Characterization, Risk, and Pathway of Microplastics in Coastal Areas of the Bay of Bengal: A Systematic Review and Quantitative Synthesis

Microplastics (MPs) have become a global concern, as they are widespread in aquatic environments and pose ecological risk, which threatens both marine and freshwater organisms. This study seeks to provide a comparative and comprehensive illustration of MP pollution in the water and sediments of the Bay of Bengal coastal areas, including islands, estuaries, and beaches. It also highlights associated risks and pathways of microplastics. The analysis is based on data reported in peer-reviewed publications from the past decade. The study found microplastics in water varied widely, from 2.35 to 263,000 MPs/m3, while sediments ranged between 1 and 815 MPs/kg. The highest levels were observed at the Thoothukudi coast in water samples and the Muttukadu backwater estuary in sediments. Transparent and white colored particles were reported as dominant in 53% and 65% studies on water and sediment, respectively, which were largely linked to packaging items, plastic bags, and other disposable materials. Microplastics sizes <1 mm were the most prevalent in the study area, which may result from the extensive degradation of plastic debris. Fibers and fragments were the dominant shapes in both water and sediment that may come from synthetic textiles, fishing gear, packaging materials, etc. Polyethylene was the most frequently reported polymer, with packaging materials and single-use plastics being possible sources, followed by polypropylene, polyamide, polystyrene, and PET. Statistical analyses, including Pearson’s correlation, PCA, and HCA, showed correlations among shapes, colors, sizes, and polymers, reflecting multiple pollution sources. Risk assessments through PLI, PHI, and ERI indices revealed that most sites exceeded extreme pollution thresholds, highlighting serious ecological threats to biodiversity and human health. Therefore, integrated regional strategies are urgently needed to mitigate this issue.