Les additifs du tabac
2. What goes into tobacco products?
2.1 What are the main tobacco products?
The SCENIHR opinion states:
A wide variety of tobacco products are available worldwide such as cigarettes, cigars, pipe tobaccos, smokeless tobacco products (STP) etc. Each of these types is produced by using different tobaccos and additives and by using different manufacturing practices (Reviewed in IARC Monographs: 1985; 1986; 2004; and 2007).
Cigarette: The most common form of tobacco is the manufactured cigarette. Cigarettes are made from fine-cut tobacco leaves and are wrapped in paper or other non-tobacco material, filter–tipped or untipped, approximately 8 mm in diameter and 70-120 mm in length. Cigarettes are highly engineered, exquisitely designed “nicotine delivery devices”. Design features encompass a wide range of design variables such as tobacco type and blend, chemical processing and additives, and in addition, physical features such as paper, filter and ventilation. It is also important to consider factors such as tobacco weight or density, and cigarette geometry (circumference and length). Cigarette additives have a range of purposes; e.g. to facilitate manufacture, increase shelf life, control burn rates, nicotine delivery, flavour and harshness/irritation etc. The physical design characteristics of the tobacco product interact with its chemical composition to influence its function and effect (WHO 2001). For example, the size of the cuttings of the tobacco in cigarettes and non-combusted and non-heated tobacco, and its level of acidity (measured as pH), interact to influence the release of nicotine from the product (Callicutt et al. 2006, Stevenson and Proctor 2008). Cigarette ventilation designs also modify free nicotine levels in the smoke. Similarly, the physical and chemical characteristics of cigarettes interact to alter the size distribution of the aerosol particles that convey nicotine and other chemicals, and thus influence absorption (WHO 2007b).
Roll your own (RYO) tobacco denotes any tobacco product which, because of its appearance, type, packaging, or labelling, is suitable for use and likely to be offered to, or purchased by, consumers as tobacco for making cigarettes. RYO cigarettes are cheaper substitutes for commercially manufactured brands and have gained popularity worldwide.
A cigar 8 is a roll of tobacco wrapped in leaf tobacco or any other substance containing tobacco. There are four main types of cigars: little cigars, small cigars (“cigarillos”), regular cigars and premium cigars. Little cigars contain air-cured and fermented tobacco and are wrapped either in reconstituted tobacco or in cigarette paper that contains tobacco and/or tobacco extract. Some little cigars have cellulose acetate filter tips and are shaped like cigarettes. Cigarillos are small, narrow cigars with no cigarette paper or acetate filter. Regular and premium cigars are available in various shapes and sizes and are rolled to a tip at one end.
Pipe tobacco can be a blend of as many as 20-25 different tobaccos, or made of Burley varieties only. Some pipe tobaccos contain midrib tissues, and casings and sauces are frequently added.
A waterpipe is one of the ancient forms of tobacco use. Cut or shredded tobacco is smouldered inside the head, which is covered by a perforated aluminium foil on which the glowing charcoal is placed. The smoke is drawn through a tube inside the waterpipe, filtered through water in a container and reaches the smoker’s mouth via a long flexible tube. A great variety of tobaccos, or mixture of tobaccos with additives, is used in such pipes.
Smokeless tobacco is consumed without burning the product, and can be used orally or nasally. It comes in two main forms: snuff (finely ground or cut tobacco leaves that can be dry or moist, loose or portion packed in sachets, and administered to the mouth, or the dry products to the nose or mouth); and chewing tobacco (loose leaf, in pouches of tobacco leaves, “plug” or “twist” form). According to the Tobacco Products Directive (2001/37/EC) chewing tobacco is not included in the definition of “tobacco for oral use”, the sale of which is banned in all EU countries except Sweden. Swedish-type moist snuff (snus) consists of finely ground dry tobacco (Kentucky and Virginia tobacco), mixed with aromatic substances, salts (sodium chloride), water, humidifying agents and chemical buffering agents (sodium carbonate). The large variety of smokeless tobacco products available worldwide has been described in detail elsewhere (SCENIHR 2008).
Electronic cigarettes, or e-cigarettes, are battery-powered devices that vaporise nicotine, flavouring, and other chemicals into an inhalable vapour (Pauly et al. 2007). Chemical analyses have detected tobacco-associated chemicals that may be harmful to humans, including known human carcinogens (Kuehn 2009). E-cigarettes have been marketed recently for a range of uses, including, as a cessation aid and as an alternative to cigarettes in smoke-free zones. The different brands vary greatly in content of nicotine and other chemicals, but the health risks or efficacy as cessation aids have not yet been sufficiently documented (Bullen et al. 2010).
2.2 How are they made?
The SCENIHR opinion states:
Tobacco – manufacturing process
The manufacturing process for cigarettes has been described in several publications (Davis and Nielsen 2006, Hoffmann and Hoffmann 1997, IARC 2004, Wigand 2006). However, while the exact composition of each brand remains a trade secret, according to the Tobacco Products Directive (2001/37/EC) tobacco industries have to report the full list of additives in tobacco products, including the exact amount, to the competent authorities in the Member States.
