Cetaceans as Bioindicators to Assess Alkylphenol Exposure and Hormone-Disrupting Effects in the South China Sea

Abstract

Alkylphenols (APs) represent one of the highest exposure levels among endocrine disrupting chemicals (EDCs) in the South China Sea (SCS) due to their extensive use as plastic additives. The concerns about EDCs, including APs, have been reiterated since the surge in plastic waste from the COVID-19 response, but far less is known about the response of AP loadings in the SCS to emerging public policies and activities, including the COVID-19 pandemic. Here, we used cetaceans as bioindicators for monitoring two major APs, 4-nonylphenol (4-NP) and 4tert-octylphenol (4-t-OP), in nine stranded cetacean species (n = 110) in the SCS between 2004 and 2021. Prior to the COVID-19, APs loads showed decreasing temporal trends for finless porpoises and humpback dolphins, most likely due to China's restrictions on AP use or a shift in dominant prey species. Unexpectedly, AP loads continued to decline after the COVID-19 outbreak, probably due to a temporal-lag response of marine AP fluxes to the pandemic. The health risk assessments based on hormone biomarkers and toxicity thresholds suggest the potential adverse effects of APs on cetaceans, while recent declines in APs, though limited, may mitigate the detrimental impacts.

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

“…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. Effects of EDCs on Endocrine Homeostasis.…”

“…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.…”

“…Sex hormones were differentiated by sex, resulting in a total of 7 hormones used. The characteristics of individual hormones, including chemical composition, distribution patterns, and particularly concentration levels, were extracted from previous research. , Details of the pretreatment method, instrumental analysis, interassay, intra-assay, and extraction efficiency were shown in previous studies; , in brief, the seven hormones were measured using enzyme immunoassay methods.…”

“…90 The determination of hepatic levels of APs in the PRE humpback dolphins revealed comparable profiles. 21 The observed decreasing trends in AP concentrations may potentially mitigate adverse impacts on the population, indicating a shift toward a state of moderate importance. However, it is essential to consider the potential temporal-lag response of AP variation in dolphins after the COVID-19 outbreak.…”

“…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.…”