Effects associated with exposure to the emerging contaminant octyl-methoxycinnamate (a UV-B filter) in the aquatic environment: a review.

Given the increasing concern surrounding ultraviolet (UV) radiation-induced skin damage, there has been a rise in demand for UV filters. Currently, UV-filters are considered emerging contaminants. The extensive production and use of UV filters have led to their widespread release into the aquatic environment. Thus, there is growing concern that UV filters may bioaccumulate and exhibit persistent properties within the environment, raising several safety health concerns. Octyl-methoxycinnamate (OMC) is extensively employed as a UV-B filter in the cosmetic industry. While initially designed to mitigate the adverse photobiological effects attributed to UV radiation, the safety of OMC has been questioned with some studies reporting toxic effects on environment. The aim of this review to provide an overview of the scientific information regarding the most widely used organic UV-filter (OMC), and its effects on biodiversity and aquatic environment.

Biomineralization: A new tool for developing eco-sustainable Ti-doped hydroxyapatite-based hybrid UV filters.

It is well known that the prolonged exposure to UV radiation from sunlight can compromise human health and is particularly damaging to the skin, leading to sunburn, photo-aging and skin cancer. Sunscreen formulations containing UV-filters present a barrier against solar UV and help to mitigate the harmful effects however, concern about their safety for both human and environmental health is still a much-debated topic. EC regulations classify UV-filters depending on their chemical nature, particle size, and mechanism of action. Furthermore, it regulates their use in cosmetic products with specific limitations in terms of concentration (organic UV filters) and particle size and surface modification to reduce their photo-activity (mineral UV filters). The regulations have prompted researchers to identify new materials that show promise for use in sunscreens. In this work, biomimetic hybrid materials composed of titanium-doped hydroxyapatite (TiHA) grown on two different organic templates, derived from animal (gelatin - from pig skin) and vegetable (alginate - from algae) sources. These novel materials were developed and characterized to obtain sustainable UV-filters as a safer alternative for both human and ecosystem health. This 'biomineralization' process yielded TiHA nanoparticles that demonstrated high UV reflectance, low photoactivity, good biocompatibility and an aggregate morphology which prevents dermal penetration. The materials are safe for topical application and for the marine environment; moreover, they can protect organic sunscreen components from photodegradation and yield long-lasting protection.

The Impact of Flavonoid-Loaded Nanoparticles in the UV Protection and Safety Profile of Topical Sunscreens.

Excessive UV radiation exposure is harmful to skin cells since sunburn is accompanied by oxidative burst, leading to a rapid increase in skin cancer. However, the insufficient UV photoprotection of approved sunscreens and the negative impact of their compositions on ecosystems and human health makes the utility of sunscreen a questionable recommendation. Therefore, discovering UV filters with significant antioxidant activity and improved topical performance and photostability is an urgent need. Recently, the use of nanosized natural molecules incorporated in sunscreens has been a scientific hot topic, as it has been suggested that they provide a synergistic effect with synthetic UV filters, improving overall SPF and antioxidant activity, higher retention on the epidermis, and less toxicity. The aim of this review was to verify the usefulness of sunscreens incorporating flavonoid-loaded nanoparticles. A literature review was performed, where original and review articles published in the last 6 years were analyzed. Formulations containing nanosized flavonoids with improved UVA photoprotection and safer toxicological profiles, associated or not with synthetic filters, are promising sunscreens and more clinical investigation must be performed to validate these findings.

How to Control Powder Alignment to Maximize Functionality and Performance of Color Cosmetics and Sunscreen.

Control of powder alignment is essential for maximizing the functionality of color cosmetics and sunscreens. Various surface treatments were applied to nanosized titanium dioxide to modify their surface characteristics. Such modifications can be used to control the behavior of dispersions in cosmetics, enabling them to align uniformly. The powders were mixed with solvents and applied to a cellulose triacetate film. The features of powder alignment on the film were evaluated using several approaches. When the type of surface treatment changed by varying the weight ratio, there was no significant correlation between its alignment and treatment. However, when we focused on the pseudo-HLB each treated pigment, their alignments were correlated. It was confirmed that the powders subjected to the appropriate surface treatment combinations from the pseudo-HLB standpoint made it possible to align uniformly and create a smooth coating film. As a result, it has a high UV-shielding ability. The surface-treated powders in this study were found to change the UV shielding ability and surface roughness of the layer formed when they were formed by spreading the sample powder dispersion and drying of the film. It was suggested that the pseudoHLB, which is calculated based on the chemical structure after the surface treatment process, is useful for choosing the optimum surface treatment to create a uniformly aligned pigment layer.

