Commercial formulation containing 2,4-Dichlorophenoxyacetic Acid (2,4-D) induces cellular damage, tissue injury, and...

2,4-Dichlorophenoxyacetic acid (2,4-D) is one of the oldest and most widely used herbicides globally. Although effective as a pesticide, increasing evidence suggests it may exert toxic effects on non-target aquatic organisms. This study aimed to evaluate morphological, ultrastructural, and biochemical changes in the gills of adult zebrafish (Danio rerio) following short-term exposure to commercial formulation containing 2,4-D. Fish were exposed to 0 (control), 0.03, 0.3, and 3.0 mg/L of the herbicide for seven days. After exposure, gills were collected for analysis. Histological examination revealed cellular alterations in the secondary lamellae, including hyperplasia, hypertrophy of pavement and mitochondria-rich cells (MRCs), and epithelial lifting. Histopathological assessment indicated mild damage at 0.3 mg/L and moderate damage at 3.0 mg/L. Ultrastructural analysis showed mitochondrial disruption in MRCs and damage to pillar cells at the highest concentration. Biochemical analyses revealed decreased levels of both reduced glutathione (GSH) and oxidized glutathione (GSSG), along with increased nitrite concentrations in the group exposed to 3.0 mg/L. No lipid peroxidation was detected following herbicide exposure. The combination of elevated nitrite levels, reduced GSH and GSSG, vascular dilation, mitochondrial damage, and inflammatory cell infiltration strongly supports a link between nitric oxide (NO)-mediated inflammation and the vascular lesions observed in the 3.0 mg/L group. These findings demonstrate that the herbicide can compromise gill structure. Taken together, our results underscore the need for stricter environmental regulations and highlight the potential ecological risks associated with the use of commercial formulations containing 2,4-D.