Appendix D Food Codes for NHANES - OEHHA

Scientific Review Panel Draft February, 2012
protocols. They attributed this difference to the higher doses used in the present
study (10 times higher when expressed in µg/cm 2 ) stating that saturation might
have occurred at higher doses, resulting in a lower fractional absorption.
F. 4.6.2 Discussion and Recommendation for a Diethylhexylphthalate ABS
Although two in vitro dermal absorption studies have been carried out with pure
DEHP on human skin, data were not provided to determine ABS values.
However, absorption rates were determined for both rat and human skin under
similar exposure conditions and compared. The DEHP absorption rate for
humans was 2-4 times less than that for rats (Scott et al., 1987; Barber et al.,
1992).
In vivo studies in rats and guinea pigs that determined absorption of DEHP by
total mass balance provide the best estimates for fractional dermal absorption in
these species. Deisinger et al. (1998) used PVC film as the vehicle for transfer
of DEHP to the skin of rats. Using PVC film as the vehicle will slow absorption,
as DEHP requires transfer from the film before partitioning into skin can occur.
This type of chemical transfer may give a closer estimate of a DEHP ABS from
soil, compared to skin application of the pure compound as performed by the
other studies. Including both systemic absorption and compound in skin at the
site of application, a fractional dermal absorption value of 17.2% is attained from
the Deisinger study. The rat-to-human absorption rate ratio of 2.1 determined by
Scott et al. (1987) is then applied to give a final ABS of 9% (rounded up from
8.6%).
DEHP in the skin is included in this estimate, as Ng et al. (1992) and Chu et al.
(1996) found there is significant systemic absorption of DEHP in skin up to 7 or
more days after removal of DEHP from the skin surface. For this reason, the rat
study by Melnick et al. (1987) was not considered in this assessment. The
Melnick study did not wash DEHP off the site of skin application prior to analysis,
so it is unknown how much DEHP was on or retained in the skin at the end of the
5 day exposure.
Similar to rats, Chu et al. (1996) also noted that guinea pig skin is considered
generally more permeable to chemicals than human skin. Thus, it is not
unexpected that the rat ABS of 17.2% is within the range of 9.5 to 18.9% (DEHP
systemically absorbed + DEHP in skin) determined by the authors in guinea pigs.
A limitation for this ABS is that both Ng et al. (1992) and Chu et al. (1996)
reported that the percent absorbed in guinea pigs appeared to be higher at low
application concentrations, although nearly identical experimental protocols were
used. They attributed this difference to possible skin saturation occurring at
higher doses (about 119-529 µg/cm 2 ), resulting in a lower fractional absorption.
If saturation of DEHP in rat skin has occurred in the Deisinger et al. (1998) study,
this may result in an underestimation of the fractional absorption value at soil
concentrations associated with airborne releases.
F-65