Triplet stabilization for enhanced drug photorelease from sunscreen-based photocages.

Recently, sunscreen-based drug photocages have been introduced to provide UV protection to photoactive drugs, thus increasing their photosafety. Here, combined experimental and theoretical studies performed on a photocage based on the commercial UVA filter avobenzone (AB) and on the photosensitizing non-steroidal anti-inflammatory drug ketoprofen (KP) are presented unveiling the photophysical processes responsible for the light-triggered release. Particular attention is paid to solvent stabilization of the drug and UV filter excited states, respectively, which leads to a switching between the triplet excited state energies of the AB and KP units. Most notably, we show that the stabilization of the AB triplet excited state in ethanol solution is the key requirement for an efficient photouncaging. By contrast, in apolar solvents, in particular hexane, KP has the lowest triplet excited state, hence acting as an energy acceptor quenching the AB triplet manifold, thus inhibiting the desired photoreaction.

Substitution effect on the nonradiative decay and trans → cis photoisomerization route: a guideline to develop efficient cinnamate-based sunscreens.

Cinnamate derivatives are very useful as UV protectors in nature and as sunscreen reagents in daily life. They convert harmful UV energy to thermal energy through effective nonradiative decay (NRD) including trans → cis photoisomerization. However, the mechanism is not simple because different photoisomeirzation routes have been observed for different substituted cinnamates. Here, we theoretically examined the substitution effects at the phenyl ring of methylcinnamate (MC), a non-substituted cinnamate, on the electronic structure and the NRD route involving trans → cis isomerization based on time-dependent density functional theory. A systematic reaction pathway search using the single-component artificial force-induced reaction method shows that the very efficient photoisomerization route of MC can be essentially described as "1ππ* (trans) → 1nπ* → T1 (3ππ*) → S0 (trans or cis)". We found that for efficient 1ππ* (trans) → 1nπ* internal conversion (IC), MC should have the substituent at the appropriate position of the phenyl ring to stabilize the highest occupied π orbital. Substitution at the para position of MC slightly lowers the 1ππ* state energy and photoisomerization occurs via a slightly less efficient "1ππ* (trans) → 3nπ* → T1 (3ππ*) → S0 (trans or cis)" pathway. Substitution at the meta or ortho positions of MC significantly lowers the 1ππ* state energy so that the energy barrier of IC (1ππ* → 1nπ*) becomes very high. This substitution leads to a much longer 1ππ* state lifetime than that of MC and para-substituted MC, and a change in the dominant photoisomerization route to "1ππ* (trans) → C[double bond, length as m-dash]C bond twisting on 1ππ* → S0 (trans or cis)". As a whole, the "1ππ* → 1nπ*" IC observed in MC is the most important initial step for the rapid change of UV energy to thermal energy. We also found that the stabilization of the π orbital (i) minimizes the energy gap between 1ππ* and 1nπ* at the 1ππ* minimum and (ii) makes the 0-0 level of 1ππ* higher than 1nπ* as observed in MC. These MC-like relationships between the 1ππ* and 1nπ* energies should be ideal to maximize the "1ππ* → 1nπ*" IC rate constant according to Marcus theory.

Unravelling the Photoprotective Mechanisms of Nature-Inspired Ultraviolet Filters Using Ultrafast Spectroscopy.

There are several drawbacks with the current commercially available ultraviolet (UV) filters used in sunscreen formulations, namely deleterious human and ecotoxic effects. As a result of the drawbacks, a current research interest is in identifying and designing new UV filters. One approach that has been explored in recent years is to use nature as inspiration, which is the focus of this review. Both plants and microorganisms have adapted to synthesize their own photoprotective molecules to guard their DNA from potentially harmful UV radiation. The relaxation mechanism of a molecule after it has been photoexcited can be unravelled by several techniques, the ones of most interest for this review being ultrafast spectroscopy and computational methods. Within the literature, both techniques have been implemented on plant-, and microbial-inspired UV filters to better understand their photoprotective roles in nature. This review aims to explore these findings for both families of nature-inspired UV filters in the hope of guiding the future design of sunscreens.

Sodium cationization can disrupt the intramolecular hydrogen bond that mediates the sunscreen activity of oxybenzone.

