in-vivo importance of this activity have not yet been
In summary, the range of variability of PON1 status
observed in this study, taken together with data from
‘humanized mice’ expressing hPON1
in place of mouse PON1, predict a 65-fold variability in
DZO sensitivity and a 131–164-fold range in sensitivity to
CPO exposure in this population, with an average four-
fold difference in sensitivity to DZO exposure and an
average eight-to ten-fold variability in sensitivity to CPO
between groups of mothers and their newborns. These
data predict that most, if not all, newborns, as well as
a subpopulation of adults , will exhibit significantly
increased sensitivity to organophosphate exposure. These
findings highlight the significance of understanding the
susceptibility of young children to organophosphate
exposure and developing science-based risk standards
for pesticide regulation as required by the 1996 Food
We gratefully acknowledge CHAMACOS staff, students
and community partners, and especially the CHAMACOS
participants and their families, without whom this study
would not have been possible. We thank Katie Kogut and
Erin Weltzien for their help with statistical analyses and
Dr Toby Cole for helpful comments and suggestions.
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