VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

torch cutter and the other from a gasoline-powered saw operator. In 99 other samples, concentrations of CO ranged from 0.2 to 242.0 ppm. This high value was from a 32 minute sample, and it exceeded the NIOSH limit of 200 ppm and would have exceeded the PEL of 50 ppm had it been sustained for 2 hours.

CDC (2002) contains descriptions of all other contaminants measured. In general, nearly all samples were below relevant limits. An “Editorial note” at the end of the article (CDC, 2002, p. 455) concludes that, “At the time of the NIOSH sampling, the ambient air did not appear to be contaminated with toxic substances from the building or their contents or with combustion products to an extent that posed an occupational health hazard.”

Vl.a.3. Occupational Exposure to PCBs and Dioxins These two classes of compounds were measured at Ground Zero (WTC Building 5 monitor) and for several locations just off-site. It was judged that EPA’s 8-hour continuous air monitoring data on these two classes of compounds was adequate to be evaluating worker exposures in Section IV. These evaluations are contained in Sections IV.c (PCBs) and IV.d (dioxins), and are summarized here.

For PCBs, the highest concentration measured was 153 ng/m\ which was measured at Ground Zero. All other measurements were less than 100 ng/m^, with most at ND or within a typical urban range of 1-8 ng/m’. These are much lower than the NIOSH REL at 1000 ng PCB/m’ as an 8-hr time weighted average air concentration (NIOSH, 2002) and the OSHA PEL at 500,000 ng PCB/m^ as an 8-hr time weighted average air concentration (NIOSH, 2002). Using EPA procedures for estimating 95% upper bound cancer risk, an individual exposed to the highest concentration found at 153 ng PCB/m^ for a period of one month is estimated to have an excess lifetime cancer risk of about 2*10’^. EPA regulatory programs, such as the Superfund Program, typically consider individual incremental cancer risk estimates made in this manner (i.e., in the context of a scenario-based risk assessment) in the range of 10** to IO"® 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.

For dioxins, potential cancer and non-cancer risk were assessed using methods that are detailed in EPA’s Draft Dioxin Reassessment (EPA, 2000). First, a “scenario” is defined, which describes the pathways of exposures, contact rates with dioxin within these pathways, and the concentrations of dioxin in the exposure media. The scenario for the Ground Zero worker was as follows: this individual is exposed 10 hours per day, 5 days per week, in the time period between September 12 until November 30, 2001. The pathway of exposure is via inhalation, and the rate of inhalation for a WTC worker is 1.3 mVhr. Using data from the Ground Zero monitor, the average concentration during this time was calculated as 60.7 pg TEQ/m\ Exposure during that time, expressed in terms of mass inhaled divided by body weight and time (pg TEQ/kg-day) is converted to a lifetime dose, and when combined with the appropriate dioxin cancer slope, a 95% upper bound estimate of cancer risk was estimated as 3*10'®, which is about 2 orders of magnitude lower (100 times lower) than current US background cancer risk to dioxin-like compounds. This background risk is primarily due to ingestion of foods of animal origin. For non-cancer risk, a newer approach based on calculation of an incremental increase to background body burden was employed. The dose over the three month exposure period was used in a

DRAFT-DO NOT QUOTE OR CITE 127 October 2002

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