A chemical found in many products labeled "BPA-free" can produce many of the same or worse health problems as the original chemical, including hyperactivity and heart arrhythmia, according to a pair of studies recently presented at the joint meeting of the International Society of Endocrinology and the Endocrine Society in Chicago.
BPS, touted as a safe alternative to BPA, may be just as harmful to the developing brain," said Deborah Kurrasch of the University of Calgary, lead researcher on one of the studies. "Society needs to put more pressure on policymakers to eliminate all bisphenol compounds from manufacturing processes.
The "safer" alternative is not so safe
Bisphenol A, or BPA, is a widely used chemical that is a known endocrine disruptor and has been linked to health problems as diverse as cancer, heart disease and stroke.obesityhyperactivity and reproductive problems.
Growing concern about the health effects of BPA has led many manufacturers to offer "BPA-free" products. Yet many - but not all - of these products rely on a closely related chemical, bisphenol S (BPS).
BPS is one of the substitutes used in BPA-free products," said Hong-Sheng Wang of the University of Cincinnati, lead researcher of the second study. "He is involved in the safety of BPA-free products. BPA analogues - such as BPS, which is one of them - have not been tested for safety in humans.
BPS disrupts multiple hormones
In the first study, Kurrasch and colleagues found that zebrafish that were exposed to BPS became hyperactive in a manner similar to those exposed to BPA.
The study was designed to simulate a prenatal chemical exposure, as would occur in pregnant women exposed to BPA or BPS. Researchers exposed zebrafish embryos to similar levels of BPA found in the Oldman River in Alberta, a major source of drinking water. We then counted the number of neurons in the brain.
The researchers found that fish exposed to BPA had 170% more neurons at the time of neuronal birth than fish that were not exposed to chemicals. Fish exposed to equivalent concentrations of BPS had 240% more. In addition, fish exposed to both BPA and BPS demonstrated greater hyperactive behavior (as determined by motion tracking software) than fish in unexposed control groups.
The second study, which Wang called, "one of the first evaluations of BPS with effect in primary mammalian cells or organs,"
found that BPS produces arrhythmia - heart rhythm abnormalities - in a similar way to BPA.
The researchers exposed about 50 rats to a dose of 1 nanomole of BPS, roughly equivalent to the concentrations that previous studies have found in human urine. The hearts of the rats were stimulated with catecholamine hormone to mimic a natural stress response, and then BPS was delivered into the arteries and heart. A group of 30 control rats was treated with catecholamine, but not with BPS.
The researchers found that the hearts of female rats (but not male rats) exposed to BPS showed an increased heart rate (ventricular tachycardia) and extra heartbeats. This problem seems to occur because of abnormal calcium cycling which is similar to that caused by BPA.
When the researchers blocked estrogen receptors in female rats, the BPS-induced arrhythmia calmed, confirming an estrogen-like role for BPS, as well as BPA.
Notably, the Calgary researchers found that BPA, and possibly BPS as well, may disrupt hormones through pathways other than those related to estrogen. In the zebrafish study, BPA mimics testosterone, a predominantly male sex hormone.
Wang's summary: "Our results call into question the safety of BPA-free products containing BPS," he said. "BPS and other BPA analogs need to be evaluated before further use by humans. "