UV filter occurrence in beach water of the Mediterranean coast - A field survey over 2 years in Palavas-les-Flots, France.

OBJECTIVE: A 2-year sampling campaign was realized on French Mediterranean beach (Palavas-les-Flots Hérault) in order to measure the concentration of UV filters released from the sunscreen used by bathers. Multiple factors suspected of playing determining roles in the UV filter pattern in water were explored, such as the seasonal and daily time evolutions, or the vertical and horizontal distributions, and they were regarded through the UV filter characteristics. METHODS: The beach was monitored during periods of high and low tourist attendance, typically before, during and after the summer peak. The beachgoers attendance was counted. Bathing water was sampled distinctly from the bulk column and from the top surface layer, testing different sampling tools. Sediments and mussels were also sampled and analysed as potential UV filter sinks. Three organic UV filters (octocrylene OCR, avobenzone BMDBM and octyl methoxycinnamate OMC) and one mineral (titanium dioxide TiO2 ) were studied here as representatives of the current cosmetic market. RESULTS: Summer peak attendance on the beach was confirmed associated with peak levels of UV filter concentration in the bathing water, even more pronounced during a heat wave period. This relation was also observed at day scale with an afternoon peak, suggesting a rapid evolution of the UV filter pattern in water. Contrasted fates were measured between the four studied UV filters, that could be mainly explained by their respective characteristics, i.e. particulate or dissolved, hydrophilic or lipophilic, lifetime. Generally, this resulted in a concentration ranking TiO2 > OCR > OMC > BMDBM, ranging from 0.5 to 500 µg/L. The most lipophilic and recalcitrant OCR was found most vertically differentiated and over concentrated in the top surface layer of water. Finally, a large horizontal heterogeneity was also observed in the UV filter concentration pattern, raising the need for sample replicates that cover a significant area. CONCLUSION: This work fulfils some knowledge gaps on the issue of UV filter release in coastal environments, not only by providing original field data and methodological recommendations but also importantly in the comparison made of organic and mineral UV filters, which are often considered separately and rarely evaluated at the same time.

OBJECTIF: Une campagne d'échantillonnage de deux ans a eu lieu sur une plage de la Méditerranée en France (Palavas-les-Flots dans l'Hérault) afin de mesurer la concentration de filtres UV libérés par la protection solaire utilisé par les baigneurs. Plusieurs facteurs suspectés de jouer des rôles déterminants dans le modèle de filtre UV dans l'eau ont été étudiés, comme les évolutions saisonnières et quotidiennes, ou les distributions verticales et horizontales, et ils ont été examinés à travers les caractéristiques du filtre UV. MÉTHODES: La plage a été surveillée pendant les périodes de fréquentation touristique élevée et faible, généralement avant, pendant et après le pic estival. La présence des baigneurs a été comptabilisée. L'eau de baignade a été prélevée distinctement de la colonne principale et de la couche superficielle supérieure, en testant différents outils de prélèvement d'échantillons. Des sédiments et des moules ont également été prélevés et analysés comme réservoirs de filtre UV potentiels. En l'occurrence, trois filtres UV organiques (octocrylène OCR, avobenzone BMDBM et octyl méthoxycinnamate OMC) et un minéral (dioxyde de titane TiO2 ) ont été étudiés comme représentants du marché cosmétique actuel. RÉSULTATS: Les pics estivaux de présence de baigneurs sur la plage ont été confirmés comme étant associés à des pics de concentration du filtre UV dans l'eau de baignade, encore plus prononcés pendant une période de vague de chaleur. Cette relation a également été observée à l'échelle d'une journée, avec un pic l'après-midi, suggérant une évolution rapide du profil de filtre UV dans l'eau. Les effets de contraste ont été mesurés entre les quatre filtres UV étudiés, ce qui pourrait s'expliquer principalement par leurs caractéristiques respectives, c'est-à-dire particulaires ou dissous, hydrophiles ou lipophiles, tout au long de la vie. En général, cela a donné lieu à un classement de la concentration : TiO2 > OCR > OMC > BMDBM, comprise entre 0,5 et 500 ug/L. Il est apparu que c'est l'OCR le plus lipophile et le plus récalcitrant qui est le plus différencié verticalement et sur-concentré dans la couche supérieure de l'eau. Enfin, on a observé une grande hétérogénéité horizontale dans le profil de concentration du filtre UV, ce qui a nécessité des réplicats d'échantillons couvrant une zone significative. CONCLUSION: Ce travail comble certaines lacunes en matière de connaissances sur la libération des filtres UV dans les environnements côtiers, non seulement en fournissant des données originales sur le terrain et des recommandations méthodologiques, mais également en comparant des filtres UV organiques et minéraux, qui sont souvent pris en compte séparément et rarement évalués en même temps.

