VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

orders of magnitude below the OSHA PEL of 5*10^ ng/m\ The NIOSH REL is an 8-hr time-weighted average air concentration. It is associated with long-term or repeated exposures, and is protective of effects on the liver and the reproductive system. The OSHA PEL is also an 8-hr time-weighted average air concentration. It is associated with long-term or repeated exposures and is protective of effects on the ski (dermatitis).

Dioxins. Monitoring data indicate that dioxin toxic equivalent (TEQ) levels in air near the WTC were up to three orders ofmagnitude higher (1000 times higher) than is typicalfor urban areas in the United States. Typical levels for urban areas are 0.1 to 0.2 picograms of TEQ per cubic meter (pg TEQ/nP), while levels found in Ground Zero and near Ground Zero, starting September 23 (the date of thefirst sample taken) and continuing through late November ranged from 10 to over 150 pg TEQ/m^. Concentrations measured several blocksfrom Ground Zero were still elevated above typical urban background, but considerably lower than sites in or near ground zero, rangingfrom 1 to 10 pg TEQ/m^ during this same time period. Everywhere these elevations dropped rapidly, and the data suggest that by December 2001, levels decreased to background levels. These levels need to be considered in the context of total exposure to dioxin, 95% of which is attributed to dietary intake in normal background settings. Therefore, although inhalation exposure to dioxin at these elevated air concentrations is significantly higher than typical inhalation exposure to dioxin, an individual’s overall exposure to dioxin may not be impacted significantly. An exposure and risk screening exercise was conducted with available monitoring data, and the results suggest that these elevations did not result in a significant elevation in cancer or non-cancer risk over the background riskfor exposure to dioxin-like compounds.

The monitoring data indicate that, through late November, dioxin TEQ levels in air near the WTC were distinctly elevated compared with typical levels in urban air. An exposure and risk screening exercise based on these high concentrations suggest a temporary elevation in exposures for Ground Zero workers but very minimal impact for nearby residents and office workers. It is concluded that these potential exposures during 2001 do not constitute a public health concern. Dietary intake of dioxins is much higher than inhalation intake, and thus, the ambient concentrations of dioxin within and near Ground Zero, although considerably elevated above typical urban air concentrations of dioxin, are not as significant as suggested by the orders of magnitude in elevation indicated above.

However, much of the data obtained from within and near the WTC site are of limited interpretive value due to high detection limits. When dioxin-like compounds were not detected in an air sample, the TEQ concentration was determined by assuming that each dioxin-like compound was present in the air at one-half the detection limit for that compound. This is typical for calculating dioxin TEQ concentrations, and for other contaminants as well. Because dioxin-like compound concentrations were considerably elevated in the ambient air from September through late November 2001 within and near Ground Zero, these concentrations were able to be measured, despite high detection limits. Concentrations ranged from 10 to 150 pg TEQ/m’ during this time, which was between 100 and over 1500 times higher than typically found in urban air.

DRAFT-DO NOT QUOTE OR CITE 7 October 2002

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