VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

Safety and Health Administration (OSHA) and the National Institute for Occupation Safety and Health (NIOSH), who employed personal air monitors for their analysis. These monitors are much more appropriate for human exposure assessment. The OSHA data, as posted on then- website (http://www.osha.gov ), are summarized in Section VI. The NIOSH data are also summarized there, with a reference provided for further information (CDC, 2002).

On the other hand, an evaluation of Ground Zero worker exposure was conducted for dioxin-like compounds. Unlike the case with VOCs, the dioxin monitors were stationary high- volume monitors operating for 8-hour periods. High concentrations captured by these monitors in the few months after September 11 are representative of air quality to which unprotected workers were potentially exposed (i.e, those not wearing respirators). Exposures to asbestos at the Staten Island Landfill were also evaluated using ambient air data. Although workers were not specifically identified as the exposed population, conservative assumptions in an exposure and risk assessment suggest that even continuous exposure for the limited time period when asbestos at the Landfill may have been elevated would not have resulted in exposures that suggest a potential human health risk.

Exposures that were specific to the indoor environment were also not explicitly addressed in this assessment. Section VI describes completed and ongoing studies which have measured levels of contaminants, mostly asbestos, in indoor environments. A major study completed by the Agency for Toxic Substances and Disease Registry (ATSDR) is summarized in that section. Also, ERA Region 2 is currently conducting indoor measurements during the clean-up of residences in lower Manhattan. Clearly, this will reduce future indoor exposures. It is expected that this EPA effort, and future compilations of all available indoor data, will allow for a more complete evaluation of impacts on residents and office workers to contaminants that were present as a result of the collapse of the WTC Towers.

This assessment focuses on the inhalation pathway. Exposure can potentially occur via inhalation, dust ingestion and dermal contact with contaminated dust on surfaces. Dermal contact and dust ingestion were not assessed due to a lack of appropriate data and reliable methods. For residents, contacts with contaminated dust will occur mostly indoors where people spend the majority of their time. The health assessment conducted in this study assumed that ambient air measurements were representative of long- and short-term exposures. In some cases, this could be misleading or inappropriate, particularly if indoor concentrations are higher than outdoor concentrations. It is emphasized that the evaluations in this document focus on ambient, outdoor measurements.

Because of the difficulties in setting up an effective monitoring program in such circumstances, very little data for most chemicals were collected prior to September 18,2001. As a result, exposures occurring on September 11 and during the week after are poorly characterized. It can reasonably be assumed that the concentrations within and near Ground Zero would have been at least as high and more likely higher than the first measurements taken near September 18. Section V reviews this hypothesis and demonstrates that, for many critical contaminants, the highest concentrations were the first ones taken. The individual contaminant assessments address this lack of data in different ways. For dioxin, it was assumed that the first concentrations measured on September 23 were representative of the period between September

DRAFT-DO NOT QUOTE OR CITE 13 October 2002

NYC-WTC_000149094