There are a few
=LRTYR
facts about BPA
3Z]XZYP^
that everyone
agrees on. one is
that people are
constantly exposed to the compound.
Babies—particularly those fed canned
formula via polycarbonate bottles—
are at the highest risk from BPA; their
undeveloped digestive systems metab-
olize it poorly. It’s also undisputed
that BPA mimics the female sex hor-
mone estrogen, and that some syn-
thetic estrogens can cause infertility
and cancer.
What ^h in dispute is whether the
tiny doses of BPA we’re exposed to
are enough to trigger such hormonal
effects. For decades, the assumption
was that they didn’t. this was based
on traditional toxicology, which holds that “the dose makes the
poison.” In other words, a threshold exists below which a com-
pound is harmless. this makes intuitive sense. Consider alco-
hol: the more you drink, the drunker you get; but if you drink
just a little—below the threshold—you may not feel anything. In
the 1970s and 1980s, government scientists used standard toxi-
cology to test BPA. they concluded that, at doses far higher
than those found in humans, it may cause organ failure, leuke-
mia, and severe weight loss. Yet as BPA products have made
their way into every part of our lives, biologists have discovered
evidence that very low doses may have a completely different
set of effects—on the endocrine system, which influences
human development, metabolism, and behavior.
At first, these discoveries emerged by accident, when test
tubes and petri dishes in laboratories were switched from glass
to plastic. A group of stanford researchers in 1993 found that
breast-cancer cells it was studying reacted with a mysterious
estrogen, which it traced to polycarbonate lab flasks. A few
years later, Patricia Hunt, a geneticist at Case Western Reserve
University, discovered abnormalities in the chromosomes of
her lab mice. she eventually concluded that damaged poly-
carbonate cages were at fault.
In 1995, a developmental biologist named Frederick vom saal
stepped into the picture. A tenured professor at the University
of Missouri–Columbia, with funding from the national Insti-
tutes of Health, vom saal tested BPA to see how it interacted
with samples of human blood. He found that, because it
bypassed mechanisms that control the dose of hormones in the
body, its estrogenic effects were magnified. “We said, ‘Wow,
that’s bad. this stuff should be considered a lot more potent
than it is,’” vom saal recalls. He then fed small amounts of
BPA— 25,000 times lower than the ePA’s toxic threshold—to