A key decay pathway by which organic sunscreen molecules dissipate harmful UV energy involves excited-state hydrogen atom transfer between proximal enol and keto functional groups. Structural modifications of this molecular architecture have the potential to block ultrafast decay processes, and hence promote direct excited-state molecular dissociation, profoundly affecting the efficiency of an organic sunscreen. Herein, we investigate the binding of alkali metal cations to a prototype organic sunscreen molecule, oxybenzone, using IR characterization. Mass-selective IR action spectroscopy was conducted at the free electron laser for infrared experiments, FELIX (600-1800 cm-1), on complexes of Na+, K+ and Rb+ bound to oxybenzone. The IR spectra reveal that K+ and Rb+ adopt binding positions away from the key OH intermolecular hydrogen bond, while the smaller Na+ cation binds directly between the keto and enol oxygens, thus breaking the intramolecular hydrogen bond. UV laser photodissociation spectroscopy was also performed on the series of complexes, with the Na+ complex displaying a distinctive electronic spectrum compared to those of K+ and Rb+, in line with the IR spectroscopy results. TD-DFT calculations reveal that the origin of the changes in the electronic spectra can be linked to rupture of the intramolecular bond in the sodium cationized complex. The implications of our results for the performance of sunscreens in mixtures and environments with high concentrations of metal cations are discussed.

Survey of cytotoxic and UV protection effects of biosynthesized cerium oxide nanoparticles.

Cerium oxide nanoparticles (CeO2 NPs) are among the important nanoparticles that are extensively utilized in cosmetics, automotive industries, ultraviolet (UV) filtration, gas sensors, and pharmaceutical products. In this study, CeO2 NPs were synthesized using an aqueous extract of Ziziphus jujube fruit. The synthesized nanoparticles were characterized using UV-visible spectroscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, energy-dispersive spectroscopy, field energy scanning electron microscopy, and Raman methods. The results indicated that the size of synthesized nanoparticles is between 18 and 25 nm, and they have a spherical shape. UV absorbance of the synthesized nanoparticles was measured through spectrophotometric method in the range of 290 to 320 nm. The cytotoxic activity of synthesized CeO2 NPs against colon (HT-29) cancer cell line was surveyed through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The results showed that synthesized nanoparticles are nontoxic on HT-29 cells under 400 µg/mL concentrations after 24 hours of treatment time periods. The increase in treatment time cases increases cytotoxic activity of synthesized nanoparticles. Sun protection factor of CeO2 NPs, as a criterion for amount of sunlight radiation protection, was determined by applying Mansur equation. The results demonstrated that synthesized CeO2 NPs have excellent UV protection and sunscreen physical absorption properties.

The Influence of Short-Wave and Long-Wave Radiation Spectrum on the Photostability of Sunscreens.

BACKGROUND: Sunscreen products aim to help protect the skin against UV radiation and consequently reduce the risk of early skin ageing and skin cancer. However, it is well known that some sunscreen ingredients are not photostable, but this usually refers to irradiation with UV light. Moreover, it has to be mentioned that a relative cumulative erythema effectiveness compliant light source is used for the in vivo sun protection factor (SPF) testing. Here, UV simulators equipped with a xenon arc lamp use filters such as WG320 and UG11 (thickness 1 mm) to minimize infrared (IR) radiation and wavelength below 300 nm. However, under practical conditions, the sunscreen product is not only exposed to UVA/B light, but also to visible light (VIS) and IR light. In fact, the spectrum of solar radiation is composed of approximately 7% UV, 39% VIS and 54% IR. AIMS: To investigate the influence of short-wave and long-wave radiation on the photostability of sunscreens. METHODS: Irradiation was performed with the Suntest CPS+ that is considered to closely imitate solar radiation. The filter UG11 (thickness 1 mm), which absorbs much of the VIS and IR light, and the glass filter WG320 (thickness 2 mm), which effectively absorbs radiation of wavelengths less than 300 nm, were used in the Suntest CPS+ both individually and in combination and were inserted between the light source and the samples. The following transmission measurements were carried out with Labsphere's UV-2000s device. Here, the effectiveness (percentage change of SPF before irradiation to SPF after irradiation) as a measure of the photostability was calculated. RESULTS: As expected after total solar spectrum irradiation, the effectiveness in all tested sunscreens is lower compared to relative cumulative erythema effectiveness light used for in vitro testing of SPF. In the reference sunscreen formula S2 as well as in the two different sunscreen products, especially long-wave radiation (>400 nm) had an effect on photostability, whereas short-wave radiation had only a minor impact. In contrast, in the BASF sun care gel line only short-wave radiation below 300 nm had an effect on photostability, and blocking VIS and IR light had no effect at all. CONCLUSION: Based on these data, we can conclude that short waves and/or VIS + IR light have an influence on the photostability of sunscreens.

