When "Safer" Isn't Safe: Bisphenol-S and Bisphenol-A

Most of us try to be conscious of what foods and drinks we put into our bodies. However, are we always conscious of what we could be ingesting through the plastic in our water bottles? In 2012, the US Food and Drug Administration officially banned the ubiquitous chemical bisphenol-A (BPA), found in many types of plastic, from baby bottles due to being linked with estrogen mimicry, among other concerns such as harming brain and reproductive development in children and fetuses. For many, it was a sigh of relief as many BPA alternatives became available, from BPA-free canned food to water bottles to cash register receipts. However, a 2013 study performed by Cheryl Watson at the University of Texas at Galveston shows that its so-called “safer” replacement, bisphenol-S (BPS) could be just as harmful as its predecessor. Nearly 81-97% of Americans in these studies had significant levels of BPS in their urine. Watson discovered that even concentrations as minimal as one part per trillion can disrupt normal cell functioning and endocrine functions, leading to serious metabolic disorders like obesity and diabetes, as well as asthma, birth defects or even some forms of cancer. 

The structural similarities between BPA and BPS

Concerns about the presence of BPS in water bottles began to arise following this study, yet manufacturers still put “BPA-free” on the labels of their products and neglect to mention that their substitute has not been tested for the same problems BPA has been known to cause. Environmental Health Perspectives published a study in 2011 that stated nearly all of the 455 commercially available plastics leached estrogen-mimicking chemicals. Some independent scientists have attempted to address this claim by performing in vivo testing of these chemicals to prove their toxicity. A study from the University of Calgary studied brain development in zebra fish when dosed with BPS in similar concentrations to those found in a nearby river and found neuronal growth increasing by 170% in BPA-exposed fish and 240% for BPS-exposed fish. Based on the fishes’ erratic behavior and energy levels over time, the researchers concluded that increased neural growth could lead to hyperactivity. Because BPA and BPS are endocrine disruptors, these chemicals generate a U-shaped dose profile, in which very low doses promote activity but higher doses inhibit it. 

The U-shaped dose response profile seen in BPA and BPS toxicology testing

Past toxicity testing typically used a chemical that would have no detrimental effect below a certain dose and most tests were conducted using high doses until an adverse effect was seen. For BPS, however, a second threshold below that where similar or new adverse effects occur has been identified. These effects are associated typically with the endocrine system, which handles long-term processes like brain development, growth and metabolism. BPS has also been proven to block an estrogen receptor in female rats, which lead to the disruption of calcium channels, potentially causing heart arrhythmia in humans.

This knowledge of the dangers of BPS doesn’t seem to be stopping manufacturers from including this chemical in their products, and the majority of the problem lies in a lack of industry regulation. As of right now, there is no federal agency that tests the toxicity of new materials before they are allowed on the market, although continued studies and research is being conducted on the toxicity of BPS. Nevertheless, for the time being, we should all think twice before taking a swig out of a new plastic water bottle.

Posted by: Rebecca Quirie (C)