Sex-dependent acute oral toxicity and in vivo distribution of 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) in rats.

6:2 Chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA), a widely used substitute for perfluorooctane sulfonic acid (PFOS), has raised increasing concern due to its environmental persistence and potential health risks. However, its acute toxicity profile and sex-dependent effects remain insufficiently characterized. This study conducted a 14-day acute oral toxicity study for single exposure (46.4-464 mg/kg·BW) in male and female Sprague-Dawley (SD) rats to quantify lethality and evaluate sex-dependent differences. The median lethal dose (LD50) was estimated to be 147 mg/kg·BW for both sexes, classifying 6:2 Cl-PFESA as moderately toxic (GHS Category Ⅲ) with neurotoxicity signs, more acutely hazardous than PFOS. Sex dependence produced different internal exposure patterns, leading to divergent toxic effects: females maintained higher circulating burdens, accompanied by pronounced thrombocytopenia, whereas males exhibited strong hepatic sequestration and erythrocyte toxicity. Gonadal accumulation was also sex-dependent, with substantially higher levels in the ovaries than in the testes. Histopathology identified the liver and kidneys as primary targets and further revealed the lung as a potential target organ marked by foam cell infiltration and lymphoid depletion. Collectively, these findings demonstrate that 6:2 Cl-PFESA induces acute, multi-organ toxicity through strongly sex-dependent mechanisms, highlighting the necessity of additional attention to the pulmonary and reproductive toxicity hazards of 6:2 Cl-PFESA and the necessity of integrating sex as a critical biological variable in future toxicological evaluation and regulatory assessment of PFAS alternatives.