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Research Letter
April 2016

Repetitive Application of Sunscreen Containing Titanium Dioxide Nanoparticles on Human Skin

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

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.

The protocol for the study was approved by the Research Involving Human Subjects Committee of the US Food and Drug Administration, and informed written consent was obtained from each of the study participants. The participants were 6 fair-skinned individuals with phototypes II and III skin as defined by a UV-sensitivity questionnaire 1 and dermatological evaluation, who were recruited from the Washington, DC area. Daily applications of sunscreen with and without TiO2 nanoparticles at a concentration of 2 mg/cm2 were made to 2 test sites (5 x 5 cm) on the lower back of each participant, with a separate site as an untreated control. Except for the absence of tocopheryl acetate, the 2 custom-prepared sunscreen formulations used in the study (sunscreen with uncoated TiO2 nanoparticles [sunscreen plus TiO2] and [sunscreen only]) were identical to previously reported formulations.2 The sunscreens were applied once daily for 3 days to 2 of the participants. To further detect penetration of TiO2 nanoparticles, sunscreen was applied once-daily for 8 days to the 4 other participants. One day after the final sunscreen application, 5 shave biopsy specimens were acquired from each participant (2 from the sunscreen plus TiO2 site, 2 from the sunscreen-only site; and 1 from the control site). Details of the procedures for biopsy and tissue specimen processing, and of the biomarkers for immunohistochemistry, have been described,3 as have details of the biopsy-sample preparation for electron microscopy.2 Transmission electron microscopy was used to assess the penetration of TiO2 particles through epidermal-dermal skin layers. Confirmatory identification was done with scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDX) analysis as previously described.2

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