Appendix D Food Codes for NHANES - OEHHA

Scientific Review Panel Draft February, 2012
the oral route relative to other metals, up to 90% absorption in the acidic
environment of the stomach (Ruby et al., 1999). A limitation for this ABS is the
reliance on studies in which lead is applied neat to skin, rather than combined
with soil, for estimation of fractional dermal absorption. Kissel (2011) has noted
that fractional absorption is dependent on skin loading conditions for application
of organic chemicals directly to skin. However, Baranowska-Dutkiewicz (1981)
showed that for Cr(VI) the flux through skin increases proportionally with
increasing Cr(VI) load applied to skin, resulting similar fractional absorption
values independent of load onto skin. Thus, metal salts of lead applied neat
probably adhere closer to the dermal absorption kinetics of Cr(VI), rather than to
organic compounds.
F. 3.7 Inorganic Mercury Compounds
Recommended point estimate for dermal uptake from soil: 3%
F. 3.7.1 Studies Considered
Quantitative in vivo dermal absorption studies of Hg-contaminated soils have not
been performed. A summary of the in vitro dermal studies exposing human and
animal skin to Hg-contaminated soil are shown in Table F-2.
A. Key Studies
The dermal bioavailability of 203 HgCl2 was tested in vitro on dermatomed male
pig skin as pure compound or following addition to sandy soil or clay soil
(Skowronski et al., 2000). The Yorkshire pig model was chosen due to
histological, physiological, biochemical and pharmacological similarities to human
skin. The sandy and clay soil consisted of 4.4% and 1.6% organic matter,
respectively, and a majority of the soil particles were in the range of 50-250 µm.
A soil loading of 47 mg/cm 2 was calculated from the data provided and the HgCl2
concentration was 5.3 ng/mg soil. Absorption was estimated up to 16 hrs
following application.
In general, dermal absorption of Hg was greater from sandy soil than from clay
soil. In both soils, the rate of appearance of Hg in the receptor fluid was rapid
during the first hour, then decreased to a steady state for the remaining 15 hrs.
In sandy soil freshly spiked with Hg, 0.28% and 37.5% of the applied dose had
penetrated the skin to the receptor fluid and was bound to skin, respectively, at
16 hrs. In clay soil freshly spiked with Hg, 0.08% and 39.7% of the applied dose
had penetrated the skin to the receptor fluid and was bound to skin, respectively,
at 16 hrs. For the pure compound, Skowronski et al. (2000) observed a skin
penetration of 0.18%, but the amount bound to skin was 66.3%. For Hg aged 3
months in soil, dermal absorption was reduced to 3.3% in sandy soil and 2.6% in
clay soil. Only 0.04% and 0.01% of these totals in the sandy and clay soil,
F-36