Appendix D Food Codes for NHANES - OEHHA

Scientific Review Panel Draft February, 2012
fractional absorption of 8% by the disappearance method and a plasma
concentration of 56.3 pg/ml. The authors suggested that the lack of measurable
serum levels of PCBs was partly due to evaporative loss during exposure.
Dermal absorption of HCB in vivo and in vitro was investigated in young (33 days
of age) and adult (82 days of age) female rats (Fisher et al., 1989). Young rats
absorbed 3.37 times as much HCB dermally as adults in the first 6 hrs of
exposure. This resulted from a lag time for penetration of about 1 hr in young
and 4 hrs in adult rats. At 72 hrs in vivo dermal penetration was 35% in young
and 26% in adults compared to 1.5% for young and 1.0% for adult as measured
with a continuous flow in vitro system, and 2.9% for young and 1.9% for adults as
measured with a static in vitro system. By 120 hrs both young and adult rats
have the same cumulative dermal absorption.
F. 4.1.2 Discussion and Recommendation for a Polychlorinated Biphenyl ABS
The Wester et al. (1993b) study provided the highest fractional dermal absorption
value (14%) for PCBs in soil among the in vivo experimental animal species
considered most relevant for human exposures (i.e., monkey and pigs). Similar
to the Wester study, Mayes et al. (2002) used Rhesus monkeys to estimate
dermal absorption of PCBs, but obtained fractional absorption values of only 3-
4%. Suggested reasons for the lower value include a greater proportion of highly
chlorinated congeners, which reduce absorption. However, this may not be an
issue because Wester got similar fractional absorption values using an Arochlor
(1242) dominated by tri- and tetra-congeners, and an Arochlor (1254) dominated
by penta- and hexa-congeners. Use of a soil with higher organic carbon content
may have also resulted in a lower fraction absorption. Additionally, Spalt et al.
(2009) notes that Mayes et al. probably exceeded monolayer coverage during
the experiment, whereas Wester et al. did not.
The Wester et al. and Mayes et al. studies also used an indirect mass balance
adjustment for dermal absorption by comparing excretion of dermally-applied
PCBs to excretion of iv administered PCBs. Qiao and Riviere (2001) showed
that this may underestimate dermal absorption up to 2- to 3-fold due to greater
organ and tissue content of PCBs following dermal absorption compared to
PCBs that were injected by the iv route. Thus, the highest absorption fraction
estimate (14%) by Wester et al. (1993b) is recommended as the best health
protective value.
Wester et al. (1993b) did not age the PCBs in soil prior to dermal application on
the monkeys. However, Mayes et al. (2002) observed that aging of PCBs in soil
did not reduce dermal absorption compared to freshly spiked soil.
In vitro dermal absorption studies were not considered for estimating the ABS.
Comparison studies applying PCBs both in vivo and in vitro suggest that
estimating dermal fractional absorption with an in vitro system would
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