Long-term toxicity studies of chlorpropham and propham in mice and hamsters.

Abstraet--Isopropyl N-phenylcarbamate (propham; IPC) and isopropyl N-(3-chlorophenyl)carbamate (chlorpropham; CIPC) were tested for carcinogenic properties in hamsters and mice. The hamsters were given 0"2 ~ IPC or CIPC in the diet, while mice were given 0' 1 ~ CIPC by the same route, using 0.1% urethane as a positive control. Other mice were given sc injections of CIPC. All experiments included the necessary negative controls. Neither IPC nor CIPC caused any increase in tumour incidence in hamsters. In the mouse, urethane induced multiple lung tumours in nearly all the animals, whereas the tumour incidence in the CIPC group was of the same order as that of the controls. In both of the latter groups, only solitary lung tumours were induced. Similarly, no increase in tumour rate followed sc application of CIPC. These results, showing no tumorigenic effect with either IPC or CIPC, are discussed in the light of data on the metabolism of these compounds.