Tracing microplastic footprints in Bangladesh’s largest baors (Oxbow Lake): First insights into characterization, ecological risks, and implications for aquatic health

Microplastics (MPs) contamination has emerged as a pressing global environmental challenge, yet freshwater ecosystems remain critically understudied compared to marine systems. Addressing this gap, the present study provides the first comprehensive assessment of MP occurrence, characterization, and ecological risks across water, sediment, and biota in Bangladesh's Oxbow Lakes (Baors). Samples from three major lakes-Bukbhara, Marjat, and Jhanpa-revealed alarming MP concentrations: 36.0-356.0 items/L in water, 398.0-2763.0 items/kg in sediment, and 3.0-24.0 items/individual in biota. Fibers dominated the morphology, with multi-colored MPs detected in all matrices. Polypropylene (PP) and polyethylene (PE) were the primary polymers, likely originating from household waste, agricultural runoff, and fishing activities. Pollution indices (PLI >1; Nemerow Pollution Index (NPI) indicating moderate to severe levels) confirmed substantial contamination, while polymer-based risk assessments highlighted ecological threats ranging from low (Grade-I) to very high (Grade-V). Biota hazard indices further indicated species-specific risks, with O. mossambicus showing the highest MP accumulation in muscle tissues and A. grammepomus the lowest. Importantly, dietary exposure analysis revealed that children ingest MPs at rates 3.67 times higher than adults via biota consumption. This pioneering study quantifies MP pollution in Bangladesh's freshwater ecosystems and underscores its ecological and human health implications, calling for urgent mitigation strategies to safeguard aquatic biodiversity and public health.