Waterborne exposure to avobenzone and octinoxate induces thyroid endocrine disruption in wild-type and thrαa-/- zebrafish larvae

The dual challenge of FDA-evaluated non-GRASE UV filters: Photostability and systemic absorption - A path toward safer and more effective sunscreens

Category III Non-GRASE (Generally Recognized as Safe and Effective) UV filters (UVFs), such as avobenzone, octocrylene, oxybenzone, octinoxate, octisalate, and homosalate, face two significant challenges: photodegradation and systemic absorption. Many of these UVFs break down when exposed to sunlight, reducing their effectiveness and generating potentially harmful byproducts which will absorbed by the body. Researchers have developed various stabilization strategies to address these challenges and enhance UVF performance while minimizing health risks. Encapsulation techniques, such as embedding UVFs in silica, liposomes, and polymer matrices, help reduce systemic absorption while maintaining UV protection. Nano-Hybrid organic-inorganic formulations, a nano-scale version of pairing between organic and inorganic UVFs, have also shown promise in improving photostability and preventing degradation. Additionally, polymeric UVFs and controlled-release systems offer long-lasting sun protection, ensuring that the active ingredients remain effective over time. Multi-phase emulsions and layered sunscreen formulations further reduce photodegradation, providing more stable and reliable UV protection. With increasing regulatory scrutiny and growing concerns about environmental and human health impacts, this review explores the dual challenge (balancing stability and safety) faced by non-GRASE UVFs. By integrating advanced materials and innovative formulation technologies, next-generation sunscreens have the potential to deliver superior photoprotection while being safe to human.

Blood Biochemical Biomarkers in Fish Toxicology-A Review

Blood-based biochemical assays are used as predictive and diagnostic methods to evaluate fish welfare in aquaculture and research. The variations of blood biochemical parameters in fish are commonly used as biomarkers of exposure to toxic agents. Blood biochemical parameters can help identify the magnitude of toxicity and the mechanisms by which particular toxic agents act on the organisms. Some parameters typically measured in the blood can also be evaluated in the whole body in the early developmental stages of fish (embryos and larvae) that are often used in toxicological studies. This review assessed the usefulness of various blood biochemical indices as toxicity biomarkers. Analysis of multiple studies showed that toxicity-induced changes in most blood biochemical parameters in fish often depend on toxic agent concentration and exposure duration. Also, various parameters manifest different sensitivity to intoxication, and diverse directions of changes may occur. Among biochemical parameters, some are biomarkers of general physiological stress, while others indicate dysfunctions of particular organs. Moreover, hormonal endpoints seem to be sensitive but nonspecific biomarkers of intoxication in fish.

A novel approach for unveiling co-occurrence patterns of UV filter mixtures in sunscreens: Prioritization for hazard and risk assessment

In recent years, concerns regarding the toxicity of organic UV filters in sunscreen products have increased. While sunscreen products contain multiple UV filters in combination, current understanding on their co-occurrence patterns and mixture toxicities is still limited. This study utilized a public database, "Hwahae", and analyzed 2183 sunscreen products marketed in South Korea as of 2019, using an association rule mining (ARM) to elucidate their co-occurrence patterns. We identified twenty-two UV filters in the sunscreen products, with titanium dioxide (TiO2) being the most prevalent (68 %), followed by ethylhexyl methoxycinnamate (EHMC, 60 %) and ethylhexyl salicylate (EHS, 49 %). Sunscreen products typically contained a median of five UV filters per product. Usage patterns of UV filter mixtures varied by the target user group of the product, i.e., general, susceptible, and male users. EHMC and EHS were commonly combined in most products, except those marketed for susceptible users. For susceptible users, inorganic UV filters such as TiO2 and zinc oxide (ZnO) were dominantly used. Combinations of UV filters that provide protection against different types of UV light, e.g., butyl methoxydibenzoylmethane (BMDBM) for UVA, and octocrylene (OCT), EHS, or homosalate (HS) for UVB, were also frequently used together, with high lift values. In conclusion, our study demonstrated that ARM approach can be useful to identify major combinations of UV filters present in sunscreen products, and prioritize the UV filter combinations requiring safety assessment and regulatory attention.

