on bisphenol A
BS, MK Murray, DA Damassa, JC King and AM Soto. 2001. Perinatal Exposure
to Low Doses of Bisphenol A Affects Body Weight, Patterns of Estrous Cyclicity,
and Plasma LH Levels. Environmental
Health Perspectives 109: 675-680.
experiments with rats, Rubin et al. confirm results obtained by
Howdeshell et al.
(1999) on the effects of early exposure to bisphenol A on adult female
weight, and extend the understanding of bisphenol A impacts to include
effects on other aspects of reproduction.
results are important for three reasons.
they provide additional confirmation from an independent, non-industry
based laboratory that exposure to low-level bisphenol A has adverse
effects. They thus contribute significantly to resolving
debates about the reality of low-dose impacts of bisphenol A.
they report a non-monotonic
relationship between dose and effect. In the female offspring, the
lower of the two BPA doses produced a larger and more persistent effect
on body weight relative to the higher dose. This is consistent with
the nonmonotonic or inverted-U-shaped dose-response curve that reported
for the imact of bisphenol A on prostate
their results on estrous cyclicity and plasma LH levels extend the suite
of endpoints affected by bisphenol A. The more the compound is studied
by independent laboratories, the wider is the range of impacts detected.
did they do?
et al. exposed pregnant female rats to bisphenol A from day 6 of
pregancy through to the end of lactation. BPA exposure was via drinking
water. They then examined the impact of two levels of exposure to bisphenol
A, compared to controls, on aspects of growth, development and hormonal
status of the offspring whose exposure had begun in the womb.
BPA was delivered via drinking water available through drinking bottles,
Rubin et al. could not calculate the precise amount of BPA consumed
by the females. Some leakage may have occurred. They estimate that the
low level of exposure delivered up to 0.1 mg/kg body weight/day and the
high level delivered 1.2 mg/kg bw/day. The actual exposure may have been
significantly lower than this upper estimate. While this entailed contamination
levels much lower than most studies on the effect of BPA (usually >10
mg/kg), it was much higher than levels used by vom
Saal and his colleagues (<.01ppm).
did they find?
birth, bisphenol A exposed pups were heavier than control animals. For
females, this effect persisted through adulthood, even though exposure
to BPA ended at weaning. Females receiving the low dose of BPA showed
a larger effect than animals receiving the higher dose.
to the authors, "most females exposed perinatally to high-dose
BPA failed to exhibit evidence of regular estrous cycles when examined
at 4 months (only 21% exhibited regular estrous cycles) and at 6 months
[only 23% exhibited regular estrous cycles (Figure 3A)]. The defect
in the pattern of estrous cyclicity varied in individual females and
was not easily defined."
also observed differences in adult hormonal status as a result of perinatal
BPA exposure: females receiving the higher dose exposures had low plasma
differences in time to sexual maturity were observed.