DOI: https://doi.org/10.55373/mjchem.v25i3.120

Keywords: Microplastics; freshwater sediments; polymer composition; Southeast Asia

Abstract

The presence of microplastics is a growing concern because of their ubiquity, persistence, ability to transmit environmental pollutants, and potential for bioaccumulation through food chains. Although ASEAN countries contribute significantly to the generation of marine litter globally, there has been limited research on microplastics in freshwater environments. This study aims to provide a comprehensive review of the existing state of knowledge regarding methodologies, occurrence levels, and the effects of microplastics on freshwater ecosystems in ASEAN countries. Our review focuses specifically on sediment matrices due to their long-term sink for microplastic pollution, with accumulation in sediment posing a risk to aquatic organisms and human health. Based on publications from 2018 to April 2022, 17 studies were examined. Sediment samples collected from rivers and aquaculture ponds revealed a range of microplastics concentrations between 4 and 66016 particles per kilogram. A comparative analysis was difficult because each study used non-standardised procedures and measurement units. Fibres are consistently found to be the most common shape, with black or blue microplastics being the most common colour across countries. Polyethylene or polypropylene was identified as the most common polymer type in the microplastic samples. The levels of microplastic in freshwater ecosystems have been linked to land use activities such as fishing, tourism, aquaculture, domestic wastewater, and industries. The high accumulation of microplastics in freshwater has been linked to the ingestion by fish species and gastropods. Future research should seek to standardise microplastic collection, extraction, and quality control methodologies to effectively quantify and assess the amounts of microplastic pollution for monitoring purposes, allowing for more comprehensive comparisons and evaluation for risk assessments.