Assessment of Microplastic Contamination and Associated Health Risk in Ajiwa Reservoir Katsina, Nigeria

Abstract

Microplastic pollution in freshwater reservoirs poses significant ecological and public health concerns, particularly in semi-arid regions where surface water is a primary resource. This study investigated microplastic contamination and associated health risks in Ajiwa Reservoir, Katsina State, Nigeria, over six months (April–September 2025), covering dry and rainy seasons. Water, sediment, and fish tissue samples (Clarias gariepinus and Oreochromis niloticus) were collected from nine stations and analyzed for microplastic abundance, distribution, and polymer composition using wet peroxide oxidation, density separation, and FTIR-ATR spectroscopy. Health risk was quantified through contamination factor, estimated daily intake, and cumulative risk index. Physico-chemical parameters (pH: 9.3–10.7; temperature: 26–34°C; turbidity: 163.3–416.7 NTU) exceeded WHO limits. Microplastics were detected in all matrices, with water recording the highest concentration at 775 particles/L. Rayon/Cellulose fibers dominated across all months, linked to textile wastewater, while Polyethylene and Polystyrene appeared exclusively during the rainy season, driven by surface runoff. Seasonal differences in polymer distribution were statistically significant (p < 0.001). Health risk assessment revealed a very high cumulative risk from drinking water (CRI = 0.503), while fish consumption posed low risk. These findings establish baseline data on microplastic contamination in Ajiwa Reservoir, underscoring an urgent public health threat requiring immediate intervention, including advanced water treatment, regular monitoring, improved sewage management, and runoff control measures.