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There is increasing evidence that sunscreen, more specifically the organic ultra-violet filters (O-UVFs), are toxic for aquatic organisms. In the present study, we simulated an environmental sunscreen exposure on the teleost fish, Chelon auratus. The first objective was to assess their spatial avoidance of environmental concentrations of sunscreen products (i.e. a few μg.L -1 of O-UVFs). Our results showed that the fish did not avoid the contaminated area. Therefore, the second objective was to evaluate the toxicological impacts of such pollutants after 35 days exposure to concentrations of a few μg.L -1 of O-UVFs. At the individual level, O-UVFs increased the hepatosomatic index which could suggest pathological alterations of the liver or the initiation of the detoxification processes. At the cellular level, a significant increase of malondialdehyde was measured in the muscle of fish exposed to O-UVFs which suggests a failure of antioxidant defences and/or an excess of reactive oxygen species., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

Aquatic environments have been found to be contaminated with a variety of inorganic and organic UV filters. This includes novel nano-sized titanium dioxide (TiO 2 ) 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 TiO 2 UV filters with different surface coatings, namely Eusolex® T-Avo (SiO 2 -coated), T-Lite™ SF (Al(OH) 3 /PDMS-coated), and Eusolex® T-S (Al 2 O 3 /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 TiO 2 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 TiO 2 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., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Tobias Lammel reports financial support was provided by Swedish Research Council Formas. Tobias Lammel reports financial support was provided by German Research Foundation. Tobias Lammel reports financial support was provided by Stiftelsen Wilhelm och Martina Lundgrens Vetenskapsfond. Tobias Lammel reports financial support was provided by Helge Axelsson Johnsons Stiftelse., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

The fate of sunscreen residues released during bathing activities around recreational areas is an emerging concern regarding the potential ecotoxicity of some of their ingredients, including nanoparticulate TiO 2 UV-filters. To assess the extent of contamination in the natural medium, sand-packed column experiments were carried out with bare TiO 2 engineered nanoparticles (ENPs) and two commercial nano-TiO 2 UV-filters coated with either SiO 2 (hydrophilic) or a combination of Al 2 O 3 and simethicone (amphiphilic). The high sensitivity of (single particle)ICPMS online monitoring of the breakthrough curves made it possible to inject the ENPs at trace levels (2-100 μg L -1 ) in eluents composed of 10 -3 and 10 -2  M NaCl and pHs of 5.7 and 7.8. The deposition of all ENPs in the sand increased with the ionic strength and decreased with the pH of the carrier. Both bare and SiO 2 -coated ENPs showed a clear control by the electrostatic interactions between the particles and the quartz grains surfaces, in partial agreement with classical DLVO theory. Unexpectedly high rates of transfer were observed with the amphiphilic UV-filter, which could be explained by the addition of a contribution to the DLVO model to account for the steric repulsion between the sand collector and the polysiloxane surface layer of this ENP. These results demonstrate the major role played by the coating of UV-filters regarding their fate in porous media like soils, sediments and aquifers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

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 TiO 2 , 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., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