Synergistic effects of binary oil mixtures on the solubility of sunscreen UV absorbers.

Sunscreens for the photoprotection of human skin often are prepared as emulsions, containing organic UV-absorber molecules dissolved in the oil phase. The solubility of such oil-soluble UV-absorbers can be a limiting factor when aiming for high protection against UV-radiation. Possible synergistic effects of combinations of oil components toward UV-absorber solubility are therefore of great interest. Since a multitude of different combinations of oil components are possible, it would be desirable to predict synergistic effects by computational methods. As a model system, the solubility of a hydroxyphenyl triazine type UV-absorber was studied in several binary oil mixtures, experimentally and also by using a computational procedure based on density functional theory (DFT) and the continuum solvation model COSMO-RS. We have found good agreement of experimental and computational results. Computational methods may thus be employed to predict synergistic behaviour of solubility for systems containing two or more solvents.

Discovery of Novel UV-Filters with Favorable Safety Profiles in the 5-Arylideneimidazolidine-2,4-dione Derivatives Group.

Effective protection from the harmful effects of UV radiation may be achieved by using sunscreens containing organic or inorganic UV filters. The number of currently available UV filters is limited and some of the allowed molecules possess limitations such as systemic absorption, endocrine disruption properties, contact and photocontact allergy induction, and low photostability. In the search for new organic UV filters we designed and synthesized a series consisting of 5-benzylidene and 5-(3-phenylprop-2-en-1-ylidene)imidazolidine-2,4-dione (hydantoin) derivatives. The photoprotective activity of the tested compounds was confirmed in methanol solutions and macrogol formulations. The most promising compounds possessed similar UV protection parameter values as selected commercially available UV filters. The compound diethyl 2,2'-((Z)-4-((E)-3-(4-methoxyphenyl)allylidene)-2,5-dioxoimidazolidine-1,3-diyl)diacetate (4g) was characterized as an especially efficient UVA photoprotective agent with a UVA PF of 6.83 ± 0.05 and favorable photostability. Diethyl 2,2'-((Z)-4-(4-methoxybenzylidene)-2,5-dioxo- imidazolidine-1,3-diyl)diacetate (3b) was the most promising UVB-filter, with a SPFin vitro of 3.07 ± 0.04 and very good solubility and photostability. The main photodegradation products were geometric isomers of the parent compounds. These compounds were also shown to be non-cytotoxic at concentrations up to 50 µM when tested on three types of human skin cells and possess no estrogenic activity, according to the results of a MCF-7 breast cancer model.

Elimination efficiency of organic UV filters during ozonation and UV/H2O2 treatment of drinking water and wastewater effluent.

The efficiency of elimination of organic UV filters by ozonation and UV254nm/H2O2 processes was assessed and predicted in simulated treatments of sewage-impaired drinking water and wastewater effluent in bench-scale experiments. Second-order rate constants (k) for the reactions of the eight UV filters with ozone and OH were determined by quantum chemical calculations and competition kinetics methods, respectively. The UV filters containing phenolic (ethylhexyl-salicylate, homosalate, and benzophenone-3) and olefinic moieties (4-methylbenzylidene-camphor, benzyl-cinnamate, and 2-ethylhexyl-4-methoxycinnamate) showed high ozone reactivity (k ≥ 8 × 104 M-1s-1 at pH 7), while those without such electron-rich moieties (isoamyl-benzoate and benzophenone) were ozone-refractory. All the UV filters showed high OH reactivity (k ≥ 6.2 × 109 M-1s-1). In concordance with the rate constant information, the phenolic and olefinic UV filters were efficiently eliminated by ozone treatment, requiring specific ozone doses of <0.5 mgO3/mgDOC for ∼100% elimination. The UV filters were eliminated by ≤ 38% at a UV fluence of 1500 mJ/cm2 in the UV254nm-only treatment. Rapid photoisomerisation between the E and Z geometric isomers was observed for the olefinic UV filter, benzyl-cinnamate. The addition of H2O2 (10 mg/L) greatly enhanced the elimination of all UV filters, indicating that OH was the main contributor to their elimination in the UV254nm/H2O2 treatment. A chemical kinetics approach developed previously for ozonation and UV/H2O2 processes was shown to predict the elimination of the UV filters in the tested water matrices reasonably well, demonstrating that the chemical kinetics method can be used for a priori prediction of micropollutant elimination in oxidative treatment processes for potable reuse of municipal wastewater effluents.

