Microplastics as Carriers of Co-Occurring Pollutants in Freshwater Ecosystems: Mechanisms, Environmental Fate, and Ecotoxicological Risks

Microplastics are increasingly recognized as prevalent contaminants in freshwater ecosystems, where they interact with a wide range of co-occurring pollutants, including heavy metals, pesticides, pharmaceuticals, and persistent organic pollutants. Evidence indicates that microplastics can act as vectors, enhancing pollutant mobility and facilitating trophic transfer, while also modulating toxicity through synergistic or antagonistic effects. Ecotoxicological studies reveal adverse impacts on aquatic organisms, ranging from physiological stress and impaired reproduction to altered community dynamics, with implications for ecosystem functioning and human health. Despite growing knowledge, significant gaps remain in understanding long-term environmental behavior, standardized methodologies, and risk assessment frameworks. This review synthesizes current findings on microplastic–pollutant interactions in freshwater systems, highlights emerging ecotoxicological risks, and identifies critical research needs to inform effective management and policy interventions.