VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

10 to 20 pg TEQ/m\ Further, the Church & Dey measurements of 10 - 20 pg TEQ/m^ for mid to late October are consistent with the WTC measurements for that time period of20 - 50 pg TEQ/mR In other words, the highest measurements are onsite (WTC); the next highest measurements are slightly offsite (Church & Dey), and slightly lower concentrations are farther offsite (Park Row). This is strong evidence that emissions from the WTC site are the cause for elevated air concentrations within and near the WTC site.

The Park Row measurements from December 2001 through the last reported measurements of March 18, 2002, are less than 0.11 pg TEQ/m^ and all the 2002 measurements are less than or equal to 0.05 pg TRQ/m\ These values are consistent with those of the other two Region 2/7 samplers (see Figure 22). They are also consistent with typical urban concentrations of dioxin TEQs (see discussion after bullets), which leads one to believe that these concentrations might be representative of typical “background” New York conditions.

The December through April measurements from the WTC Building 5 and Church & Dey monitors are nearly all non-detects. The reported concentrations average about 1.4 pg TEQ/m\ but this is of limited interpretive value since the detection limits were too high. The actual concentrations could be more like the concentrations of about 0.05 pg TEQ/m’ found at the Park Row sampler, but it is not possible to conclude that since the data are not available.

Other measurements made in the United States and around the world can be used to put these measurements in perspective. As noted earlier, EPA’s draft Dioxin Reassessment compiled urban and rural air monitoring studies and found average ambient concentrations of 0.12 pg TEQ/m’ for urban and 0.017 pg TEQ/m’ for rural settings. Higher concentrations have been identified in the literature, particularly near a known source of dioxin emissions. The highest TEQ concentration reported in the U.S. was > 1.0 pg/m\ downwind of an incinerator in Niagara Falls, NY. Concentrations in the plume of a solid waste incinerator in Columbus, OH, that was known to be emitting large amounts of dioxins were about 0.25 pg TEQ/m^ In this case, the stack was very tall (about 80 meters) and air measurements were taken about 2 kilometers away. Background air concentrations in Columbus were measured to be about 0.05 pg TEQ/m\

Air concentrations near an incinerator in Japan adjacent to a U.S. Naval Air Base were regularly measured on the base for dioxin-like compounds. Measurements at the nearest downwind monitor, at about 200 meters, averaged 3.5 pg TEQ/m^ for weekly samples over a 15- month period. For five samplers (including the nearest downwind sampler) at various locations on the base up to 800 meters, the average air concentration was 1.6 pg TEQ/m\ An examination of the air concentration data on this base in conjunction with wind rose data, suggested that a background air concentration in this area was less than 0.5 pg TEQ/m^ and that measurements above that were due to the influence of the incinerator (Walker, et al., 2002). Other measurements in cities in Japan have been in the 0.3 to 0.7 pg TEQ/m’ range, and these are the highest that have been reported as typical air concentrations worldwide.

DRAFT-DO NOT QUOTE OR CITE 76 October 2002

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