Dynamics of Microfibers Discharged into the Urban and Suburban Environment

Microfibers (MFs), fibrous microplastics less than 5 mm, are recognized as ubiquitous in ecosystems. MFs adsorb hydrophobic persistent organic pollutants. Due to their fibrous form, MFs may adversely affect the human respiratory system. In terms of shape, their fibrous shape increases their specific surface area, but their minimum cross-sectional area is small. As a research case study, this chapter compares MF contamination in urban and suburban areas of Japan in East Asia. As a result, we found that the pollution of rivers and lakes in the ocean by MFs may occur via atmospheric fallout, although there are many point sources of sewage and road dust origin. The concentration of microplastics (MPs), including MFs, from atmospheric fallout in this study ranged from 190 to 5,800 pieces/m2/day in urban areas (Osaka City, Japan), particularly in densely populated areas. This concentration was found to be higher than in previous studies conducted in France and China. In suburban areas, the concentration of MPs was found to be extremely low, ranging from 0.18 to 1.2 pieces/m2/day (Otsu, Japan). The emission sources of MFs in this study would be road dust generated by vehicles and human clothing. Furthermore, the concentration of MFs was found to be higher in areas with greater human economic activity.