The commercial growth of tobacco plants, the processing of tobacco and the manufacture of cigarettes are part of a highly profitable industry. As such, these processes have all been optimised by the industry to maximise profits. The steps from tobacco plant to final product, described herein, lead to the production of highly addictive cigarettes containing and emitting toxic chemicals, with a range of appealing tastes and aromas, that are made with a disregard for their effects on the health of consumers.
This section describes the tobacco used in the commercial manufacture of cigarettes – it’s a journey to the final product from the growing of the plant and the varieties of plants that are used. Tobacco manufactured for use in roll-your-own cigarettes and other tobacco products is described in Section 12.2.
12.1.1 Tobacco plant growth and the curing process
Tobacco is made from several species of plants in the genus Nicotiana. The most common species of tobacco plant is Nicotiana tabacum, which is the one used in most cigarettes and other commercial tobacco products. The species Nicotiana rustica and Nicotiana alata are also used to make some tobacco products. All these plants produce nicotine as a natural defence against pests.
Tobacco plants are grown in many different countries and climates. The largest tobacco producers are China, India, USA and Brazil. 1 , 2 Tobacco is grown as a monocrop—without rotation with other crops. This leaves the plant vulnerable to pests and diseases. Tobacco crops therefore require relatively large amounts of fertilisers, pesticides and herbicides 1 (see Section 12.3.2 for more information).
As with most industries that rely on agricultural commodities, tobacco companies have developed and promoted farming practices that optimise growth, yield, and desired characteristics of the leaf they purchase. 2 Agricultural practices, such as removing the flowers (‘topping’), aim to increase leaf and nicotine yields from the plants. For some varieties, the whole plant is harvested and cured, rather than just the leaves. Chemically modified, reconstituted tobacco, which is made from stems and other non-leaf parts of the plant, is also used to make cigarettes. 3 , 4
After tobacco plants or leaves are harvested, they are cured (dried) and aged. Curing is necessary because the fresh leaves are too wet to ignite. It reduces the moisture in the plant material from 80% to almost zero. 5 Curing changes the colour of the leaves and the type of chemicals present in the leaves. 6 It destroys chlorophyll in the leaves, which turns them from green to yellow. 5 Curing also breaks down complex carbohydrates into simple sugars, such as glucose, which contribute to the flavour and aroma of the final product. 5
Tobacco plants are aged by keeping them in storage for one to three years. 7 They may be aged in the field after cutting. After curing, tobacco is stored in warehouses and usually shipped before cigarette manufacture. Curing and aging of tobacco leads to the formation of toxic and carcinogenic chemicals. 8 , 9 See Section 12.3.3 for more information.
There are four main methods for curing tobacco: 1
Air curing. Tobacco leaves are air-cured by hanging in well-ventilated barns at ambient temperatures. The tobacco dries over four to eight weeks. Air-cured tobacco usually has a high nicotine content and low sugar. 1
Fire curing. During fire curing, tobacco leaves are hung in barns with continuous hardwood fires or smoulder. Fire curing is performed for at least three days but up to ten weeks. This process also results in high nicotine content and low sugar. Fire curing is commonly used for pipe tobacco, chewing tobacco and snuff. 1
Flue curing. Tobacco leaves are flue-cured in heated barns for about a week. These barns have flues running into the barn from an external fire, which heats and dries the tobacco without exposing it to smoke. Cigarette tobacco is most commonly flue-cured. This process usually produces tobacco that is high in sugars and has medium to high levels of nicotine. 1 In the past, flue curing exposed the tobacco to exhaust gases from natural gas and propane fires; a practice that is now discontinued (see Section 12.3.3).
Sun curing. Popular in India, sun curing involves placing tobacco leaves uncovered in the sun to dry out. Sun curing is often used for oriental tobacco and tobacco used in bidis, chewing, hookah, and snuff. 1
12.1.2 Manufacture of cigarettes
The cured leaves from one tobacco plant are sufficient to make approximately 300 standard sized cigarettes. 1
After curing, tobacco is usually stored in warehouses before shipping and cigarette manufacture. Although the nicotine in tobacco is toxic for most pests, stored tobacco and tobacco products remain susceptible to the cigarette beetle ( Lasioderma serricorne) and tobacco moth ( Ephestia elutella). 10 , 11 Stored raw tobacco can also be affected by these pests. Fumigation of warehouses with the toxic gas phosphine (and formerly, methyl bromide) is used to remove these insect pests. 12 , 13
After curing and aging, the leaves are cut before being processed into cigarettes. Tobacco cut widths vary from approximately 1.5 mm to 0.4 mm fine cut. Cigarettes made from fine-cut tobacco have faster static burn rates (the rate of cigarette consumption in a smouldering state), 14 which can lead to fewer puffs by the smoker. 9
Different varieties of tobacco are often blended together to make the final product. Many different chemicals are added to the tobacco for reasons such as pH adjustment, increasing moisture, reducing the ‘harsh’ taste of smoke, controlling the burn rate and adjusting the smoke flavour, 9 discussed in Sections 12.3, 12.4 and 12.6. The tobacco blend is treated with steam and water to optimise moisture. 15 Various processes, such as puffing, expanding and freeze-drying tobacco, can be used to decrease the amount of tobacco used in each cigarette. A process called dried-ice expanding may be used to reduce the amount of tobacco leaf in each cigarette by expanding the product with high-pressure carbon dioxide. 1 These methods can also reduce the amount of tar, nicotine and some other chemicals found in cigarette smoke, as they reduce the total amount of tobacco in the rod. 16
Cigarettes are manufactured in a highly automated process. Machines make a long rod of tobacco wrapped in paper, which is then cut into smaller pieces. Filters are inserted at each end of the smaller rods, connected by adhesive “tipping paper”. These smaller rods are then cut in half to produce two cigarettes. These are packaged with others to produce the final product – a pack of cigarettes. 17
Tobacco plant agriculture, curing and manufacture of cigarettes generate environmental problems from the use of fossil fuels, clearing of land and production of hazardous waste. 1 The issues are discussed further in Section 10.15.
