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Chemical & Engineering News, Dec. 6, 2006

 

*BISPHENOL-A MAY TRIGGER HUMAN BREAST CANCER*

 

*Study in rats provides strongest case yet against common environmental

chemical*

 

By Bette Hileman

 

A new study finds the strongest evidence yet for the hypothesis that

widespread environmental exposure to bisphenol A during fetal life

causes breast cancer in adult women. The research, led by Ana M.

Soto <http://www.tufts.edu/sackler/facultyIntros/sotoA.html

<http://www.tufts.edu/sackler/facultyIntros/sotoA.html>>, professor of

anatomy and cellular biology at Tufts University

School of Medicine <http://www.tufts.edu/med/

<http://www.tufts.edu/med/>>, in Boston, was published Dec.

6 in the online

edition of Reproductive Toxicology (DOI: 10.1016/j.reprotox.2006.10.0

02

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5e1110f051a3c60ae8acc09>>).

 

Soto and her colleagues exposed pregnant rats to bisphenol A at doses

ranging from 2.5 to 1,000 micrograms per kg of body weight per day. By

the time the pups exposed at the lowest dose reached the equivalent of

puberty (50 days old), about 25% of their mammary ducts had

precancerous lesions, a proportion three to four times higher than

among the nonexposed controls. Mammary ducts from all other exposure

groups showed elevated levels of lesions. Cancerous lesions were found

in the mammary glands of one-third of the rats exposed to 250

micrograms/kg/day.

 

Bisphenol A, a known estrogenic compound, is ubiquitous in the

environment. Many people receive exposures of about 2.5

micrograms/kg/day, and mammary gland development in rats and humans is

very similar. Therefore, Soto says, " bisphenol A could be one factor

causing the increase in breast cancer incidence over the past 50

years. "

 

Bisphenol A is used in the manufacture of polycarbonate plastics and

epoxy resins. It is found in many food and beverage containers,

including baby bottles. It is also found in canned food linings and

dental composites, and it leaches from all of these products. In one

study, Soto notes, urine samples from 95% of the human subjects

contained the chemical.

 

According to Soto, a large body of previous research suggests

bisphenol A might cause breast cancer. One study shows that the

daughters of women who took the potent synthetic nonsteroidal estrogen

diethylstilbestrol (DES) during their pregnancies between 1948 and

1971 have 2.5 times the normal incidence of breast cancer. Bisphenol

A, which is structurally similar to DES, may act by a similar

mechanism, she explains.

 

" What is important to note is that Soto's research is not a one-shot

finding, " says Frederick vom Saal, professor of biology at the

University of Missouri. " It follows five years of research

demonstrating precancerous changes in the mammary glands of mice with

prenatal bisphenol A exposure. Now, Soto has switched to the rat,

which is considered a much better animal model for studying human

carcinogenesis. "

 

The Environmental Protection Agency has set a safe human intake dose

of 50 micrograms/kg/day for bisphenol A. " On the basis of the effects

observed in recent studies, this seems to be an unsafe level, " Soto

says.

 

Copyright 2006 American Chemical Society