In a recent study by Chen et al, published in PLOS Genetics, the chemical Bisphenol-S (BPS) which is an increasingly common replacement for Bisphenol-A (BPA) in many plastic products, have been found to be harmful to the reproductive system. BPA has been used to make certain plastics and resins since the 1960s and it was detected in polycarbonate plastics. These type of plastics are often used in containers for food storage and beverages, such as water bottles and also in a lot of products for children and babies like sippy cups, nursing bottles, plates and bowls. BPA has also been detected in epoxy resins which are used to coat the inside of metal products such as, food cans bottle tops and also in water supply lines.
Concern against BPA was raised due to its estrogen mimicking, hormone-like properties. The primary source of exposure for most people is through the diet by leaking into food from protective internal epoxy resin coatings of canned foods and also from consumer products such as plastic (polycarbonate) tableware, water bottles, baby bottles and food storage containers. It has been shown that the temperature of the plasticware is important for how much BPA that is leaking into the food and therefore one advise is to not microwave polycarbonate plastic food containers.
Due to these concerns regarding BPA, many countries banned BPA in several products, like baby bottles or food containers for children under the age of 3. However, several of the compounds that substituted BPA such as BPS, share a high degree of structural similarity to BPA, suggesting that these substitutes may interact and disrupt similar reproductive and developmental pathways. BPS can now be found in “BPA free products” and because BPA and BPS have similar physical properties there is an increased interest in finding out if BPS could have similar effects on human health as BPA?
Chen et al., working at UCLA raised the question whether BPS could have any harmful effects on reproduction similar to BPA’s. In this study, C. elegans which is a roundworm (nematode), a model organism commonly used for genetic and developmental studies, were exposed to different concentrations of BPA and BPS that approximated the levels of BPA/BPS found in humans. The worms were followed through the duration of their reproductive periods and their fertility was measured. The study show that worms exposed to either BPA or BPS, or a combination of the two, had decreased fertility. The researchers found that BPS caused severe reproductive defects including embryonic lethality. In addition, it was also shown that BPS affected fertility negatively in lower doses than BPA, suggesting that BPS might be even more damaging to the reproductive system than BPA.
It was indicated that some of these effects were partly achieved via mechanisms distinct from BPA which may raise new concerns about the safety of BPA-subsitutes as well as combinations of BPA and the alternatives. Of course, one can always question whether these results in worm are relevant for us humans, but biologically we share many of the genes and pathways that are important for the reproductive processes, and this study showed that several of these processes were damaged by BPS. Therefore there is a great need for comprehensive testing of BPA-substitutes in particular and coordinated safety assessments of multiple substitutes in general, before we use these chemicals as replacements of known harmful compounds.
The pictures in this blog post was borrowed from:
Fig 1. from Chen et al, PLOS Genetics