WTC environmental health assessment draft, May 2002

NYC 9/11 Public Portal Document

2) Do = (Ds X FTSM x ABSo)/(BW x AT)

Do = Oral dose (mg/kg/day) FTSM = Fraction transferred from skin to mouth ABSo = Oral absorption fraction BW = Body weight (kilograms) AT = Averaging time (days)

3) Dd = (Dsx(l-FTSM)xABSd)/(BWx AT)

Dd = Dermal dose (mg/kg/day) FTSM = Fraction transferred from skin to mouth ABSd = Dermal absorption fraction BW = Body weight (kilograms) AT = Averaging time (days)

Several assumptions are incorporated into these equations. They assume that volatilization of the chemical on the surface is negligible, and that the chemical is available on the surface for the entire exposure duration (that is, that the chemical on a surface is not carried away each time the surface is touched). It is assumed that there is a maximum amount of chemical that can be deposited on skin (a maximum Ds) in a single day, but that maximum Ds is unknown. Therefore, this method tends to be conservatively biased with respect to oral and dermal exposure. If inhalation exposure is to be considered, the volatilized amount should be subtracted before estimating the amount available for dermal transfer.

Although these equations are limited by the above assumptions, they are basically sound in theory. The difficulty is in defining the specific inputs to the equations, since some of the input parameters have very little or no experimentally determined values in literature. Assessments usually rely on professional judgment.

The daily dose (Do and Dd above) is converted to a probability of carcinogenic risk by multiplying it by a carcinogenic slope factor (CSF). The CSF is a chemical-specific value indicating the risk per intake dose of that chemical.

? <Need more information & table of inputs to the equations>

The following tables show the benchmark levels developed for each contaminant of potential concern The screening values developed for each potential indicator chemical arc shown in five tables? FoHowing Each table is accompanied by a summary of any contaminant-specific assumptions that were made in developing the benchmark values.

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CONFIDENTIAL, CITY_21MC100_003423793 SUBJECT TO PROTECTIVE ORDER NO. 2, SEPT. 2008

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