Source Apportionment and Health Risk Analysis of Microplastics in Water and Sediment in Aluu River

Aquatic ecosystems in rapidly urbanizing regions are increasingly threatened by emerging contaminants such as microplastics which pose significant ecological and human health risks due to their persistence, bioaccumulation potential, and toxicity. Rivers serving as sources of domestic water, fishing, and agriculture are particularly vulnerable to these pollutants.  This study aimed at the source apportionment, and potential ecological and human health risks of selected microplastics in surface water and sediment of the Aluu River. The specific objective were to quantify and characterize microplastic contamination, determine the sources of these contaminants and the health risks associated with exposure to microplastics. Surface water and sediment samples were collected from multiple locations along the Aluu River using standard sampling protocols. Microplastics were extracted, quantified, and polymer types identified using standard density separation and spectroscopic techniques. Source apportionment was conducted using principal component analysis (PCA), while ecological and human health risk assessments were performed using hazard quotient (HQ) and cancer risk (CR) models. Microplastic analysis identified five predominant polymers: polyvinyl chloride (PVC), polystyrene (PS), polyethylene (PE), polyurethane (PU), and polypropylene (PP) with higher cumulative concentrations in sediments (up to 26.96 µg/g) than in surface water. Risk assessment showed varying non-cancer hazard quotients (HQ) across all locations, with polyurethane and polyvinyl chloride contributing the most to potential health risks in both matrices. Cancer risk (CR) values for these polymers ranged from 5.3 × 10⁻⁵ to 1.42 × 10⁻⁴, approaching or exceeding acceptable limits. The findings demonstrate significant contamination of the Aluu River by microplastics with sediment acting as a major sink for these pollutants. The dominance of high-risk polymers, coupled with elevated health risk indices, indicates potential long-term ecological degradation and serious public health concerns for populations dependent on the river. Continuous environmental monitoring, strict regulation of industrial discharges, improved waste management practices, and public awareness initiatives are strongly recommended.