Long-Term Monitoring of Polybrominated Diphenyl Ethers (PBDEs) in Indo-Pacific Humpback Dolphins (Sousa chinensis) from the Pearl River Estuary Reveals High Risks for Calves due to Maternal Exposure

Abstract

Although many studies have documented the wide occurrence of polybrominated diphenyl ethers (PBDEs) in cetaceans, little evidence exists regarding the detrimental effects of PBDE exposure on calf death rates for freeranging cetaceans. This study analyzed life-history-associated PBDE bioaccumulation patterns in 128 stranding Indo-Pacific humpback dolphin (Sousa chinensis) samples over an 18-year timespan from the Pearl River Estuary (PRE). In comparison to the records of PBDE levels in cetaceans worldwide, the median levels of PBDEs (median = 10600 ng g −1 lw, range = 721−50900 ng g −1 lw) in all samples were the highest to date. One-way analysis of variance (ANOVA) showed that adult males (median = 16100 ng g −1 lw, range = 4070−50900 ng g −1 lw) and calves (12000 ng g −1 lw, range = 1250−35300 ng g −1 lw) both had the highest levels of PBDEs compared to the rest of the age/sex groups (p < 0.05). Concentrations of PBDEs in noncalves significantly decreased over the studied period, while those in calves had a slightly increasing trend, which may be due to different exposure routes via fish or milk, respectively. A significant and positive relationship was found between annual calf stranding death rates and body-length-adjusted PBDE concentrations in calves (r = 0.62, p < 0.05), suggesting that maternal exposure of calves to elevated levels of PBDEs may have contributed to the high annual stranding death rates of calves in the last two decades.

Endocrine-Disrupting Chemical Exposure Induces Adverse Effects on the Population Dynamics of the Indo-Pacific Humpback Dolphin

“…58 Stranded dolphins reveal high levels of various pollutants, with EDC levels notably elevated on a global scale. 10,18,19,33 EDC contaminants are identified as one of the most critical stressors contributing to the decline of the PRE humpback dolphin population. 15,21 3.2.…”

“…The characteristics of all pollutants, such as chemical composition, distribution patterns, and particularly concentration levels, were extracted from previous research. ,− ,− Notably, this analysis excluded only a small portion of trace elements, the concentrations of which in the liver were analyzed according to a previous study. , All sample treatment and instrumental methods followed established procedures detailed in the Supporting Information. In brief, liver samples for trace element, AP, BP, PFAS, and TC analysis and blubber for DDTs, PBDEs, and PCBs underwent various treatment methods, including freeze-drying, grinding, acid digestion, solvent extraction, chromatographic purification, and instrumental analysis using mass spectrometry or chromatography.…”

“…Furthermore, there is a significant and positive correlation between annual calf stranding death rates and PBDE concentrations in calves. 19 Despite a general decrease in overall concentrations, traditional contaminants such as PBDEs still have significant effects on the population. PBDEs pose a health risk that goes beyond simple quantities, as they appear to affect specific age groups differently.…”

“…One of the most significant threats to this population arises from the accumulation of pollutants. Significant concentrations of various EDCs, including polybrominated diphenyl ethers (PBDEs), bisphenols (BPs), alkylphenols (APs), per- and polyfluoroalkyl substances (PFASs), polychlorinated biphenyls (PCBs), triclosan, dichlorodiphenyltrichloroethane (DDT), Cr, and As, have been detected in PRE humpback dolphins, surpassing global averages. − Although there are assumed correlations between EDCs and reproductive toxicity, immunotoxicity, developmental toxicity, and neurotoxicity, ,, there are limited empirical studies that explicitly address the impacts on this humpback dolphin population.…”

Bioaccumulation and Potential Endocrine Disruption Risk of Legacy and Emerging Organophosphate Esters in Cetaceans from the Northern South China Sea

“…In particular, the northern SCS (NSCS) along South China has long been regarded as a significant hotspot for anthropogenically sourced pollutants . Until now, high concentrations of organic pollutants (OCs), such as dichlorodiphenyltrichloroethanes (DDTs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), alternative halogenated flame retardants (AHFRs), and perfluoroalkyl substances (PFASs), have been detected in the NSCS cetaceans. − These OCs have been shown to potentially adversely affect the NSCS cetaceans, including disease susceptibility, lipid metabolism disorder, and reproductive and developmental toxicity. − While OPEs, as emerging alternatives to legacy BFRs, have been widely detected in various environmental and biological samples in the NSCS, such as seawater, sediment, air, plankton, bivalve mollusks, crabs, coral, and fish, ,, limited information is available regarding the extent of OPE contamination and potential endocrine-disrupting effects in the NSCS cetaceans.…”