Tar (tobacco residue)

Tar is the name for the resinous, combusted particulate matter made by the burning of tobacco and other plant material in the act of smoking. Tar is toxic and damages the smoker's lungs over time through various biochemical and mechanical processes.^[1] Tar also damages the mouth by rotting and blackening teeth, damaging gums, and desensitizing taste buds. Tar includes the majority of mutagenic and carcinogenic agents in tobacco smoke. Polycyclic aromatic hydrocarbons (PAH), for example, are genotoxic and epoxidative.^[2]

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,^[3] a backronym coined in the mid-1960s.^[4]

Tar, when in the lungs, coats the cilia causing them to stop working and eventually die, causing conditions such as lung cancer as the toxic particles in tobacco smoke are no longer trapped by the cilia but enter the alveoli directly. ^{[citation needed]} Thus, the alveoli cannot come through with the process that is called ‘gas exchange’ which is the cause of rough breathing.^{[citation needed]}

Cannabis when burned also creates residue that is very similar to the "tar" created by tobacco smoke.^[5]