Contamination, potential sources, and risk assessment of microplastics in surface waters of two public bathing beaches along the Northern Bay of Bengal

Understanding microplastics (MPs) pollution and its associated risks in bathing beaches, particularly those characterized by heavy commercial trading, is essential for the protection of marine ecosystems and human health. Despite the global concern regarding MPs, contamination levels along the Bangladesh coast, especially on popular bathing beaches, remain largely unexplored. This study aimed to investigate the levels, characteristics, and associated risks of MPs at Patenga and Parki beaches along the Bay of Bengal coast. The results revealed that MPs concentrations ranged from 305.56 to 116.67 MPs/m³ at Patenga and from 250.00 to 83.33 MPs/m³ at Parki Beach, indicating significant differences in contamination levels between the two sites. The predominant characteristics of the MPs included violet coloration, fibrous structures, and sizes measuring less than 0.5 mm, with identified polymers such as PET, PP, PS, ABS, PE, and Nylon. The pollution load indexes (PLI) for both beaches exceeded 1, highlighting substantial risks to the marine ecosystem. The Coefficient of Microplastic Impact (CMPI) indicated varying degrees of impact, ranging from severe to minimal, while the polymeric risk evaluation (Hi) suggested considerable risks, particularly at Patenga. Furthermore, the MPs pollution risk index (PRI) values indicated a higher threat level at Patenga (H Patenga = 7.9) compared to Parki (H Parki = 1.9). The Microplastics Pollution Index (MPPI) further indicated a significant abundance of microplastics, with Patenga exhibiting higher levels than Parki. These findings led to the development of a conceptual model illustrating the sources and transport pathways of MPs, underscoring the urgent need for effective management strategies to mitigate MPs pollution and safeguard public health on these bathing beaches. • MP varied from 305.56 to 116.67 item/m 3 (Patenga) and 250.00–83.33 item/m 3 (Parki) beach. • Predominant shape was fibers (<0.5 mm) in water samples of bathing beaches. • FTIR confirmed six types of polymers including PET, PP, PS, ABS, PE, Nylon. • Risk indices, PLI, CMPI, Hi, PRI, MPPI revealed contamination severity and associated risks. • Results inform conceptual model depicting origin and transport path of microplastics.