OCCURRENCE, DISTRIBUTION AND HEALTH IMPLICATION OF MICROPLASTICS IN NILE TILAPIA (Oreochromis niloticus) FROM AJIWA RESERVOIR, KATSINA STATE, NIGERIA

Microplastic (MP) contamination in freshwater ecosystems poses emerging risks to food security and public health, yet data from African inland fisheries remain scarce. This study investigated the occurrence, distribution, and human health implications of MPs in Oreochromis niloticus from Ajiwa Reservoir, Katsina State, Nigeria, a critical protein source for local communities. Thirty fish were analyzed for MPs in gills, gastrointestinal tract (GIT), and muscle using 10% KOH digestion, Nile Blue staining, and Fourier Transform Infrared Spectroscopy (FTIR) for polymer confirmation. Estimated Daily Intake (EDI) was modeled to assess human exposure risk. MPs were detected in 100% of tissues examined, with highest abundance in gills > GIT > muscle. Fragments were the dominant morphology across all organs. FTIR identified polyamide (PA) as the most prevalent polymer, likely derived from degraded synthetic fishing gear, followed by polypropylene (PP), polyethylene terephthalate (PET), and polyvinyl chloride (PVC). Human health risk assessment revealed significantly higher EDI values for children than adults for all tissues, indicating greater vulnerability of children to potential carcinogenic and endocrine-disrupting effects from MP-contaminated fish consumption. This ubiquitous contamination of a commercially vital species highlights an urgent threat to both aquatic ecosystem integrity and regional food safety. Results demonstrate the utility of O. niloticus as a bioindicator for freshwater MP pollution and underscore the need for immediate policy interventions, waste management strategies, and long-term monitoring to mitigate plastic inflow into Ajiwa Reservoir and protect consumer health.