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EPA interim final report on WTC background study, April 2003

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Interim final report from EPA Region 2 detailing a background study of environmental conditions at the World Trade Center site.

NYC-WTC_000145869–000146029

Folder label: “INTERIM FINAL April 2003

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NYC 9/11 Public Portal Document

Air - There were forty-six air samples collected with thirty-two collected from residential areas and fourteen collected from common areas. The samples were analyzed for tridymite. Tridymite was not detected in any sample. However, since the detection limit for the samples varied slightly, a theoretical background concentration can be calculated using the entire combined data set from the residential and common areas. The 95% UCL for the combined data set is 9.3 pg/m’, which can be used as an estimate of the background concentration of tridymite in air.

Wipe - There were 114 wipe samples collected with eighty collected from residential areas and thirty-four collected from common areas. The samples were collected from hard surfaces including counters, floors, and walls. The samples were analyzed for tridymite. Tridymite was not detected in any sample, however since the detection limit for the samples varied slightly, a theoretical background concentration can be calculated using the entire combined data set for all surfaces from the residential and common areas. The 95% UCL for the combined data set is 99.8 pg/ft^, which can be used as an estimate of the background concentration of tridymite on hard surfaces.

6.3.2 Calcite Bulk Dust - There were nine bulk dust samples collected from residential areas. These samples were analyzed for calcite. There were no bulk samples collected from common areas. Only one of the samples detected calcite above the detection limit. The 95% UCL for calcite in bulk dust is 3.41% and this value can be used as an estimate of the background concentration.

Air - There were forty-six air samples collected with thirty-two collected from residential areas and fourteen collected from common areas. The samples were analyzed for calcite. Calcite was not detected in any sample. However, since the detection limit for the samples varied slightly, a theoretical background concentration was calculated using the entire combined data set from the residential and common areas. The 95% UCL for the combined data set is 9.3 pg/m’, which can be used as an estimate of the background concentration of calcite in air.

Wipe - There were 114 wipe samples collected with eighty samples collected in residential areas and thirty-four in common areas. The samples were collected from hard surfaces including counters, floors, and walls. The samples were analyzed for calcite. The frequency of detection for the residential areas (3%) and the common areas (3%) were the same, and the range of detection and mean concentrations were similar. Based on the similarity of the data sets between spaces and between surfaces, it is recommended to use the entire data set, combined for surfaces, to estimate the background concentration. The 95% UCL from this data set provides a value of 132.3 pg/tf as an estimate of the background concentration of calcite on hard surfaces.

WORLD TRADE CENTER BACKGROUND STUDY 29

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