Health effects of World Trade Center (WTC) Dust: An unprecedented disaster's inadequate risk management

Abstract

The World Trade Center (WTC) twin towers in New York City collapsed on 9/11/2001, converting much of the buildings' huge masses into dense dust clouds of particles that settled on the streets and within buildings throughout Lower Manhattan. About 80-90% of the settled WTC Dust, ranging in particle size from ∼2.5 μm upward, was a highly alkaline mixture of crushed concrete, gypsum, and synthetic vitreous fibers (SVFs) that was readily resuspendable by physical disturbance and low-velocity air currents. High concentrations of coarse and supercoarse WTC Dust were inhaled and deposited in the conductive airways in the head and lungs, and subsequently swallowed, causing both physical and chemical irritation to the respiratory and gastroesophageal epithelia. There were both acute and chronic adverse health effects in rescue/recovery workers; cleanup workers; residents; and office workers, especially in those lacking effective personal respiratory protective equipment. The numerous health effects in these people were not those associated with the monitored PM2.5 toxicants, which were present at low concentrations, that is, asbestos fibers, transition and heavy metals, polyaromatic hydrocarbons or PAHs, and dioxins. Attention was never directed at the very high concentrations of the larger-sized and highly alkaline WTC Dust particles that, in retrospect, contained the more likely causal toxicants. Unfortunately, the initial focus of the air quality monitoring and guidance on exposure prevention programs on low-concentration components was never revised. Public agencies need to be better prepared to provide reliable guidance to the public on more appropriate means of exposure assessment, risk assessment, and preventive measures.

Keywords: World Trade Center; alkalinity; coarse particles; exposure assessment; overloading of clearance; particle resuspension; risk management; supercoarse particles; synthetic vitreous fibers.

Figure 1

(A) View along plaza heading toward Chase Building on 9/13/11. (B) Scene from an indoor residence near Ground Zero. (photographs property of C. Prophete, M. Cohen, and L. Chen).

Figure 2

Particle size distribution from indoor and outdoor dust samples collected in the period of 9/12-13/11 (modification of the original figure from Maciejczyk et al.2004).

Figure 3

Sampling sites for Chen et al. analyses (from McGee et al. 2003).

Figure 4

Alkalinity and pH of WTC Dusts in relation to other alkaline materials (from USGS internet posting [2002]).

Figure 5

pH of the suspensions of the selected dust samples. Sample size fraction is indicated in parenthesis unless bulk dust (from Maciejczyk et al. 2004).

Figure 6

Thoracic PM or TPM sample criterion for particles entering the mouth during oral inhalation given as sample collection efficiency for those particles that penetrate a separator whose size collection efficiency is described by a cumulative lognormal function with median cut size of 11.64-μm aerodynamic diameter and with geometric standard deviation of 1.5. Also, the selected data for the observed human head penetration during inhalation by mouth corrected to the appropriate aerodynamic diameter for reference worker for an inspiratory flow rate of 43.5 L/min are shown.

Figure 7

Sampling efficiency versus particle aerodynamic diameter for the PM_2.5 Federal Reference Method sampler (EPA, 1997a).

Figure 8

Bronchoalveolar lavage cell numbers recovered from mice 1 day after aspiration of WTC or standard PM samples in saline or saline vehicle alone. WTCX represents pooled WTC Dust samples. Number following particle type reflects dose (μg). Bars are mean (± SE) from n = 12 mice per treatment. *Significant at p < 0.05 (adapted from Gavett et al. 2003).

Figure 9

Airway hyperresponsiveness of mice exposed intratracheally to test WTC, PM standards, or saline and tested one day later (n = 8/group; data are mean ± SEM). When power function equations were fitted to each respective treatment set: ^‡significantly (p < 0.001) different exponent versus that seen with saline-treated mice or *significantly (p < 0.03) different coefficient versus saline coefficient.