Investigation of chronic toxicity of (14)C-fenitrothion and its degradation products on stored soybeans.

Grains of soybeans were treated with the recommended dose of fenitrothion insecticide, 5mg/kg, and double that dose, before storage for 30 weeks under ambient local conditions. During the storage period, the penetration and distribution of insecticide residues were studied. The amount of surface residues on stored soybeans, internal extractable and bound residues were determined. Surface residues were found to decrease with the increase in time of storage, whereas internal residues showed a gradual increase with time to reach 56%, 54% of applied doses after 30 weeks. The amount of bound residues inside the matrix showed a slow increase with time. Toxicity of the total internal residues of fenitrothion in stored soybeans was studied in mice through a sub-chronic feeding experiment for 3 months. The maximum inhibition in plasma and erythrocyte cholinesterase activity was 37% and 13% after the first month, respectively. Treated mice suffered from deterioration of hepatic and renal functions as indicated by the increase level of blood serum esterase's and blood urea nitrogen. Percentage increase in alanine aminotransferase (ALT) and aspartate aminotransferase (AST) was reached to about 62% and 55%, respectively as compared with control animals with the end of feeding period.