Appendix D Food Codes for NHANES - OEHHA

Scientific Review Panel Draft February, 2012
3.43 and 4.26%, respectively, while a group exposed for 24 hrs to soil freshly
spiked with PCBs exhibited a dermal absorption value of 4.07%.
Mayes et al. (2002) stated that the reduction in fractional absorption compared to
the Wester et al. (1993b) study was due to greater soil content of organic matter,
which absorbs highly lipophilic compounds such as PCBs. However, the dermal
load of 42 mg/cm 2 used by Mayes et al. likely exceeded monolayer coverage and
caused a reduction in fractional absorption. No statistically significant difference
was observed between the 12- and 24-hr exposure groups, suggesting PCBs
partition quickly into lipid components of the stratum corneum. Likewise, aging of
PCBs in soil had no effect on dermal absorption, suggesting rapid binding to the
organic fraction of soil. The authors noted that Aroclor 1260 has a slightly higher
octanol/water partition coefficient (log Kow) than Aroclors 1242 and 1254 used by
Wester et al. (1993b). A higher log Kow would favor greater dermal absorption.
However, the higher percentage of congeners with seven or more chlorines in
Aroclor 1260 compared to Aroclors 1242 and 1254 tends to reduce dermal
absorption, as shown by Garner and Matthews (1998).
The dermal absorption of radiolabeled 3,3',4,4'-tetrachlorobiphenyl (TCB) from
liquid and soil mixtures was studied in an ex-vivo Yorkshire-Landrace pig-skinflap
model (Qiao and Riviere, 2000). The soil was described as a dust containing
31.2% sand, 16.8% silt, 53.0% clay (90% kaolinite) and 0.3% organic matter. No
particle size fractionation was given. Sixty-five to 70 mg soil containing 200 µg of
14 C-TCB (40 µg/cm 2 ) was applied onto 5 cm 2 skin surface for 8 hrs, and the area
was either left open (non-occlusive) or closed with Parafilm (occlusive). Greatest
dermal absorption of TCB occurred from non-occluded soil. Fractional
penetration of skin into the perfusate was 0.66%, absorption into dermis and
other local tissues excluding stratum corneum was 2.48%, and stratum corneum
absorption was 0.90%. Occlusion of the soil mixture significantly decreased
dermal absorption 2-3-fold. In addition, dermal absorption from the liquid
formulations (acetone, water-acetone mixture, or methylene chloride) was also
significantly lower, suggesting TCB dermal absorption data from liquid
formulations may considerably underestimate the risk of exposure to TCB in a
soil matrix.
Qiao and Riviere (2001) performed a full mass balance in vivo study in Yorkshire-
Landrace pigs after iv and dermal exposure to identical doses of 300 µg 14 C-
TCB. For dermal exposure, TCB in acetone vehicle was applied to a 7.5 cm 2
abdominal area of three pigs and protected by a glass chamber with holes,
followed by covering with a nylon sieve screening. Urine and feces were
collected for 11 days, with quantitative tissue analysis and tape stripping of the
TCB-exposed dermal region conducted at the end of the 11 day exposure. On
average, about 70-71% of the applied dermal and iv doses were recovered.
After iv dosing, a total of 60% of the dose was excreted via urinary and fecal
routes with 8% of the initial dose remaining in body tissues. However, when TCB
was given topically, the total excretion was only 5% but with a much larger tissue
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