WTC health criteria appendix, Dec 2001

NYC 9/11 Public Portal Document

The standard default factor for workplace ED is 25 years (USEPA, 1991).

The central tendency value of 5 years may be used as a low-end estimate (USEPA, 1993a).

Fraction Transferred from Skin to Mouth (FTSM)

This factor accounts for the apportionment between dermal and oral exposure. This factor must be greater than or equal to zero, and less than or equal to 1. In fact, the closer it is to 1, the greater the risk, since the oral route contributes relatively more than the dermal route to the overall risk.

Michaud et al (1994) assumed that the contamination that had been transferred to the surface area of the fingertips would be transferred to the mouth, twice per day. In the Binghamton reentry guideline derivation, a range of factors was used, which assumed 0.05, 0.1, and 0.25 of the hand surface area was transferred (New York State Dept, of Health, 1985).

It may be assumed that approximately 10% of the material on the hand surface area will be transferred to the mouth. Using the values of 200 to 400 cnr for total palm-side hand area (both hands), the area would be approximately 30 ciif' (USEPA-EMSL; USEPA, 1989b; Michaud et al, 1994; New York State Dept, of Health, 1985). This must then be correlated to total SA in order to derive the FTSM fraction.

Oral Absorption Fraction (ABSO)

For chemicals whose dose-response parameters are based on orally administered doses, ABSo is assumed to be 1, and there is no need to adjust the RfD or CSF for absorption (which usually must be done when assessing dermal risks).

Body Weight (BW)

The standard default exposure factor for an adult worker's BW is 70 kilograms, which is an average (USEPA, 1991).

Averaging Time (AT)

For non-carcinogens, AT is the exposure duration expressed in days. For carcinogens, exposure is averaged over a 70-year lifetime (the factor on which the cancer slope factors are based), and the AT is 70 years, in days.

Dermal Absorption Fraction (ABSD)

This parameter is assumed to be chemical-specific. USEPA's dermal exposure assessment

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CONFIDENTIAL, CITY_21MC100_003423739 SUBJECT TO PROTECTIVE ORDER NO. 2, SEPT. 2008

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