In vitro study of the UV-filter homosalate effects on rat and human thyroid cells

Homosalate is a UV-B filter, commonly used in sunscreens and personal-care products. Homosalate was shown to exert estrogenic and anti-androgenic effects in animal models, while few data are available on the effects of Homosalate on thyroid cells. The aim of this study was to evaluate if Homosalate exposure could exert adverse effect on thyroid cells in vitro. FRTL-5 and NHT were treated with increasing concentration of Homosalate for 24-48-72 h. Cell viability was assessed by WST-1. Cell proliferation was evaluated by cristal violet. Micronucleus staining was performed to assess genotoxicity. mRNA levels of thyroid-related genes (TSHR, TPO, TG, NIS, and PAX8) were evaluated by RT-PCR. Changes in ROS production by FRTL-5 and NHT were assessed with H2DCFDA. Homosalate significantly reduced cell viability after 72 h in FRTL-5 starting from the concentration 250 μM, while in NHT, Homosalate exposure significantly reduced cell viability after 48 and 72 h only at highest concentration (2000 μM). Cell proliferation was not modified by Homosalate at any concentration and time-point. Homosalate significantly up-regulated mRNA expression levels of TPO and Tg genes in FRTL-5, while a significant increase only in Tg mRNA expression was observed in NHT. No changes in ROS production was found in both cell types. The present study suggest that the effects of Homosalate exposure may differ according to the type of cell tested. The in vitro exposure of thyroid cells to Homosalate produces: i) cytotoxicity at high concentrations or after long time of incubation, ii) genotoxicity only in rat thyroid cells at the highest concentration, iii) upregulation of Tg mRNA in both thyroid cell types and of TPO mRNA in rat thyroid cells, iv) no changes in cell proliferation or oxidative stress. Further studies on the effects of Homosalate on thyroid cells should be encouraged.

Organic Sunscreens-Is Their Placenta Permeability the Only Issue Associated with Exposure During Pregnancy? In Silico Studies of Sunscreens' Placenta Permeability and Interactions with Selected Placental Enzymes

One of the functions of placenta is to protect the fetus against harmful xenobiotics. Protective mechanisms of placenta are based on enzymes, e.g., antioxidant enzymes from the glutathione S-transferases group (GST) or human N-acetyltransferase 2 (NAT2). Many organic sunscreens are known to cross biological barriers-they are detected in mother's milk, semen, umbilical cord blood or placental tissues. Some organic sunscreens are able to cross the placenta and to interfere with fetal development; they are known or suspected endocrine disruptors or neurotoxins. In this study, 16 organic sunscreens were investigated in the context of their placenta permeability and interactions with gluthatione S-transferase and human N-acetyltransferase 2 enzymes present in the human placenta. Binary permeability models based on discriminant analysis and artificial neural networks proved that the majority of studied compounds are likely to cross the placenta by passive diffusion. Molecular docking analysis suggested that some sunscreens show stronger affinity for glutathione S-transferase and human N-acetyltransferase 2 that native ligands (glutathione and Coenzyme A for GST and NAT2, respectively)-it is therefore possible that they are able to reduce the enzyme's protective activity. It was established that sunscreens bind to the studied enzymes mainly by alkyl, hydrogen bonds, van der Waals, π-π, π-alkyl and π-sulfur interactions. To conclude, sunscreens may become stressors affecting humans by different mechanisms and at different stages of development.

