By Ariel Schwartz

Bisphenol-A (BPA), an estrogen-mimicking compound found in plastic, store receipts, soup cans, water bottles, and other products, is potentially toxic. That has been drilled into our heads so much over the past few years that companies have scrambled to remove the compound from their products. Next time you're in the grocery store, count the products that proudly proclaim they're BPA-free. There's just one problem. Bisphenol-S (BPS), the so-called safe alternative to BPA, disrupts estrogen hormones in disturbingly similar ways to BPA. The safe alternative isn't so safe after all.

In a paper recently published in Environmental Health Perspectives, researchers from the University of Texas examined the effect of BPS in rats, where they found that "BPS can induce rapid non-genomic signaling in estrogen-responsive pituitary cells at low (femtomolar-picomolar) concentrations." In other words, BPS can mimic the body's estrogen hormones.

This shouldn't be all that surprising--BPS is basically the same shape and size as BPA, with just one difference: one of the linking chemicals in the middle of the molecule is a sulfur. "When molecules are exactly the same shape, you suspect them of acting on the same receptors," explains Cheryl Watson, co-author of the paper and a professor of biochemistry and molecular biology at the University of Texas Medical Branch. And yet, manufacturers started using BPS as a BPA replacement without knowing whether it was harmful.

Part of the reasoning was that BPS doesn't leak out of plastic as much as BPA--but it doesn't matter. Says Watson: "The problem is that hormones and things that mimic hormones are so potent that if you have just tiny amounts of them they still cause these responses."

We only know for sure that BPS is used in thermal paper products--like receipts--but it's possible that manufacturers are using it in other items now labeled BPA-free. In a study conducted by the New York State Department of Health, 97% of urine samples taken from Albany, NY residents contained BPS. Clearly, we're all being exposed to it somehow.

It's hard to say exactly how BPS affects human health; it's new enough that extensive studies haven't been done. It stands to reason, though, that it acts similarly to BPA, which has been linked to diabetes, asthma, issues with neurodevelopment, obesity, and more. Watson says that she is is "suspicious" of BPS's potential to cause similar effects as BPA.

If there's one lesson to take out of all this, it's that chemicals need to be analyzed for toxicity before they go into our products, not after. TiPED, a tool developed by a team of chemists and biologists (including Watson), will make it easier for chemists and manufacturers to do that--as long as they want to, that is.

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