VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

inadequate, but suggestive of PCB carcinogenicity.

From the dose-response data derived from animal studies, the EPA has calculated an upper bound cancer slope factor of 1*10"^ [gg/m’]"' associated with continuous lifetime inhalation exposure to PCBs. This slope factor pertains to exposure to total PCBs, which may or may not contain dioxin-like PCBs. For exposure to dioxin-like PCB congeners alone, the slope factor developed for dioxin-like compounds should be applied (EPA, 2000a). This assessment does not consider exposure and risk from dioxin-like PCBs because these congeners were not measured separately. The Toxic Equivalent (TEQ) concentrations discussed in the dioxin section below are specific to dioxin and furan congeners only.

A cancer risk from a less-than-lifetime inhalation exposure to total PCBs is given as:

Risk = LAC* UR (2)

where LAC is the air concentration averaged over a lifetime, calculated as: AC * [ED/LT], where AC is the average air concentration during the period of exposure (pg/m’), ED is the exposure duration (days), LT is lifetime (days), typically 70 years, and UR is the unit risk factor, expressed in units of 1/concentration.

In order to conduct a simple screening exercise to evaluate the cancer risk from inhalation of elevated levels of PCBs near the WTC site, a representative air concentration and a time during which exposure to that concentration occurred need to be determined. The areas in which PCB air concentrations were elevated were generally located within the “restricted zone”. Still, even if an individual were exposed to the highest concentration found at 153 ng PCB/m’ for a period of 1 month (and all the data suggests that elevations did not exist beyond 1 month), the lifetime cancer risk would be estimated at about 2*10'® (calculated as: [0.153 gg/m’] * [30 days/ (70 years*365 d/yr)] * [1*10"^ (gg/m^)"']). EPA regulatory programs, such as the Superfimd Program, typically consider individual incremental cancer risk estimates made in this maimer (i.e., in the context of a scenario-based risk assessment) in the range of 10"^ to 10"® to be of potential significance, depending on the circumstances. On this basis, an incremental cancer risk estimate in the range of 10’® is judged to be insignificant.

ATSDR has published a Toxicological Profile for PCBs (ATSDR, 2000a). This Toxicological Profile is a comprehensive review and summary of existing health effects information relevant to human exposures. From this review, it is concluded that all the measured PCB levels in air in or around the WTC site were well below the levels of significant exposure to PCB mixtures that were found not to cause adverse effects in experimental animals as a consequence of short-term inhalation exposure. These no-observed-adverse-effect-levels (NOAELs) in experimental animals ranged from 1.5 x 10® ng/m’ for renal effects to 9 xlO^ng/m’ for hepatic effects. These NOAELs are one to six orders of magnitude higher than the highest PCB air levels measured in Lower Manhattan.

Occupational exposure limits provide an additional perspective by which to evaluate potential noh-cancer health effects that may be associated with inhalation exposure to PCBs measured in the air at or near the WTC site. NIOSH publishes RELs and OSHA publishes PELs

DRAFT-DO NOT QUOTE OR CITE 68 October 2002

NYC-WTC_000149012