WASHINGTON — Conflicting claims by separate BPA exposure studies are adding fuel the fire in the continuing saga of bisphenol A.
Findings by Cincinnati Cancer Center researchers published in PLOS ONE say small amounts of BPA in men's urine could be a cancer marker, making it the first study to claim that low-dose BPA may cause cancer development in the prostate.
In the study, published in early March, researchers assessed the prostate-specific antigen of 60 urology patients using urine samples. Higher levels of BPA were found in prostate cancer patients than in non-prostate cancer patients, and the difference was more significant in patients younger than 65.
Principle investigator Shuk-mei Ho, director of the Cincinnati Cancer Center, and professor at the University of Cincinnati College of Medicine, said human exposure to BPA is a common occurrence and while animal studies have shown that BPA contributes to development of prostate cancer, human data is scarce.
“We examined the centrosome profile of prostate cancer cells treated with BPA and found that treatment with BPA increased the number of cells with abnormal centrosomes,” Ho said in a news release. “All of these findings reveal a previously unknown relationship between BPA exposure and prostate cancer and suggest a mechanism underlying the role of BPA in cellular transformation and disease progression. With this insight, we hope to further investigate ways we can decrease exposures to potentially cancerous-causing chemicals in every day products and substances and reduce the onset of prostate cancer in men.”
The American Chemistry Council, however, says the UC study is flawed and misleading because it is based on a misunderstanding about how BPA is processed in the human body.
“The fundamental flaw in this report is the authors' complete misunderstanding of important analysis from the U.S. Centers for Disease Control and Prevention (CDC) on interpretation of BPA exposure measurements from single urinary spot samples. Because BPA is processed quickly in the body and eliminated, measuring BPA levels at one point in time provides essentially no information about BPA levels at an earlier time period,” said Steven Hentges of ACC's Polycarbonate/BPA Global Group via email. “In direct contrast, the authors suggest that a single urine sample collected from study participants when prostate cancer is diagnosed could represent their exposures when prostate cancer initiated and developed, which likely would have been many decades earlier. This suggestion is absolutely contrary to the analysis from CDC and, accordingly, this study has no capability to establish a cause-and-effect relationship from the reported statistical associations.”
BPA, which is a feedstock for polycarbonate and epoxy, has been the subject of hundreds of studies, some of which suggest a link with adverse health effects while others exonerate it.
In fact, another BPA study by the U.S. Food and Drug Administration and the National Toxicology Program at the National Institutes of Health, released weeks before the UC study, found that low doses of BPA had no effect on the health of rats.
While rats exposed in the womb and as newborns to the two highest doses of BPA had lower body weights, abnormal female reproductive development and altered hormone levels, there were no such effects when the rats were exposed to the low doses that humans are routinely exposed to.
Researchers exposed rats to BPA a few days after conception and continued through sexual maturity. Doses ranged from about 70 times the amount that Americans typically get through their diet to millions of times that amount. Even when rats got more than 70,000 times what a typical American ingests, there was no change in body weight, reproductive organs or hormone levels, the scientists reported. It took exposures millions of times higher than what humans typically receive to cause adverse effects like lower body weights, abnormal reproductive development or altered hormone levels, the study said.
The research is part of a two-year FDA project — funded by the FDA and the National Institutes of Health — to determine the toxicity of BPA, which is critical to setting any future regulations on its use in food products. A group of academics from several universities working with the FDA will be conducting more studies over the next year.