In vivo toxicity of Dioctyl Phthalate in adult and zebrafish larvae

Dioctyl phthalate (DOP), a widely used plasticizer in flexible plastics, was evaluated for acute toxicity in zebrafish (Danio rerio) embryos and adults as a vertebrate model. Embryos were exposed to 1.0-300 mg/L DOP following OECD guideline 236, and adults were assessed under OECD guideline 203 at concentrations range of 1-600 mg/L. Embryonic exposure at ≥ 100 mg/L produced significant developmental abnormalities, including pericardial edema, spinal deformities, and delayed hatching, with 100 % mortality at 200 mg/L. In adults, at concentrations above 400 mg/L of DOP complete mortality within 24 h was observed, and histopathology demonstrated dose-dependent injury in the liver, kidney, and testes; notably, 400 mg/L induced fatty liver changes, renal tubular necrosis, and oligospermia. The median lethal concentration (LC50) values obtained in this study were 238 mg/L for adult zebrafish and 126 mg/L for larvae, indicating higher sensitivity in early life stages. Collectively, these results demonstrate severe, dose-dependent acute toxicity of DOP across developmental stages and underscore the need for regulatory measures to limit its use and to prioritize safer alternatives in consumer and medical products.