Commercial mixtures of PCBs and their congeners have been discovered to be hepatically carcinogenic by their induction of mono-oxygenase cytochrome P450-dependent pathways in the liver.23 This is due to the activity of tumor initiation of the lower chlorinated congeners and tumor promoting activity of highly chlorinated PCB congeners.24 Furthermore, it was found that PCB3 is responsible for the induction of gene mutation, which is a typical characteristic of tumor initiation, in the liver and lungs of rats by increasing ROS levels.25 This evidence concerns the gene CYP20A1 and neoplasm.