When purchasing a water bottle, a baby bottle, or other products that carry a “BPA-free” sticker, people assume they’re getting items made out of chemicals safer than bisphenol A.
But BPA’s supposedly benign replacement, bisphenol S, may not be so safe, according to a study published Tuesday in the journal Endocrinology.
Researchers at the University of California, Los Angeles, found BPS accelerated development of zebra-fish larvae exposed to the chemical, leading to premature births.
“Our findings are frightening,” said Nancy Wayne, the study’s lead author and a reproductive endocrinologist at UCLA’s David Geffen School of Medicine. “Consider it the aquatic version of the canary in the coal mine.”
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BPA is a chemical often added to plastic products to strengthen them. It’s a hormone disruptor that mimics the effects of estrogen and testosterone. More than a decade’s worth of research has linked BPA to reproductive development issues, early-onset puberty, and breast and prostate cancers. The Food and Drug Administration in 2012 banned BPA use in baby bottles and children’s cups, but the chemical is still used in products ranging from canned foods to cash register receipts.
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Wayne and fellow researchers exposed zebra fish to low levels of BPA and BPS—the same concentrations fish could encounter in polluted rivers—to see what impact the chemicals would have on genes and brain cells that control reproduction.
Apart from sharing about 80 percent of their genes with humans, zebra fish are good case studies for developmental effects because their embryos are transparent. That allowed researchers to watch in real time the effect the chemicals were having on the embryos. Within 25 hours of exposure, the team saw changes.
“Egg-hatching time accelerated, leading to premature birth,” Wayne said. “The embryos developed much faster than normal in the presence of BPA or BPS.”
Researchers also tracked the development of zebra-fish brain cells that control hormones that trigger puberty and fertility. They found the number of endocrine neurons increased up to 40 percent with exposure to the chemicals. The findings could help explain the rise in cases of premature puberty and reproduction-system issues in human populations.
Wayne, who studied BPA’s impact on embryos in 2008, said she was most surprised by how similarly the fish reacted to BPA and BPS.
“In 2008, we were kind of just starting to gather data on bisphenol A, but the research has accumulated, and the FDA is still dragging its feet on doing much about it,” she said. “We’ve raised a red flag here on how safe bisphenol S is, but the main issue is whether any endocrine-disrupting chemicals can be safe to use at any level—there’s just not enough research yet.”
The American Chemistry Council, the chemical industry’s largest trade organization, contends that the new study has little bearing on human health.
“The relevance for human health of this limited study on zebra fish is unclear,” the group said in a statement. “Many government bodies around the world have evaluated the scientific evidence on BPA and have clearly stated that BPA is safe for use.”
But most research done so far hasn’t studied what impacts endocrine disruptors such as BPA and BPS have on the development of organisms, says Maricel Maffini, a former senior scientist with the Natural Resources Defense Council, who is unaffiliated with the study.
“The development process is like a symphony—it’s a synchronization of chemical signals, neuron releases, and correct timing,” Maffini said. “This study highlights the fact that you can easily change and disrupt the process with small amounts of either chemical. If we’re going to continue to release this chemical into the environment, we need more testing like this to see how it affects developing organisms.”