A synthesis of human health and ecological risk assessment indicators for microplastics in Nigerian water systems

Microplastics contaminate water systems globally, posing risks to human and ecological health. This review synthesizes evidence from peer-reviewed studies (2021-2025) that report health, ecological, or pollution risk indices for microplastics in Nigerian waters. Studies from Nigeria's six geopolitical zones were included alongside international studies for comparison of methodological approaches and polymer patterns. Concentrations are highest in surface waters (1.5-705 particles/L) and lowest in bottled water (1.4-44.6 particles/L). Health risks are consistently higher for children than adults; treated water and groundwater present medium risk for children. Ecological risks are high in several surface waters. Polyethylene, polypropylene, and polyethylene terephthalate are the dominant polymers. Methodological limitations include inconsistent risk indices, neglect of co-contaminants, and limited attention to vulnerable populations. Research coverage is uneven, with the Northeast and Northcentral underrepresented. Polymer composition mirrors global patterns, but Nigerian risk assessments are less diverse in methodology. The findings highlight the need for harmonized methods, expanded monitoring, and policy interventions aligned with Sustainable Development Goals 3, 6, 12, and 14 to protect water quality and public health in Nigeria.