Appendix D Food Codes for NHANES - OEHHA

Scientific Review Panel Draft February, 2012
content in the stratum corneum of infants was thought to be the reason for
increased absorption of fatty acids. In addition, a layer of subcutaneous fat
develops at approximately 2-3 months of age in infants and continues to exist
through the early toddler period (Thompson, 1946; Banks et al., 1990; Cohen
Hubal et al., 2000). This layer of fat may act as a sink for lipophilic chemicals
absorbed through the skin.
Age-related changes in dermal absorption have also been investigated in
experimental animal models. Using TCDD or 2,3,4,7,8-pentachlorodibenzo-pdioxin
(4-PeCDD) in solvent, Banks et al. (1990) observed greater absorption of
TCDD or 4-PeCDD in 10-week old rats than 36 - 120-week old rats.
2,4,5,2’,4’,5’-Hexachlorobiphenyl showed significantly higher fractional
penetration in young rats (33 days old) compared to adult rats (82 days old) in
vivo, but only at one of three dose levels tested (Shah et al., 1987). Overall, the
authors concluded that no clear age-related pattern of dermal absorption was
found among a total of 14 pesticides including 2,4,5,2’,4’,5’-hexachlorobiphenyl.
F.2.11 Use of Default ABS Values
The California South Coast Air Quality Management District’s Multi-Pathway
Health Risk Assessment Input Parameters Guidance Document (SCAQMD,
1988) recommended using default values of 10% for organic chemicals and 1%
for inorganic chemicals when quantitative data are not available to estimate
chemical-specific dermal absorption fractions from soil.
Use of these default factors was proposed based on a review of the dermal
absorption literature and recommendations by McLaughlin (1984). In his US
EPA report, McLaughlin suggests it may be possible to group penetrants into a
numerical system using an “order of magnitude” approach (i.e., 100% - 10% - 1%
- 0.1% fractional absorption groupings), depending on physical parameters such
as partition coefficients and diffusion constants. For example, many of the
organic compounds were found to fall into the 10% absorption range. Exceptions
included some pesticides, such as the very lipophilic pesticide carbaryl that
exhibited a fractional absorption closer to 100%, and the polar pesticide diquat
that exhibited a fractional absorption closer to 1%.
More recently, US EPA (2004) also recommended a default dermal absorption
fraction for semivolatile organic compounds (SVOCs) of 10% as a screening
method for the majority of SVOCs without dermal absorption values. This
fraction was suggested because the experimental values for SVOCs determined
by US EPA are assumed to be representative of all SVOCs as a class. US EPA
(2004) notes that chemicals within classes can vary widely in structure and
chemical properties, potentially resulting in a wide range of fractional absorption
values. However, OEHHA agrees that a 10% fractional absorption default value
is acceptable at this time, based on the range of values (3 to 14%) estimated in
F-15