Developmental, behavioral, and biochemical effects of chronic exposure to sublethal concentrations of organic UV-filter compounds on a freshwater model species

The prevalence of organic/chemical UV-filter compounds in aquatic ecosystems represents a growing environmental issue. The long-term toxicity risks of many UV-filters at environmentally relevant concentrations to aquatic biota are still less studied, especially in the case of invertebrates. This study was designed to evaluate the chronic toxicity of avobenzone (AVO), octocrylene (OCTO), and octinoxate (OCTI), three UV-filters which frequently occur in the aquatic environment, to the water flea (Daphnia magna) at an environmentally relevant concentration of 200 ng l-1 in a 21-day exposure. Potential alterations in the growth, reproduction, and heart rate were continuously monitored during the treatments. Filtration rate, swimming, and the state of the antioxidant- and metabolic functions were evaluated at the end of exposures. Avobenzone significantly increased the reproductive output, heart rate, and filtration rate, while evoked a significant decrease of swimming behavior, and inhibited the activity of catalase (CAT) and glutathione S-transferase (GST) enzymes. The body size, reproduction, heart rate, and superoxide dismutase (SOD) activity were significantly increased whereas the activity of GST and CAT was significantly reduced by OCTO. OCTI significantly increased reproduction, heart rate, CAT and SOD activity but significantly decreased the swimming behavior. Our results confirmed that chronic exposure to organic UV-filters even at environmentally relevant concentrations affect basic physiological traits and cellular defense pathways in D. magna. Highlighting, our observations revealed previously unknown physiological changes (e.g., altered heart rate, filtration rate, SOD activity) caused by the investigated UV-filter compounds. Future research is to be aimed at investigating the mixture effects of these compounds and at the understanding of the potential cellular and molecular mechanisms underlying the changes induced.

Thyroid and growth hormone endocrine disruption and mechanisms of homosalate and octisalate using wild-type, thrαa-/-, and dre-miR-499-/- zebrafish embryo/larvae

Homosalate (HS) and octisalate (OS), which are used in sunscreen for the purpose of blocking ultraviolet rays, are frequently detected in water environment. Although effects on estrogens and androgens have been reported, studies on thyroid and growth hormone endocrine disruption are limited. In the present study, larval mortality was compared in wild-type and two knockout fish (thyroid hormone receptor alpha a knockout (thrαa-/-) and dre-miR-499 knockout (dre-miR-499-/-)) after 96 h of exposure to HS and OS (0, 0.003, 0.03, 0.3, 3, 30 and 300 µg/L). To investigate the mechanisms of thyroid and growth hormone endocrine disruption, we measured the levels of triiodothyronine (T3), thyroxine (T4), thyroid stimulating hormone (TSH), growth hormone (GH), and insulin-like growth factor-1 (IGF-1), and the regulation of representative genes related to the hypothalamus-pituitary-thyroid (HPT) and GH/IGF axis in wild-type zebrafish exposed to target chemicals. The significantly lower larval survival rate of thrαa-/- and dre-miR-499-/- fish exposed to 300 μg/L of HS and OS suggest that thyroid hormone receptors and dre-miR-499 play a crucial role in the toxic effects of HS and OS. The finding of a significant increase in T3 and T4 in zebrafish larvae exposed to HS and OS supports a significant decrease in the crh gene. The reduction of GH and IGF-1 in fish exposed to HS and OS is well supported by the regulation of genes involved in the GH/IGF axis. Our observations suggest that exposure to HS and OS affects not only thyroid hormone receptors and their associated miRNAs, but also the feedback routes of HPT and GH/IGF axes, ultimately leading to growth reduction.

Thyroid, neurodevelopmental, and kidney toxicities of common organic UV filters in embryo-larval zebrafish (Danio rerio), and their potential links

