Underestimated ecological risks of 2,4-D in aquatic systems revealed by sublethal effects and recovery assessment

Pesticides are widely detected in aquatic environments, raising concerns about ecological risks not captured by conventional toxicity assessments. The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is extensively used, yet its sublethal effects and the reversibility of those effects following exposure remain poorly understood. It was evaluated lethal and sublethal endpoints, including morphological alterations, and assessed post-exposure recovery in Artemia salina nauplii exposed to a commercial 2,4-D formulation. Mortality increased in a concentration-dependent manner, with LC 10 , LC 25 , LC 50 , and LC80 values of 1.69, 4.45, 7.52, and 11.34 mg L − 1 , respectively. Exposure also induced morphological alterations, including changes in body coloration and deformities in eyes, digestive tract, and abdomen, particularly during the first hours after hatching (6–12 h). Sublethal endpoints revealed effects not captured by mortality alone. After herbicide removal, morphological alterations decreased within 24 h, indicating partial morphological recovery. These results show that 2,4-D induces both lethal and sublethal effects. Moreover, apparent morphological recovery does not eliminate ecological risk. These findings support the inclusion of sublethal and recovery endpoints in ecotoxicological assessments to better identify and predict the underestimated impacts of pesticide contamination in aquatic systems.