Marine mammals are sentinels of chemical exposure in the ocean, and per- and polyfluoroalkyl substances (PFAS) are toxic chemicals to marine life globally.  However, the impacts of PFASs on the health of Cetaceans in a subtropical water of the Beibu Gulf remains underrepresented. We quantified 37 PFAS in cetaceans—one calf Omura’s whale (Balaenoptera omurai; to our knowledge the first report of PFAS in this species) and three Indo-Pacific humpback dolphins (Sousa chinensis) spanning sex and age classes—to establish a regional baseline and evaluate tissue-specific burdens and risks. Legacy compounds dominated profiles, with perfluorooctane sulfonate (PFOS) prevailing across most tissues, while long-chain C9–C12 perfluorocarboxylic acids and the emerging replacement 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) contributed substantially. The intestine exhibited among the higher PFAS loads, highlighting a likely underappreciated toxicological compartment. Concentrations varied by species and life history: multiple legacy PFAS were higher in S. chinensis than in B. omurai; within S. chinensis, the juvenile exceeded adults, and the adult female exceeded the adult male. In a global context, PFAS burdens were generally low—one to two orders of magnitude below reports from hotspots such as the Pearl River Estuary and the Mediterranean. Hazard quotients for individual PFAS were below 1, yet HFPO-DA and PFO4DA posed risk levels comparable to perfluorooctanoic acid, warranting attention. These data fill a geographic and taxonomic gap, underscore the need to include gastrointestinal tissues in marine-mammal PFAS evaluations, and provide an evidence base for targeted monitoring and proportionate management aligned with SDGs 3 and 14.

Cetaceans,Balaenoptera omurai,Sousa chinensis,Emerging pollutants,Ecological risk