Influence of TiO2 nanocomposite UV filter surface chemistry and their interactions with organic UV filters on uptake and toxicity toward cultured fish gill cells.

Aquatic environments have been found to be contaminated with a variety of inorganic and organic UV filters. This includes novel nano-sized titanium dioxide (TiO2) composite particles, which have been increasingly developed and incorporated into commercial sunscreens in recent years. So far, relatively little is known about the effects of this novel class of UV filters on aquatic life. Therefore, this study aimed to determine and compare the toxicity of three such nanoparticulate TiO2 UV filters with different surface coatings, namely Eusolex® T-Avo (SiO2-coated), T-Lite™ SF (Al(OH)3/PDMS-coated), and Eusolex® T-S (Al2O3/stearic acid-coated) either alone, or in the presence of selected organic UV filters (octinoxate, avobenzone, octocrylene), toward fish using RTgill-W1 cell cultures as an in vitro experimental model. Besides standard exposure protocols, alternative approaches (i.e., exposure to water accommodated fractions (WAFs), hanging-drop exposure) were explored to account for nanoparticle (NP)-specific fate in the medium and obtain additional/complementary information on their toxicity in different conditions. The AlamarBlue, CFDA-AM and Neutral Red Retention (NR) assays were used to measure effects on different cellular endpoints. Transmission electron microscopy (TEM) was used to examine NP uptake. Our results showed that none of the TiO2 NP UV filters were cytotoxic at the concentrations tested (0.1-10 µg/mL; 24 h) but there were differences in their uptake by the cells. Thus, only the hydrophilic T-AVO was detected inside cells, but the hydrophobic T-Lite SF and T-S were not. In addition, our results show that the presence of NPs (or the used dispersant) tended to decrease organic UV filter toxicity. The level of combination effect depended on both NP-type (surface chemistry) and concentration, suggesting that the reduced toxicity resulted from reduced availability of the organic UV filters due to their adsorption to the NP surface. Thus, mixtures of TiO2 NP UV filters and organic UV filters may have a different toxicological profile compared to the single substances, but probably do not pose an increased hazard.

Cyto-Genotoxicity of Tritiated Stainless Steel and Cement Particles in Human Lung Cell Models.

During the decommissioning of nuclear facilities, the tritiated materials must be removed. These operations generate tritiated steel and cement particles that could be accidentally inhaled by workers. Thus, the consequences of human exposure by inhalation to these particles in terms of radiotoxicology were investigated. Their cyto-genotoxicity was studied using two human lung models: the BEAS-2B cell line and the 3D MucilAirTM model. Exposures of the BEAS-2B cell line to particles (2 and 24 h) did not induce significant cytotoxicity. Nevertheless, DNA damage occurred upon exposure to tritiated and non-tritiated particles, as observed by alkaline comet assay. Tritiated particles only induced cytostasis; however, both induced a significant increase in centromere negative micronuclei. Particles were also assessed for their effects on epithelial integrity and metabolic activity using the MucilAirTM model in a 14-day kinetic mode. No effect was noted. Tritium transfer through the epithelium was observed without intracellular accumulation. Overall, tritiated and non-tritiated stainless steel and cement particles were associated with moderate toxicity. However, these particles induce DNA lesions and chromosome breakage to which tritium seems to contribute. These data should help in a better management of the risk related to the inhalation of these types of particles.

Aquatic Mesocosm Strategies for the Environmental Fate and Risk Assessment of Engineered Nanomaterials.

