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

Abstract

AbstractEthyl‐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 (1O2) 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 1O2 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 (O2.‐) which was validated by significant O2.– 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.