Lab experiments provide another source of evidence supporting the
endocrine disruption hypothesis. Medical doctors Ana Soto and Carlos
Sonnenschein spent months tracing the source of the problem when their
experiment on multiplication of breast cancer cells went awry. The cells
were multiplying beyond reason. Ultimately, the two determined that an
estrogenic chemical was leaching into the contents of the plastic
container from the plastic itself. This substance had induced the cells'
proliferation.
By accident, Stanford University researchers found that bisphenol-A, an
estrogen mimic, leached from lab flasks made of polycarbonate plastic,
which is the same kind that is used in many consumer products such as
bottled water jugs. A research team at University of Granada in Spain
found this estrogen mimic in a variety of canned foods, including corn,
artichokes, and peas. The likely source: biologically active plastic
coatings inside the cans, used to prevent contamination of food by the
metal container.
Other lab researchers, looking at the exposure of rats and mice to
endocrine disruptors, are finding plenty to ponder. A University of
Wisconsin team reported in 1990 that a single, tiny dose of dioxin given
to a female rat during a critical point in pregnancy damaged her male
offspring's reproductive system. EPA toxicologists conducted experiments
exposing female rats during pregnancy to vinclozolin, a synthetic
fungicide used on fruit. The rats' offspring that were genetically male
were born with female traits, including vaginal sacs, no penises, and
nipples. This fungicide was acting as a male hormone-blocker. It bound to
the testosterone receptor and prevented the natural male hormone from
directing normal development. The same team of toxicologists discovered
only recently that DDE, a persistent breakdown product of DDT found in
almost all living tissue, behaves in the same manner.