Bisphenol-A (BPA), an industrial chemical used in some plastics that has been linked to birth defects and developmental problems with fetuses and infants, has already been banned in baby products by the FDA in 2012. Companies are now advertising “BPA-free” plastic that contains the purportedly much safer alternative Bisphenol-S (BPS). Yet researchers at the University of California, Los Angeles have recently demonstrated that BPS may be just as harmful as BPA by disrupting the reproductive system of animals and speeding up embryonic development.
“Our study shows that making plastic products with BPA alternatives does not necessarily leave them safer,” Nancy Wayne, a reproductive endocrinologist and professor of physiology at the David Geffen School of Medicine at UCLA, said. “Our findings are frightening — consider it the aquatic version of the canary in the coal mine.”
Wayne and her colleagues conducted experiments on BPS using zebrafish, because their transparent embryos would make it easier to witness cell growth as it occurs. They exposed the zebrafish to either low levels of BPA or BPS, equivalent to an amount found in polluted rivers. The team used fluorescent green protein tags to track the development of the reproductive endocrine brain cells, which control puberty and fertility. Changes in embryonic physiology occurred in as little as 25 hours after exposure.
“The embryos developed much faster than normal in the presence of BPA or BPS,” Wayne said. “Egg-hatching time accelerated, leading to premature birth.”
The researchers also found that the number of endocrine neurons increased by about 40 percent, suggesting that both BPA and BPS overstimulate the reproductive system. “Exposure to low levels of BPA had a significant impact on the embryos’ development of brain cells that control reproduction and the genes that control reproduction later in life,” Wayne added. “We saw many of these same effects with BPS found in BPA-free products. BPS is not harmless.”
The scientists found that both BPA and BPS act partly through both the estrogen system and the thyroid hormone system by mimicking the effects of each one. Wayne said, “Because of thyroid hormone’s important influence on brain development during gestation, our work holds important implications for general embryonic and fetal development, including in humans.”
In spite of these findings, a general consensus remains inconclusive. The American Chemistry Society released a statement raising questions about whether or not the research would be of any importance to humans.
“The relevance for human health of this limited study on zebrafish is unclear,” Wayne said. “The study examines effects of BPA and one alternative on zebrafish embryos in water. In contrast, we know humans are exposed to only trace levels of BPA through the diet. The U.S. Food and Drug Administration (FDA) responded recently to the question, ‘Is BPA safe?’ with one unambiguous word: ‘Yes.’”
Nevertheless, many researchers continue to claim that endocrine disrupting chemicals like BPA, and now BPS, may be contributing to the recent rise in premature human births and the early onset of puberty in the US, including the team at UCLA.
“I am not the first researcher to show that BPS is having effects on cellular systems,” Wayne explained in a press release citing prior research on the chemical. “Consumers should be cautious about the assumption that ‘BPA-free’ means a product is safe. If BPA is impacting a wide variety of animal species, then it’s likely to be affecting human health. Our study is the latest to help show this with BPA, and now with BPS.”
While the FDA has banned the use of BPA in bottles and children’s cups, it continues to be contained in an array of other plastic products, like water bottles, plastic containers and even contact and eyeglass lenses, CDs and ATM receipts. It is estimated that this year, the US and Europe will manufacture over 5 million tons of products containing BPA; this doesn’t even include products that contain BPS.
“This is a classic case of ‘regrettable substitution’ in which the replacement chemical is as toxic as the chemical it was replacing,” Sharima Rasanayagam, director of science for the Breast Cancer Fund, which tracks environmental causes of breast cancer, said. “The lack of transparency regarding the identity and safety of the chemicals used as BPA replacements makes it very difficult to assess the overall safety of the alternative.”