Microplastics in dust from different indoor environments

Microplastics (MPs) are present in global indoor dust, which is an important source of MPs for humans. However, few researchers have investigated differences in the abundance and characteristics of MPs in dust in different indoor environments. In this study, we found that residential apartments (mean: 1174 MPs/g; n = 47) had the highest abundance of MPs in indoor dust samples, followed by offices (896 MPs/g; n = 50), business hotels (843 MPs/g; n = 53), university dormitories (775 MPs/g; n = 48), and university classrooms (209 MPs/g; n = 44). The predominant shape of MPs was fiber in most indoor dust samples. The main size fraction of the MPs in the indoor dust samples from university classrooms and business hotels was 201-500 μm, and it was 501-1000 μm in those from offices, university dormitories, and residential apartments. The main MP polymer in indoor dust samples from business hotels, university dormitories, and residential apartments was polyester, whereas those from offices and university classrooms were mainly polyethylene and polypropylene. We calculated the estimated daily intake (EDI) of MPs through the inhalation of indoor dust, and found that infants (7.4 MPs/kg bw/day) had a higher mean EDI of MPs than toddlers (1.4 MPs/kg bw/day), children (0.49 MPs/kg bw/day), adults (0.23 MPs/kg bw/day), and university students (0.22 MPs/kg bw/day). To the best of our knowledge, we are the first to report differences in MP occurrence in dust samples from different indoor environments, and our findings provide a more accurate understanding of exposure risks of MPs to humans.