Bisphenol A (BPA), a chemical used to harden plastics, has been used since the 1960s to make a number of consumer goods such as bottles and cans. In the past several years, potential health risks associated with the chemical have come to the fore.
"There is a lot of evidence associating daily exposure to a slew of events in humans from behavioral issues in children to metabolism to malformations in organs when they develop," said Maricel Maffini, a senior scientist with the Natural Resource Defense Council's (NRDC) health team. "If the exposure occurs to a specific window of the susceptibility during developnent, the impact is greater."
In 2010, the U.S. Food and Drug Administration (FDA) issued a report identifying possible hazards to fetuses, infants and young children, later requiring that BPA be removed from all baby bottles and infant formula.
Many scientists have been studying the effects of BPA exposure, including Gail Prins, professor of physiology at the University of Illinois at Chicago. In 2006, her lab found that exposed rats had a heightened sensitivity to developing hormone-driven cancers.
Her latest study – released today in the journal Endocrinology – found similar results in human tissues.
To mimic the fetal development of the prostate, Prins implanted mice with human prostate stem cells from healthy donors. For two weeks before the structure reached maturity, her team then fed the mice BPA at levels that pregnant women are typically exposed.
"When the prostate structure was mature, we initiated prostate carcinogenesis, and what we found was that transplants that had been exposed to BPA were much more susceptible to hormone-triggered cancer," Prins said.
A third of the tissues had either pre-cancerous lesions or prostate cancer, compared to only 13 percent in the oil-fed control group. In another group where the stem cells were exposed to BPA before implantation and again as they produced the prostate tissue in the mice, the prevalence of pre-cancerous lesions or cancer rose to 45 percent.
"This was rather unequivocal proof that the stem cell is a direct target for BPA, at least in the prostate," Prins said. She added that she might expect to see similar responses in other estrogen-targeted organs.
Prins was quick to point out that she doesn't claim BPA is driving the cancer itself. "We don't have absolute proof of that," she said. "We believe that BPA is reprogramming the stem cells and leading to heightened susceptibility to cancer as the tissues age."
NRDC's Maffini explained that while the changes to organs by BPA may not be initially observed, "those effects in the normal development of an organ are manifested years later when, for instance, after puberty, when the normal hormones start kicking in, the organs do not respond in a normal way."
Maffini also noted that because of the way hormones operate, very small amounts of BPA exposure can have an impact.
"Our concern about BPA is that it's such a high-volume chemical that we just do not know where it is," Prins said. "I would support regulations to make BPA in products more transparent so we know which products have BPA in it. I would like to get it out of my life and I can't."
The most common presence of BPA is in packaging such as water bottles and soup cans. But even people who avoid such packaging are still found to have BPA in their systems.
One study out of the University of Washington last year suggested that our food – rather than its packaging – could also be contaminated with BPA, possibly from manufacturing and processing.
Those researchers gave one group of families instructions for avoiding BPA exposure. The other group got a five-day catered diet of local, fresh, organic food that was not prepared, cooked or stored in plastic containers. Unexpectedly, the scientists found that the families on the catered diet had increased levels of BPA.
"In the absence of regulation to reduce phthalate and BPA concentrations in food production, it may be difficult to develop effective interventions that are feasible in the general population," the study read.
In dealing with BPA exposure, Prins said she would like to see three things: more transparency about which products it's in, government encouragement of more innovation and funding for alternative products, and more robust testing before products go out to market.
"We know that BPA is harmful and I would like to see it replaced, but I don't want to see it replaced by other harmful chemicals," Prins said.
