Characteristics, influencing factors, and risk assessment of indoor dustfall microplastics: Emphasizing the elevated risks of fragmented forms

Microplastics (MPs) are a significant environmental pollutant, and the indoor environment serves as both a source and a medium for human exposure to these particles. The influence of different MP shapes on health risks, particularly concerning intestinal absorption, remains poorly understood. This study investigated MPs in indoor dustfall, with an emphasis on shape-dependent characteristics and risks. Dustfall samples from urban residences were analyzed using density separation, microscopy, and micro-Fourier-transform infrared spectroscopy (μ-FTIR). Our findings showed that the dustfall MPs consisted of fragmented, fibrous, and spherical shapes, with fragmented MPs accounting for 31 % of the total. Due to their larger specific surface area (SSA), fragmented MPs exhibited a higher absorption capacity. A health risk model for human intestinal absorption of MPs in indoor dustfall was developed, revealing that fragmented MPs contributed the highest absorption rate (0.0289), followed by spherical MPs (0.0136) and fibers (0.0088). Indoor surveys further indicated that practices such as choosing low-emission wall materials, increasing ventilation, and using air purifiers can reduce indoor MP levels. Our results underscore the importance of targeting fragmented MPs in risk assessments and mitigation strategies.