BPA "analogues" BPS and BPF can disrupt thyroid function in aquatic organisms, and may even be more potent in this regard than BPA, according to a study by scientists in South Korea.
The finding will increase concerns about the growing trend of manufacturers substituting BPA in their products for these compounds, which are structurally similar at the molecular level, but are much less well understood in terms of toxicity.
Sangwoo Lee, a postdoctoral researcher at the Korea Institute of Toxicology, led the team, which was affiliated with Seoul National University, the CRI Global Institute of Toxicology and Eulji University.
They tested the substances on zebrafish embryos and larva to investigate effects on thyroid function, an indicator of endocrine disruption.
BPS and BPF both caused significant increases in thyroid hormones levels. Furthermore, BPF caused increases in levels of hormone T4 at exposure levels that were lower than those for BPA.
The overall picture, however, was complex. BPZ caused decreases in levels of T4 and another hormone, T3. Meanwhile, despite causing similar thyroid effects, the impact on gene transcription was subtly different for BPS compared with BPA and BPF, suggesting different modes of action.
"Our findings suggest that BPF and BPS might not be safer alternatives to BPA in terms of thyroid hormone disruption," the scientists conclude in their paper, published in Chemosphere.
"Thyroid hormones play a essential role in various physiological processes, such as development, growth, reproduction and energy metabolism," Dr Lee told Chemical Watch. "They regulate the basal metabolic rate, protein synthesis and neural maturation. Thyroid hormones act on nearly every cell in our body."
An Echa market survey published last year found that EU paper manufacturers were increasingly substituting BPA with BPS in thermal paper.
Echa and EU member states identified BPA as an SVHC for endocrine disruption in the environment in 2017, a decision that was strongly opposed by trade association Plastics Europe.
BPS is currently under evaluation by the Belgian competent authority, which requested further exposure data from the registrants in 2016.