Both the make-up of cigarettes and the composition of cigarette smoke have gradually changed in the last 50-60 years, including the use of a larger range of additives. The sales-weighted average “tar” and nicotine yields have declined. These changes have been primarily achieved by the introduction of filter tips, with and without perforation, selection of tobacco types and varieties, utilization of highly porous cigarette paper, and incorporation into the tobacco blend of reconstituted tobacco, opened and cut ribs, and “expanded tobacco” together with the use of a large number of additives/ingredients. At least four of the physical parameters of cigarettes have a decisive influence on smoke yields. These are the length of a cigarette, its circumference, the cut of the tobacco, and the packing density (Hoffmann and Hoffmann 1997). Agronomic factors such as production practices and soil characteristics, and environmental conditions such as rainfall, reportedly influence the accumulation of metals, including cadmium, beryllium, chromium, nickel and arsenic in the leaf.
Commercial tobacco products are predominantly produced from Nicotiana tabacum, while Nicotiana rustica is used on a limited commercial scale. Within the species N. tabacum one distinguishes four types: bright (Virginia), Burley, Maryland, and Turkish tobaccos. Bright tobacco is flue-cured by drying with artificial heat; Burley and Maryland tobaccos are air-cured; Turkish tobaccos are sun-cured. The properties of tobacco are based primarily on curing methods, locality of growth, position on the stalk from which the leaves have originated and factors such as colour quality and ripeness at harvest. Curing is the process for drying freshly harvested tobacco with partially or fully controlled temperature and moisture schedules. Freshly cured leaf is then threshed to separate stem from lamina, sometimes blended with other tobacco lamina and then re-dried to a uniform moisture level then packed into bales or hogsheads.
Virginia tobacco leaves contain a higher carbohydrate (e.g. sugars) level and lower nitrogen level than Burley leaves. The natural drying of the Burley leaves at relatively low temperatures allows plant respiration which continues to consume sugars during the process, leaving negligible sucrose and reducing sugars in the cured leaf. Burley leaves contain higher levels of nitrogen than Virginia leaves. The smoke of Virginia or flue-cured leaves is more aromatic and less alkaline than that of Burley tobacco, with a slight acidic taste resulting from the high levels of natural sugars. Burley tobacco produces a more alkaline smoke than flue-cured tobacco (Weeks 1999) and therefore imparts a bitter aroma and taste to cigarettes. Oriental leaves tend to have a low nitrogen content and moderate levels of carbohydrates, but fewer proteins, than the other varieties (Philip Morris 2010, Wolfe 1962).
A comprehensive integrated pest management programme is used to avoid insect infestation, e.g. chemical fumigation. The tobacco then undergoes aging and fermentation, usually for 1-3 years.
For the manufacture of cigarettes, specific tobacco blends utilizing desired tobacco types are prepared. Blending is the selection and thorough mixing of the tobacco-based components plus any associated casings, humectants and flavouring required for a particular product or brand. The tobacco based components may include the leaf lamina, cut and rolled stem, reconstituted sheet and expanded tobacco. The tobaccos stored in bales are broken up, cut into specific dimensions, and combined with other blend components such as casing and top dressing, and adjustment of the moisture content. American blend cigarettes contain the four types of tobacco mentioned above plus reconstituted or homogenised sheet tobacco. This is made from tobacco dust, fines and particles, and leaf ribs and stems (IARC 2004). Reconstituted tobacco or homogenised sheet tobacco is a paper-like sheet approaching the thickness of tobacco laminae. It is made from tobacco dust, fines, and particles, and from ribs and stems; various additives may be incorporated. In the past, most of these “tobacco by-products” were wasted. The introduction of reconstituted tobacco or RECON is the primary means by which ammonia chemistry and other chemicals are introduced into a cigarette. Expansion is a process which increases the shred filling power, e.g. puffed tobacco. Puffed, expanded, and freeze-dried tobaccos are modified preparations of cigarette tobacco and have up to twice the filling power, thus requiring less tobacco per cigarette. The principle applied here is to expand the tobacco cell walls by quick evaporation of water and other agents that readily volatilize. Blending is carried out to achieve specific pH, taste, burning characteristics, and nicotine content. The pH strongly influences the concentration of free (i.e. non-protonated) nicotine in tobacco smoke, whereas the nitrate content influences the carcinogenic potential of smoke (IARC 2004).
Table 2 presents the classification of tobacco types based on curing methods and function.
|Tobacco type||Characteristics/alternate names||Main use|
|Flue-cured||Leaves are yellow, blond, bright therefore also called Bright or Virginia||Cigarettes and also roll your own (RYO) cigarettes and pipe tobacco|
|Fire-cured||Light to dark brown cured over open fires (Kentucky)||RYO, chewing tobacco, cigars and smoking tobacco|
|Light air-cured||Burley (cured without supplementary heat)
|Mainly in cigarettes (also RYO, pipe tobacco and cigars)
|Dark air-cured||Light to medium brown||Chewing tobacco and snuff, snus, dark cigarettes|
|Sun-cured||Oriental tobacco varieties
|Turkish cigarettes (also RYO and pipe tobacco)
Some pipe tobaccos
|Tobacco types for use as cigar fillers, binders and wrappers||Used for cigars|
Two principal types of commercial cigarettes have traditionally been sold throughout the world: (i) American Blend cigarettes, which are made from a blend of Virginia, Burley and Oriental tobaccos; and (ii) Virginia cigarettes, which contain exclusively Virginia tobacco.
