Microplastics in Indian Freshwater Systems: Sources, Distribution, Characterization and Ecological Risks

Abstract

Microplastic (MP) pollution has emerged as a critical environmental issue in freshwater ecosystems, yet a comprehensive synthesis for Indian freshwater systems remains limited. This review compiles and critically evaluates published studies on the sources, distribution, physicochemical characteristics, and ecological risks of microplastics across rivers, lakes, reservoirs, and wetlands in India. Urban wastewater, industrial discharge, tourism activities, and agricultural runoff are identified as major sources of MP contamination. Reported MP concentrations vary widely among systems, with fibers dominating morphological composition, followed by fragments and films. Polymer analyses using Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy reveal that polypropylene (PP) and polyethylene (PE) are the most prevalent polymers, with additional contributions from polyethylene terephthalate (PET), PVC (Polyvinyl chloride), and polyamide linked to packaging materials, textiles, and fishing activities. Microplastics also function as vectors for heavy metals and plastic additives, enhancing their environmental persistence and toxicity. Evidence of MP ingestion and trophic transfer in fish and other aquatic organisms highlights potential implications for food web integrity and human exposure. Risk assessment indices including Pollution Load Index (PLI), Polymer Hazard Index (PHI), and Potential Ecological Risk Index (PERI) indicate increasing ecological risks in several freshwater systems, particularly in urbanized basins. Despite growing research, key knowledge gaps remain in nanoplastic detection, long-term monitoring, and human health risk assessment, emphasizing the need for standardized methodologies and integrated management strategies to mitigate microplastic pollution in Indian freshwater ecosystems.