Carcinogenicity study of the pesticide fenvalerate in mice.

Fenvalerate is a widely used pesticide, which has been shown recently to be nonmutagenic. We studied its carcinogenicity in a long-term experiment in inbred C57Bl/6 mice given 0, 40 and 80 mg/kg body weight fenvalerate (99% pure) by gavage on 5 days/week for 104 weeks. Survival was decreased especially among females receiving the high dose. Exposure to fenvalerate resulted in a slight increase in the incidence of liver-cell tumours over that in controls only in male mice receiving the high dose. No significant difference in the incidence of other types of tumours was observed in treated groups when compared with controls. Fenvalerate-induced microgranulomas occurred concomitantly in the liver, spleen and lymph nodes of male and female mice, but their overall incidence did not increase with dose. In a separate experiment, groups of SJL/ola female mice were administered two different samples of fenvalerate (92% and 99% pure) once per week for 12 weeks. In animals that received 92% pure compound, the latent period for induction of lymphomas was shortened and their incidence increased, when compared with the group receiving 99% pure fenvalerate and with controls.