Bioaccumulation dynamics and trophic transfer of polychlorinated biphenyls in mud crabs ( <i>Scylla Paramamosain</i> ) – a multi-matrix assessment of water and sediment from Araromi Beach, Nigeria

Polychlorinated biphenyls (PCBs) remain persistent contaminants in tropical coastal ecosystems and pose potential risks to aquatic food webs and human health. PCB inputs at Araromi Beach likely originate from informal e-waste handling and artisanal fishing activities common to Nigeria's coastal communities. This study investigated the bioaccumulation dynamics and trophic transfer of PCBs in mud crabs, Scylla paramamosain, from Araromi Beach through a multi-matrix assessment of water, sediment and crab tissues. Nineteen PCB congeners were quantified using gas chromatography–mass spectrometry, and congener-specific bioaccumulation factors were calculated to evaluate matrix-to-organism transfer. Human health risks associated with crab consumption were assessed using toxic equivalency, lifetime average daily dose, lifetime cancer risk and hazard quotient metrics for adult and child exposure scenarios. Total PCB concentrations followed the hierarchy crab (2.09 ± 0.02 ppm) greater than sediment (0.89 ± 0.01 ppm) greater than water (0.10 ± 0.00 ppm), with significant differences observed among matrices. PCB180 exhibited the highest concentration in crab tissues (1.40 ± 0.00 ppm) and showed the greatest bioaccumulation potential relative to environmental media. Bioaccumulation patterns indicated preferential accumulation of highly chlorinated congeners, suggesting strong hydrophobic partitioning and trophic transfer potential. Human health risk assessment indicated elevated lifetime cancer risk values for crab consumers, with children exhibiting higher susceptibility than adults. These findings highlight the need for continuous monitoring of PCB contamination and the implementation of seafood safety management strategies in coastal environments.