Appendix D Food Codes for NHANES - OEHHA

Scientific Review Panel Draft February, 2012
also showed rapid absorption of lead oxide and elemental lead through the
human skin of volunteers and detection in the sweat within a few hours. Only
PbCO3 was not absorbed through skin. In mice, skin-absorbed lead
concentrated more strongly in skin and muscle, and less in blood and other
organs compared to intravenously injected lead (Florence et al., 1998).
The authors proposed that the behavior of skin-absorbed lead in the body is
different from lead that is ingested or injected, in that lead which passed through
skin is in a physicochemical form with low affinity for erythrocytes and a high
affinity for extracellular fluid compartments. The implication is that testing blood
for lead exposure may not fully account for absorption of lead through the skin.
Stauber et al. (1994) examined dermal lead absorption by placing lead nitrate
and lead nitrate spiked with 204 Pb on the arms of volunteers for 24 hrs. Rapid
increases of lead were observed in sweat samples from the unexposed arm and
in saliva, but only small concentrations of lead in blood and urine. However, high
levels of 204 Pb in blood and urine were measured 2 and 16 days, respectively,
after exposure ended suggesting slow absorption of lead into the blood from lead
retained in the skin.
In order to quantify dermal lead absorption, 4.4 mg lead (as 0.5 M Pb(NO3)2)
was dispensed onto filter paper and secured with plastic wrap to the left arm of
one subject. After 24 hours, the filter paper was removed and the arm was
washed. Of the 4.4 mg lead, 3.1 mg was recovered from the filter paper and
wash fluid. Using this disappearance technique, the authors estimated that 29%
of the lead was absorbed into or through the skin. In two volunteers, the
estimated excretion of skin-absorbed 204 Pb in the sweat of two volunteers over
24 hrs was 16 and 46 µg lead/L. Assuming an average sweat production of 500
ml/day, the authors estimated 0.6% and 1.5% of the total lead that was absorbed
was excreted in sweat.
Lead acetate or nitrate was also applied to the skin of mice by the researchers in
order to quantitate the amount of lead absorbed and retained in organs and
tissues (Florence et al., 1998). Forty µl of aqueous solutions of the lead salts
(6.4 mg of lead) were applied to a shaved area of skin and covered with Parafilm.
Mice were sacrificed and organs and tissues analyzed for lead content after time
periods of 2 hrs to 1 week. A total analysis of the organs, feces, and urine
showed that, of the 6.4 mg of lead applied to the skin, 26 µg (0.4%) was
absorbed through the skin and entered the circulatory system in 21 hrs. This
analysis does not appear to include skin-absorbed lead at the site of application.
No differences in absorption of the two lead salts were observed. Increased
organ content of lead was noted by 6 hrs of exposure, with maximal organ
concentrations generally occurring after 24-48 hrs of exposure.
To investigate the stratum corneum depth profiles of lead in lead battery workers,
10 repeated skin strips were collected from exposed skin (dorsal hand) and
F-33