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Research Letter |

Repetitive Application of Sunscreen Containing Titanium Dioxide Nanoparticles on Human Skin

Sergio G. Coelho, PhD1; Anil K. Patri, PhD2; Anna M. Wokovich, BS, Chem3; Scott E. McNeil, PhD2; Paul C. Howard, PhD4; Sharon A. Miller, MSEE5
[+] Author Affiliations
1Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
2Nanotechnology Characterization Laboratory, Cancer Research Technology Program, Leidos Biomedical Research, Inc, Frederick National Laboratory for Cancer Research, Frederick, Maryland
3Division of Pharmaceutical Analysis, Office of Testing and Research, Office of Pharmaceutical Science, Center for Drug Evaluation and Research, US Food and Drug Administration, St Louis, Missouri
4National Center for Toxicological Research, US Food and Drug Administration, Jefferson, Arkansas
5Division of Radiological Health, Office of In Vitro Diagnostics and Radiological Health, Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, Maryland
JAMA Dermatol. 2016;152(4):470-472. doi:10.1001/jamadermatol.2015.5944.
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This study examines the relative risk of skin penetration by nanoscale TiO2 nanoparticles in healthy fair-skinned individuals.

Titanium dioxide (TiO2) has for decades been approved for use in sunscreens as a physical sunblock. It is not known whether reducing the size of TiO2 particles in sunscreens creates new issues of safety and/or effectiveness. A study was therefore conducted to investigate the relative risk of skin penetration by TiO2 nanoparticles in healthy fair-skinned individuals.

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TiO2 Nanoparticle Application and Maximal Dermal Presentation

A, Image made with light microscopy of a thick section. B, Images made with transmission electron microscopy (TEM) of thin sections from a study participant treated with titanium dioxide (TiO2)–containing sunscreen and showing maximal dermal presentation of TiO2 nanoparticles. Each boxed area in the image correlates with a TEM micrograph of a grid hole. Each grid hole is approximately 220 x 220 μm. The dotted pink line in the montage of TEM micrographs shows the division between epidermis and dermis. Grid holes 12 and 14 seen on TEM contain the epidermal layer and part of the dermal layer, whereas grid holes 13 and 15 contain only the dermal layer. A hair follicle structure was observed with TEM in this sample in grid holes 10 and 11. Electron-dense regions of the appropriate size and morphology to be TiO2 particles are indicated with dotted blue circles in the TEM micrographs. All particles were confirmed to contain TiO2 using scanning electron microscopy and energy dispersive X-ray spectroscopy as previously described.2

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