Lack of genotoxicity of piperonyl butoxide.

The genotoxicity of piperonyl butoxide has been investigated in bacterial mutation assays using tester strains TA98, TA100, TA1535, TA1537 and TA1538. The assays were conducted both with and without metabolic activation. Piperonyl butoxide was tested for mutation with and without metabolic activation in the CHO/HGPRT assay. Chromosomal aberrations were investigated also using Chinese hamster ovary (CHO) cells and effects on DNA were evaluated by in vitro unscheduled DNA synthesis (UDS) test using rat liver primary cell cultures. Piperonyl butoxide was not shown to be genotoxic in any assay system. The data presented supports the view that the liver tumors observed in rodents at dose levels above the maximally tolerated dose (MTD) result from a secondary non-genotoxic mechanism.