Comparative Molecular Insights into Developmental and Behavioral Toxicity Induced by Octocrylene and Ethylhexyl Salicylate Exposure on Zebrafish.

Octocrylene (OC) and ethylhexyl salicylate (EHS), widely used organic ultraviolet (UV) filters, are persistently detected in natural environments, raising concerns about their ecological toxicity. However, their toxicity at environmentally relevant concentrations remains poorly understood, and a comparative assessment of their aquatic effects is lacking. This study exposed zebrafish embryos (≤4 h post-fertilization, hpf) to OC and EHS (0.05, 0.5, 5, and 50 mg/L) until 120 hpf. Both chemicals induced developmental abnormalities, including deformities and reduced heart rates. Exposure to 50 mg/L EHS resulted in 54.72% mortality, while the same concentration of OC caused 13.33% mortality at 96 hpf, indicating higher acute toxicity of EHS. Behavioral assays revealed that 50 mg/L OC and 5 mg/L EHS induced hyperactivity, whereas 50 mg/L EHS caused locomotor suppression, suggesting neurodevelopmental toxicity. Transcriptomic analysis showed OC regulated hypoxia response, cytochrome P450, and extracellular matrix, while EHS affected immunity, nucleotide/amino-sugar metabolism, and lipid homeostasis. Oxidative stress biomarkers (superoxide dismutase, glutathione peroxidase, and glutathione) and triglyceride (TG) levels were monitored. Both chemicals induced oxidative stress, but only EHS significantly upregulated TG, disrupting lipid metabolism. These findings highlight that EHS exhibits broader and more severe toxicity than OC, emphasizing the need for further research and regulatory measures to mitigate the ecological risks of these UV filters.