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Tobacco smoke is an aerosol produced by the incomplete combustion of tobacco during the smoking of cigarettes, pipes, or cigars. Temperatures in burning cigarettes range from ambient to 950 ℃, depending on the amount of oxygen present. During the burning of 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. == Composition == 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). The droplets are present in high concentrations (some estimates are as high as 10¹⁰ droplets per cm³). Most cigarettes today contain a cigarette filter, which can reduce "tar" and nicotine smoke yields up to 50 % by several different mechanisms, with an even greater removal rate for other classes of compounds (e.g., phenols).〔 Tobacco smoke may be grouped into a particulate phase (trapped on a glass-fiber pad, and termed "TPM" (total particulate matter)) and a gas/vapor phase (which passes through such a glass-fiber pad). "Tar" is mathematically determined by subtracting the weight of the nicotine and water from the TPM. However, several components of tobacco smoke (e.g., hydrogen cyanide, formaldehyde, phenanthrene, and pyrene) do not fit neatly into this rather arbitrary classification, because they are distributed among the solid, liquid and gaseous phases.〔 Tobacco smoke contains a number of toxicologically significant chemicals and groups of chemicals, including polycyclic aromatic hydrocarbons (benzopyrene), tobacco-specific nitrosamines (NNK, NNN), aldehydes (acrolein, formaldehyde), carbon monoxide, hydrogen cyanide, nitrogen oxides, benzene, toluene, phenols (phenol, cresol), and aromatic amines (nicotine, ABP (4-Aminobiphenyl)). The radioactive element polonium-210 is also known to occur in tobacco smoke.〔 The chemical composition of smoke depends on puff frequency, intensity, volume, and duration at different stages of cigarette consumption. Between 1933 and the late 1940s, the yields from an average cigarette varied from 33 to 49 mg "tar" and from < 1 to 3 mg nicotine. However, in the 1960s and 1970s, the average yield from cigarettes in Western Europe and the USA was around 16 mg tar and 1.5 mg nicotine per cigarette. Current average levels are lower. This has been achieved in a variety of ways including use of selected strains of tobacco plant, changes in agricultural and curing procedures, use of reconstituted sheets (reprocessed tobacco leaf wastes), incorporation of tobacco stalks, reduction of the amount of tobacco needed to fill a cigarette by expanding it (like puffed wheat) to increase its "filling power", and by the use of filters and high-porosity wrapping papers. The development of lower "tar" and nicotine cigarettes has tended to yield products that lacked the taste components to which the smoker had become accustomed. In order to keep such products acceptable to the consumer, the manufacturers reconstitute aroma or flavor.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Tobacco smoke」の詳細全文を読む スポンサード リンク
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