In the past decade, mesocosms have emerged as a useful tool for the environmental study of engineered nanomaterials (ENMs) as they can mimic the relevant exposure scenario of contamination. Herein, we analyzed the scientific outcomes of aquatic mesocosm experiments, with regard to their designs, the ENMs tested, and the end points investigated. Several mesocosm designs were consistently applied in the past decade to virtually mimic various contamination scenarios with regard to ecosystem setting as well as ENMs class, dose, and dosing. Statistical analyses were carried out with the literature data to identify the main parameters driving ENM distribution in the mesocosms and the potential risk posed to benthic and planktonic communities as well as global ecosystem responses. These analyses showed that at the end of the exposure, mesocosm size (water volume), experiment duration, and location indoor/outdoor had major roles in defining the ENMs/metal partitioning. Moreover, a higher exposure of the benthic communities is often observed but did not necessarily translate to a higher risk due to the lower hazard posed by transformed ENMs in the sediments (e.g., aggregated, sulfidized). However, planktonic organisms were generally exposed to lower concentrations of potentially more reactive and toxic ENM species. Hence, mesocosms can be complementary tools to existing standard operational procedures for regulatory purposes and environmental fate and risk assessment of ENMs. To date, the research was markedly unbalanced toward the investigation of metal-based ENMs compared to metalloid- and carbon-based ENMs but also nanoenabled products. Future studies are expected to fill this gap, with special regard to high production volume and potentially hazardous ENMs. Finally, to take full advantage of mesocosms, future studies must be carefully planned to incorporate interdisciplinary approaches and ensure that the large data sets produced are fully exploited.

A network perspective reveals decreasing material diversity in studies on nanoparticle interactions with dissolved organic matter.

Dissolved organic matter (DOM) strongly influences the properties and fate of engineered nanoparticles (ENPs) in aquatic environments. There is an extensive body of experiments on interactions between DOM and ENPs and also larger particles. [We denote particles on the nano- and micrometer scale as particulate matter (PM).] However, the experimental results are very heterogeneous, and a general mechanistic understanding of DOM-PM interactions is still missing. In this situation, recent reviews have called to expand the range of DOM and ENPs studied. Therefore, our work focuses on the diversity of the DOM and PM types investigated. Because the experimental results reported in the literature are highly disparate and difficult to structure, a new format of organizing, visualizing, and interpreting the results is needed. To this end, we perform a network analysis of 951 experimental results on DOM-PM interactions, which enabled us to analyze and quantify the diversity of the materials investigated. The diversity of the DOM-PM combinations studied has mostly been decreasing over the last 25 y, which is driven by an increasing focus on several frequently investigated materials, such as DOM isolated from fresh water, DOM in whole-water samples, and TiO2 and silver PM. Furthermore, there is an underrepresentation of studies into the effect of particle coating on PM-DOM interactions. Finally, it is of great importance that the properties of DOM used in experiments with PM, in particular the molecular weight and the content of aromatic and aliphatic carbon, are reported more comprehensively and systematically.

Nitric oxide-releasing quaternary ammonium-modified poly(amidoamine) dendrimers as dual action antibacterial agents.

Herein we describe the synthesis of nitric oxide (NO)-releasing quaternary ammonium (QA)-functionalized generation 1 (G1) and generation 4 (G4) poly(amidoamine) (PAMAM) dendrimers. Dendrimers were modified with QA moieties of different alkyl chain lengths (i.e., methyl, butyl, octyl, dodecyl) via a ring-opening reaction. The resultant secondary amines were then modified with N-diazeniumdiolate NO donors to yield NO-releasing QA-modified PAMAM dendrimers capable of spontaneous NO release (payloads of ~0.75 µmol/mg over 4 h). The bactericidal efficacy of individual (i.e., non-NO-releasing) and dual action (i.e., NO-releasing) QA-modified PAMAM dendrimers was evaluated against Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa bacteria. Bactericidal activity was found to be dependent on dendrimer generation, QA alkyl chain length, and bacterial Gram class for both systems. Shorter alkyl chains (i.e., methylQA, butylQA) demonstrated increased bactericidal activity against P. aeruginosa versus S. aureus for both generations, with NO release markedly enhancing overall killing.

Tritiated stainless steel (nano)particle release following a nuclear dismantling incident scenario: Significant exposure of freshwater ecosystem benthic zone.

