Toxicity of Four Common Environmental Chemicals Across <scp> <i>Caenorhabditis elegans</i> </scp> Life Stages Supporting the One Health Concept

Pesticides and pharmaceuticals are among the most common chemical groups in waterbodies and soils, and their universal distribution raises concerns about potential adverse effects on nontarget organisms and humans. Reproductive output disruption is of particular concern, as it transposes effects from the individual to the next generations at the population level, requiring precise identification of the affected processes. Caenorhabditis elegans, with its well-known lifecycle, is an excellent model organism for investigating such effects within the One Health framework. The present study evaluated the toxicity of four globally prevalent chemicals: the insecticides cypermethrin and flupyradifurone, the herbicide MCPA, and the pharmaceutical diclofenac, at different C. elegans life stages to determine possible effects on different reproductive processes. Embryotoxicity was evaluated by the hatching rates of exposed eggs. Developmental toxicity was assessed by exposing L1 larvae for 96 h and measuring total offspring production and feeding rate. Intergenerational effects were evaluated by hatching rates of in utero exposed eggs (removed from exposed adults). Our results indicate that all substances affected C. elegans in one or more different life stages. Cypermethrin and MCPA showed the highest developmental toxicity, while the latter was also the most toxic for embryo development and intergenerational effects. This targeted approach highlights unexpected reproductive impacts unrelated to the chemicals' primary modes of action. Our findings emphasize the potential of C. elegans in developing adverse outcome pathways, contributing to more realistic hazard predictions regarding human health and animal well-being and protecting the environment within the One Health approach.