Combining QSAR and SSD to predict aquatic toxicity and species sensitivity of pyrethroid and organophosphate pesticides.

The widespread use of pyrethroid and organophosphate pesticides necessitates accurate toxicity predictions for regulatory compliance. In this study QSAR and SSD models for six pyrethroid and four organophosphate compounds using QSAR Toolbox and SSD Toolbox have been developed. The QSAR models, described by the formula 48 h-EC50 or 96 h-LC50 = x + y * log Kow, were validated for predicting 48 h-EC50 values for acute Daphnia toxicity and 96 h-LC50 values for acute fish toxicity, meeting criteria of n ≥10, r² ≥0.7, and Q² >0.5. Predicted 48 h-EC50 values for pyrethroids ranged from 3.95 × 10^-5 mg/L (permethrin) to 8.21 × 10^-3 mg/L (fenpropathrin), and 96 h-LC50 values from 3.89 × 10^-5 mg/L (permethrin) to 1.68 × 10^-2 mg/L (metofluthrin). For organophosphates, 48 h-EC50 values ranged from 2.00 × 10^-5 mg/L (carbophenothion) to 3.76 × 10^-2 mg/L (crufomate) and 96 h-LC50 values from 3.81 × 10^-3 mg/L (carbophenothion) to 12.3 mg/L (crufomate). These values show a good agreement with experimental data, though some, like Carbophenothion, overestimated toxicity. HC05 values, indicating hazardous concentrations for 5% of species, range from 0.029 to 0.061 µg/L for pyrethroids and 0.030 to 0.072 µg/L for organophosphates. These values aid in establishing environmental quality standards (EQS). Compared to existing EQS, HC05 values for pyrethroids were less conservative, while those for organophosphates were comparable.