Sunlight-Induced Degradation of Dissolved Ethyl-Parathion and Coupled Molecular Toxicity Investigation

摘要

Ethyl-parathion (EP) is a globally-distributed organophosphorus (OP) pesticide where environmental release is a standard use case. The present study sought to determine if sunlight degraded EP and if the degraded products were toxic to biological molecules in cell-free assays. A 24 mg/L solution of EP (water solubility limit) was exposed to direct sunlight for 0, 1, 2, 3 and 4 hrs where as much as 64.6 of EP was degraded relative to the 0 hr sunlight exposure. Singlet oxygen formation (O-1(2)) increased by 15.9, 20.6, 29.8, and 64.4 in the 1, 2, 3 and 4 hr sunlight exposures, respectively. Ultra-high performance liquid chromatography further confirmed the sunlight-induced transformation of EP and the increased O-1(2) formation through time, likely via a type-II photochemical mechanism. The degradation of DNA nucleotides (8-hydroxy 2-deoxyguanosine), the formation of superoxide anion radical (O-2.-) which was validated by significant O-2.- quenching by superoxide dismutase (SOD), and peroxidation of membrane lipid (linoleic acid), increased significantly in sunlight exposures, however the presence of EP at 24 mg/L had no significant influence on this effect. Overall, sunlight quickly degraded EP in solution, however the sunlight-irradiated EP caused no discernable toxic effects in cell-free assays relative to sunlight alone.