Regrettable, if predictable: Bisphenol S mimics estrogen just like its better-studied cousin, bisphenol A

Richard Denison, Ph.D., is a Senior Scientist.

A rule of thumb in chemistry is that chemicals that look alike will more often than not act alike.  (If it looks like a duck … .)  Indeed, when chemical companies are faced with testing requirements for one of their chemicals, they routinely argue that they should be allowed to submit test data on a structurally related chemical instead. 

So when it was revealed that companies making products (such as thermal receipt paper) that contain the estrogen-mimicking compound bisphenol A (BPA) were switching to another chemical called bisphenol S (BPS), many scientists’ eyebrows quickly arched. 

Take a look at these two chemical structures:

It doesn’t take a chemist to see they’re close cousins.  The one on the left is BPA, and the one on the right is BPS.  If there’s reason to worry about exposure to one, odds are there’s also reason to worry about exposure to the other. 

Now a new peer-reviewed paper in Environmental Health Perspectives (Viňas and Watson, 2013) confirms suspicions that BPS, too, is an estrogen-mimicking chemical.  (Two earlier papers published by Japanese researchers in 2002 and 2005 found similar results.)

The new paper reports that BPS, like BPA, acts at low doses and, at least in studies conducted on cultured cells, alters cell proliferation and accelerates cell death at doses similar to those to which the human population is exposed.  (If anything, exposure to BPS may be even more widespread than exposure to BPA:  testing of urine samples collected from residents of Albany, NY found BPS in 97% of the samples, compared to a 93% occurrence for BPA in CDC biomonitoring.)

A very informative news article on the new findings is available here.

Add this example to the long list of so-called “regrettable substitutions” – or the more vernacular “whack-a-mole” – whereby companies under scrutiny for their use of one toxic chemical rush to use a less well-studied or less-regulated but closely related chemical.  Often, as in the case of the BPA to BPS switcheroo for “BPA-free” thermal paper made by Appleton Paper, this is accompanied by prominent marketing claims that the product is now free of the offending substance.

So what’s the solution to avoiding these “regrettable substitutions”?  I delved into that question in an earlier blog post that discussed two other egregious such cases.

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