Appendix D Food Codes for NHANES - OEHHA

Scientific Review Panel Draft February, 2012
nonexposed skin (lower back) of 10 volunteers (Sun et al., 2002). Skin areas to
be sampled were washed with soap and water, then ethanol, prior to collection in
the morning before work. Total lead in stratum corneum strippings ranged from
20.74 to 86.53 µg (mean = 42.8 µg) from the hand, and 8.94 to 28.32 µg (mean =
17.4 µg) from the back. Approximately 20.8 µg (49%) of the total lead in the
stratum corneum were in the first two tape strippings. There was a decreasing
amount of lead content from both skin regions going from the outer to the inner
layers, suggesting both regions had been contaminated with lead. Total amount
of lead in the hand, but not the back, was linearly correlated with the amount of
lead in blood. These findings indicate the source of lead in skin was from dermal
exposure, rather than absorption of lead from the circulatory system into the skin.
Although the lead compound, which workers were exposed to, was not specified
in the Sun et al. (2002) study, the primary lead compounds emitted during leadacid
battery production are identified as PbO and elemental lead (USEPA, 1998;
Ruby et al., 1999). Elemental lead particles that are deposited in soils quickly
form coatings of highly bioavailable PbO.
The leaching behavior of lead-contaminated soil can be divided into three stages
based on the leachate pH: a high alkalinity leaching stage at pH > 12, where Pb
formed soluble hydroxide anion complexes and leached out; a neutral to alkaline
immobilization stage in the pH range of 6-12, which was characterized by low Pb
leachability by adsorption and precipitation; and an acid leaching stage with pH <
6, where leachability increased exponentially with decreasing pH and was
characterized as free Pb-ion (Jing et al., 2004). This study indicates that soluble
Pb at the neutral pH found in most soils would only be a fraction of the total Pb
content of the soil.
Several leaching studies of Pb-contaminated soils suggest the bioaccessible Pb
in soil can vary greatly. Within a pH range of 7-8, soluble Pb ranged from less
than 0.01% to 48% of total Pb content of soil (LaPerche et al., 1996; Yang et al.,
2001; 2002; Jing et al., 2004). In a major Pb contamination due to a paint spill
the Pb soil content was 34,592 mg/kg, which is roughly an order of magnitude
greater than many Pb-contaminated soils (Zhang et al., 1998). Soluble Pb at pH
7 was roughly estimated to be 18% of total soil Pb. At pH 5, fractional soluble Pb
increased to about 41% of total soil Pb.
F. 3.6.2 Discussion and Recommendation for a Lead and Inorganic Lead
Compound ABS
The accumulated in vivo absorption data did not provide enough quantitative
information to estimate an ABS point estimate of lead including both systemic
absorption and that retained in skin. Additionally, no data could be found that
measured dermal absorption of lead from contaminated soil. Thus, the lead ABS
point estimate incorporated data from an in vitro human study of lead applied
neat and soil leaching tests for lead-contaminated soil.
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