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Some prominent medical sources even claim that there are over 7000 chemicals in tobacco smoke. The rumor seems to be passed around with no reference.

Wikipedia makes a more believable claim that "[m]ore than 4,000 chemical compounds are created by burning a cigarette."

If you look at the list of additives to cigarettes, many of them, like maple syrup, basil oil, cocoa, are safe elsewhere and probably not present in most cigarettes. However, my question is what the claimed 4,000 compounds really mean. Does it mean that if you burn every type of cigarette in the world, you'll get over 4,000 different possibilities of chemical? Or does it mean that the average cigarette, when burned, contains over 4,000 compounds?

Is it even unusual for 4,000 different chemicals to be in smoke? Would a grilling steak subject to the same methods produce as many carcinogenic compounds in its smoke?

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    I think your final sentence is the important bit here - is 4000 good? How many chemical compounds are in a cow? Quite a few, I'd imagine :-) – Rory Alsop Feb 27 '13 at 10:31
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    A count of the additives is misleading, as some are made of several compounds, and generate more when burnt. The "Generally Regarded As Safe" (GRAS) status of items like maple syrup probably doesn't necessarily apply to their smoke. – Oddthinking Feb 27 '13 at 11:57
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    Dihydrogen monoxide is a chemical. – Andrew Grimm Feb 27 '13 at 12:08
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    The number of different chemicals is a rather meaningless value. The important parts are the amounts of specific chemicals and their toxicity. And I would assume that the number refers to the chemicals produced while burning a cigarette, which is a very complicated set of reactions that can easily produce lots of different chemicals. – Mad Scientist Feb 27 '13 at 13:09
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    There are probably more than 4,000 chemicals in a glass of good wine, but we don't usually regard that as a bad thing. Cigarettes are generally agreed to be bad things, but it isn't because there are 4,000 chemicals in them; it is because some of the 4,000 are potent carcinogens. – matt_black Feb 27 '13 at 22:44
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One of the latest (Jan 2013) studies on this topic" published by the Journal of Separation Science begins by writing that "smoke is an extremely complex and dynamic aerosol" which forms from "a series of complex processes including combustion, pyrolysis, pyrosynthesis, distillation, sublimation, condensation, filtration, and elution." The same study isolates "almost 2,500 individual compounds" from cigarette smoke (by using comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry).

An earlier and widely-cited study by Green and Rodgman puts that number at 4,800, using a different method. Other studies (which I saw cited, but have not reviewed myself) range from 900 to 10,000 compounds. The important thing to note here is that "cigarette smoke composition is known to be sensitive to cigarette construction and the way the cigarette is smoked" and that the results of divergent findings "cannot be compared with other studies" directly when the methodologies differ.

A 2007 study by a group of Chinese scientists isolates 141 compounds in burning straw, but they again use a different methodology from the studies cited above. "The carcinogenic compounds in oil smoke particulates from Chinese cooking practice have not yet been characterized," concludes another research paper in the Chemical Research in Toxicology, circa 2000.

Some tentative conclusions after reviewing the literature:

  • the range of numbers in the original claim are reasonable and depend on the methodology used,
  • claimed numbers are not unusual in burning organic matter,
  • smoke is generally bad for you, including smoke from cooking oils, incense, and candles,
  • burning things is different from eating them, because combustion sets off many complex chemical reactions.
  • Of course, everything is carcinogenic , the Surgeon General warned us. – user1873 Mar 11 '13 at 14:32
  • Are you implying that nothing is carcinogenic or that the word has no scientific meaning? – denten Mar 11 '13 at 15:58
  • I think user1873 is implying that everything is carcinogenic, as in it's impossible to avoid carcinogens and radiation. – Muz Mar 12 '13 at 8:38
  • In the literature I reviewed above, carcinogenic has a specific meaning. The designation is also legally regulated by several agencies. So for example, only a fraction of the thousands smoke particulates is carcinogenic. Could be a topic for another question! – denten Mar 12 '13 at 14:03

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