Microplastic Fallout in Different Indoor Environments

Microplastics in the air have gradually attracted our attention in recent years; however, temporal and spatial trends of microplastics in indoor air are rarely discussed. In the present study, we tracked microplastic fallout in a dormitory, an office, and a corridor on both workdays and weekends for three months. In addition, an air conditioner was used to understand airflow influence on microplastic resuspension in the dorm. Among the three sampling sites, the highest average microplastic abundance appeared in the dormitory (9.9 × 10³ MPs/m²/d), followed by the office (1.8 × 10³ MPs/m²/d) and the corridor (1.5 × 10³ MPs/m²/d). In the dormitory, the average MP abundance on weekends (1.4 × 10⁴ MPs/m²/d) was approximately three times of that on weekdays (5.8 × 10³ MPs/m²/d). In the office; however, the abundance on weekends (1.2 × 10³ MPs/m²/d) was 50% of that on weekdays (2.4 × 10³ MPs/m²/d). Microplastic fallout existed mostly in the form of fibers and showed similar polymer compositions to the textile products used in indoor environments. The airflow tests using an air conditioner suggested that airflow turbulence increased resuspension of microplastics. Taken together, we conclude that indoor environments are prone to serious microplastic pollution, but microplastic level varies greatly due to different characteristics of indoor setting. Our results also indicate that textile quantity is one of the main factors affecting microplastic abundance in indoor air, whereas air conditioner-induced airflow turbulence can cause microplastic migration in indoor environments.