NanoTiO2 Sunscreen Does Not Prevent Systemic Oxidative Stress Caused by UV Radiation and a Minor Amount of NanoTiO2 is Absorbed in Humans

Abstract

The present pilot study tested the efficiency of nanoTiO2 sunscreen to prevent the oxidative stress/inflammation caused by ultraviolet (UV) radiation using biomarkers in subjects’ blood, urine, and exhaled breath condensate (EBC). In addition, the skin absorption of nanoTiO2 was studied. Six identical subjects participated in three tests: (A) nanoTiO2 sunscreen, (B) UV radiation, and (C) sunscreen + UV. The first samples were collected before the test and the second after sunscreen application and/or UV exposure. On day 4, the third samples were collected, and the sunscreen was washed off, and the fourth samples were collected on day 11. The following biomarkers were measured: malondialdehyde, 4-hydroxy-trans-hexenal, 4-hydroxy-trans-nonenal, aldehydes C6-C12, 8-iso-Prostaglandin F2α, o-tyrosine, 3-chlorotyrosine, 3-nitrotyrosine, 8-hydroxy-2-deoxyguanosine, 8-hydroxyguanosine, 5-hydroxymethyl uracil, and leukotrienes, using liquid chromatography-electrospray ionisation-tandem mass spectrometry. Titania was measured using inductively coupled plasma mass spectrometry and TiO2 nanoparticles by transmission and scanning electron microscopy. Sunscreen alone did not elevate the markers, but UV increased the biomarkers in the plasma, urine, and EBC. The sunscreen prevented skin redness, however it did not inhibit the elevation of oxidative stress/inflammatory markers. Titania and nanoTiO2 particles were found in the plasma and urine (but not in the EBC) in all sunscreen users, suggesting their skin absorption.

Markers of oxidative stress after three days of nanoTiO₂ sunscreen use in humans: a pilot study

“…It was shown that the skin absorption of nanoTiO 2 already occurs after the first 6 hours of exposure, although in a small quantity (19). This agrees with the histological proof of nanoTiO 2 particles in the viable cells of both the epidermis and dermis in the study by Tan et al (26).…”

“…Two subjects reported allergic rhinitis without treatment, and one woman was being treated with thyroxin for hypothyroidism and with local corticosteroids for bronchial asthma; these subjects also participated in the previous study (19). No subject had symptoms of an acute viral disease, chronic bronchitis, or dyspnoea.…”

“…The sunscreen type was identical to the sunscreen used in the published study (19). It had a skin protection factor (SPF) of 50.…”

“…EBC samples were collected using an Ecoscreen Turbo (DECCS, Jaeger, Hochberg, Germany). All subjects wore a nose clip to avoid nasal contamination and breathed tidally for approximately 15 min through a mouthpiece connected to the condenser (−20 °C), as described in our previous study (19).…”

Silicon dioxide and titanium dioxide particles found in human tissues

“…While inhalation may be the primary route for TiO 2 exposure in the workplace, in non-occupational settings Ti concentrations in air are very low, in the range of 0.01-0.1 lg/m 3 , resulting in a maximum exposure through inhalation of only 1 lg Ti/day (WHO 1982). Most dermal exposure studies, whether in vitro, ex vivo or in vivo, report that TiO 2 particles do not penetrate the (intact) skin (Crosera et al 2015;Shi et al 2013), or that only minor amounts of nano TiO 2 are absorbed in humans (Pelclova et al 2019). Medical implants have a strongly bound oxide layer which makes them inert, however, due to corrosion a Ti implant surface can be a potential source for the release of micro-and nano-sized particles (Frisken et al 2002;Sarmiento-Gonzalez et al 2009).…”