Ecotoxicological Effects of a Commercial Fenthion-Based Formulation on the Survival, Hatching, and Growth of Artemia salina L.: Implications for Risk Assessment in Marine and Estuarine Environments

This present study evaluated the effects of a commercial formulation based on fenthion on survival, hatching, and growth of Artemia salina, and characterized the environmental risk of this insecticide to marine and estuarine ecosystems. The fenthion-based commercial formulation was tested at concentrations ranging from 0.001 up to 731 mg/L using different bioassays: a standard 48-h acute test, a 14-day long-term test, and also two 72-h assays (one for cyst hatching, another for growth inhibition). Obtained EC50 values were fully integrated with available literature data to construct a species sensitivity distribution (SSD) curve, which then determined the hazardous concentration for 5% of species (HC5), the predicted no-effect concentration (PNEC), and the risk quotient (RQ). In the acute assay, the formulation showed low toxicity, with EC50 of 212.36 mg/L at 24 h and 16.64 mg/L at 48 h. In contrast, high toxicity was observed in long-term tests, with EC50 of 0.0752 mg/L after 8 days and 0.0052 mg/L after 14 days of exposure. Minor effects were observed on hatching rate (EC50 = 101.75 mg/L), whereas more pronounced effects were seen on hatching speed (EC50 = 19.88 mg/L) and nauplii growth (EC10 = 0.076 mg/L). The HC5 from the SSD was 0.000104 mg/L, while PNEC was 0.000020 mg/L. The average RQ was 1.86, indicating high risk. Overall, these results demonstrate the ecotoxicological potential of a fenthion-based commercial formulation for relevant organisms in marine and estuarine ecosystems, reinforcing the importance of regulatory measures and environmental monitoring in areas subject to contamination by this insecticide.