VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

IV.a.3. Evaluation of Potential Particulate Matter Human Exposures and Health Impacts

Because no direct measurements were obtained for airborne particle concentrations present in the dense dust/smoke cloud that enveloped lower Manhattan for up to about 4 hours after the collapse of the WTC buildings on September 11, estimates of likely exposures to airborne PM for individuals caught in the initial dust/smoke cloud can only be deduced from indirect evidence and are subject to great uncertainty. Nevertheless, several tentative conclusions appear to be warranted on the basis of available inputs thus far.

First, it is likely that many persons caught outdoors (or some even indoors) in the initial dust/smoke cloud were exposed for several hours to extremely high levels of airborne particles. This exposure probably included inhalation of PM concentrations in the milligrams per cubic meter range, well in excess of 1 to 2 mg/m^ (1000-2000 ^g/m^), for both fine (PM < 2.5 pm diameter) and coarse (PM > 2.5 pm) inhalable particles. Although there were no measurements available during this critical time period, an examination of available photographs in combination with an empirical relationship based on visibility suggests that concentrations could very easily have been this high and likely were even much higher (e.g., possibly > 5 mg/m^). Such a finding is also supported by analyses of bulk dust samples conducted by Lioy et al. (2002).

The coarse inhalable particles (PM >2.5 pm) likely included substantial quantities of particles in the PM,0.2.5 range, which are capable of reaching lower respiratory tract (thoracic) regions of the lung, even though such coarse particles made up less than 0.5% of the particles found in WTC-derived settled dust by Lioy et al. (2002). Individuals who inhaled such high concentrations of WTC dust particles, even for a few hours, would logically be expected to be at potential risk for immediate acute respiratory and other symptoms and/or, possibly, more chronic health impacts associated with lung deposition of notable quantities of constituent PM materials (e.g., calcium, silicon, potassium, lead, other metals).

Persons exposed to the very high PM levels in the initial dust cloud and who continued to work at Ground Zero or returned to work there within a few days without wearing adequate protective respiratory gear might be at especially increased risk for potential acute or chronic health effects, depending on the extent of any ensuing exposures to high PM levels on or immediately around the Ground Zero rubble pile. The latter could include additional exposures to coarse PM constituents (e.g., calcium or silicon) present in re-entrained dust particles from the initial WTC building collapse and/or exposures to newly formed fine particle constituents (e.g., metals), as well as to organic constituents (e.g., PAHs present in both size ranges) emitted from the WTC fires.

Evaluation of potential health impacts associated with the above types of PM exposures should be further facilitated by disease registry efforts and retrospective epidemiologic analyses of physician/emergency department visits and hospital admission records being sponsored by the Centers for Disease Control (CDC), the Agency for Toxic Substances and Disease Registry (ATSDR), the National Institute of Environmental Health Sciences (NIEHS), and other federal, state, and NYC agencies and that are now under way. Recent reports (Prezant et al., 2002)

DRAFT-DO NOT QUOTE OR CITE 37 October 2002

NYC-WTC_000149118