Microplastic Emissions from Domestic Laundry in China

Domestic laundry is a major source of microplastic fibers (MPFs), but national inventories rarely combine China-specific hand-washing behavior, spatially explicit wastewater treatment, and river-basin receptor allocation. We developed an ∼1 km × 1 km gridded model for household-generated synthetic textile fibers in China by integrating machine- and hand-washing shedding profiles, demographic and socioeconomic rasters, and 2,486 active wastewater treatment plants. We projected future original emissions to 2050 under five Shared Socioeconomic Pathway scenarios. In 2020, domestic laundry generated 21.3 million kg of MPFs (interquartile range: 13.8-31.1 million kg); wastewater treatment removed 47.53% of this mass, leaving 11.17 million kg (interquartile range: 7.18-16.17 million kg) entering the environment. Under the assumed fiber geometries, this post-treatment load corresponds to approximately 5.2 × 1015 to 1.0 × 1017 fibers. The top 15 river systems received 69.05% of post-treatment discharge. By 2050, national original generation is projected to reach 61.3-98.3 million kg yr-1, with the fastest relative growth in central and western provinces. These findings establish a spatiotemporal baseline for prioritizing regional wastewater infrastructure upgrades and formulating targeted mitigation policies to reduce increasing microplastic emissions.