Appendix D Food Codes for NHANES - OEHHA

Scientific Review Panel Draft February, 2012
The most comprehensive human data available were the in vitro study by Filon et
al. (2006), which observed 0.06% of applied lead penetrating to the receiving
solution and 6.4% of applied lead retained in skin following dermal exposure of
PbO in a synthetic sweat solution. The skin depth profile of lead shows 49% of
the total lead in the stratum corneum was in the first two tape strippings, and
might be removed through desquamation prior to systemic absorption (Sun et al.,
2002). However, human in vivo dermal exposure data suggest a relatively short
lag time for appearance of lead in blood and continual absorption of lead into the
blood from the skin reservoir (Lilly et al., 1988; Stauber et al., 1994). Until further
studies are conducted to estimate the fraction of lead removed via desquamation
prior to systemic absorption, it is presumed that all the lead absorbed in skin is
available for systemic absorption.
Although only 0.06% of the lead reached the receiving solution in the in vitro
study by Filon et al. (2006), in vitro dermal absorption studies of metal salts
generally do not include a full accounting of absorption due to skin shunts such
as hair follicles and sweat ducts. Hostynek (2003) noted that these skin shunts
swell shut upon hydration during in vitro dermal absorption studies, and can
reduce the movement of some dermally applied metal salts directly into lower
skin layers. The human in vivo data support the importance of sweat ducts for
lead dermal absorption (Lilly et al., 1988; Stauber et al., 1994). In addition, the
rapid reduction of lead dermal absorption early during exposure in the Filon et al.
(2006) in vitro study has been considered evidence for skin shunts becoming
hydrated and reducing lead absorption by these pathways (Hostynek, 2003).
These data further support the reasoning that the lead retained in skin observed
by Filon et al. (2006) cannot be discounted for potential systemic absorption.
In soil, aqueous leaching studies suggest soluble Pb can vary greatly depending
on the soil characteristics. If sweat is the leachate, the pH can range between 4
and 7, with an average in male Caucasians of 4.85 (Wainman et al., 1994). The
acidic nature of sweat will likely enhance Pb bioaccessibility from soil compared
to the soil pH ranges of 7-8. Because of the wide range of solubilities of Pb in
soil, a health protective point estimate based on the solubility of a heavily Pb
contaminated soil at pH 5 (average pH of sweat) is warranted. Zhang et al.
(1998) observed an approximate 41% Pb solubility at pH 5 from soil that may
have been saturated with Pb paint (Pb content = 34,592 mg/kg soil). Adjusting
the total fractional dermal absorption of 6.46% observed by Filon et al. (2006) by
multiplying the fraction of soluble Pb in a highly impacted soil (0.41) determined
by Zhang et al. (1998) results in an ABS point estimate of 3% after rounding to
the nearest whole number.
A health protectiveThe ABS of 3% for Pb salts is higher than the most other
metal salts investigated. However, most of the soil leaching experiments used
soils that were environmentally contaminated or incorporated time as a factor to
control for soil aging. Absorption of Pb salts has also been shown to be high by
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