Organic UV filters (OUVFs) have been commonly used in sunscreen and many consumer products. Following dermal application, these compounds can enter circulation and may cause systemic effects in humans. In the present study, we chose four OUVFs frequently detected in the environment, i.e., avobenzone (AVB), benzophenone-3 (BP-3), octocrylene (OC), and octyl methoxycinnamate (OMC), and evaluated their thyroid, neurodevelopmental, and kidney toxicities. For this purpose, zebrafish embryos (<4 h post fertilization, hpf) were exposed to sublethal concentrations of AVB, BP-3, OC, or OMC until 120 hpf. Exposure to all OUVFs decreased thyroid hormone (TH) levels, probably by enhanced metabolism and excretion of THs (ugt1ab and/or sult1 st5) in the larval fish. Exposure to the OUVFs also induced hypoactivities and/or anxiety-like behaviors: Regulatory changes of mbp, gfap, c-fos, syn2a, sty1a, and stxbp1b genes, support the changes in normal neurobehavior of the larval fish. Moreover, the OUVFs exposure caused increased proteinuria in the fish, along with transcriptional changes of wt1, nephrin, podocin, and cdh17 genes, which could explain the observed reduction in kidney functions. Principal component analysis (PCA) implied the potential interplay of THs with neurogenesis, or podocyte differentiation of the larval fish. Toxicological consequences of altered TH homeostasis, neurobehavior, and kidney function at the early life stage warrant further investigations not only in humans but also in aquatic ecosystems.

Effects of Insecticide and Herbicides on Thyroid Disturbances in Zebrafish

Thyroid cancer usually begins with thyroid dysfunction and nodules and has become the most common cancer globally, especially in women. Although the causes of thyroid dysfunction are complex, the presence of environmental pollutants, especially certain pesticides as established mutagens, has been widely accepted. Zebrafish (Danio rerio) have similar toxic reactions and signal transduction pathways to humans and are very similar to humans in physiology, development, and metabolic function. Here, the direct toxicity effects and mechanisms of different insecticides and herbicides on zebrafish thyroid functions and indirect toxicity effects originating from thyroid dysfunction were summarized and compared. The overall toxicity of insecticides on the zebrafish thyroid was greater than that of herbicides based on effective concentrations. Penpropathrin and atrazine were more typical thyroid disruptors than other pesticides. Meanwhile, chiral pesticides showed more sophisticated single/combined toxicity effects on both parental and offspring zebrafish. Besides thyroid hormone levels and HPT axis-related gene expression alteration, developmental toxicity, immunotoxicity, and oxidative damage effects were all observed. These data are necessary for understanding the thyroid interference effect of pesticides on humans and for screening for thyroid disruptors in surface water with zebrafish models for the pre-assessment of human health risks and ecological risk control in the future.

Prospecting toxicity of the avobenzone sunscreen in plants

Avobenzone (AVO) is a sunscreen with high global production and is constantly released into the environment. Incorporating sewage biosolids for fertilization purposes, the leaching from cultivated soils, and the use of wastewater for irrigation explain its presence in the soil. There is a lack of information about the impact of this sunscreen on plants. In the present study, the ecotoxicity of AVO was tested at concentrations 1, 10, 100, and 1,000 ng/L. All concentrations caused a reduction in root growth of Allium cepa, Cucumis sativus, and Lycopersicum esculentum seeds, as well as a mitodepressive effect, changes in the mitotic spindle and a reduction in root growth of A. cepa bulbs. The cell cycle was disturbed because AVO disarmed the enzymatic defense system of root meristems, leading to an accumulation of hydroxyl radicals and superoxides, besides lipid peroxidation in cells. Therefore, AVO shows a high potential to cause damage to plants and can negatively affect agricultural production and the growth of non-cultivated plants.

Combined effects of organic and mineral UV-filters on the lugworm Arenicola marina

