Persistence of the vinyl phosphate insecticide 14C-dichlorvos in stored soybeans and its toxicological significance to experimental animals

ABSTRACT

Soybeans were treated with the recommended dose of dichlorvos insecticide [12.0mg pesticide/kg seeds] and its duplicate [24 mg pesticide / kg seeds] and stored for 7 months under normal local storage conditions. The rate of penetration of the pesticide through the seeds and the percentage of bound residues were apparently not dose dependent. The amount of surface residues decreased with time to 18% of the applied dose while the amount of extracted and bound residues inside the seeds showed a slow but definite increase with time of storage and reached more than 61% and 9%, respectively, at the end of the experiment. The incomplete recovery of the applied radioactivity by extraction and combustion may be attributed at least to volatilization of the parent substance. Toxicity of the total internal residues of dichlorvos in stored soybeans was studied in mice through a subchronic feeding experiment for three months. The maximum inhibition in plasma and erythrocyte cholinesterase activity was 60% and 52% after the first month, respectively. Blood picture showed a slight decrease in hemoglobin concentration [18%] and red blood cell counts [19%] and a significant decrease [55%] in white blood cell-counts at the end of experimental period. Treated mice suffered from deterioration of hepatic and renal functions as indicated by the obtained results. Percentage increase in alanine aminotransferase [ALT], aspartate aminotransferase [AST] and alkaline phosphatase [ALP] reached to about 93, 61, and 20%, respectively as compared with control animals at the end of feeding period. A significant increase in blood urea [65%] was observed whereas creatinine concentration showed only a slight increase [17%] as compared with control group