VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

calculations presented in this section, would not result in changing any of the principal findings, and would possibly be confusing to those who notice a difference in the concentrations described here compared to those posted on the EPA web site.

Some of the major health risks associated with dioxin exposure include, but are not limited to, cancer and noncancer effects, including reproductive, developmental, and immunologic effects. A complete discussion of the health effects of exposure to dioxin-like compounds can be found in EPA’s draft Dioxin Reassessment Document (EPA, 2000). This WTC report draws on procedures outlined in that document for conducting simple screening assessments relating to potential long-term cancer and noncancer effects from exposure to dioxin concentrations measured on and near the WTC site.

IV.d.l. Dioxin Air Monitoring Data Figure 22 shows the location of 16 air monitoring sites at which dioxin measurements have been taken. Four of the sites had very few samples, so the focus in this section is on the 12 samplers that had a significant number of samples. At all sites, high-volume air samplers were used. Each sampler contained both a GFF and a PUF cartridge. The GFF is used to collect and retain particle-phase dioxins, whereas the PUF material is used to capture gas-phase dioxins. The GFFs and PUFs were sent to laboratories for measurement of the 17 dioxin-like congeners using EPA method SW8290.

Two different groups conducted the dioxin monitoring. Nine of the 12 sites measuring a significant number of dioxin samples were “lettered” sites managed by the EPA’s Environmental Response Team (EPA ERT). These 9 sites sampled for 8 hours per sampling event. On the other hand, 3 of the 12 sites were “numbered” sites were established by the New York State Department of Environmental Conservation (NYSDEC), and they monitored for 72 hours per sampling event. For dioxin sampling, these 3 NYSDEC samplers were managed by EPA’s Region 2 persoimel, who sent the samples to EPA’s Region 7 laboratory for analysis. For this reason, these will be referred to as the Region 2/7 monitors/samples.

The amount of time the monitor operates directly affects the amount of air that went through the monitors for dioxin collection: the Region 2/7 sampling captured dioxins contained in about 1000 m^ of air (i.e., about this much air was drawn into the sampler over 72 hours), whereas the EPA ERT sampling captured dioxins in about 7 m^ air. The majority of the EPA ERT samples simply did not contain enough mass of dioxins to be able to detect, much less quantify, the dioxin-like congeners in the sample. When the method cannot detect the congener in the sample, a result of “nondetect” (ND) is reported, and the detection limit (DL) is supplied. The method’s detection limit is calculated by dividing the lowest amount of dioxin that it can detect (on the GFF and PUF) by the air that contained that amount, namely the air that flowed through the sampler. The greater the air flow, the greater the divisor for the unchanging detection amount, and the lower the detection limit. Except for the high concentrations measured within and near Ground Zero from September through late November, most of the samples taken by the EPA ERT samplers contained mostly non-detects. Therefore, TEQ concentrations ended up being calculated with all or most congeners set equal to a value of one- half the detection limit.

DRAFT-DO NOT QUOTE OR CITE 74 October 2002

NYC-WTC_000149018