Surface Structures of Cosmetic Standard Poly Methyl Methacrylate UV Evaluation Plates and their Influence on the in vitro Evaluation of UV Protection Abilities of Cosmetic Sunscreens.

Cosmetic standard poly methyl methacrylate (PMMA) UV evaluation plates, i.e., roughened PMMA plates, are used in the EU and the US for the in vitro evaluation of UV protection abilities of sunscreen, such as in vitro UVA-PF and critical wavelength for the Broad-spectrum approval. In our previous studies, inhomogeneity in the thickness of a pseudo-sunscreen layer applied on a flat quartz plate was observed to alter UV transmission. Thus, the surface roughness of the standard plates should have a significant influence on the in vitro evaluation. In the present study, we have analyzed the surface structures of three cosmetic standard PMMA UV evaluation plates: Helioplates HD6 (Sa = 6 µm) and ISO plates (Ra = 2 and 5 µm). A decamethylcyclopentasiloxane and 2-propanol-mixed solvent solution of acrylsilicone resin was prepared, and the solution was added dropwise onto the plates. After the evaporation of the solvents, the plates were cut and the cross section was analyzed using SEM-EDS. The distribution of silicon atoms at the cross-section suggested that the maximum depth of penetrating of acrylsilicone resin was larger than Ra for all the standard plates, and the surface structure was significantly different for each standard plate. In addition, cracks into which the acrylsilicone resin deeply penetrated were observed on the surface of some plates. Clear-solution-type pseudo-sunscreen samples in which UV absorbers and acrylsilicone resin were dissolved were deposited on the standard roughened PMMA plates. It was observed that the addition of acrylsilicone resin drastically changed the net UV transmission. The degree to which the hollows of the roughened surface were filled with the pseudo-sunscreen samples determined the variation of UV transmittance.

Comparison of UVB effects on growth and induction of UVB screening compounds in isolates of metaphytic algae from temperate zone streams and ponds.

Filaments in the surface layers of metaphytic mats are exposed to high photon flux densities of PAR and UVBR. We investigated the effect of UVBR exposure on growth of eight isolates of common metaphytic algae (Cladophora, Mougeotia, Oedogonium, Pithophora, Spirogyra, and Zygnema) acclimated to either high or low PAR levels prior to UVBR exposure. All isolates acclimated to low PAR exhibited significant reductions in growth rate caused by the UVBR exposure (P < 0.05). Acclimation to high PAR resulted in seven of the isolates being more tolerant of the UVB exposure. The two Zygnema isolates exhibited the most pronounced effect of high PAR acclimation with growth rates of UVB exposed treatments being equal to that of controls (P > 0.05). High PAR acclimation also protected chlorophyll a levels in the Zygnema isolates. Absorption of UVB by methanol extracts increased 322%-381% for the two Zygnema isolates when high PAR acclimated. The broad absorption peak at 270 nm suggests that phenolic compounds were responsible. Previous studies have shown that Zygnema isolates from extreme environments tolerate UVBR and contain UVB screening compounds, but our results extend these adaptions to Zygnema from typical temperate zone habitats. Although none of the other metaphytic algae produced UVB absorbing compounds, they all exhibited higher growth rates under UVBR exposure following high PAR acclimation. This suggests that the algae evaluated have inducible defenses against UVBR exposure that coupled with their mat structure would provide an adaption to the challenging light environment in shallow-water habitats.

Comparative behavior between sunscreens based on free or encapsulated UV filters in term of skin penetration, retention and photo-stability.

