VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

programs that have tracked exposures in New York since that time. This is an issue that warrants further examination. Also, the ambient monitoring did not begin immediately on September 12. The earliest reported data are from asbestos monitoring, which began on September 14. The dioxin monitoring did not begin until September 23. It is highly likely that air concentrations within and near Ground Zero were highest during these first several days, but monitoring is unavailable to confirm that hypothesis. This issue is addressed in more detail in Section V, which observes that the highest concentrations were among the first ones measured, Many monitoring programs and studies are currently under way to help us understand health outcomes that have resulted from acute exposures on September 11 and the next several days. These studies are discussed in the final section of this report.

This report should be viewed as the first phase of an ongoing analysis, and the conclusions and findings cited below should not be considered the final EPA judgement. At this point, the available data and analyses are still too preliminary to support reliable quantitative predictions of potential human health risks. Although a complete quantitative evaluation of the health impacts of the disaster may never be possible, future EPA analyses will attempt to develop more quantitative estimates of risks and health impacts using additional exposure- related data and possibly, the results of epidemiological studies that are currently underway. An overview of epidemiological studies that are underway is provided in Section VII.

Following are assessments on the individual pollutants.

IV.a. Particulate Matter Airborne particulate matter (PM) is a complex mixture of inorganic and organic substances transported in air as solid particles or liquid droplets. PM in ambient (outdoor) air can typically be divided by size into two groups: fine particles (less than ~2.5 pm diameter) and larger, or coarse, particles (ranging from ~2.5 pm to 50 pm or more). Fine PM includes primary particles formed by combustion (including condensed metal and organic vapors), as well as secondary aerosols (formed by gas-to-particle conversions). Coarse PM consists mainly of earth crustal materials formed by natural erosion processes or by human activities such as driving on paved or unpaved roads, agriculture and mining operations, industry, and construction/demolition.

PM exposures and associated potential human health risks are addressed in this preliminary analysis because the collapse of WTC buildings resulted in vast quantities of structural materials and building contents being crushed and pulverized into airborne particles in a wide range of sizes, including both fine and coarse particles. These particles, along with particles and gases emitted from burning jet fuel, aircraft parts, and building debris, formed the immense dust/smoke cloud that rapidly spread across the NYC area and dispersed over hundreds of square miles. Thus, PM air monitoring was essential to help characterize potential health effects resulting from human exposure to the initial dust/smoke cloud, particles produced by the ensuing fires, and reentrained particles stirred up into the air during recovery activities and transport of debris away from the WTC site.

Airborne PM exposures are of concern for human health because they can be associated with a wide variety of adverse human health effects. Some health impacts could include

DRAFT-DO NOT QUOTE OR CITE 24 October 2002

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