PAPER REPRISE: Aerosol Mineral Sunscreens Have Nanoparticles, But Not Enough to be Dangerous

In this undergraduate-led research project that we concluded in 2020, we found small quantities of nanoparticles in the breathing zone during application of aerosol mineral sunscreens recommended for use on children (https://doi.org/10.1007/s41810-020-00079-x). Overall, 85% of the particles by count had diameters less than 100 nm, and this project captured direct images of several different particle types with some clearly the product of mineral grinding processes, while others show signs of having been manufactured. Interestingly, plume sizes for the 3 tested products were widely different with some extending more than 2.5 m from the pressurized can. There seems to be little risk under the particular scenario we tested, as the highest measured concentration for all particles was 0.8 micrograms per cubic meter, and the lowest recommended exposure limit for titanium dioxide nanoparticles (from NIOSH) is 300 micrograms per cubic meter.