Titanium dioxide particles frequently present in face masks intended for general use require regulatory control.

Although titanium dioxide (TiO) is a suspected human carcinogen when inhaled, fiber-grade TiO (nano)particles were demonstrated in synthetic textile fibers of face masks intended for the general public. STEM-EDX analysis on sections of a variety of single use and reusable face masks visualized agglomerated near-spherical TiO particles in non-woven fabrics, polyester, polyamide and bi-component fibers. Median sizes of constituent particles ranged from 89 to 184 nm, implying an important fraction of nano-sized particles (< 100 nm).