Microplastic contamination in fish and surface water from Dhaleshwari river, Dhaka, Bangladesh

Abstract

Microplastic (MP) particles, widely acknowledged emerging contaminants are increasingly recognized as a threat to aquatic ecosystems, fish, and human health. This study investigated the abundance and characteristics of MPs in surface water and freshwater fish from the Dhaleshwari River, Bangladesh. A total of 42 samples were analyzed, including surface water samples (n = 12 from each of four sites) and fish gastrointestinal tract samples (n = 30; five individuals from each of six species). Microplastics were isolated from water and fish samples using wet peroxide oxidation and potassium hydroxide digestion methods, respectively, and identified under a stereo microscope. MPs were found in all samples with abundances ranged from 0.09 to 0.21 items mL⁻¹ in surface water and 1.6 to 4.2 items per fish species. There was no significant correlation between MPs ingestion and fish total length or body weight. Most of the MPs were fiber-shaped and tiny small (<1 mm). Fourier Transform Infrared Spectrophotometry (FT-IR) for polymer characterization identified polyethylene, nylon, and polystyrene as the major polymer types present in the river system. These findings revealed widespread MP contamination in the Dhaleshwari River and emphasize the need for further investigation to assess the impacts of microplastics on water quality, fish health, ecosystem functioning, and potential risks to human health. Bangladesh J. Zool. 54(1): 17-29, 2026