dust cloud on 9/11 itself. For residents and area workers, however, only the acute exposure was associated with continued report of skin rash.
In this study, we excluded those who indicated at W1 enrollment that their post-9/11 skin rash began before 9/11 and those with a clinical diagnosis of skin cancer at the time of W1 to exclude skin symptoms that could not be associated with 9/11 events. The higher cumulative incidence of skin rash reported only at W2 (16%) than only at W1 may be due to the aging of the study population; selection bias, with the 68% of W1 participants taking part in W2 more likely to report symptoms than those who did not participate; and differences in recall bias between remembering skin rash “since 9/11,” 2 to 3 years before W1, versus “in the last 30 days.” The 16% cumulative incidence of skin rash reported only at W2 was not associated with dust exposure among residents and area workers but was significantly associated with comorbid asthma and hay fever, further supporting the association of 9/11 exposure with post-9/11 skin rash reported at W1 in this study. Among rescue/recovery workers, intense dust cloud and working 8 to 30 days at the WTC site were significantly associated with skin rash reported at W2 only. Because these exposures were not related to continued report of post-9/11 skin rash at W2, it seems unlikely that these reported symptoms are related to 9/11 5 to 6 years later. It is possible that selection or recall bias played a role here.
Skin rash or irritation has been associated with occupational exposure to materials made from fibrous glass, rock wool or slag wool,22 and cement and concrete.23–25 It has been suggested that components of cement may produce irritation, corrosive effects, and sensitization leading to contact dermatitis, one of the most frequently reported health problems among construction workers.24 Given that higher concentrations of synthetic vitreous fibers and mineral components of concrete and building wallboard were reported in settled dust of residential areas collected during November 4 to December 11, 2001, in Lower Manhattan than in Upper Manhattan,26 it is conceivable that post-9/11 skin rash or irritation may be linked to 9/11-related dust exposure among residents and area workers in Lower Manhattan of NYC.
This study is subject to limitations similar to other studies drawn from WTCHR data.5,6 As a registry of individuals identified by their exposure to the WTC disaster and followed over time, there is no completely unexposed control group for comparison and no measure of background skin rash prevalence. The registry does, however, include individuals with varying degrees of exposure to the dust cloud, work or home damage, and rescue/recovery work at the WTC site, and comparisons between more exposed and less exposed individuals revealed significant differences. Further limitations stem from the self-reported nature of the data. Although enrollees with probable PTSD and moderate and severe nonspecific psychological distress were excluded from this analysis, mild psychological distress or subsyndromal PTSD could still have played a role in greater reporting of skin rash among those with greater exposure to 9/11. Nevertheless, we are unable to explore this issue further in this study. Recall bias is another limitation of the self-reported data. Enrollees who were more affected by 9/11 may have been more likely to remember symptoms such as skin rash after 9/11 than those less affected. Given that among residents and area workers, post-9/11 skin rash was associated with pre-9/11 or early post-9/11 diagnosis (September 2001 to 2003) of asthma and not with asthma that was diagnosed between 2003 and 2007 after adjustment for 9/11-related exposure and other covariates, it is less likely that the significant findings in this study were simply due to differential recall bias.
The nonspecific and subjective nature of reported skin rash or irritation symptoms is a fundamental limitation of this study because we have no further information regarding what clinical diagnoses may correspond to self-reports, when the skin rash started between 9/11 and W1, or how frequent and severe the skin rash had been. Further surveys or clinical investigations would be required to examine what clinically diagnosed specific skin diseases were associated with the 9/11-related exposure. In addition, because skin rash is a subjective symptom that may be interpreted variously by different individuals as a nonissue, a minor nuisance, or a serious health problem, it may be more subject to recall bias than other health outcomes.
This study presents the effect of disasters on self-reported skin conditions among 9/11-exposed individuals. Along with other reported health effects, skin rash or irritation may be another 9/11-related health outcome among Lower Manhattan residents and area workers and rescue/recovery workers and volunteers. Skin symptoms are rarely life-threatening but can significantly affect quality of life among sufferers.27 Our results suggest that in addition to acute exposure to the 9/11 disaster itself, lingering environmental contaminants may also have played a role in the development of health problems over time as people returned to affected areas and workers continued long-term recovery and cleanup at the WTC site. Skin protection may be an important consideration for future disaster preparedness.
The authors gratefully acknowledge the participation of all Registry enrollees. They also thank Drs Mark R. Farfel and Steven D. Stellman from the New York City Department of Health and Mental Hygiene, WTCHR, for their thorough and critical review of the manuscript.
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