VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

Although none of these literature measurements can be assumed to represent New York levels, they provide some basis for perspective. Certainly, no reports in the literature could be found on similar circumstance where there is, what is essentially, an area source at ground level continually emitting dioxins near to where individuals are exposed. It would be reasonable to conclude that the concentrations to which individuals could potentially be exposed, in the range 10.0 to 170.0 pg TEQ/m’ within and near the WTC site found through the latter part of November, are likely the highest ambient concentrations that have ever been reported.

IV.d.2. Potential Human Health Consequences of Exposure to Dioxins in Air The exposure of humans to dioxins is predominantly through the food supply; about 95% of exposure is through consumption of animal food products. Inhalation exposure and absorption via the skin are generally minor pathways for the average U.S. citizen (i.e., the background population). EPA has estimated that about 4% of the background human dose of dioxin is due to inhalation, based on an average urban level of 0.12 pg TEQ/m^ and an inhalation rate of 13.3 m’/day. If the concentration of dioxin in the air is increased, the amount of exposure due to inhalation would be increased, but the total amount of dioxins contributed by the inhalation pathway might still be small in comparison to the contribution made by food ingestion.

In the WTC situation, elevated dioxin concentrations in the air can be expected to increase the proportion and extent of human exposure via inhalation and possibly skin contact routes for those people residing or working close to the WTC location. The extent to which these elevated atmospheric levels will translate into increased human doses depends on an individual’s pattern of exposure, considering, for example, his or her location in relation to the WTC and downwind areas; the duration and time period of exposure such as workshift and return to residence patterns, movement and activity patterns during the time of elevated atmospheric levels; and whether respiratory protection devices were used. Dioxin-like compounds exist substantially in the atmosphere attached to particles, and these devices would remove a substantial portion of the dioxins through the removal of particulates; if these respirators contained a carbon filter, a substantial portion of the dioxins in vapor phase would also be removed.

This section will use the data shown in Table 4 to conduct cancer and non-cancer assessments of an individual’s inhalation exposure to dioxins. The procedures used are described in detail in the draft Dioxin Reassessment (EPA, 2000; available at, http://www.epa.gov/ncea/dioxin.htm), with further references supplied below as necessary.

1. Daily Inhalation Doses Cancer and non-cancer assessments entail the development of a “dose” term, which in this case is the dose received via inhalation. Inhalation dose estimates require assumptions about the hoiu-ly rate of inhalation (m’/hr), the number of hours per day a person inhales at the site where he or she could be exposed (which could obviously be less than 24 horns if the individual does not live in the vicinity where air concentrations measurements were taken), the time period during which this exposure occurs, and, of course, the air concentration to which the individual is exposed.

Daily inhalation exposure dose is given by:

DRAFT-DO NOT QUOTE OR CITE 77 October 2002

NYC-WTC_000149021