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Download fileQuantitative Identification of Unknown Exposure Pathways of Phthalates Based on Measuring Their Metabolites in Human Urine
journal contribution
posted on 01.07.2007, 00:00 authored by Hiroaki Itoh, Kikuo Yoshida, Shigeki MasunagaHumans are exposed to ubiquitous phthalates via multiple
pathways. Exposures to phthalates have been estimated
in some previous risk assessments in Japan based on point-of-contact measurement or scenario evaluation approaches.
While the Japanese national government has regulated
the use of di(2-ethylhexyl)phthalate (DEHP) and excluded
several other phthalates from its regulation based on some
of them, it is unclear whether such past exposure
assessment studies fully assessed total human exposure
to phthalates. In the present study, we measured their urinary
metabolites, which show direct evidence of human
exposure to phthalates. We recruited voluntary participants
(N = 36) who agreed to donate urine samples, and
measured the urinary concentrations of phthalate metabolites
using enzymatic deconjugation, solid-phase extraction,
and high-performance liquid-chromatography isotope-dilution
tandem mass spectrometry. We then derived the daily
intakes of their respective phthalates based on steady state
assumption and finally compared them with the corre
sponding estimated daily intakes of each phthalate via diet
and air derived from previous exposure or risk assessments
in Japan. These comparisons showed that exposures
to dimethyl phthalate, diethyl phthalate, and di-n-butyl
phthalate via diet and air accounted for less than half of
their respective total exposures. On the other hand, it appears
that dietary intake was more predictive for the total
exposure to n-butyl-benzyl phthalate and DEHP. The
probabilities that the lognormal distribution of each phthalate
daily intake estimated from the present study exceeds
the corresponding tolerable daily intake were estimated
to be less than 10-4.