 During the burning of the cigarette tobacco (itself a complex mixture), thousands of chemical substances are generated by combustion, distillation, pyrolysis and pyrosynthesis.Tobacco smoke is used as a fumigant and inhalant.The particles in tobacco smoke are liquid aerosol droplets (~ 20% water), with a mass median aerodynamic diameter (MMAD) that is submicrometer (and thus, fairly "lung-respirable" by humans).