Appendix D Food Codes for NHANES - OEHHA

Scientific Review Panel Draft February, 2012
Total absorption (receptor fluid plus bound to stratum corneum) was 1.65, 1.49,
0.92, and 0.12 % for the sulfate, nitrate, chloride, and acetate salts, respectively.
Total recovery of absorbed and unabsorbed nickel was virtually complete for all
the salts except nickel nitrate, in which 84% recovery was attained.
Permeation of the salts was attributed by Tanojo et al. (2001) solely to the
diffusion across the transcellular/intercellular barrier, as hair follicle and gland
shunts were shut upon hydration by the aqueous solutions. These pathways
swelling shut early during in vitro exposure may explain the decreased rate of
absorption of nickel following an initial surge. Lack of ability to account for
absorption of nickel via skin shunts may underestimate absorption.
B. Supporting Studies
Nickel reversibly binds to constituents of the epidermis when human epidermis
was homogenized and incubated with nickel chloride solutions (Fullerton and
Hoelgaard, 1988). Spruit et al. (1965) utilizing human cadaver skin has shown
that nickel ions also reversibly bind to the dermis. Nickel powder has also been
shown to oxidize when suspended in synthetic sweat, whereupon the metallic
ions can be absorbed in vitro through human skin (Larese et al., 2007).
Under the same experimental exposure conditions as used by Hostynek et al.,
(2001a), nickel metal powder (particle size 3 µm) values were found to decrease
from the superficial to the deeper layers of the stratum corneum (Hostynek et al.,
2001b). However, nickel was still present at the deepest levels of stratum
corneum removed by adhesive stripping, indicating that the metal has likely
reached the viable epidermis and has potentially become systemically available.
Although the data did not lend itself to estimation of a skin permeation rate, total
nickel removed with 20 strips from the skin after 24 hr occlusion with 21.7
mg/cm 2 nickel powder was 38.7 µg/cm 2 (i.e., approximately 0.18% of the total
nickel metal applied was found in the stratum corneum). These data indicated
that in intact skin, nickel metal is oxidized to form soluble, stratum corneumdiffusible
compounds which penetrate the intact stratum corneum.
Dermal absorption of nickel chloride as 63 NiCl2 from two different soils was
determined in vitro through dermatomed pig skin cut 200 µm thick (Abdel-
Rahman et al., 1997). Soil types included a sandy soil with 4.4% organic matter
and a clay soil with 1.6% organic matter. Skin applications included 63 NiCl2
added immediately after the addition of the two soils (30 mg each) to skin, or
after each soil was aged for 6 months with 63 NiCl2. Nickel chloride was also
added alone in ethanol vehicle to separate skin samples. The chemical dose
was 113.8 ng/cm 2 and the soil loading was calculated to be 47 mg/cm 2 .
Monolayer coverage was probably exceeded with a soil loading of 47 mg/cm 2 ,
causing a reduction in the observed fractional absorption.
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