Editing Tobacco smoke (section)

== Composition ==
{{See also|List of additives in cigarettes}}
The particles in tobacco smoke are liquid aerosol droplets (about 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 [[concentration]]s (some estimates are as high as 10<sup>10</sup> droplets per cm<sup>3</sup>).

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.<ref name="kapp" />

Tobacco smoke contains a number of toxicologically significant chemicals and groups of chemicals, including [[polycyclic aromatic hydrocarbon]]s ([[benzopyrene]]), [[tobacco-specific nitrosamines]] ([[NNK]], [[N-Nitrosonornicotine|NNN]]), [[aldehyde]]s ([[acrolein]], [[formaldehyde]]), [[carbon monoxide]], [[hydrogen cyanide]], [[nitrogen oxide]]s ([[nitrogen dioxide]]), [[benzene]], [[toluene]], [[phenol]]s ([[phenol]], [[cresol]]), [[aromatic amine]]s ([[nicotine]], ABP ([[4-Aminobiphenyl|4-aminobiphenyl]])), and [[harmala alkaloid]]s. The radioactive element [[polonium-210]] is also known to occur in tobacco smoke.<ref name="kapp" /> The chemical composition of smoke depends on puff frequency, intensity, volume, and duration at different stages of cigarette consumption.<ref name="health">{{citation | title=The Health Consequences of Smoking: The Changing Cigarette | page=49 | publisher=U.S. Dept. of Health and Human Services | url=http://profiles.nlm.nih.gov/ps/access/NNBBSN.pdf}}</ref>

Between 1933 and the late 1940s, the yields from an average cigarette varied from 33 to 49&nbsp;mg "tar" and from less than 1 to 3&nbsp;mg nicotine. In the 1960s and 1970s, the average yield from cigarettes in Western Europe and the USA was around 16&nbsp;mg tar and 1.5&nbsp;mg nicotine per cigarette. Current average levels are lower.<ref>{{citation | author=K. Rothwell | title=Health effects of interactions between tobacco use and exposure to other agents | series=[[Environmental Health Criteria]] | issue=211 | publisher=[[World Health Organization]] | year=1999 | url=http://www.inchem.org/documents/ehc/ehc/ehc211.htm|display-authors=etal}}</ref> 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 [[Cigarette filter|filters]] and high-porosity [[Cigarette paper|wrapping papers]].<ref name="russell">{{citation | editor1=Murray E. Jarvik | editor2=Joseph W. Cullen | editor3=Ellen R. Gritz | editor4=Thomas M. Vogt | editor5=Louis Jolyon West | title=Research on Smoking Behavior | author=Michael A. H. Russell | contribution=Smoking Problems: An Overview | series=NIDA Research Monograph | issue=17 | year=1977 | pages=13–34 | url=http://archives.drugabuse.gov/pdf/monographs/17.pdf | url-status=dead | archive-url=https://web.archive.org/web/20150723034328/http://archives.drugabuse.gov/pdf/monographs/17.pdf | archive-date=2015-07-23 }}</ref> 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.<ref name="health" />

Tobacco [[polyphenols]] (e. g., [[caffeic acid]], [[chlorogenic acid]], [[scopoletin]], [[rutin]]) determine the taste and quality of the smoke. Freshly cured tobacco leaf is unfit for use because of its pungent and irritating smoke. After [[fermentation]] and aging, the leaf delivers mild and aromatic smoke.<ref>{{citation | author=T. C. Tso | contribution=Tobacco | title=Ullmann's Encyclopedia of Industrial Chemistry | edition=7th | publisher=Wiley | year=2007 | pages=1–26 | doi=10.1002/14356007.a27_123| title-link=Ullmann's Encyclopedia of Industrial Chemistry | isbn=978-3527306732 }}</ref>

