Inhalable microplastics (1–10 µm) in indoor environments might be present at levels 100-fold higher than previous estimates. In this study (conducted in France), median microplastic (MP) concentrations were 528 MPs/m³ in residences and 2,238 MPs/m³ in car cabins, mainly comprising polyethylene and polyamide. They estimate that an adult might inhale 68,000 MPs/day at this level of exposure.