Appendix D Food Codes for NHANES - OEHHA

Scientific Review Panel Draft February, 2012
Following 24 hour dermal exposure + 24 hour post-exposure (total of 48 hours
from initiation of exposure), the TCDD content of the liver was determined. The
uptake of TCDD under the experimental protocols ranged from 0.54 ± 0.06 to
1.01 ± 0.22% and averaged 0.76 ± 0.16%. The percent uptake of TCDD in liver
was not affected by the applied TCDD dose (12.5 or 125 ng/kg BW), the
presence of crankcase oil in the soil, the use of soil that had been
environmentally contaminated with TCDD, or by the use of haired or hairless
rats.
Peak liver concentrations for TCDD administered orally and dermally were used
to correct for incomplete absorption in the calculation of relative dermal
absorption. The calculation is based on the assumption that the source of fecal
TCDD following oral exposure is unabsorbed TCDD. The estimated relative
dermal bioavailability is 1.5% from laboratory-contaminated soil and 1.6% from
environmentally contaminated soil.
Diliberto et al. (1996) note that during the first 48 hours following oral exposure,
TCDD in rat feces included both unabsorbed TCDD and absorbed TCDD that
was excreted in bile. However the data suggest that at 48 hours, absorbed
TCDD contributes only about 10% of the fecal TCDD.
Poiger and Schlatter (1980) applied radiolabeled TCDD in a soil/water paste
formulation (26, 350, or 1300 ng in 14.3 mg soil/cm 2 skin) to the backs of hairless
rats and measured the appearance of label in the livers. The soil (organic carbon
content unspecified) was taken from the Seveso region and was TCDD-free.
Measurements were taken 48 hours after the initiation of a 24 hour exposure
period.
The average percentage of dose in the liver after dermal application was 0.05,
1.7, and 2.2% for the 26, 350, and 1300 ng dose groups, respectively. The
authors noted that other researchers observed that 70% of total body burden of
administered TCDD is found in the liver of rats. Using this estimate, the
corrected dermal absorption of total applied dose is 0.07, 2.4, and 3.1% for the
26, 350, and 1300 ng dose groups, respectively. The authors also compared the
liver uptake of dermally applied TCDD from a soil/water paste to the uptake from
methanol, and found the soil/water paste caused a reduction in the fractional
uptake (compared to methanol) of 12 percent (1.6 ng TCDD/kg BW) or 15
percent (5.8 ng/kg BW).
TCDD in acetone vehicle was applied to human skin in vitro to estimate the
capacity of skin to store TCDD (Weber et al., 1991). Although TCDD did not
readily penetrate the skin into the saline receptor fluid (0.03% of dose) after 16.7
hrs exposure, a major portion of the dose was found in skin. The percent of dose
absorbed in skin at 16.7 hrs was 56% at a skin loading of 65 ng/cm 2 , and 40% at
a skin loading of 6.5 ng/cm 2 .
F-52