ANALYSIS OF CARCINOGENIC ACTIVITY OF SOME PESTICIDES IN A MEDIUM-TERMLIVER BIOASSAY IN THE RAT

Eight pesticides were tested in a medium-term bioassay based upon the induction of preneoplastic lesions in the liver. Rats were initially g iven diethylnitrosamine intraperitoneally at a dose of 200 mg/kg body weight and 2 weeks later were treated with the pesticides for 6 weeks and then killed; all rats had a partial hepatectomy at week 3. Hepatoc arcinogenic potential was assessed by comparing the number and area of glutathione S-transferase placental form positive foci in the liver w ith those of controls given diethylnitrosamine (DEN) alone. Positive r esults were seen with p,p-DDT and Triadimefon. Permethrin (mixture of 39% cis form and 61 % trans form) showed borderline results. Permethri n (25/75), Deltamethrin, Cypermethrin (52/48), while Trimorphamide and Propineb gave negative results. Our findings provide experimental evi dence to indicate that compounds active in this assay have a potential for liver carcinogenicity in rodents.