Pollution from personal care products, such as UV-filters like avobenzone and nano-zinc oxide (nZnO), poses a growing threat to marine ecosystems. To better understand this hazard, especially for lesser-studied sediment-dwelling marine organisms, we investigated the physiological impacts of simultaneous exposure to nZnO and avobenzone on the lugworm Arenicola marina. Lugworms were exposed to nZnO, avobenzone, or their combination for three weeks. We assessed pollutant-induced metabolic changes by measuring key metabolic intermediates in the body wall and coelomic fluid, and oxidative stress by analyzing antioxidant levels and oxidative lesions in proteins and lipids of the body wall. Exposure to UV filters resulted in shifts in the concentrations of Krebs' cycle and urea cycle intermediates, as well as alterations in certain amino acids in the body wall and coelomic fluid of the lugworms. Pathway enrichment analyses revealed that nZnO induced more pronounced metabolic shifts compared to avobenzone or their combination. Exposure to avobenzone or nZnO alone prompted an increase in tissue antioxidant capacity, indicating a compensatory response to restore redox balance, which effectively prevented oxidative damage to proteins or lipids. However, co-exposure to nZnO and avobenzone suppressed superoxide dismutase and lead to accumulation of lipid peroxides and methionine sulfoxide, indicating oxidative stress and damage to lipids and proteins. Our findings highlight oxidative stress as a significant mechanism of toxicity for both nZnO and avobenzone, especially when combined, and underscores the importance of further investigating the fitness implications of oxidative stress induced by these common UV filters in benthic marine organisms.

Adverse Effects of Avobenzone on Boar Sperm Function: Disruption of Protein Kinase A Activity and Tyrosine Phosphorylation

Avobenzone (AVO), an ultraviolet (UV) filter, is frequently used as an ingredient in personal cosmetics. This UV filter has been found to be easily exposed in swimming pools and beaches, and it has been detected in human urine and blood. Moreover, numerous studies have demonstrated that AVO exhibits endocrine-disrupting properties. Nevertheless, the effects of AVO on male fertility have not yet fully understood. Therefore, this study aimed to assess the effects of AVO on various sperm functions during capacitation. First, boar spermatozoa were treated with various AVO concentrations. After treatment, sperm motility and kinetic characteristics, capacitation status, intracellular adenosine triphosphate (ATP) levels, and sperm viability were evaluated. Moreover, Western blot analysis w.as conducted to evaluate protein kinase A (PKA) activity and tyrosine phosphorylation. As a result, AVO treatment significantly decreased total motility, progressive motility, and several kinetic characteristics at high concentrations (50 and 100 μM). Furthermore, the capacitation status dose-dependently decreased. Conversely, no significant differences in acrosome reaction, cell viability, and intracellular ATP levels were observed. However, the intracellular ATP level tended to decrease. In addition, AVO dose-dependently induced abnormal changes in PKA activity and tyrosine phosphorylation. Although AVO did not directly exert a toxic effect on cell viability, it ultimately negatively affected sperm functions through abnormal alterations in PKA activity and tyrosine phosphorylation. Thus, the potential implications on male fertility must be considered when contemplating the safe utilization of AVO.

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.

Single and mixture toxicity evaluation of avobenzone and homosalate to male zebrafish and H295R cells

Avobenzone and homosalate are widely used in sunscreens to provide ultraviolet (UV) protection, either as single compounds or in combination. Some UV filters exhibit estrogenic or anti-androgenic activities, however, studies regarding their interactions and toxicity in mixtures are limited. In this study, the effect of the toxicity of a binary mixture comprising avobenzone (0.72 μg L-1) and homosalate (1.02 and 103 μg L-1) on steroid hormone biosynthesis were investigated using male zebrafish and human adrenocortical carcinoma (H295R) cells. In fish exposed to homosalate, a significant decrease in the gonadosomatic index, testosterone level, and transcription of several genes (e.g, hsd3b2, cyp17a1, and hsd17b1) and a significant increase in the hepatosomatic index, liver steatosis, 17β-estradiol level, and transcription of vtg gene were observed. These results suggest that estrogenic and anti-androgenic effects of homosalate were mediated by the steroidogenic pathway. The presence of 0.72 μg L-1 of avobenzone augmented the anti-androgenic responses in male fish. The testosterone level in the H295R cells were significantly decreased after they were exposed to homosalate alone or in combination with avobenzone, which is consistent with observations in male zebrafish. Further studies need to be conducted to understand the endocrine disrupting properties of long-term exposure to substances typically used in sunscreens.