Appendix D Food Codes for NHANES - OEHHA

Scientific Review Panel Draft February, 2012
On the other hand, dermal absorption of some chemicals does not appear to be
affected by the viability status of the skin samples. Dermal penetration of TCDD
through viable and non-viable pig skin was found to be similar (Weber, 1993).
F.2.10 Human Adult and Infant Variability in Skin Permeability
Animal studies are designed to ensure uniformity within the experimental
population by using inbred strains and often only one sex. The variability
between animals is much less than the genetically diverse human population.
Human studies also rarely use children or infants, the elderly, pregnant women
and the infirm, partially because of ethical considerations. Dermal uptake may
vary due to genetic diversity in the human population and differences in age.
This variability will not necessarily be accounted for by experimental data.
A review of the data on human skin permeability to chemicals suggest at least a
mean intra-individual coefficient of variation of approximately 40% and a mean
inter-individual variation of about 70% (Loth et al., 2000; Hostynek, 2003). A
leading cause in the variation is the lipid composition of the stratum corneum,
which influences solubility and permeability of drugs. This factor is partly
responsible for the high variability in accumulation and permeation
measurements (Loth et al., 2000).
There has been increasing awareness in recent years that infants and children
are more susceptible than adults to the harmful effects of some pollutants. This
can be due to differences in exposure, physiology, absorption, distribution,
metabolism, and excretion. Further, organ development and faster cell division
influence targets of toxicity. Finally, a large skin surface area to body weight ratio
would increase the dose of an absorbed chemical on a mg/kg body weight basis.
Only a few studies have examined age-related differences in the dermal
absorption capacity of chemicals in infants and children compared to adults.
Preterm infants lack a fully developed dermal barrier function and are particularly
prone to accidental poisoning of toxic agents applied to the skin surface (Barrett
and Rutter, 1994). In an in vitro system, McCormack et al. (1982) observed
increased penetration of some alcohols and fatty acids through skin of premature
infants compared to full term infant skin and adult skin. Dermal absorption of
sodium salicylate was found to be a hundred- to a thousand-fold greater in
infants of 30 weeks gestation or less compared to full term infants (Barker et al.,
1987).
In full-term infants, epidermal structure and function matures by 2-3 weeks of age
(Holbrook, 1998; Makri et al., 2004). In general, the in vitro system of
McCormack et al. (1982) showed full-term baby skin to be a good barrier for
some compounds. No difference in penetration of alcohols through full term
infant and adult skin was seen. However, penetration of some fatty acids
through full term infant skin was greater than that through adult skin. Higher lipid
F-14