Studies link chemicals to genital, breast
Researchers have reported for the first time that they have found a
highly significant link between human exposure to chemicals used in
consumer products and adverse changes in the genitals of baby boys.
The sons whose mothers' urine contained higher levels of phthalates,
a family of compounds used to soften vinyl and other plastics, were
more likely to show the physical changes, according to the
University of Rochester study released Thursday.
A second study, released Wednesday, looked at another chemical,
bisphenol A, and found that pregnant lab animals exposed to very low
levels of it produced offspring with impaired mammary-gland
development. The exposure levels in the study, conducted by
researchers at the Tufts University School of Medicine, were 2,000
times lower than the Environment Protection Agency's safe dose for
The EPA and the National Institutes of Health contributed funds for
the studies to learn more about possible ill health effects from
these industrial chemicals, which are produced in billions of pounds
In low levels, neither is illegal in the United States, but the
California Legislature is considering two separate bills that would
place curbs on the chemicals.
The legislation is opposed by representatives of the chemical-
manufacturing industry, who criticized the new studies Thursday,
saying they don't document a link to testicular or breast cancer in
Bisphenol A has been used for decades in tough polycarbonate
plastic. Polycarbonate plastic makes up the hard, brittle drinking
water bottles, which may be clear or tinted, sold under the name of
Nalgene and other brands, as well as baby bottles and tableware. The
chemical is also used in dental sealants, medical devices and in the
resin lining of most food cans.
Phthalates are used in soft vinyl products and some perfumes,
shampoos, soaps, makeup, pesticides, pill coatings and paints. Two
forms, DBP and DEHP, are listed as reproductive toxicants and
carcinogens by the state EPA, and the European Union has banned both
in cosmetics. The chemical has been found at low levels in milk,
drinking water and household dust.
Lead author of the phthalates study, Dr. Shanna H. Swan, professor
in obstetrics and gynecology at the University of Rochester School
of Medicine and Dentistry, launched her study based on previous
In clinical settings in Los Angeles, Minneapolis and Columbia, Mo.,
researchers examined 134 babies ages 3 months to 24 months,
assessing the development of male genitals and the distance between
the anus and the genitals.
In animals, the "ano-genital" distance has served as an important
marker, associated with immediate physiological changes in the
reproductive system, as well as later changes at puberty and
adulthood, including alterations in behavior.
In the study, published in Environmental Health Perspectives, the
researchers sent the urine from 85 of the pregnant mothers to the
Centers for Disease Control in Atlanta for testing of phthalates.
The researchers found that the boys' ano-genital distance was
significantly associated with the level of metabolites, or breakdown
products, of four commonly used phthalates in their mothers' urine.
"These changes are seen at phthalate levels below those found in
one- quarter of the female population of the United States,'' Swan
said at a telephone press conference.
Twenty-one percent of the boys with short ano-genital distances had
incomplete testicular descent, compared to 8 percent of other boys,
and a short ano-genital distance was significantly correlated with a
The strongest associations were seen when the mother was exposed to
high levels of multiple phthalates. Eleven of the 12 boys with the
highest exposure to these phthalates had a short ano-genital
Swan said the study's sample was relatively small but the results
"highly significant,'' indicating a need for additional study with a
larger body of subjects. The researchers also want to follow the 134
boys to adulthood.
Marian Stanley, manager of the Phthalate Esters Panel, an industry
group, said, "The authors are not reporting any negative health
effect on the male reproductive system.'' The ano-genital distance
"has no known significance, and is in fact a biomarker of exposure
only.'' The distance could be a natural variability, she said.
In the bisphenol A study, published in the journal Endocrinology,
Tufts University School of Medicine researchers said they used
extremely low levels of the chemical, yet still found changes in
patterns of mammary-gland development at the time of puberty in the
The researchers said the changes in the mammary glands in the lab
animals when exposed to bisphenol A were consistent with changes
that in humans are associated with a higher risk of breast cancer,
such as an increase in the number of "terminal end buds'' in the
Steve Hentges, a spokesman for the American Plastics Council, said
the study only hypothesizes that mammary gland problems in rodents
would portend breast cancer in humans.
Because the EPA's safe-dose is based on oral exposure to humans, it
can't be compared to the level given to the lab animals, Hentges
said, which get their doses by inoculation.