=== Tumorigenic agents ===
{{Main|List of cigarette smoke carcinogens}}
{| class="wikitable"
|+ '''Tumorigenic agents in tobacco and tobacco smoke'''
|-
! rowspan="2" | Compounds
! rowspan="2" | In processed tobacco, per gram
! rowspan="2" | In mainstream smoke, per cigarette
! colspan="2" | IARC evaluation of evidence of carcinogenicity
|-
! In laboratory animals
! In humans
|-
| colspan="5" | '''[[Polycyclic aromatic hydrocarbon]]s'''
|-
| [[Benz(a)anthracene]]
| &nbsp;
| 20–70&nbsp;ng
| sufficient
| &nbsp;
|-
| [[Benzo(b)fluoranthene]]
| &nbsp;
| 4–22&nbsp;ng
| sufficient
| &nbsp;
|-
| [[Benzo(j)fluoranthene]]
| &nbsp;
| 6–21&nbsp;ng
| sufficient
| &nbsp;
|-
| [[Benzo(k)fluoranthene]]
| &nbsp;
| 6–12&nbsp;ng
| sufficient
| &nbsp;
|-
| [[Benzo(a)pyrene]]
| 0.1–90&nbsp;ng
| 20–40&nbsp;ng
| sufficient
| probable
|-
| [[Chrysene]]
| &nbsp;
| 40–60&nbsp;ng
| sufficient
| &nbsp;
|-
| [[Dibenz(a,h)anthracene]]
| &nbsp;
| 4&nbsp;ng
| sufficient
| &nbsp;
|-
| [[Dibenzo(a,i)pyrene]]
| &nbsp;
| 1.7–3.2&nbsp;ng
| sufficient
| &nbsp;
|-
| [[Dibenzo(a,l)pyrene]]
| &nbsp;
| present
| sufficient
| &nbsp;
|-
| [[Indeno(1,2,3-c,d)pyrene]]
| &nbsp;
| 4–20&nbsp;ng
| sufficient
| &nbsp;
|-
| [[5-Methylchrysene]]
| &nbsp;
| 0.6&nbsp;ng
| sufficient
| &nbsp;
|-
| colspan="5" | '''[[Aza-arene]]s'''
|-
| [[Quinoline]]
| 1–2 μg
| &nbsp;
| &nbsp;
| &nbsp;
|-
| [[Dibenz(a,h)acridine]]
| &nbsp;
| 0.1&nbsp;ng
| sufficient
| &nbsp;
|-
| [[Dibenz(a,j)acridine]]
| &nbsp;
| 3–10&nbsp;ng
| sufficient
| &nbsp;
|-
| [[7H-Dibenzo(c,g)carbazole]]
| &nbsp;
| 0.7&nbsp;ng
| sufficient
| &nbsp;
|-
| colspan="5" | '''[[N-Nitrosamine]]s'''
|-
| [[N-Nitrosodimethylamine]]
| 0–215&nbsp;ng
| 0.1–180&nbsp;ng
| sufficient
| &nbsp;
|-
| [[N-Nitrosoethylmethylamine]]
| &nbsp;
| 3–13&nbsp;ng
| sufficient
| &nbsp;
|-
| [[N-Nitrosodiethylamine]]
| &nbsp;
| 0–25&nbsp;ng
| sufficient
| &nbsp;
|-
| [[N-Nitrosonornicotine]]
| 0.3–89 μg
| 0.12–3.7 μg
| sufficient
| &nbsp;
|-
| [[NNK|4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone]]
| 0.2–7 μg
| 0.08–0.77 μg
| sufficient
| &nbsp;
|-
| [[N-Nitrosoanabasine]]
| 0.01–1.9 μg
| 0.14–4.6 μg
| limited
| &nbsp;
|-
| [[N-Nitrosomorpholine]]
| 0–690&nbsp;ng
| &nbsp;
| sufficient
| &nbsp;
|-
| colspan="5" | '''[[Aromatic amine]]s'''
|-
| [[2-Toluidine]]
| &nbsp;
| 30–200&nbsp;ng
| sufficient
| inadequate
|-
| [[2-Naphthylamine]]
| &nbsp;
| 1–22&nbsp;ng
| sufficient
| sufficient
|-
| [[4-Aminobiphenyl]]
| &nbsp;
| 2–5&nbsp;ng
| sufficient
| sufficient
|-
| colspan="5" | '''[[Aldehyde]]s'''
|-
| [[Formaldehyde]]
| 1.6–7.4 μg
| 70–100 μg
| sufficient
| &nbsp;
|-
| [[Acetaldehyde]]
| 1.4–7.4 μg
| 18–1400 μg
| sufficient
| &nbsp;
|-
| [[Crotonaldehyde]]
| 0.2–2.4 μg
| 10–20 μg
| &nbsp;
| &nbsp;
|-
| colspan="5" | '''[[Volatile organic compound|Miscellaneous organic compound]]s'''
|-
| [[Benzene]]
| &nbsp;
| 12–48 μg
| sufficient
| sufficient
|-
| [[Acrylonitrile]]
| &nbsp;
| 3.2–15 μg
| sufficient
| limited
|-
| [[1,1-Dimethylhydrazine]]
| 60–147 μg
| &nbsp;
| sufficient
| &nbsp;
|-
| [[2-Nitropropane]]
| &nbsp;
| 0.73–1.21 μg
| sufficient
| &nbsp;
|-
| [[Ethyl carbamate]]
| 310–375&nbsp;ng
| 20–38&nbsp;ng
| sufficient
| &nbsp;
|-
| [[Vinyl chloride]]
| &nbsp;
| 1–16&nbsp;ng
| sufficient
| sufficient
|-
| colspan="5" | '''[[Inorganic compound]]s'''
|-
| [[Hydrazine]]
| 14–51&nbsp;ng
| 24–43&nbsp;ng
| sufficient
| inadequate
|-
| [[Arsenic]]
| 500–900&nbsp;ng
| 40–120&nbsp;ng
| inadequate
| sufficient
|-
| [[Nickel]]
| 2000–6000&nbsp;ng
| 0–600&nbsp;ng
| sufficient
| limited
|-
| [[Chromium]]
| 1000–2000&nbsp;ng
| 4–70&nbsp;ng
| sufficient
| sufficient
|-
| [[Cadmium]]
| 1300–1600&nbsp;ng
| 41–62&nbsp;ng
| sufficient
| limited
|-
| [[Lead]]
| 8–10 μg
| 35–85&nbsp;ng
| sufficient
| inadequate
|-
| [[Polonium-210]]
| 0.2–1.2 pCi
| 0.03–1.0 pCi
| sufficient
| sufficient
|}