Microplastic pollution across Bangladesh: A review of current evidence and research gaps

Pollution caused by microplastics (MP) has become an emerging environmental and public health concern in Bangladesh, which has a large number of people per square mile as well as an extensive system of rivers. This paper reviews a selection of the latest research regarding MP, including frequency and causes, routes through and methods of analysis, and environmental and human health consequences, for MP found in water, land and food in Bangladesh. MP is found in a wide variety of compartments including rivers, estuaries, coastal sediments, lakes, aquatic organisms, salt, milk, rice, wheat flour etc. The concentrations reported are extremely variable depending on the matrix, such as up to 350 ± 69.22 items/m³ reported in river water, and MPs found in 58.93% of commercially important fish species sampled across the country, with an average concentration of 118.33 ± 26.81 items/kg in estuarine sediment. Fibers and fragments are found as dominant MP types with polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC) as the commonly identified polymer types. Sources include municipal solid waste, textile effluents, and industrial discharge with riverine systems acting as the major transport route of MPs into the Bay of Bengal. Several methods have been employed in various studies such as density separation, wet peroxide oxidation digestion and ATR-FTIR spectroscopy. However, it has become difficult to compare data across studies as a result of varied analytical methodologies used. The knowledge gap still continues to exist in trophic transfer pathways of MPs, long term chronic effects on human health, seasonality of MP flow and terrestrial exposure pathways. This review emphasizes the urgent need for systematic monitoring guidelines, holistic multi-matrix risk assessment and evidence-based policy interventions for alleviating the pervasive threat of MPs to the various environmental matrices in Bangladesh.