Quantitative structure–toxicity relationships of organophosphorous pesticides to fish (Cyprinus carpio)

This study was conducted to determine the relationships between 1381 chemical and structural parameters of 43 organophosphorus pesticides (OPs) and their toxicity to fish, Cyprinus carpio, using ChemOffice 8.03 and Dragon 2.1. By multivariate linear regression and intervariable regression analyses, various equations have been derived to calculate the lethal toxicity value, LC50, for 43 OPs found in fish with different levels of toxicity. Results show that for all selected OPs, especially those of low toxic OPs (LC50 < 2.5 mM), the equation, LC50 = 56.259 − 13.071 lg Kow + 17.510 MATS8P − 17.455 Mor24u − 0.085 MW + 1.706 (lg Kow)2 + 2.306 (Mor14e)2 + 6.849 Mor20m (n = 43, F = 36.815, r = 0.942, radj2=0.862, SE = 2.899, p < 10−6), could account for 86.2% of the variability of the toxic effect. The steric and electronic characteristics and the hydrophobicity of OPs, in particular, are among the most important parameters determining the toxicity of OPs to fish. For the OPs with high toxicity, different structural parameters were introduced into the following two equations: LC50 = 3.795 − 1.195 (H1p)2 − 0.037 U − 2.225 MATS3v − 19.593 Tcon (n = 16, F = 56.820, r = 0.977, radj2=0.937, SE = 0.143, p < 10−6), where LC50 is less than 2.5 mM, and LC50 = 0.341 − 0.561 (HOMA)2 + 0.231 HOMA (n=3,radj2=1), where LC50 is less than 0.3 mM. These results suggest that chemical and structural parameters could be useful in modeling chemical reactivity within homologous series of OP compounds and elucidating possible mechanisms associated with different levels of toxicity to fish.