Adults received three sunscreens containing titanium dioxide nanoparticles, one of them also containing zinc oxide, either at about 0.5 to 1.0 mg/cm2 for 2 hours or at the 2 mg/cm2 sun-protection-factor test thickness. Cryosections were mapped for titanium and zinc. Titanium and, when zinc oxide was present, zinc were high in the stratum corneum and fell to undetectable titanium and physiological zinc below it. Occlusion for 48 hours and tape stripping did not produce a printed titanium signal in the subcorneal epidermis.
Key numbers
Figures below are copied as printed. Units are not converted. Species are not merged.
| Analyte | What was reported | Value | Unit | Basis | Where |
|---|---|---|---|---|---|
| Ti | n.d. | n.d. | µmol/g | dry weight as printed on Fig. 4 axis (µmol/g dw); Table 1 header does not repeat dw | Table 1, p. 6 |
| Ti | n.d. | n.d. | µmol/g | dry weight as printed on Fig. 4 axis (µmol/g dw); Table 1 header does not repeat dw | Table 1, p. 6 |
| Ti | n.d. | n.d. | µmol/g | dry weight as printed on Fig. 4 axis (µmol/g dw); Table 1 header does not repeat dw | Table 1, p. 6 |
| Ti | n.d. | n.d. | µmol/g | dry weight as printed on Fig. 4 axis (µmol/g dw); Table 1 header does not repeat dw | Table 1, p. 6 |
| Ti | n.d. | n.d. | µmol/g | dry weight as printed on Fig. 4 axis (µmol/g dw); Table 1 header does not repeat dw | Table 1, p. 6 |
| Ti | n.d. | n.d. | µmol/g | dry weight as printed on Fig. 4 axis (µmol/g dw); Table 1 header does not repeat dw | Table 1, p. 6 |
| Ti | n.d. | n.d. | µmol/g | dry weight as printed on Fig. 4 axis (µmol/g dw); Table 1 header does not repeat dw | Table 1, p. 6 |
| Ti | minimum detectable concentrations of Ti and Zn in skin were determined to be 0.31 and 0.10 µmol/g, respectively | 0.31 | µmol/g | dry cryosection | Methods, p. 3 |
| Zn | 0.10 µmol/g | 0.10 | µmol/g | dry cryosection | Methods, p. 3 |
| TiO2 | The TiO2 nanoparticles (76-82%) were dispersed in hydrophobic basis gel … together with Al2O3 (8-11%) and SiO2 (1-3%) | 76-82 | % TiO2 nanoparticles | as supplied | Methods, p. 2 |
| TiO2 | sunscreen thickness of approximately 0.5-1.0 mg/cm2 within an area of 25 cm2 | 0.5-1.0 | mg/cm2 | topical sunscreen mass per area | Methods, p. 3 |
| TiO2 | thickness of sunscreen application of 2 mg/cm2 | 2 | mg/cm2 | topical | Methods, p. 3 |
| Ti | In non-treated skin, Ti was below the minimum detection limit in all strata inspected | below minimum detection limit | µmol/g | skin strata | text, p. 6 |
| Zn | 2.5580.29 | 2.55 ± 0.29 | µmol/g | dry weight as printed on Fig. 4 axis (µmol/g dw); Table 1 header does not repeat dw | Table 1, p. 6 |
The structured evidence record for this source holds 37 copied values. The table above is the short set.
Methods (brief)
Open applications covered 25 cm2 on the sacral region and buttocks. A separate group had tape stripping before dosing and 48-hour occlusion. The hydrophobic test gel contained coated rutile titanium dioxide particles with a manufacturer-stated average size of 20 nm, 76 to 82% titanium dioxide nanoparticles, 8 to 11% aluminum oxide, and 1 to 3% silicon dioxide. Commercial sunscreen percentages are not printed. Zinc oxide particles in the formulations were spherical and 20 to 60 nm by the authors’ microscopy.
Evidence fitness
These data support After 2 hours, Ti and exogenous Zn from the sunscreens were quantified in stratum corneum and were not detected as Ti in subcorneal epidermis (n.d., below 0.31 µmol/g); Stratum corneum Ti means ranged from 110 ± 44 µmol/g (test TiO2 gel) to 496 ± 207 µmol/g (TiO2 plus ZnO, lower application rate); Where the formulation contained ZnO, stratum corneum Zn was 152 ± 80 and 129 ± 35 µmol/g, versus control stratum corneum Zn of 2.55 ± 0.29 µmol/g. Subcorneal Zn stayed near the control range.
They do not support Does not support detectable TiO2 or exogenous ZnO in viable epidermis under these conditions; Does not report blood, urine, or organ concentrations; Does not give percent TiO2 or ZnO in the two commercial sunscreens; Psoriatic skin is described only qualitatively (particles at the outer stratum corneum and follicle opening), with no Table 1 numbers.
Limitations
Table means use a plus-minus glyph that the extract renders as 8. Control subcorneal titanium is a blank cell, while the text says titanium was below detection in all non-treated strata. Different formulation batches were used for the two protocols. One biopsy per person. Dry-weight basis is explicit on the figure axis and not repeated in the table header.
Related evidence
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