VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

The reported TEQ concentrations that were compromised due to high detection limits ranged in value from 0.5 to 5.0 pg TEQ/m\ which is about 5 to 50 times higher than normal urban background air concentrations. These measurements came from 9 specific air samplers which were located within Ground Zero (1 sampler) and near ±e WTC site (8 samplers). In general, the dioxin method’s detection limit is calculated by dividing the lowest mass of dioxin that the method can detect by the air that contained that amount, namely the air that flowed through the sampler. Thus, as more air is drawn through the sampler, the detection limit is lowered. These 9 air samplers operated for 8-hour periods, and drew in about 7 m’ of air. They began operation on September 23, 2001.

Three other air samplers were operated for 72-hour periods, and drew in about 1000 m’ of air. These monitors were located several blocks from the perimeter of Ground Zero, and began operation on October 12. Because much more air was drawn into these samplers, the detection limits obtained for the dioxin-like compounds were lower, and TEQ concentrations could be routinely quantified as levels less than 1.0 pg TEQ/m\ The first sampling events in October through November in these three monitors resulted in concentrations that were still elevated above typical background TEQ concentrations, at between 1 and 10 pg TEQ/m’. Starting at the beginning of December, 2001, and continuing through the termination of sampling in May of 2002, the measurements in these samplers decreased to levels that were mostly less than 0.10 pg TEQ/m\ More detail on these two sets of monitors (the 9 monitors sampling for 8 hours, and the 3 monitors sampling for 72 hours) is provided in Section IV.d below.

AU the reported TEQ measurements from these 9 monitors for 2002, and the measurements from them in upwind conditions during 2001 (i.e., when the plume was moving in a direction opposite the monitors), were in this one-half detection limit range of 0.5 to 5.0 pg TEQ/m\ Thus, the ability to assess exposure during the early months of 2002, where there may have been elevations near Ground Zero as a result of cleanup activities, was compromised. Because the health risk from dioxin exposure is associated with accumulation of residues in body tissues, continued dioxin TEQ exposure within and near Ground Zero throughout 2002 could not be evaluated. The risk screening exercises conducted for dioxin were limited to the time period when the concentrations were highest and dioxin was detected. This issue is described in more detail in Section IV.d.

Asbestos: The large majority ofoutside air measurements of asbestos were below established benchmarks and within the range of typical background levels. However, and similar to other contaminants, the few exceedences that were measured occurred near September 11 in time and close in proximity to the WTC. Limited available evidence suggest the incursion ofasbestos to the indoor environment. A small stuify which sampled the indoor environment of two apartments on September 18 showed very high indoor levels ofasbestos. A larger and more systematic study which sampled in November and December of2001 suggested that indoor levels ofasbestos in dust were slightly higher near the WTC as compared to indoor levels in dust further away. Current efforts by the EPA focus on the measurement and clean-up ofresidential apartments near the WTC.

DRAFT-DO NOT QUOTE OR CITE 8 October 2002

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