12.1 Tobacco in Australian cigarettes
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Most Australian cigarette brands are 'Virginia-only' products.4 This means that all of the tobacco used in their manufacture is Virginia or flue-cured tobacco. The other most common type of cigarette in Western countries is the blended cigarette, which contains a mixture of several different kinds of tobacco.5 A handful of brands currently sold in Australia, including Alpine and Marlboro, are blended. Smokers appear to have strong acquired preferences for either Virginia or blended cigarettes. Most Australian smokers strongly prefer Virginia cigarettes to blended ones.
Virginia tobacco is produced by hanging tobacco leaves to dry and cure in heated barns for five to seven days.5 The other kinds of tobacco include:
- air-cured (including Burley and Maryland), which is produced by drying tobacco in barns at ambient temperatures over longer periods;
- fire cured, which is produced by exposing tobacco directly to smoke from wood fires; and
- sun-cured, which is produced by hanging tobacco to dry in direct sunlight.5
Virginia tobacco has high sugar content compared to the tobacco types cured by other means. It consequently produces sweeter-tasting smoke than other tobacco types, at least when nicotine levels are comparable. However, Virginia tobacco also produces more acidic smoke, because a number of acids are produced from the combustion of sugars.
The lower smoke pH of Virginia cigarettes means that there is generally proportionately less unprotonated or 'free' nicotine in the smoke.5,18 This is the more pharmacologically active form of nicotine, which appears to produce most of the rewarding sensations associated with smoking.18 The other form—called protonated or 'bound' nicotine—acts more slowly. However, unprotonated nicotine also produces more sensations of harshness than protonated nicotine. Thus, cigarettes must be engineered to deliver unprotonated nicotine within certain tolerances. Levels of unprotonated nicotine in smoke may be increased either by increasing the ratio of unprotonated to protonated nicotine or by increasing total nicotine levels.
The smoke from Virginia cigarettes also has a different profile of known carcinogens and cardiovascular/respiratory toxicants than the smoke from cigarettes containing other tobacco types.6,7 Smokers of Virginia cigarettes probably have lower exposures to certain carcinogens and cardiovascular/respiratory toxicants than smokers of other types of cigarette but will also probably have higher exposures to other carcinogens and cardiovascular/respiratory toxicants. We shall return to this issue at the end of the chapter when dealing with the information that is available on the emissions of specific carcinogens and other toxicants in the smoke of Australian cigarettes.
As well as containing tobacco that has been cured in different ways, cigarettes contain tobacco that has been processed in different ways and tobacco from different parts of the plant.5, 6
Australian cigarettes invariably contain cut tobacco leaf (or 'lamina'), which will vary in flavour and nicotine content, depending on which part of the plant it has been taken from. Leaf taken from high on the plant will have higher nicotine content and will generally also have a richer flavour.
Cigarettes may also contain expanded and reconstituted tobacco. Expanded tobacco is lamina or stem that has been puffed up with carbon dioxide to restore individual cells to their thickness prior to curing. It is used to control burning properties, as well as to control the weight/firmness combination of the tobacco rod. Expanded stem, in particular, imparts firmness to tobacco rods. Reconstituted tobacco is a paper-like sheet that is produced from 'tobacco fines' — the small scraps that are produced at all stages of processing tobacco. Thus incorporating reconstituted tobacco in cigarettes is a means for utilising material that would otherwise be discarded. It can also be used as a means for reducing standard ISO tar and nicotine yields (which are explained in Section 12.2 below).5–7
Tobacco industry documents, which have been made public as a result of legal action in the US, strongly suggest that the use of reconstituted tobacco was phased out in Australian cigarettes in the 1980s and 1990s.8 It also appears that unusually high levels of expanded leaf and stem were used in Australian cigarettes during this period (as is explained below when Australian and US cigarettes are compared).
During this period, Australian cigarettes were re-engineered to minimise tobacco weight.4 This occurred in response to a by-weight excise system that remained in place until 1998 and had involved a marked increases in duties levied during the early 1980s.9 Australian manufacturers thus had a strong incentive to reduce the weight of cigarettes. In order to produce low weight cigarettes that were sufficiently firm to hold together prior to smoking and also to retain the integrity of the burning coal during smoking, it was apparently necessary to replace reconstituted tobacco with expanded tobacco, particularly expanded stem.
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