Microplastics (MPs) are an emerging pollutant in the aquatic environment, and this has gradually been recognized in the Asian region. This systematic review study, using the Scopus database, provides an insightful understanding of the spatial distribution of scientific studies on MPs in freshwater conducted across the Asian region, utilized sampling methods, and a detailed assessment of the effects of MPs on different biotic components in freshwater ecosystems, with special focus on its potential risks on human health. The results of this review indicate that research on microplastics in Asia has gained attention since 2014, with a significant increase in the number of studies in 2018, and the number of scientific studies quadrupled in 2021 compared to 2018. Results indicated that despite a significant amount of research has been conducted in many Asian countries, they were not distributed evenly, as multiple studies selected specific rivers and lakes. Additionally, around two-thirds of all the papers focused their studies in China, followed by India and South Korea. It was also found that most of the studies focused primarily on reporting the occurrence levels of MPs in freshwater systems, such as water and sediments, and aquatic organisms, with a lack of studies investigating the human intake of MPs and their potential risks to human health. Notably, comparing the results is a challenge because diverse sampling, separation, and identification methods were applied to estimate MPs. This review study suggests that further research on the dynamics and transport of microplastics in biota and humans is needed, as Asia is a major consumer of seafood products and contributes significantly to the generation of plastic litter in the marine environment. Moreover, this review study revealed that only a few studies extended their discussions to policies and governance aspects of MPs. This implies the need for further research on policy and governance frameworks to address this emerging water pollutant more holistically.

Although environmental sustainability provides a foundation for maintaining economic and social sustainability, it is often neglected in favor of economic sustainability. Ameliorating water impairment is costly, and policymakers do not always prioritize this problem because its economic benefits are often intangible. This study explored the potential economic value for Tokyo’s regional economy of past improvements in the water quality of its rivers. Transitioning the rivers from their previous role as sewage drainage pipes to venues for spending leisure time created economic incentives in the local economy. An input-output analysis showed that in 1985, the inland navigation sector in the Sumida River generated 1.5 times the economic output by increasing demand. While this impact decreased to 1.3 times in 2005, the results clearly indicate that the regional economy can generate amenity values by improving the environmental quality. This study provides useful information to guide policymakers in allocating the budget for environmental management. In particular, it allows them to envision possible development plans to promote the livelihood of urban residents as well as understand the linkage between the environment and the economy.