VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

measured mostly within and very near Ground Zero, and they lastedfor 1 to 3 months after September 11.

While the conclusions reached in this report represent ±e current scientific understanding of the toxicity that these contaminants pose to people, combined with EPA’s evaluation of exposure to these contaminants based on available air monitoring data, it cannot be stated with certainty what effects resulted when people were engulfed in the initial cloud of dust or were subsequently exposed to the elevated concentrations that were found. Epidemiologic studies of the exposed populations that are currently being conducted by various agencies and institutions should provide a more scientifically robust evaluation for future evaluations of health effects.

The risk evaluation approach taken in most instances was to compare the measured air levels at locations near Ground Zero to established health benchmarks for inhalation exposure and to typical urban background levels. OSHA Permissible Exposure Levels (PELs), NIOSH Recommended Exposure Levels (RELs), and Agency for Toxic Substances and Disease Registry (ATSDR) Minimum Risk Levels (MRLs) were among the benchmarks included in this evaluation. Where available, benchmarks established to protect against acute and subchronic exposures were used. Benchmarks that are intended to protect against exposures lasting over one year or throughout a lifetime, like the EPA Reference Concentration (RfC), were only used if other more appropriate benchmark values were not available.

A simple comparison of air measurements to health benchmarks or to typical background levels can be thought of as a “screening” exercise; the purpose of the exercise is to identify possible problems. If the majority of samples are much less than a benchmark, in most cases it would be appropriate to conclude that a health impact is unlikely. Similarly, if most air measurements are similar to typical background levels, then it can be concluded that emissions from the WTC are not impacting air or influencing exposure and health. On the other hand, if most samples exceed a benchmark, then it may be appropriate to consider the possibility that a health impact may have occurred, or could occur, depending on the circumstances.

Efforts will continue at EPA to further characterize exposures and health impacts that resulted from the collapse of the WTC Towers, and to build on the risk evaluation presented in this report. Some additional future considerations could include: evaluating other contaminants that were measured, evaluating the indoor environment in more depth, evaluating other pathways of exposure and other exposure media such as dermal contact to contaminated dust, investigating the combined effects of exposure to more than one contaminant, conducting further toxicity testing with laboratory animals, and considering results from ongoing epidemiological studies.

Summaries of the findings for each contaminant/class of contaminants are presented below:

Particulate Matter. People caught in the initial dust/smoke cloud that encompassed lower Manhattan after the collapse of the WTC buildings on September 11 were briefly exposed (4-8 hours) to quite high levels (in the milligrams per cubic meter, mg/m\ range) of airborne particulate matter (PM). Also, during the flrst several days after the disaster, PM levels in the air at the WTCperimeter exceededEPA’s daily PM2J NAAQS (65 pg/m\ 24-hr); andPM2^

DRAFT-DO NOT QUOTE OR CITE 3 October 2002

NYC-WTC_000149084