Oncogenicity studies of piperonyl butoxide in rats and mice

Area of Science:

• Toxicology
• Carcinogenesis
• Rodent Studies

Background:

• Piperonyl butoxide (PBO) is a compound whose toxicological profile requires thorough investigation.
• Understanding PBO's long-term effects is crucial for risk assessment.

Purpose of the Study:

• To evaluate the oncogenicity of Piperonyl butoxide (PBO) in CD-1 mice and Sprague-Dawley rats through chronic dietary administration.
• To assess potential dose-dependent toxicological and carcinogenic effects of PBO.

Main Methods:

• Mice were fed PBO at 0, 30, 100, and 300 mg/kg/day for 79 weeks.
• Rats received PBO at 0, 30, 100, and 500 mg/kg/day for 104/105 weeks.
• Histopathological examination and organ weight analysis were conducted at study termination.

Main Results:

• Mice exhibited increased liver weights and a higher incidence of eosinophilic adenomas at 100 and 300 mg/kg/day (males) and 300 mg/kg/day (females).
• Rats showed increased liver weights with hepatocyte hypertrophy at 100 and 500 mg/kg/day, and thyroid follicular hypertrophy/hyperplasia at 500 mg/kg/day.
• No increased incidence of neoplasia was observed in rats at any site.

Conclusions:

• Observed changes in rodents are consistent with the induction of mixed-function oxygenase enzymes.
• The increased incidence of eosinophilic adenomas in mice is not deemed relevant for human risk evaluation.
• PBO exposure in rats primarily resulted in adaptive liver and thyroid changes, without evidence of carcinogenicity.