Appendix D Food Codes for NHANES - OEHHA

Scientific Review Panel Draft February, 2012
solution concentrations) with 168 hr exposure did not result in increased Cr
content in skin. Long lag times for appearance of Cr in the recipient phase
combined with lack of increased skin concentration with time indicates a high
binding capacity for Cr that will interfere with diffusion through the skin, although
skin binding sites can eventually be exhausted with time. Gammelgaard et al.
(1992) also observed the ratio of Cr(VI) to Cr(III) at pH 10 in the recipient phase
to increase over 160 hr of exposure. Appearance of chromium as Cr(VI) in the
recipient phase increased from about 60% at 40 hrs, to greater than 90% at 120
hrs. This finding indicated reduced capacity for dermal Cr(VI) reduction,
eventually resulting in increased Cr(VI) passing through the skin.
Baranowska-Dutkiewicz (1981) found chromium (VI) from aqueous solutions to
be readily absorbed by human skin. Seven volunteers were exposed to sodium
chromate solutions (0.01, 0.1, and 0.2 M) on an area of the forearm for 15, 30 or
60 minutes, in a series of experiments. The exposure area was covered with a
watch glass throughout the exposure period. Absorption was calculated from the
difference between the applied and recovered dose of chromium (VI). The
authors reported that percutaneous absorption of chromium is dependent on both
concentration and time. Specifically, they found that (1) absorption was highest
from the 0.01 molar solution (7.7-23% of applied dose) and lowest from the 0.2
molar solution (3.4-10.6% of applied dose), (2) the rate of absorption decreased
as exposure time increased, and (3) the rate of absorption increased
proportionally as exposure concentration increased. Individual data were not
provided.
Wahlberg and Skog (1963) used disappearance measurements of radiolabeled
chromium to estimate dermal absorption of hexavalent chromium in vivo in
guinea pigs. Animals were exposed for 5 hours to various concentrations
(0.00048 - 4.870 molar) of sodium chromate labeled with 51 Cr. Dermal
absorption of chromium was confirmed qualitatively by organ analysis. The
maximal disappearance of hexavalent chromium was observed from a 0.261
molar solution. Of the 10 animals exposed to this concentration, the mean
disappearance percentage per 5-hour period was 4% of the applied dose.
No studies could be located that examined dermal uptake of Cr(VI) from soils.
However, chromium fate in soil and soil bioaccessibility studies (gastrointestinal
and sweat leaching) have been conducted.
The relationship between Cr(VI) and Cr(III) in soil is a dynamic one, which is
affected by soil type and mineral content, pH, solubility, and other factors
(Bartlett, 1991; Fendorf, 1995; Stewart et al., 2003). Cr(VI) exhibits greater
mobility and less adsorption in soils compared to Cr(III). Organic matter, Fe(II),
and sulfides in soils are capable of reducing Cr(VI) to Cr(III), while manganese
oxides in soils are capable of oxidizing Cr(III) to Cr(VI). Usually, part of any
Cr(VI) added to soil will be reduced instantly, especially under acid conditions.
However, high concentrations of polluting Cr(VI) may quickly exhaust the readily
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