Biochemical and Molecular Toxicity of Microplastics in African Freshwater and Marine Systems: A Critical Review of Mechanisms, Biomarkers, and Research Gaps

Microplastics (MPs) are now among the most pervasive contaminants of global water bodies, driven by large-scale plastic mismanagement and industrial discharge. In Africa, MPs have been repeatedly detected in fish tissue, sediment, and surface water, most extensively in Nigeria and South Africa, yet the biochemical and molecular consequences of this contamination remain far less studied than its occurrence. This critical narrative review synthesizes January 2009 – August 2026 peer-reviewed literature on the biochemical toxicology of MPs in African aquatic systems, drawing on international mechanistic studies to interpret findings from the sparser African evidence base. It identifies four structural gaps that limit risk assessment in the region. First, the few African laboratory toxicity studies rely on short-term (typically 15-day), mg/L-range exposures to virgin, commercially sourced particles (polystyrene or polyethylene) rather than weathered, contaminant-loaded particles. Second, sampling, extraction and polymer-identification protocols are inconsistent. Third, nanoplastic, epigenetic and multi-omics approaches are rarely used. Fourth, research is concentrated in a handful of countries, leaving major freshwater systems unassessed. Evidence is extracted study by study and classified by evidence type, so that African experimental data, African field occurrence data and international mechanistic data are not conflated. Closing these gaps will require standardized analytical protocols, environmentally realistic and co-exposure study designs, regional biomonitoring networks built around indigenous sentinel species, and stronger integration of biochemical biomarkers into environmental policy . Fish are an important protein source in many African communities, but the human-health consequences of MP exposure in this setting remain unquantified.