Fatty Acid Profiles Linked to Organohalogen Exposure in Cetaceans from the Northern South China Sea

Increasing evidence suggests that organohalogen contaminants (OHCs) could disrupt lipid metabolism in organisms, prompting consideration of fatty acids (FAs) as biological tools for assessing chemical stress in biological systems. This study examined 87 OHCs and 32 FAs in two sentinel cetacean species─Indo-Pacific humpback dolphins (n = 128) and Indo-Pacific finless porpoises (n = 26)─from the northern South China Sea (NSCS), a global hotspot for OHCs. Our results revealed higher OHC levels in these cetaceans than global averages. We identified 347 significant correlations between 79 OHCs and 32 FAs, including 32 associations with long-chain n-3 polyunsaturated fatty acids, which are critical for cetacean health. Furthermore, 45 significant correlations were found between OHC levels and desaturated enzyme activities/lipogenic indexes, suggesting that OHCs may disrupt lipid metabolism in these cetaceans. Polybrominated diphenyl ethers as legacy flame retardants were major contributors to the OHC–FA relationships. Moreover, alternative halogenated flame retardants, as PBDE substitutes, may similarly impact FA metabolism, raising concerns regarding their safety. Our findings support the potential use of FAs as bioindicators for evaluating OHC exposure risks in cetaceans. Future research is needed to elucidate the mechanisms and consequences of these OHC exposure-associated lipid-disrupting effects occurring in the NSCS cetaceans.