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 TiO 2 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 TiO 2 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 (NOM tot ) 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 TiO 2 NPs remained in suspension when only NOM <0.8 was present compared to the unfiltered water containing mineral particulate matter and NOM tot . These results demonstrate the contrasting NP fates in the aquatic environment according to the presence of NOM tot 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., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Successive transport experiments of TiO 2 nanoparticles (NP) suspension through fractured hard-rock column were done in laboratory. A low ionic strength (IS) water (0.8-1.3 10 -3 M) at pH ∼4.5 was used, corresponding to the chemical composition of groundwater where the rock was collected (Naizin, France). The surface charge of TiO 2 NP was positive while that of rock was negative favoring NP deposition. SEM/EDX reveals that NP were retained on a broad distribution of mineral collectors along the preferential flow pathways (i.e., fractures). However, a non-negligible amount of NP (∼10%) was transferred through the rock. Divalent cation (Ca 2+ ) was responsible for the reduction of the negative charge of the rock and thus contributed to limit the NP deposition as attested by DLVO model. Blocking of rock surfaces by NP favored NP transfer while the ripening process and the size exclusion of aggregates decreased NP mobility. Decrease of water flow favored the exchange of solutes from the immobile to the mobile water in the porous medium, which in turn favored the aggregation of the NP and led to their natural attenuation. The result evidences how slight modifications of the environmental conditions can strongly influence the fate of NP in groundwater., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Engineered nanoparticle (ENP) fate models developed to date - aimed at predicting ENP concentration in the aqueous environment - have limited applicability because they employ constant environmental conditions along the modeled system or a highly specific environmental representation; both approaches do not show the effects of spatial and/or temporal variability. To address this conceptual gap, we developed a novel modeling strategy that: 1) incorporates spatial variability in environmental conditions in an existing ENP fate model; and 2) analyzes the effect of a wide range of randomly sampled environmental conditions (representing variations in water chemistry). This approach was employed to investigate the transport of nano-TiO2 in the Lower Rhône River (France) under numerous sets of environmental conditions. The predicted spatial concentration profiles of nano-TiO2 were then grouped according to their similarity by using cluster analysis. The analysis resulted in a small number of clusters representing groups of spatial concentration profiles. All clusters show nano-TiO2 accumulation in the sediment layer, supporting results from previous studies. Analysis of the characteristic features of each cluster demonstrated a strong association between the water conditions in regions close to the ENP emission source and the cluster membership of the corresponding spatial concentration profiles. In particular, water compositions favoring heteroaggregation between the ENPs and suspended particulate matter resulted in clusters of low variability. These conditions are, therefore, reliable predictors of the eventual fate of the modeled ENPs. The conclusions from this study are also valid for ENP fate in other large river systems. Our results, therefore, shift the focus of future modeling and experimental research of ENP environmental fate to the water characteristic in regions near the expected ENP emission sources. Under conditions favoring heteroaggregation in these regions, the fate of the ENPs can be readily predicted., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Water flow and TiO2 nanoparticle (NP) transfer in a fractured hard-rock aquifer were studied in a tracer test experiment at a pilot site in Brittany, France. Results from the Br tracer test show that the schist aquifer can be represented by a two-layer medium comprising i) fractures with low longitudinal dispersivity in which water and solute transport is relatively fast, and ii) a network of small fissures with high longitudinal dispersivity in which transport is slower. Although a large amount of NPs was retained within the aquifer, a significant TiO2 concentration was measured in a well 15m downstream of the NP injection well, clearly confirming the potential for TiO2 NPs to be transported in groundwater. The Ti concentration profile in the downstream well was modelled using a two-layer medium approach. The delay used for the TiO2 NPs simulation compared to the Br concentration profiles in the downstream well indicate that the aggregated TiO2 NPs interacted with the rock. Unlike Br, NPs do not penetrate the entire pore network during transfer because of electrostatic interactions between NP aggregates and the rock and also to the aggregate size and the hydrodynamic conditions, especially where the porosity is very low; NPs with a weak negative charge can be attached onto the rock surface, and more particularly onto the positively charged iron oxyhydroxides coating the main pathways due to natural denitrification. Nevertheless, TiO2 NPs are mobile and transfer within fracture and fissure media. Any modification of the aquifer's chemical conditions is likely to impact the groundwater pH and, the nitrate content and the denitrification process, and thus affect NP aggregation and attachment., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The bacterial reverse mutation test, recommended by the Organization for Economic Co-operation and Development (OECD) to determine genotoxicity of chemical compounds, has been recently used by several authors to investigate nanoparticles. Surprisingly, test results have been negative, whereas in vitro mammalian cell tests often give positive genotoxic responses. In the present study, we used the fluctuation test procedure with the Salmonella typhimurium strains TA97a, TA98, TA100 and TA102 to determine the mutagenic potential of TiO(2) nanoparticles (NP-TiO(2)) and showed that, when it is used conventionally, this test is not suitable for nanoparticle genotoxicity assessment. Indeed, the medium used during exposure prevents electrostatic interactions between bacterial cells and nanoparticles, leading to false-negative responses. We showed that a simple pre-exposure of bacteria to NP-TiO(2) in a low ionic strength solution (NaCl 10mM) at a pH below the nanoparticle isoelectric points (pH 5.5) can strongly improve the accuracy of the test. Thus, based on these improvements, we have demonstrated the genotoxicity of the engineered NP-TiO(2) tested and a NP-TiO(2) byproduct from a sunscreen nanocomposite. It was also shown that strain TA102 is more sensitive than the other strains, suggesting an oxidative stress-mediated mechanism of genotoxicity., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)