Microplastic Pollution in the Urban Water Cycle: A Comprehensive Review

Microplastic contamination in aquatic systems in urban areas is a cause for concern due to its ability to move from one location to another. This review investigates microplastic levels across different aquatic environments and its potential transport through the urban water cycle. This study explores current research on the presence and pathways of microplastics movement within the water cycle. It includes a comprehensive bibliometric analysis that identifies publication trends, dominant research themes, influential journals, and leading contributing countries. It covers microplastic occurrence across various natural environments, including marine, river, lake, and groundwater systems, and extends into the built environment such as water treatment facilities, wastewater systems, bottled water, and drinking water distribution networks. Results indicate that microplastic levels vary within the urban water cycle, with concentrations differing widely depending on geography, type of infrastructure, and sampling methodology. Despite some removal efficiency during treatment processes, residual microplastics remain prevalent in effluents and drinking water, posing potential ecological and health risks. This study identifies that some of the major challenges in determining the fate and transport of microplastics are inconsistent sampling methods, lack of standardization, and limited understanding of long-term impacts. This paper also identifies the necessity of coordinated global strategies that integrate policy, technology, and public awareness to mitigate microplastic contamination in urban water systems.