Bisphenol S (BPS) is an organic compound with the formula . It has two phenol functional groups on either side of a sulfonyl group. It is commonly used in curing fast-drying epoxy resin adhesives. It is classified as a bisphenol, and a close molecular analog of bisphenol A (BPA). BPS differentiates from BPA by possessing a sulfone group as the central linker of the molecule instead of a dimethylmethylene group , which is the case of bisphenol A.
Use
BPS is used in curing fast-drying epoxy glues and as a corrosion inhibitor. It is also commonly used as a reactant in polymer reactions.
BPS has become increasingly common as a building block in polyethersulfone and some epoxies, following the public awareness that BPA has estrogen-mimicking properties, and widespread-belief that enough of it remains in the products to be dangerous. However, BPS may have comparable estrogenic effects to BPA. BPS is now used to a variety of common consumer products. In some cases, BPS is used where the legal prohibition on BPA allows products (esp. plastic containers) containing BPS to be labelled "BPA free". BPS also has the advantage of being more stable to heat and light than BPA.
To comply with restrictions and regulations on BPA due to its confirmed toxicity, manufacturers are gradually replacing BPA with other related compounds, mainly bisphenol S, as substitutes in industrial applications.
BPS is also used as an anticorrosive agent in epoxy glues. Chemically, BPS is being used as a reagent in polymer reactions. BPS has also been reported to occur in canned foodstuffs, such as tin cans.
In a 2015 study analyzing BPS in a variety of paper products worldwide, BPS was found in 100% of tickets, mailing envelopes, airplane boarding passes, and airplane luggage tags. In this study, very high concentrations of BPS were detected in thermal receipt samples collected from cities in the United States, Japan, Korea, and Vietnam. The BPS concentrations were large but varied greatly, from a few tens of nanograms per gram to several milligrams per gram. Nevertheless, concentrations of BPS used in thermal paper are usually lower compared to those of BPA. Finally, BPS can get into the human body through dermal absorption from handling banknotes.
Health effects
Cardiac effects
Although there is no direct link established between BPS and cardiac disease, it is thought that BPS may operate by a similar mechanism to BPA and could cause cardiac toxicity. In animal studies, BPS has been shown to hinder MI recovery, induce cardiac arrhythmias and cause cardiac developmental deformities. Rats exposed to high doses of BPS were reported to have increased risk of atherosclerosis (a significant risk factor in cardiac disease) due to BPS inducing synthesis of cholesterol in peripheral tissues.
Neurobehavioral effects
BPS has the potential to have an effect on a wide range of neurological functions. A recent study showed that exposure to BPS during pregnancy may disrupt thyroid hormone levels. These are important in foetal neurodevelopment and prenatal exposure to BPS has been linked to impaired psychomotor development in children. In a study using human embryonic stem cells, BPS was shown to cause a reduction in length of neurites in neuron-like cells. This disruption could lead to neurobehavioral problems such as ASD.
The mechanism of the neurological impact of BPS is thought to be related to its oestrogenic effect which can interfere in the levels and action of thyroid hormone, which is essential for normal development of the nervous system; it regulates migration and differentiation of neural cells, synaptogenesis and myelination.
Effects on obesity
It has been proposed that BPS has the potential to affect body weight, and several studies have found a correlation between exposure to bisphenols and increased body weight. This is thought to be due to an accumulation of lipids in adipocytes i.e. a build-up of fat in fat cells. It has also been suggested that BPS leads to the formation of new adipocytes as exposure to it increases the expression of related markers. A correlation between exposure to BPS before birth and being overweight has been found in mice, although this was only found when they were also fed a high fat diet.
The pathway through which BPS acts on cells to increase body weight is suggested to be different to the pathway through which BPA acts, even though they have very similar chemical structures.
Only one study has demonstrated a decrease in body weight after BPS exposure, and the affected mice quickly regained the weight they had lost.