12.1.3 Varieties of tobacco used in cigarettes
The most common species of tobacco plant, N. tabacum, has different varieties and many different cultivated versions (cultivars). There are over 1,600 cultivars listed by the National Plant Germplasm System, a network led by the United States Department of Agriculture. 18
The three main tobacco varieties used in factory-made cigarettes are Virginia (Bright or Brightleaf), Burley and Oriental. 19 Blended cigarettes usually contain all three varieties of tobacco, whereas most of the tobacco in Virginia cigarettes is the Virginia variety. 19 The different varieties of tobacco that are combined to produce a specific blend have a significant influence on the levels of toxic and carcinogenic chemicals in cigarette emissions. 3 , 9 , 20
Virginia tobacco is flue-cured, usually for one week. 19 It has a relatively low nitrogen level, therefore lower protein content than the other common varieties. 9 The faster curing process for Virginia tobacco results in it having a higher sugar content than other tobacco varieties, leading to a sweeter taste. Virginia cigarettes (that are mostly Virginia tobacco) may have a sweeter, milder taste than blended cigarettes. Virginia tobacco also produces a more acidic smoke, as a number of acids are produced from the combustion of these sugars. 9
Burley tobacco is air-cured in barns for up to two months. 19 It typically has a relatively high nicotine content and low sugar content. 9 Air-cured Burley tobacco produces a less acidic smoke. Adding more Burley tobacco to a blend can therefore make the smoke less acidic. 9 , 21
Oriental tobacco is sun-cured for at least two weeks. 19 Oriental tobacco has lower nitrate levels than other common varieties, affecting the range of toxic and carcinogenic chemicals produced in its smoke. The distinctive aroma of Oriental tobacco contributes to the aroma of blended cigarettes containing this tobacco. 9
The variety of tobacco used in a cigarette can affect the form of nicotine found in the smoke. When tobacco smoke is less acidic, the nicotine in the smoke may be likely to move from the airways into the body and be delivered to the brain, making it more addictive 9 (see Section 12.4.3.1 for more detail). The smoke from Burley and Oriental tobacco is less acidic than that from Virginia tobacco. However, the acidity of the smoke can be adjusted by tip ventilation and added chemicals (additives) during the manufacturing process, to make it less acidic, ensuring that the smoke contains sufficient nicotine in an addictive form. 9
12.1.4 Tobacco used in Australian cigarettes
12.1.4.1 Tobacco in contemporary Australian cigarettes
In the past, most tobacco products sold in Australia were made in Australia, and only a small number of specialty brands were imported from overseas—see Section 10.3. Since 2016, no cigarettes or roll-your-own tobacco products have been commercially manufactured in Australia (see Section 10.3.1). There is limited available information on the ingredients and construction of cigarettes imported into Australia.
The majority of cigarettes imported and sold in Australia come from three multi-national corporations: Philip Morris International (PMI), British American Tobacco (BAT) and Imperial Tobacco. Each of these companies provides yearly voluntary disclosures of ingredients in the cigarettes they sell, with the most recent at the time of writing being from 2020. 22 These disclosures do not state the varieties of tobacco used in cigarettes sold in Australia, but do provide a weight of tobacco used per product, with ranges summarised in Table 12.1.1. For more details on the ingredients in cigarettes sold in Australia, see Sections 12.6.7 and 12.7.6.
In the past, Australian cigarettes tended to have a greater proportion of Virginia tobacco, which produces a sweeter tasting smoke than other varieties and was considered to appeal to Australian tastes. Some cigarettes currently sold in Australia use the word ‘Virginia’ or ‘blend’ in the variant name. However, there are no reliable reports on which varieties of tobacco are currently used in the cigarettes sold in Australia.
12.1.4.2 Tobacco in Australian cigarettes in the past
In the past, most cigarettes sold in Australia were ‘Virginia-only’ products. 23 This made Australian cigarettes taste sweeter and less “harsh” than cigarettes from many other parts of the world.
During the 1980s and 1990s, Australian cigarettes were re-engineered to minimise tobacco weight. 23 This occurred in response to a by-weight excise system that remained in place until November 1999. The more tobacco used in each cigarette, the more excise duty it attracted. In addition, state licenses fees (levied on the wholesale price of tobacco products) were also higher for heavier cigarettes. The level of these state fees increased markedly from about 10% in most states in 1980 to 100% by the mid-1990s—see Section 13.6.2. Australian manufacturers thus had a very strong incentive to minimise the weight of their cigarettes. In order to produce low-weight cigarettes that were sufficiently firm to hold together prior to smoking, it was apparently necessary to replace reconstituted tobacco with expanded tobacco, especially expanded stem. 24 After state fees were abolished in 1997 and the excise system changed in 1999, the Australian manufacturers re-engineered most brands to increase the weights of both the filter (which had previously been included in the excisable weight) and the weight of the tobacco used in the cigarette, presumably because this increased their consumer attractiveness over the previous designs. A study from 2008 indicated that the majority of Australian cigarette brands had remained stable in construction from when re-engineered after 1999 until 2005. 25
Tobacco industry documents, which have been made public since 1997 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. 24 It also appears that higher levels of expanded leaf and stem were used in Australian cigarettes during this period.
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References
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