Appendix D Food Codes for NHANES - OEHHA

Scientific Review Panel Draft February, 2012
different skin sources for each of the two soil loadings). In addition, coarse
particle soil loadings of 20 and 40 mg/cm 2 may result in a reduced fractional
absorption, although the data suggest monolayer coverage of skin was probably
not exceeded (Spalt et al., 2009). The high bioavailability and apparent low
capacity for aging of cadmium in some soils indicates that sequestration of
cadmium in soil will be small relative to other inorganic metals in soil.
F. 3.4 Soluble Compounds of Hexavalent Chromium
Recommended point estimate for dermal uptake: 2%
F. 3.4.1 Studies Considered
A. Key Study
Czernielewski et al. (1965) exposed guinea pigs to hexavalent chromium
(chromium (VI)) as sodium chromate solution labeled with Cr 51 . A single dose
(15 µg sodium chromate in 0.1 ml solution) was applied to a 4 cm 2 shaved area
of skin for 24 hours (n=9 animals). Absorption was estimated by measurement of
the Cr 51 content of the following: urine, feces, blood (1 ml), heart, liver, spleen,
adrenals, kidneys, lungs, lymphatics, and skin. Dermal absorption of chromium
(VI) was estimated to be 2.9% of the applied dose from the 24 hour exposure.
Based on the average blood volume of adult guinea pigs (27 ml), 1.6% of applied
dose was found in blood, 1.1% in excreta, and only 0.2% in organs and tissues
including skin.
B. Supporting Studies
Chromium in the hexavalent [Cr(VI)] state does not measurably bind with
proteins, whereas the trivalent chromic ion [Cr(III)] shows strong affinity for
protein in epithelial and dermal tissues (Samitz et al., 1969; Gammelgaard et al.,
1992). Thus, Cr(VI) can permeate through skin relatively easily compared to
Cr(III). However, skin has the capacity, though limited, to reduce Cr(VI) to Cr(III)
resulting in binding of chromium to skin protein and decreasing the rate of
diffusion (Gammelgaard et al., 1992; Hostynek, 2003). Binding of chromium in
the skin is characterized as irreversible, leading to protein denaturation with
formation of permanent depots in the epidermis (Hostynek, 2003). Some of the
bound chromium is likely subject to the counter-current effect of continuous
sloughing of the outer skin layers, although no studies have attempted to quantify
this removal pathway.
To investigate the level of penetration of Cr(VI) into human skin, Liden and
Lundberg (1979) cut 10 µm tangential sections of skin biopsies after application
of a 0.5% aqueous potassium chromate solution on a 79 mm 2 patch of skin on
the back of volunteers. Dermal exposure durations to the chromate were 5, 24,
or 72 hrs. Highest chromium levels were found in stratum corneum. Chromium
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