Appendix D Food Codes for NHANES - OEHHA

Scientific Review PanelSRP Draft Version 2 February,June 2012
Similar to the inhalation Tco derivation, limitations of the oral Tco derivations
include the small number of women examined for PAHs in mother’s milk (n=21)
and the large number of “below detection limit” results for milk concentrations,
particularly for the larger PAHs with more than four rings. OEHHA assumed that
the arithmetic estimates, minimum and maximum values reported by
investigators represented a lognormal distribution and converted estimates from
arithmetic to geometric. Nevertheless, the use of sparse data to derive an
inhalation Tco and data from potentially two different study populations to
generate an oral Tco – one for dietary PAH intake and another for mother’s milk
PAH concentrations - introduces considerable uncertainty.
J.3.3 Comparison and Use of Inhalation and Oral PAH Tcos
Comparison of the oral and inhalation Tcos also presents a number of interesting
findings. For example, comparing the averaged inhalation and oral mother’s milk
Tcos generated from the Italian studies for carcinogenic PAHs, the mean
inhalation Tco is about four times greater than the oral Tcos based on Italian
study data.
Although studies in humans are lacking, (Grova et al., 2002) showed that BaP is
poorly absorbed through the gut in goats when administered orally in vegetable
oil. Radiolabeled BaP fed to these animals led to 88% recovery of the
radioactivity in feces, indicating little BaP reached the bloodstream where it could
be taken up in mother’s milk. In contrast, respiratory absorption of PAHs in
particulate form through smoking is about 75% efficient (Van Rooij et al., 1994).
The following factors may have influenced the difference between oral Tco
values and inhalation Tco values:
• First-pass metabolism in the liver following oral intake before reaching the
blood supply of the breast versus entering systemic blood circulation prior
to passage through the liver with the inhalation route (however, some PAH
metabolism occurs in the lung)
• Gut assimilation of PAHs is likely to occur at a different rate than the rate
of passage across the lung
Looking at mother’s milk Tcos in terms of carryover rate suggests that
accumulation of PAHs in the mother’s body occurs more readily when inhaled
versus ingested. Carryover rate, defined here as the daily output of PAHs in
mother’s milk (µg/day) over the daily intake of PAHs (µg/day), can be estimated
by multiplying a PAH Tco by the daily output of mother’s milk. Since milk
production in human mothers are about 1.0 kg/day, the calculated carryover rate
turns out to be the same as the PAH Tco value. A carryover rate greater than
one in PAH transfer suggests that accumulation occurs in the mother’s body prior
to lactation.
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