Phenyltins may pose a higher health risk to Indo-Pacific finless porpoises than butyltins

Organotin (OT) compounds are commonly used in antifouling paints, but can cause toxic effects in various marine organisms, including gastropods, amphibians, and teleosts. The effects of these chemicals on marine mammals remain largely unknown. We comprehensively investigated the accumulation patterns and health risks of six OTs in Indo-Pacific finless porpoises (Neophocaenaphocaenoides) from the Pearl River Estuary (PRE), China, from 2007 to 2020. Six OTs were detected in all the finless porpoise samples, with tributyltin (TPT) and dibutyltin (DBT) being the dominant chemicals in the liver and muscle, respectively. The mean hepatic concentration of TPT (516.1 ng g-1 wet weight) exceeded the levels reported for cetaceans from other regions. Despite the observed decreasing trends of butyltins (BTs) in recent years, which aligns with the global restriction of OT-based antifouling paints since 2008, phenyltins (PTs) have continued to increase in porpoise tissues, suggesting continued deposition of PTs in the PRE. In vitro, the tissue-relative concentrations of TPT, tributyltin, and DBTinduced lipid disruption by activating the finless porpoise peroxisome proliferator-activated receptor alpha/gamma (npPPAR alpha/gamma). In silico simulations further revealed a higher toxic potential of PTs than BTs on npPPAR alpha/gamma. Our results underscore the urgency for further monitoring and elimination of PTs in China.