Assessment of Microplastic Ingestion by Commercially Important Fish Species in Lagos Lagoon and Its Food Safety Implications

Microplastic pollution in Lagos Lagoon has been increasingly documented, yet the extent of microplastic ingestion by commercially important fish species and the associated food safety risks for consumers in South West Nigeria have not been empirically investigated. This study assesses the prevalence, abundance, morphology, and polymer identity of microplastics in the gastrointestinal tracts of four commercially important fish species from Lagos Lagoon: Chrysichthys nigrodigitatus, Oreochromis niloticus, Tilapia zillii, and Ethmalosa fimbriata. A total of 320 fish, 80 per species, were sampled from landing sites at Badore, Isale Eko, and Ijede over six months. Gastrointestinal tracts were dissected, and microplastics were extracted by wet peroxide oxidation, filtered, and characterised by stereomicroscopy and Fourier-transform infrared spectroscopy. Microplastics were detected in 68.4% of all fish examined, with significantly higher prevalence in Ethmalosa fimbriata (83%) compared to other species. Mean microplastic burden per fish ranged from 1.8 to 4.6 particles. Fibres were the dominant morphotype, and polyethylene terephthalate and nylon were the most frequently identified polymers. Estimated daily human microplastic exposure from consuming Lagos Lagoon fish was calculated under standard consumption scenarios. The study provides empirical data on microplastic ingestion in Lagos Lagoon fish and identifies specific food safety exposure pathways for urban consumers, recommending the inclusion of microplastic monitoring in Nigeria's National Food Safety Standards for fish and fishery products.

Keywords: microplastics, Lagos Lagoon, fish ingestion, food safety, FTIR