A method for reducing the mutagenicity of polycyclic aromatic compounds (PAC's) having one or more bay regions which involves alkylating the PAC's with an alkylating agent in the presence of a catalyst to lower the mutagenicity down to as much as about 0.1. The resulting alkylated polycyclic aromatic compounds retain their physical and chemical properties for safe industrial use including as rubber processing oils, inks, etc.