Nuclear facilities continue to be developed to help meet global energy demands while reducing fossil fuel use. However, an incident during the dismantling of these facilities could accidentally release tritiated particles (e.g. stainless steel) into the environment. Herein, we investigated the environmental dosimetry, fate, and impact of tritiated stainless steel (nano)particles (1 mg.L-1 particles and 1 MBq.L-1 tritium) using indoor freshwater aquatic mesocosms to mimic a pond ecosystem. The tritium (bio)distribution and particle fate and (bio)transformation were monitored in the different environmental compartments over 4 weeks using beta counting and chemical analysis. Impacts on picoplanktonic and picobenthic communities, and the benthic freshwater snail, Anisus vortex, were assessed as indicators of environmental health. Following contamination, some tritium (∼16%) desorbed into the water column while the particles rapidly settled onto the sediment. After 4 weeks, the particles and the majority of the tritium (>80%) had accumulated in the sediment, indicating a high exposure of the benthic ecological niche. Indeed, the benthic grazers presented significant behavioral changes despite low steel uptake (<0.01%). These results provide knowledge on the potential environmental impacts of incidental tritiated (nano)particles, which will allow for improved hazard and risk management.

Shape- and nitric oxide flux-dependent bactericidal activity of nitric oxide-releasing silica nanorods.

Silica nanorods (SNRs) are synthesized and then functionalized with aminoalkoxysilanes to prepare a new class of nitric oxide (NO)-releasing materials. The aspect ratio and size of the SNRs are tuned by varying the temperature, pH, and silane concentration used during the surfactant-templated synthesis. N-Diazeniumdiolate nitric oxide (NO) donors are formed on the secondary amine-functionalized SNRs by reaction with NO gas under basic conditions. Particle surface modifications are employed to manipulate the NO release kinetics. The diverse morphology (i.e., aspect ratio ∼1-8), NO-release kinetics (2000-14,000 ppb NO/mg particle) and similar sizes (i.e., particle volume ∼0.02 µm³) of the resulting NO-releasing SNRs facilitates further studies of how particle shape and NO flux impacts bactericidal activity against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Pseudomonas aeruginosa (P. aeruginosa) bacteria. The bactericidal efficacies of these materials improves with increasing particle aspect ratio and initial NO flux. Both chemical (i.e., NO-release kinetics) and physical (i.e., morphology) properties greatly influenced the bactericidal activity of these materials.

Nitric oxide-releasing amphiphilic poly(amidoamine) (PAMAM) dendrimers as antibacterial agents.

A series of amphiphilic nitric oxide (NO)-releasing poly(amidoamine) (PAMAM) dendrimers with different exterior functionalities were synthesized by a ring-opening reaction between primary amines on the dendrimer and propylene oxide (PO), 1,2-epoxy-9-decene (ED), or a ratio of the two, followed by reaction with NO at 10 atm to produce N-diazeniumdiolate-modified scaffolds with a total storage of ~1 µmol/mg. The hydrophobicity of the exterior functionality was tuned by varying the ratio of PO and ED grafted onto the dendrimers. The bactericidal efficacy of these NO-releasing vehicles against established Gram-negative Pseudomonas aeruginosa biofilms was then evaluated as a function of dendrimer exterior hydrophobicity (i.e., ratio of PO/ED), size (i.e., generation), and NO release. Both the size and exterior functionalization of dendrimer proved important to a number of parameters including dendrimer-bacteria association, NO delivery efficiency, bacteria membrane disruption, migration within the biofilm, and toxicity to mammalian cells. Although enhanced bactericidal efficacy was observed for the hydrophobic chains (e.g., ED), toxicity to L929 mouse fibroblast cells was also noted at concentrations necessary to reduce bacterial viability by 5-logs (99.999% killing). The optimal PO to ED ratios for biofilm eradication with minimal toxicity against L929 mouse fibroblast cells were 7:3 and 5:5. The study presented herein demonstrated the importance of both dendrimer size and exterior properties in determining efficacy against established biofilms without compromising biocompatibility to mammalian cells.

Tritiated Steel Micro-Particles: Computational Dosimetry and Prediction of Radiation-Induced DNA Damage for In Vitro Cell Culture Exposures.