BACKGROUND: The growing incidence of photodamaging effects caused by UV radiation (e.g. sunburn, skin cancer) has increased the attention from health authorities which recommend the topical application of sunscreens to prevent these skin damages. The economic stakes for those companies involved in this international market are to develop new UV filters and innovative technologies to provide the most efficient, flexible and robust sunscreen products. Today the development of innovative and competitive sunscreen products is a complex formulation challenge. Indeed, the current sunscreens must protect against skin damages, while also being safe for the skin and being sensory and visually pleasant for the customers when applied on the skin. Organic UV filters, while proposing great advantages, also present the risk to penetrate the stratum corneum and diffuse into underlying structures with unknown consequences; moreover, their photo-stability are noted thorny outcomes in sunscreen development and subsequent performance. In recent years, the evaluation of the interaction between skin and sunscreen in terms of penetration after topical application has been considered from European authority but still its testing as their photo-stability assessment are not mandatory in most countries. OBJECTIVE: This study, based on in-vitro approaches, was performed to evaluate and compare the retention and the penetration of organic UV filters in free or encapsulated form inside the skin as well as their respective photo-stability. METHODS: Sunscreen formulation with a combination of Avobenzone and Octocrylene in "free form" and a formulation using the same UV filters but encapsulated in a sol-gel silica capsule, were analyzed and compared by FTIR Imaging Spectroscopy. Tape stripping method was used to investigate the penetration of these UV filters inside the stratum corneum. Their photo-stabilities were evaluated by spectroscopic measurements (FTIR, UV/Vis) and standard measurements were calculated: AUC (Area Under the Curve) and SPF (Sun Protection Factor). RESULT: With traditional formulation, the organic UV filters penetrated significantly into the stratum corneum while the same UV filters combined with encapsulation technology remained on the skin surface. The encapsulation technology also improved significantly their stability. CONCLUSION: Encapsulation technology is a promising strategy to improve the efficacy of sunscreen product using organic UV filters and to reduce safety problem. On the other hand, this study highlighted the pertinence of the FTIR Spectroscopy to test, compare and investigate sunscreen formulations.

Skin protection efficacy from UV irradiation and skin penetration property of polysaccharide-benzophenone conjugates as a sunscreen agent.

Sunscreen materials have been developed to protect skin from UV radiation. However, many organic sunscreen materials are small molecules and absorbed into human skin after topical application and lead to systemic side effects. To improve the adverse effects of conventional sunscreen materials, we designed a sunscreen agent using an organic sunscreen material and a polymer. Dioxybenzone, an organic sunscreen compound is selected and polymerized with natural polymer pullulan. Polymerization not only provides a long polymer backbone to dioxybenzone, but also keeps the distance between benzene rings of the dioxybenzone and prevents reduction of photoabsorption intensity. UV/vis spectrophotometry confirmed that dioxybenzone-pullulan polymer (DOB-PUL) and dioxybenzone (DOB) demonstrated similar UV absorption. To measure the accumulation of sunscreen materials on skin, Franz diffusion cell was used to confirm the accumulation of DOB and lack of penetration of DOB-PUL. Most importantly, DOB showed higher plasma concentration after multiple applications compared to that of DOB-PUL.

Trade-offs in ecosystem impacts from nanomaterial versus organic chemical ultraviolet filters in sunscreens.

Both nanoparticulate (nZnO and nTiO2) and organic chemical ultraviolet (UV) filters are active ingredients in sunscreen and protect against skin cancer, but limited research exists on the environmental effects of sunscreen release into aquatic systems. To examine the trade-offs of incorporating nanoparticles (NPs) into sunscreens over the past two decades, we targeted endpoints sensitive to the potential risks of different UV filters: solar reactive oxygen production in water and disruption of zebrafish embryo development. First, we developed methodology to extract nanoparticles from sunscreens with organic solvents. Zebrafish embryos exposed to parts-per-million NPs used in sunscreens displayed limited toxicological effects; nZnO particles appeared to be slightly more toxic than nTiO2 at the highest concentrations. In contrast, seven organic UV filters did not affect zebrafish embryogenesis at or near aqueous solubility. Second, to simulate potent photo-initiated reactions upon release into water, we examined methylene blue (MB) degradation under UV light. nTiO2 from sunscreen caused 10 times faster MB loss than nZnO and approached the photocatalytic degradation rate of a commercial nTiO2 photocatalysts (P25). Organic UV filters did not cause measurable MB degradation. Finally, we estimated that between 1 and 10 ppm of sunscreen NPs in surface waters could produce similar steady state hydroxyl radical concentrations as naturally occurring fluvic acids under sunlight irradiation. Incorporation of NPs into sunscreen may increase environmental concentrations of reactive oxygen, albeit to a limited extent, which can influence transformation of dissolved substances and potentially affect ecosystem processes.