Integrated Risk Assessment of Microplastic Pollution in the Langat River (Malaysia) Combining Surface Water Sampling and Physicochemical Characterization

The Langat River is a significant river basin in Southeast Asia, providing a vital water source to the densely populated region of the West Coast of Peninsular Malaysia. Unfortunately, the ecosystem of this river is highly polluted, resulting from mud flooding and overflows of industrial and domestic discharge. An assessment of microplastic contamination was conducted by designating six sampling stations, including seawater, estuarine, and freshwater regions. The concentration of microplastics varied from 181 to 4,157 items/L, with an average value of 2,012 items/L. Among the explanatory variables, turbidity was found to be the most influential factor determining microplastic abundance, the majority being transparent colours, fragment-shaped, and measuring 10–1000 µm in size. The microplastics’ surface showed cracks, pit holes, and adherence of particles such as diatoms and bacteria. The polymers found were mainly polyethylene and polypropylene. Risk indices were used to evaluate the ecological risk of the microplastics, which indicated a minor risk level for large microplastics (LMPs) and an extreme danger risk level for small microplastics (SMPs). These findings provide a valuable baseline for assessing the environmental risk of microplastics in tropical rivers across Southeast Asia. This holds significance in understanding the potential ecological threats posed by the dynamics of microplastic quantity and size.