Appendix D Food Codes for NHANES - OEHHA

Scientific Review Panel Draft February, 2012
tetrachloroethylene was applied neat to the skin and covered with an occlusive
patch after the vehicle had evaporated (Koizumi, 1991). The cumulative mean
absorbed body burden, not including dosed skin directly contaminated, was
2.67% after 24 hours. Approximately 5% of the total dose remained in or on the
dosed area of skin prior to washing. Washing the dosed area of skin resulted in
removal of 4% of the total dose, indicating that 1% of the total dose was
absorbed in the skin on which 14 C-HCB was directly applied.
A Monte Carlo simulation was developed to produce a probability density
function for the dermal uptake fraction of HCB in soil deposited on human skin
(McKone, 1991). A two-layer model was used that accounted for chemical
properties, skin properties, soil properties, and exposure conditions. The
resulting modeled daily dermal uptake fraction had an arithmetic mean value of
0.15 per day (24 hrs), and an arithmetic standard deviation of 0.18 per day.
F.4.4.2 Discussion and Recommendation for a Hexachlorobenzene
Compound ABS
A single dermal absorption study in rats observed a 24-hr fractional absorption of
4% (rounded to nearest whole number) for the neat compound. This estimate
includes HCB retained in skin at the site of application. Absorption of HCB may
have increased as a result of occlusion of the exposed skin area to prevent
evaporation of HCB.
A default ABS of 4% is recommended based on the rat dermal exposure study,
although the chemical was applied neat to the skin. The HCB modeling study by
suggests that the fractional absorption of HCB in soil may be 15%, so no
adjustment was made to the ABS to account for reduced absorption due to
partitioning to soil organic matter (McKone, 1991). In support, HCB is structurally
similar to hexachlorocyclohexane (HCH), which has an ABS of 3%. However,
the Kow for HCB (log Kow 5.73) is about 100 times greater than that of the HCHs,
which would suggest a greater ability for absorption into skin. On the other hand,
the high Kow also indicates that HCB will have stronger sorption to soil organic
material compared to the HCHs, which usually decreases the dermal absorption
potential. Until more relevant dermal absorption studies are conducted, an ABS
of 4% is recommended for HCB.
F. 4.5 Hexachlorocyclohexanes
Hexachlorocyclohexanes (HCHs) occur as eight isomers. The most common
isomer is the gamma, which when purified to 99%, was sold under the trade
name of lindane. Lindane was a widely used pesticide but almost all uses of
lindane have been banned in the United States due to carcinogenicity concerns,
high biopersistence and bioaccumulation. Dermal absorption data exist only for
lindane, thus all HCH isomers are considered to have the same dermal
absorption characteristics as lindane.
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