How Does PBO Cause Tumors in Mice and is There Relevance to Humans?

The data suggests that the way PBO causes liver tumors in mice is not plausible in humans.  Moreover, large quantitative differences exist between the doses of PBO that produce liver tumors in mice and human exposure to PBO.  Many non-genotoxic compounds like PBO have been shown to induce tumors in rodents and consideration of their relevance to humans has been focus of an intense effort over the past two decades (Ames et al., 1993; Butler, 1996; Cohen and Ellwein, 1990; Cohen, et al., 2003, 2004; Grasso and Hinton, 1991; Grasso et al., 1991; Holsapple, et al., 2006; Loury et al., 1987; Wilson et al., 1992).

Generally speaking, the means by which PBO causes mouse liver tumors is likely not relevant to humans.  The Piperonyl Butoxide Task Force II (PBTFII) is engaged in a multi-year research program to further strengthen this assertion.