Microplastic Contamination in the Fisheries Food Chain: Sources, Pathways, and Human Exposure Assessment in Lagos Lagoon

This research conducted a comprehensive assessment of microplastic contamination across the fisheries food chain in Lagos Lagoon, one of Nigeria's largest estuarine systems and a major source of fish for the Lagos metropolitan population. Despite growing global concern over microplastic pollution in aquatic food systems, a full food chain analysis from environmental source through to human dietary exposure has not been conducted for any Nigerian aquatic system. The study traced microplastics from lagoon water and sediment, through planktonic communities and invertebrates, to commercially important fish species and processed fish products sold in Lagos markets. Microplastic analysis was conducted using stereomicroscopy, micro-Fourier transform infrared spectroscopy for polymer characterisation, and scanning electron microscopy for surface characterisation. Probabilistic human exposure assessment was conducted using Monte Carlo simulation incorporating fish consumption survey data from 300 Lagos households. Results identified the lagoon surface water and sediment as heavily contaminated, with mean microplastic concentrations of 48 particles per litre and 1,240 particles per kilogram dry sediment. Fibre-type polyethylene and polypropylene microplastics dominated all matrices. Trophic transfer was confirmed, with accumulation factor coefficients increasing from zooplankton to small pelagic fish to predatory fish. The 95th percentile estimated human microplastic ingestion through fish consumption reached 1,180 particles per day in high-frequency fish consumers. The research delivers an original trophic transfer pathway model for microplastics in a West African estuarine fisheries system and provides evidence for regulatory action on plastic pollution sources affecting Lagos Lagoon fisheries. Keywords: microplastics, fisheries food chain, Lagos Lagoon, trophic transfer, human exposure