Tar includes the majority of mutagenic and carcinogenic agents in tobacco smoke (IARC, 1986). Polycyclic aromatic hydrocarbons (PAH), for example, are genotoxic via epoxidation.

There is a common misconception that the tar in cigarettes is equivalent to the tar used on roads. As a result of this, cigarette companies in the United States, when prompted to give tar/nicotine ratings for cigarettes, usually use "tar", in quotation marks, to indicate that it is not the road surface component. Tar is occasionally referred to as an acronym for total aerosol residue^[1] although it's possible this is a backronym.

The European Union currently limits the tar yield of cigarettes to 10mg.^[2]