Release and fate of nanoparticulate TiO2 UV filters from sunscreen: Effects of particle coating and formulation type.

Nanoparticulate mineral UV filters, such as titanium dioxide (TiO2) nanocomposites, are being increasingly used in sunscreens as an alternative to organic UV filters. However, there is still a lack of understanding regarding their fate and behavior in aquatic environments and potential environmental impacts after being released from a bather's skin during recreational activities. In this work, we assessed the release, fate, and transformation of two commercial nanocomposite TiO2 UV filters, one hydrophobic and one hydrophilic, in ultrapure water and simulated fresh- and seawater. The hydrophobic TiO2 nanocomposite, T-SA, was coated with a primary Al2O3 photopassivation layer and a secondary stearic acid layer, while the hydrophilic TiO2 nanocomposite, T-SiO2, was coated with a single SiO2 photopassivation layer. The influence of the sunscreen formulation was examined by dispersing the TiO2 nanocomposites in their typical continuous phase (i.e., oil for T-SA and water for T-SiO2) before introduction into the aqueous system. After 48 h of aqueous aging and 48 h of settling, 88-99% of the hydrophobic T-SA remained floating on top of the water column in all aqueous systems. On the other hand, 100% of the hydrophilic T-SiO2 settled out of the water column in the fresh- and seawaters. With respect to the photopassivation coatings, no loss of the T-SA Al2O3 layer was detected after aqueous aging, but 99-100% dissolution of the SiO2 layer on the T-SiO2 nanocomposite was observed after 48 h in the fresh- and seawaters. This dissolution left behind T-SiO2 by-products exhibiting a photocatalytic activity similar to that of bare rutile TiO2. Overall, the results demonstrated that the TiO2 surface coating and sunscreen formulation type drive environmental behavior and fate and that loss of the passivation layer can result in potentially harmful, photoactive by-products. These insights will help guide regulations and assist manufacturers in developing more environmentally safe sunscreens.

Safety Evaluation of TiO2 Nanoparticle-Based Sunscreen UV Filters on the Development and the Immunological State of the Sea Urchin Paracentrotus lividus.

Sunscreens are emulsions of water and oil that contain filters capable of protecting against the detrimental effects of ultraviolet radiation (UV). The widespread use of cosmetic products based on nanoparticulate UV filters has increased concerns regarding their safety and compatibility with both the environment and human health. In the present work, we evaluated the effects of titanium dioxide nanoparticle (TiO2 NP)-based UV filters with three different surface coatings on the development and immunity of the sea urchin, Paracentrotus lividus. A wide range of NP concentrations was analyzed, corresponding to different levels of dilution starting from the original cosmetic dispersion. Variations in surface coating, concentration, particle shape, and pre-dispersant medium (i.e., water or oil) influenced the embryonic development without producing a relevant developmental impairment. The most common embryonic abnormalities were related to the skeletal growth and the presence of a few cells, which were presumably involved in the particle uptake. Adult P. lividus immune cells exposed to silica-coated TiO2 NP-based filters showed a broad metabolic plasticity based on the biosynthesis of metabolites that mediate inflammation, phagocytosis, and antioxidant response. The results presented here highlight the biosafety of the TiO2 NP-based UV filters toward sea urchin, and the importance of developing safer-by-design sunscreens.

Aqueous aging of a silica coated TiO2 UV filter used in sunscreens: investigations at the molecular scale with dynamic nuclear polarization NMR.

Short-term, aqueous aging of a commercial nanocomposite TiO2 UV filter with a protective SiO2 shell was examined in abiotic simulated fresh- and seawater. Under these conditions, the SiO2 layer was quantitatively removed (∼88-98%) within 96 hours, as determined using inductively coupled plasma-atomic emission spectroscopy (ICP-AES). While these bulk ICP-AES analyses suggested almost identical SiO2 shell degradation after aging in fresh- and seawater, surface sensitive 29Si dynamic nuclear polarization (DNP) solid-state nuclear magnetic resonance (SSNMR), with signal enhancements of 5-10× compared to standard SSNMR, was able to distinguish differences in the aged nanocomposites at the molecular level. DNP-SSNMR revealed that the attachment of the silica layer to the underlying TiO2 core rested on substantial Si-O-Ti bond formation, bonds which were preserved after freshwater aging, yet barely present after aging in seawater. The removal of the protective SiO2 layer is due to ionic strength accelerated dissolution, which could present significant consequences to aqueous environments when the photoactive TiO2 core becomes exposed. This work demonstrates the importance of characterizing aged nanocomposites not only on the bulk scale, but also on the molecular level by employing surface sensitive techniques, such as DNP-NMR. Molecular level details on surface transformation and elemental speciation will be crucial for improving the environmental safety of nanocomposites.

Assessing UV filter inputs into beach waters during recreational activity: A field study of three French Mediterranean beaches from consumer survey to water analysis.

In order to assess the release of UV filters from the sunscreen used by beachgoers into seawater within the bathing zone, a field campaign was carried out during the summer of 2017 at three beaches in Marseille, along the French Mediterranean coast. A social survey analyzed beachgoer attendance, the quantities and types of suncare products used and the bathing frequencies, while the bathing water was analyzed spatially and temporally so as to quantify both mineral and organic UV filters directly released and recovered. During the peak recreational time at the three beaches, both mineral and organic UV filters were detected in higher concentrations in the bathing area than offshore. In general, higher concentrations were recovered in the water top surface layer than in the water column, giving respectively 100-900 and 20-50 µg/L for TiO2, 10-15 and 1-3 µg/L for ZnO, 40-420 and 30-150 ng/L for octocrylene, and 10-15 and 10-350 ng/L for avobenzone. More than 75% of the 471 interviewees reported bathing every time they go to the beach, with 68% using a suncare product 2.6 times on average. From these data we estimated that an average mass of 52 kg/day or 1.4 t/month of suncare products are possibly released into bathing water for a beach attended by 3000 people daily. The mass ratio of UV filters in such products typically ranges from 0.03 to 0.1, allowing us to propose theoretical maximum concentrations in the beach water. Our recovery of measured UV filter concentrations in seawater compared to the theoretical concentrations revealed two distinct scenarios for the mineral and organic filters. While up to 49% of the mineral filters used by beachgoers may be released into the seawater, the organic filters were minimally recovered in the environment, most likely due to internalization through the skin barrier or partial photodegradation.