Biological effects of radioactive particles can be experimentally investigated in vitro as a function of particle concentration, specific activity and exposure time. However, a careful dosimetric analysis is needed to elucidate the role of radiation emitted by radioactive products in inducing cyto- and geno-toxicity: the quantification of radiation dose is essential to eventually inform dose-risk correlations. This is even more fundamental when radioactive particles are short-range emitters and when they have a chemical speciation that might further concur to the heterogeneity of energy deposition at the cellular and sub-cellular level. To this aim, we need to use computational models. In this work, we made use of a Monte Carlo radiation transport code to perform a computational dosimetric reconstruction for in vitro exposure of cells to tritiated steel particles of micrometric size. Particles of this kind have been identified as worth of attention in nuclear power industry and research: tritium easily permeates in steel elements of nuclear reactor machinery, and mechanical operations on these elements (e.g., sawing) during decommissioning of old facilities can result in particle dispersion, leading to human exposure via inhalation. Considering the software replica of a representative in vitro setup to study the effect of such particles, we therefore modelled the radiation field due to the presence of particles in proximity of cells. We developed a computational approach to reconstruct the dose range to individual cell nuclei in contact with a particle, as well as the fraction of "hit" cells and the average dose for the whole cell population, as a function of particle concentration in the culture medium. The dosimetric analysis also provided the basis to make predictions on tritium-induced DNA damage: we estimated the dose-dependent expected yield of DNA double strand breaks due to tritiated steel particle radiation, as an indicator of their expected biological effectiveness.

Nitric oxide-releasing dendrimers as antibacterial agents.

The antibacterial activity of a series of nitric oxide (NO)-releasing poly(propylene imine) (PPI) dendrimers was evaluated against both Gram-positive and Gram-negative pathogenic bacteria, including methicillin-resistant Staphylococcus aureus . A direct comparison of the bactericidal efficacy between NO-releasing and control PPI dendrimers (i.e., non-NO-releasing) revealed both enhanced biocidal action of NO-releasing dendrimers and reduced toxicity against mammalian fibroblast cells. Antibacterial activity for the NO donor-functionalized PPI dendrimers was shown to be a function of both dendrimer size (molecular weight) and exterior functionality. In addition to minimal toxicity against fibroblasts, NO-releasing PPI dendrimers modified with styrene oxide exhibited the greatest biocidal activity (≥99.999% killing) against all bacterial strains tested. The N-diazeniumdiolate NO donor-functionalized PPI dendrimers presented in this study hold promise as effective NO-based therapeutics for combating bacterial infections.

Dual action antimicrobials: nitric oxide release from quaternary ammonium-functionalized silica nanoparticles.

The synthesis of quaternary ammonium (QA)-functionalized silica nanoparticles with and without nitric oxide (NO) release capabilities is described. Glycidyltrialkylammonium chlorides of varied alkyl chain lengths (i.e., methyl, butyl, octyl, and dodecyl) were tethered to the surface of amine-containing silica nanoparticles via a ring-opening reaction. Secondary amines throughout the particle were then functionalized with N-diazeniumdiolate NO donors to yield dual functional nanomaterials with surface QAs and total NO payloads of 0.3 µmol/mg. The bactericidal activities of singly (i.e., only NO-releasing or only QA-functionalized) and dual (i.e., NO-releasing and QA-functionalized) functional nanoparticles were tested against Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa . Particles with only NO release capabilities alone were found to be more effective against P. aeruginosa , while particles with only QA-functionalities exhibited greater toxicity toward S. aureus . The minimum bactericidal concentrations (MBC) of QA-functionalized particles decreased with increasing alkyl chain length against both microbes tested. Combining NO release and QA-functionalities on the same particle resulted in an increase in bactericidal efficacy against S. aureus ; however, no change in activity against P. aeruginosa was observed compared to NO-releasing particles alone.

Silica nanoparticle phytotoxicity to Arabidopsis thaliana.

The phytotoxicity of silica nanoparticles (SiNPs) was evaluated as a function of particle size (14, 50, and 200 nm), concentration (250 and 1000 mg L(-1)), and surface composition toward Arabidopsis thaliana plants grown hydroponically for 3 and 6 weeks. Reduced development and chlorosis were observed for plants exposed to highly negative SiNPs (-20.3 and -31.9 mV for the 50 and 200 nm SiNPs, respectively) regardless of particle concentration when not controlling pH of the hydroponic medium, which resulted in increased alkalinity (~pH 8). Particles were no longer toxic to the plants at either concentration upon calcination or removal of surface silanols from the SiNP surface, or adjusting the pH of the growth medium to pH 5.8. The phytotoxic effects observed for the negatively charged 50 and 200 nm SiNPs were attributed to pH effects and the adsorption of macro- and micro-nutrients to the silica surface. Size-dependent uptake of the nanoparticles by the plants was confirmed using transmission electron microscopy (TEM) and inductively coupled plasma-optical emission spectroscopy (ICP-OES) with plant roots containing 32.0, 1.85, and 7.00 × 10(-3) mg Si·kg tissue(-1)/nm(3) (normalized for SiNP volume) for the 14, 50, and 200 nm SiNPs respectively, after 6 weeks exposure at 1000 ppm (pH 5.8). This study demonstrates that the silica scaffolds are not phytotoxic up to 1000 ppm despite significant uptake of the SiNPs (14, 50, and 200 nm) into the root system of A. thaliana.

