Microplastics in indoor and outdoor environments in China: Characteristic and human exposure risk assessment

Human exposure to microplastics (MPs) has led to global health concerns, but our knowledge of the characteristics and human exposure of airborne MPs is limited. Adults may have different exposure patterns and lifestyles from other age groups. Therefore, this study aims to determine the MPs exposure among adults at various locations and during different time periods. MPs were collected and detected through passive sampling and laser direct infrared (LDIR) imaging (Agilent 8700) at five locations including: dormitory, dining hall, office, library, and outdoor; the sampling lasted for 3 months. The highest concentration of indoor MPs was detected in the dining hall (193 ± 8 MPs/m²/day), whereas the lowest was detected in the library (113 ± 4 MPs/m²/day). Among all sampling points, the outdoor locations had the lowest MPs concentrations (92 ± 4 MPs/m²/day). The length of the MPs ranged from 10 μm－760 μm. Pellets (54.6 %), fibres (21.6 %), and fragments (23.8 %) were the shapes identified in this research. Polyamide (51.7 %) was the most prevalent polymer type at all sampling points. This article conducted respiratory exposure assessments of MPs for males and females of different ages (age ranges: 18－21; 21－30; 31－40; 41－60) in different environments and at different times. For both weekends and weekdays, dormitories contributed the most to MPs respiratory exposure. Males aged 31－40 years had the highest exposure with an average of 266 particles/day, whereas females aged 18－21 (157 particles/day) had the lowest exposure. Differences in respiratory rate according to age and gender may be the main reason for these results. These findings indicate that further research into the adult MPs inhalation exposure under indoor and outdoor conditions is crucial.