- • PET and PC-based microplastics were detected in indoor dust from 12 countries.
- • High concentrations (38–120,000 µg/g) of PET-based MPs were found.
- • Positive correlations were found between monomers and corresponding MPs in dust.
- • The daily intake of MPs via indoor dust ingestion in infants was on the order of µg/kg bw.
Global marine pollution by microplastics (MPs) has received considerable attention in recent years. Nevertheless, little is known about the occurrence of MPs in indoor environments. A novel analytical method was used to quantitatively determine polyethylene terephthalate (PET)- and polycarbonate (PC)- based MPs in 286 indoor dust samples collected from 12 countries. PET-based MPs were detected in all dust samples at concentrations of 38–120,000 µg/g (median: 5900 µg/g), whereas PC-based MPs were measured at <0.11–1700 µg/g (median: 8.8 µg/g). Significant positive correlations were found between the concentrations of terephthalic acid (a PET monomer) and PET as well as between bisphenol A (a PC monomer) and PC. Based on the concentrations of MPs measured in indoor dust, the median daily intake of PET-based MPs calculated for infants was in the range of 4000–150,000 ng/kg-bw/day.