Bioaccumulation, release and genotoxicity of stainless steel particles in marine bivalve molluscs.

During the decommissioning and removal of radioactive material in nuclear facilities, fine, tritiated dusts of stainless steel, cement or tungsten are generated that could be accidently released to the environment. However, the potential radio- and ecotoxicological effects these tritiated particles may have are unknown. In this study, stainless steel particles (SSPs) representative of those likely to be tritiated are manufactured by hydrogenation and their tissue-specific bioaccumulation, release (depuration) and subsequent genotoxic response have been studied in the marine mussel, Mytilus galloprovincialis, as a baseline for future assessments of the potential effects of tritiated SSPs. Exposure to 1000 µg L-1 of SSPs and adopting Cr as a proxy for stainless steel revealed relatively rapid accumulation (∼5 h) in the various mussel tissues but mostly in the digestive gland. Over longer periods up to 18 days, SSPs were readily rejected and egested as faecal material. DNA strand breaks, as a measure of genotoxicity, were determined at each time point in mussel haemocytes using single cell gel electrophoresis, or the comet assay. Lack of chemical genotoxicity was attributed to the rapid processing of SSP particles and limited dissolution of elemental components of steel. Further work employing tritiated SSPs will enable radio-toxicology to be studied without the confounding effects of chemical toxicity.

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.

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.

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.

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.

Nanoparticle stability in lake water shaped by natural organic matter properties and presence of particulate matter.

Predicting nanoparticle (NP) fate in the environment continues to remain a challenge, especially for natural surface water systems, where NPs can hetero-aggregate with natural organic and mineral suspended matter. Here we present the interactions and aggregation behavior of TiO2 NPs with natural organic matter (NOM) in a natural lake water. NP fate in a synthetic water of the same pH and ionic composition was also tested in the presence and absence of NOM analogs to gain insight into the different stabilizing effects of each NOM type. Several complementary analytical techniques were utilized to assess lake NOM composition, including pyrolysis-gas chromatography-mass spectrometry, gel permeation chromatography, the polarity rapid-assessment method, and Nanoparticle Tracking Analysis. In the natural lake water, the TiO2 NPs preferentially interacted with mostly anionic NOM of high and medium molecular weight (~1200-1450 and 400-520 Da). Specifically, strong interactions with proteins and polyhydroxy aromatics were observed. NP fate and stability were determined in both raw lake water containing mineral particulate matter and total NOM (NOMtot) and filtered lake water containing only NOM <0.8 µm (NOM<0.8), with different aggregation profiles observed over time. Additionally, three times the number of TiO2 NPs remained in suspension when only NOM<0.8 was present compared to the unfiltered water containing mineral particulate matter and NOMtot. These results demonstrate the contrasting NP fates in the aquatic environment according to the presence of NOMtot vs. NOM<0.8 and further suggest that the use of pure NOM analogs may not accurately represent NP interactions and fate in the natural system.

The influence of past research on the design of experiments with dissolved organic matter and engineered nanoparticles.

To assess the environmental fate of engineered nanoparticles (ENPs), it is essential to understand their interactions with dissolved organic matter (DOM). The highly complex nature of the interactions between DOM and ENPs and other particulate matter (PM) requires investigating a wide range of material types under different conditions. However, despite repeated calls for an increased diversity of the DOM and PM studied, researchers increasingly focus on certain subsets of DOM and PM. Considering the discrepancy between the calls for more diversity and the research actually carried out, we hypothesize that materials that were studied more often are more visible in the scientific literature and therefore are more likely to be studied again. To investigate the plausibility of this hypothesis, we developed an agent-based model simulating the material choice in the experiments studying the interaction between DOM and PM between 1990 and 2015. The model reproduces the temporal trends in the choice of materials as well as the main properties of a network that displays the DOM and PM types investigated experimentally. The results, which support the hypothesis of a positive reinforcing material choice, help to explain why calls to increase the diversity of the materials studied are repeatedly made and why recent criticism states that the selection of materials is unbalanced.