Exposure of female fetuses to bisphenol A (BPA), an artificial estrogenic compound widely used in plastics for food containers, may likely increase their breast cancer risk in adulthood, according to a new study published Dec. 8 in the online edition of Reproductive Toxicology. The study confirmed early findings that BPA may be implicated in the development of breast cancer.
The study led by Ana M. Soto, professor of anatomy and cellular biology at Tufts University School of Medicine, in Boston and colleagues found that female rats whose mothers were exposed to bisphenol A during pregnancy were significantly more likely to develop breast cancer than those without being exposed to the compound in mothers' womb.
For the study, Soto and colleagues exposed pregnant rats to bisphenol A at a range of doses from 2.5 to 1,000 micrograms per kg of body weight per day (
µg/kg/day). About 25 percent of the mammary ducts had precancerous lesions in rats exposed to the chemical in their mother's womb when they reached their puberty (50 days old), a rate that is three to four times higher than that in controls, according to the study.
The researchers found that exposure of fetuses to any tested dose of bisphenol A resulted in an increased level of lesions and at the dose of 250
µg/kg/day caused cancerous lesions in the mammary glands of one-third of the rats.
Bisphenol A is widely used in the manufacture of polycarbonate plastics and epoxy resins for many types of food and beverage containers including baby bottles and canned food linings. Dental composites can also contain the chemical. Analysis of urine samples showed 95 percent of people have been contaminated with this toxic chemical.
According to a news story by the American Chemical Society, many people are exposed to about 2.5
µg/kg/day. Because mammary gland development in rats is similar to that in humans, "bisphenol A could be one factor causing the increase in breast cancer incidence over the past 50 years," Soto was quoted as saying.
Early studies have led to discoveries that bisphenol A may increase growth of human breast cancer cells and it may be also implicated in development of other diseases such as prostate cancer and brain tissue damages. Scott Belcher, Ph. D. and colleagues from University of Cincinnati reported in two articles in the December 2005 edition of the journal Endocrinology that bisphenol A shows negative effects in brain tissue at as low as 0.25 parts per trillion.
Early studies of nonsteroidal estrogen diethylstilbestrol (DES) show that those whose mothers received the chemical during pregnancies between 1948 and 1971were two to three times more likely to develop breast cancer. Bisphenol A is chemically similar to DES, suggesting that it may increase the risk of breast cancer as well, according to Soto, cited by the American Chemical Society.
"What is important to note is that Soto's research is not a one-shot finding," Frederick vom Saal, professor of biology at the University of Missouri, was quoted as saying. "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 results of Soto's study suggest that the current exposure limit set by the U.S. Environmental Protection Agency has put the American women at risk of breast cancer. The EPA's limit is 50
µg/kg/day for bisphenol A.