TOXICOLOGICAL POTENTIAL OF MALATHION RESIDUES IN STORED SOYBEAN SEEDS

Succinate - C-14- malathion penetrates readily into soybean seeds. The total internal residues inside the seeds amounted to 58-65% of the ap plied dose after 30 weeks, of which 8-9 % were in the form of bound re sidues. The major part of the internal methanol extractables are chlor oform soluble metabolites which include malathion (about 60%), monocar boxylic acid (15%) and its decarboxylation product (8%). The water sol uble metabolites contained only one radioactive substance, namely mala thion dicarboxylic acid. The toxicological potential of the total inte rnal residues was studied by feeding mice with the washed seeds for ab out 2.5 months. Treated mice suffered from deterioration of hepatic an d renal function as indicated by the observed increased level of blood serum esterases and blood urea nitrogen. The results of blood biochem istry are supported by the histopathological changes observed in the l iver, kidney, stomach and intestine. The organs showed degenerative ch anges including leucocytic aggregation, congestion and dilatation of b lood vessels. Other adverse effects caused by malathion residues are i ndicated from cytogenetic studies on bone marrow of treated mice. Stud ies showed an initial bone marrow toxicity as indicated by increase in percentage of polychromatic erythrocytes over controls. This effect d iminished upon prolongation of feeding period over one month. Feeding with malathion residues affected a gradual increase, with feeding peri od, in the percentage of polychromatic erythrocytes with micronuclei, a parameter recommended for detecting chemical mutagenes in animal tes t systems.