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CHICAGO -- A plasticizer commonly substituted for bisphenol A (BPA) may cause similar endocrine-disrupting effects as the original chemical, researchers reported here.
Early studies of bisphenol S (BPS) are showing effects on the heart and on the developing brain, two separate groups of researchers reported at the joint meeting of the Endocrine Society and the International Congress on Endocrinology (ICE/ENDO).
"BPA-free does not mean bisphenol-free," said Deborah Kurrasch, PhD, of the University of Calgary in Canada. "I'm not sure that's recognized in society."
The FDA has previously banned BPA in infant formula packaging, although manufacturers had largely dropped the chemical prior to the agency's action. However, the agency maintains that BPA is safe at the very low levels that occur in some foods -- although research has linked it to several disorders, including reproductive problems, obesity, and behavioral issues.
Still, companies have replaced BPA, most commonly with BPS, although none of the BPA analogs have been tested for safety in humans, Kurrasch said. Gathering evidence on the effects of BPS could take a long time, as was the case for BPA.
"We consider it more like climate change," Kurrasch said. "The evidence is pretty clear but it will be some time before we can convince the rest of the world."
Hong-Sheng Wang, PhD, of the University of Cincinnati, said that current "BPA-free" labels "imply better safety, but that safety has yet to be examined and established."
To get a better sense of the effects of BPS, Kurrasch and Wang studied zebrafish brains and rat hearts, respectively.
Kurrasch looked at zebrafish embryos during the second trimester, a crucial time for brain development, specifically, neuronal generation in the hypothalamus.
Developing embryos were exposed to a low dose of either BPA or BPS, and the researchers saw that neuronal birth increased during that time period for both bisphenol groups compared with typical zebrafish development.
Later on in life, these exposed fish were more hyperactive than those not exposed to BPS, the researchers said, suggesting BPA and BPS exposure could lead to altered brain connections that affect long-term behavior.
"BPS, termed as the 'safe alternative' of BPA-free products, is equally harmful to developing brains," they concluded, calling for a "continued societal push to eliminate all bisphenol analogs from consumer goods production."
To evaluate the effects of BPS on the heart, Wang and colleagues studied two groups of rat hearts, both of which were stimulated with catecholamine to mimic stress. Fifty of those hearts were also exposed to BPS, while 30 of those hearts were not.
They found that exposure to BPS rapidly increased heart rate and led to arrhythmias, but only in female rats. Male rats did not appear to be subjected to the same effects, although the reasons are unclear, Wang said.
He and his team also looked at individual myocytes and saw that BPS caused abnormal calcium handling. Specifically, it led to increased sarcoplasmic reticulum calcium leak and beat-to-beat calcium release and reuptake, which could be the mechanism by which female rats experience arrhythmias when exposed to BPS, he said.
Although clinical implications are unclear at this point, Kurrasch said consumers can take action to prevent exposure to BPS, which is particularly high in printed receipts.
"Just say 'No, thank you' if you don't need your receipts," she said.
Kurrasch and Wang disclosed no relevant relationships with industry.
Endocrine Society and the International Congress on EndocrinologySource Reference: Kinch CD, et al "Bisphenol A exposure induces precocious neurogenesis and hyperactivity by increasing local estrogen synthesis within the brain" ICE/ENDO 2014; Abstract OR18-1.
Endocrine Society and the International Congress on EndocrinologySource Reference: Gao X, et al "Evaluation of the rapid effects of bisphenol S (BPS) on the heart: Impact on arrythmogenesis and cardiac calcium healing" ICE/ENDO 2014; Abstract OR18-3.