The attack on the World Trade Center (WTC) created an acute environmental disaster of enormous magnitude. This study characterizes the environmental exposures resulting from destruction of the WTC and assesses their effects on health. Methods include ambient air sampling; analyses of outdoor and indoor settled dust; high-altitude imaging and modeling of the atmospheric plume; inhalation studies of WTC dust in mice; and clinical examinations, community surveys, and prospective epidemiologic studies of exposed populations. WTC dust was found to consist predominantly (95%) of coarse particles and contained pulverized cement, glass fibers, asbestos, lead, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and polychlorinated furans and dioxins. Airborne particulate levels were highest immediately after the attack and declined thereafter. Particulate levels decreased sharply with distance from the WTC. Dust pH was highly alkaline (pH 9.0-11.0). Mice exposed to WTC dust showed only moderate pulmonary inflammation but marked bronchial hyperreactivity. Evaluation of 10,116 firefighters showed exposure-related increases in cough and bronchial hyperreactivity. Evaluation of 183 cleanup workers showed new-onset cough (33%), wheeze (18%), and phlegm production (24%). Increased frequency of new-onset cough, wheeze, and shortness of breath were also observed in community residents. Follow-up of 182 pregnant women who were either inside or near the WTC on 11 September showed a 2-fold increase in small-for-gestational-age (SGA) infants. In summary, environmental exposures after the WTC disaster were associated with significant adverse effects on health. The high alkalinity of WTC dust produced bronchial hyperreactivity, persistent cough, and increased risk of asthma. Plausible causes of the observed increase in SGA infants include maternal exposures to PAH and particulates. Future risk of mesothelioma may be increased, particularly among workers and volunteers exposed occupationally to asbestos. Continuing follow-up of all exposed populations is required to document the long-term consequences of the disaster. Key words: air pollution, airway hyperresponsiveness, asbestos, occupational lung disease, P[M.sub.2.5], P[M.sub.10], small for gestational age (SGA). Environ Health Perspect 112:731-739 (2004). doi:10.1289/ehp.6702 available via http://dx.doi.org/[Online 18 February 2004]

The destruction of the World Trade Center (WTC) on 11 September 2001 caused the largest acute environmental disaster that ever has befallen New York City (Claudio 2001; Landrigan 2001). The combustion of more than 90,000 L of jet fuel at temperatures above 1,000[degrees]C released a dense and intensely toxic atmospheric plume containing soot, metals, volatile organic compounds (VOCs), and hydrochloric acid. The collapse of the towers pulverized cement, glass, and building contents and generated thousands of tons of particulate matter (PM) composed of cement dust, glass fibers, asbestos, lead, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides, and polychlorinated furans and dioxins (Clark et al. 2003; Lioy et al. 2002; McGee et al. 2003). These materials dispersed over lower Manhattan, Brooklyn, and for miles beyond. They entered nearby office, school, and residential buildings. Much remained at the site to form Ground Zero, a six-story pile of smoking rubble that burned intermittently for more than 3 months.

Populations at greatest risk of exposure included firefighters, police, paramedics, other first responders [Prezant et al. 2002; Centers for Disease Control and Prevention (CDC) 2002], and construction workers and volunteers who worked initially in rescue and recovery and then for many months cleared rubble at Ground Zero. Others at potentially elevated risk included workers who cleaned WTC dust from nearby buildings, women who were pregnant on 11 September and succeeding weeks in lower Manhattan and adjacent areas of Brooklyn, and community residents, especially the 3,000 children who resided within 1 km of the towers and the 5,500 who attended school there.

Previous studies have documented the acute traumatic consequences of the attacks on the WTC, most notably the occurrence of 2,726 deaths, including 343 deaths among firefighters and 60 among police officers (CDC 2002). Early clinical and epidemiologic assessments documented a high prevalence of respiratory symptoms, particularly, persistent cough in firefighters and rescue workers exposed to WTC dust (CDC 2002; Prezant et al. 2002). The prevalence of those symptoms was related to intensity and duration of smoke and dust exposure. Studies of the mental health consequences of the disaster have documented a high prevalence of posttraumatic stress disorder (PTSD) (Galea et al. 2002b; Fairbrother et al. 2003) and other psychological sequelae, including increased rates of drug and alcohol abuse (Boscarino et al. 2002; Galea et al. 2002a; Stuber et al. 2002; Vlahov et al. 2002a, 2002b).