Los Angeles Times  [Printer-friendly version]
June 1, 2006


Bisphenol A, found in baby bottles and microwave cookware, permanently
altered genes in newborn lab rats, a study finds.

[Rachel's introduction: Important new research has linked prostate
cancer to bisphenol A (BPA), a common chemical that leaches out of
plastic food and drink containers. The chemical industry releases 6
billion pounds of BPA each year into products and waste. The new work
reveals that small amounts of BPA can permanently change male animals
in the womb, making it more likely that they will develop prostate
cancer later in life. Prostate cancer has been steadily increasing
among human males in recent decades, tracking the rise in use of BPA.]

By Marla Cone

Linking prostate cancer to a widespread industrial compound,
scientists have found that exposure to a chemical that leaks from
plastic causes genetic changes in animals' developing prostate glands
that are precursors of the most common form of cancer in males.

The chemical, bisphenol A, or BPA, is used in the manufacture of hard,
polycarbonate plastic for baby bottles, microwave cookware and other
consumer goods, and it has been detected in nearly every human body

Scientists and health experts have theorized for more than a decade
that chemicals in the environment and in consumer products mimic
estrogens and may be contributing to male and female reproductive
diseases, particularly prostate cancer.

The new study of laboratory rats suggests that prostate cancer, which
usually strikes men over 50, may develop when BPA and other estrogen-
like, man-made chemicals pass through a pregnant woman's womb and
alter the genes of a growing prostate in the fetus. One in every six
men develops prostate cancer, a rate that has increased over the last
30 years.

Researchers at the University of Illinois at Chicago and the
University of Cincinnati exposed newborn rats to low doses of BPA and
found the structure of genes in their prostate cells was permanently
altered, a process of reprogramming in early life that promotes cancer
in adulthood. One key gene was switched on, producing too much of a
cell-damaging enzyme that has been detected in cancerous prostate
cells but not normal cells.

Also, as the rats aged, they were more likely than unexposed animals
to develop precancerous lesions, or cellular damage, in the prostate
that have been known for years to lead to prostate cancer in humans.
"The present findings provide the first evidence of a direct link
between developmental low-dose bisphenol A... and carcinogenesis of
the prostate gland," according to the researchers. Results from the
team, led by Gail S. Prins, associate professor of andrology at the
University of Illinois at Chicago, and Shuk-mei Ho, chair of
environmental health at the University of Cincinnati, are reported
today in the journal Cancer Research.

Exposure to the chemical "may provide a fetal basis for this adult
disease" in humans, the report said.

Dr. Rebecca Sokol, a USC medical school professor who specializes in
male hormone research, called the study "cutting-edge." She said it
added to a growing body of research, called epigenetics, that
suggested environmental chemicals could alter how DNA sequences turned
on and off in a fetus, permanently imprinting the genes of a child and
sensitizing him or her to disease in adulthood.

Such findings could have major implications for human disease and
could, in part, explain why the prostate cancer rate has surged. BPA,
used for about half a century, is a key building block in the
manufacture of polycarbonate plastic and ranks among the world's most
widely used industrial chemicals.

Prins, Ho and other researchers cautioned that the study was conducted
on rats, which sometimes reacted differently to chemicals than humans
did. Replicating the work in humans is virtually impossible because 50
or more years usually pass from exposure in the womb to the onset of
prostate cancer.

"You can't say from the results of this study that this is going to
affect humans," Sokol said. But she said the results were in line with
previous animal research that showed chemicals could induce genetic
changes that altered sperm and other reproductive functions. The
prostate gland, which develops in human males when they are fetuses,
is extremely sensitive to natural estrogen. As a result, scientists
have long theorized that prostate cancer could be increasing in men
because of their exposure to estrogen-like chemicals in the womb.

Unlike carcinogenic chemicals that can cause profound damage to DNA,
BPA seems to inflict subtle changes that are passed from one
generation to the next, Sokol said.

"The big focus today is whether or not environmental toxicants will
induce heritable changes in gene function.... In other words, is there
something that happens to alter genes without actually altering the
genetic code?" asked Sokol, who studies the effects of chemicals on
sperm. "This [new study] is cutting-edge research in this field and
the role that environmental toxicants may play in altering the
genetics of exposed offspring."

Steve Hentges, a representative of the American Plastics Council,
called it "fascinating research, a good piece of research" that should
be studied further. But he said the "real question is what does this
mean for human health," because there are too many limitations in the
study for it to apply to humans.

"No one has actually observed prostate cancer after any treatment with
BPA," he said.

The study's authors said the animals developed the precancerous
lesions and genetic changes when exposed to low concentrations of the
chemical similar to the amounts found in human blood and fetuses. But
Hentges said the rats were injected with doses 100 to 1,000 times
higher than the most recent human testing done by federal officials in

In recent years, evidence has been building that BPA causes changes in
the hormones and reproductive tracts of male and female animals. Lower
sperm counts, decreased testosterone and enlarged prostates were
reported in male animals, and early puberty and disrupted hormonal
cycles in female animals.

Of more than 100 studies that examined low doses of the chemical, 94
funded by government agencies found harmful effects in lab animals,
and 11 funded by industry reported no effects, according to a 2005
review by Frederick vom Saal of the University of Missouri.
Polycarbonate, which cannot be manufactured without BPA, is a clear
and shatter-free plastic. In addition to beverage bottles, utensils
and food packaging, it is used in automobiles, medical equipment and
compact discs.

Small amounts of the chemical can leach from plastic containers,
especially when heated, cleaned with harsh detergents or exposed to
acidic foods or drinks. It also is used in children's dental sealants
and as a resin lining metal food cans.

Last year, the California Legislature considered a bill, introduced by
Assemblywoman Wilma Chan (D-Oakland), that would have banned
children's products that contained BPA or other plastic compounds
called phthalates. It died in an Assembly committee after sparking a
scientific debate and intense lobbying by the plastics industry.