Bisphenol A alternatives continuously contribute to the endocrine disruption in cetaceans

The bans on bisphenol A (BPA) have facilitated the widespread use of BPA alternatives and shifted environmental contamination profiles of bisphenols (BPs). However, the continued reports of toxicities of emerging BPA al-ternatives have raised questions about whether the shifting profiles are contributed to mitigate BPs-mediated endocrine-disruption effects (EDEs). Cetaceans are commonly used as the ideal sentinel species for monitoring marine pollutants of concern and determining potential health effects, but far less is known about BP loads and BPs-mediated EDEs in cetaceans. Here we measured the hepatic concentrations of six BPs in eight stranded cetacean species (n = 41) in the South China Sea, between 2007 and 2020. The large-bodied whales generally showed higher n-ary sumation BPs concentrations than the small-bodied dolphins. In Indo-Pacific finless porpoises (Neo-phocaena phocaenoides) (n = 33), BPA concentrations first increased (2007-2014) and then decreased (2014-2020), while n-ary sumation BPAlternatives concentrations increased from 2007 to 2020. It appears that the alternatives gradually replaced BPA, probably due to the BPA-related bans in China. In order to examine the hormone disruption of BPA and its alternatives in finless porpoises, five blubber hormones (cortisol, progesterone, testosterone, triiodothyronine and tetraiodothyronine), which are proven to be validated endocrine biomarkers, were measured in 21 samples. Tetraiodothyronine, testosterone, and cortisol were significantly and positively correlated with BPA and its alternatives, suggesting that the interference of endocrine hormone homeostasis may continue to occur despite the changes of BP profiles in finless porpoises. This is the first investigation of the relationship between hormone and BP concentrations in cetaceans and represents a substantial advance in un-derstanding BPs-mediated endocrine effects on cetaceans.

Automated summary

The bans on BPA have led to the use of BPA alternatives and changed the environmental contamination of BPs. However, concerns have been raised about the toxicities of the emerging BPA alternatives and their effects on endocrine disruption. This study measured the concentrations of six BPs in stranded cetaceans in the South China Sea and found that large whales had higher BPs concentrations compared to small dolphins. The study also revealed a shift in BPs profiles and the continued disruption of endocrine hormones in finless porpoises.