Casing refers to the sauce composed of a variety of ingredients such as humectants, sugars, cocoa, liquorice and fruit extracts (Hoffmann and Hoffmann 1997). The basic material of casing for reducing harshness is sugar. A commercial solution of tannin also sweetens and softens the smoke of tobacco. The best known example of an additive that changes markedly and even masks the taste of tobacco is the use of cloves. Addition of menthol is another example, but in this case the tobacco taste is still discernible. Burley leaf has the ability to absorb up to 25% of its weight of added material (Akehurst 1981).
Casings are usually applied to tobacco strips or leaf early in the primary processing scheme to tone down or mute the strength or harshness of tobacco smoke, improve processibility of tobacco and add deep flavour notes to the smoke. Casings are traditionally added to US blended styles of product that contain significant proportions of Burley type tobacco blends. These casings are added to the Burley tobacco line through the means of the casing cylinder or Cased Leaf Dryer. Ammonia technology has been used with US blended styles of products containing cased Burley tobacco. Ammonium salts could be added at the Cased Leaf Dryer (CLD) stage or with the manufactured reconstituted tobaccos.
There are no fixed rules as to where humectants, flavours and flavourings are added to the processed tobacco but generally the more volatile ingredients are added as late as possible during tobacco processing to prevent losses. Those tobacco blends that contain flavours and flavourings are usually held in a bin to allow for equilibration across the blend before it is passed to the making machine as the final blend. Top flavourings are generally applied to the total tobacco blend as one of the last steps in processing. They are usually carried in an alcohol base. They are used to improve quality of smoke, impart a pleasant pack aroma and side-stream aroma. Menthol may be added at any of the following stages; spraying onto the final blend, through addition to the filter via a thread, or by application to the cigarette paper or the foil used to wrap the cigarettes. Due to the high level of volatility of menthol, different manufacturers have over the years developed a variety of methods for producing mentholated products that are as consistent as possible in terms of their finished product menthol levels (BAT 2010).
In cigarettes, flavours may be added to tobacco, cigarette paper, or the filter, in a plastic pellet placed in the filter or the foil wrapper, in an attempt to enhance the tobacco flavour, mask unpleasant odour, and deliver a pleasant cigarette-pack aroma. Internal industry documents reveal additional flavour technologies such as flavour microencapsulation in the paper, carbon beads, and polymer-based flavour fibres inserted into the filter, flavoured tipping etc. (WHO 2007b).
As described above, the physical elements of the cigarette such as packing density, particle size distribution, rag cut per inch, colour appearance, resistance to draw, the appropriate paper, filter, tobacco type and the final tobacco blend, are carefully controlled (Wigand 2006). The final product is manufactured using high speed automated machines.
Over the years the tobacco industry has developed genetically modified (GM) tobacco plants with an aim, among others, to manipulate nicotine levels (Dunsby and Bero 2004). Reductions of nicotine levels have been in the range of 80-98%. Philip Morris sought to use anti-sense biotechnology to disrupt enzymes involved in nicotine biosynthesis (US Patent 5684241). In 2003, Vector Tobacco began marketing a new cigarette that is produced from GM tobacco containing trace amounts of nicotine. The GM plant was produced by disrupting expression of the gene for quinolinate phosphoribosyl transferase, which encodes one of the rate-limiting enzymes in the nicotine biosynthetic pathway (Bonetta 2001). Vector Tobacco market Quest Cigarettes, which exist in three forms, ranging in nicotine content from 0.6 mg per cigarette to 0.05 mg per cigarette. They are marketed as a smoking cessation or reduction aid, with the manufacturer claiming that graded reduction of nicotine exposure through the gradual use of increasingly lower nicotine content cigarettes will lead to the eventual extinction of nicotine dependence and conditioned associations with related cues (Bonetta 2001).
Large scale field-trials have also been conducted despite consumer opposition and fear of tobacco growers that GM crops would be turned down by several countries.
Conclusions on manufacturing
Cigarettes, which are the predominant tobacco product, are highly engineered nicotine delivery devices that are mass produced by the major industries by integrated automation.
The properties of tobacco products depend on locality of growth, position of leaves on the stalk, ripeness and curing method. The different curing methods (drying procedures) determine the sugar content and colour of the tobacco leaves. During the manufacturing process of cigarettes, a number of substances are added at different stages for various reasons, such as providing consistency of the product, creating a unique brand, and promoting attractiveness.
2.3 What is added?
The SCENIHR opinion states:
According to the EU Tobacco Products Directive (2001/37/EC) tobacco companies are obliged to provide information about the ingredients added to tobacco products, and their function, to the local authorities. In Germany, this information is published on the website of the Federal Ministry of Nutrition, Agriculture, and Consumer Protection 9 . Consumers can search for brands and ingredients. The reports from 2008 showed the amount of each ingredient listed. However, only the amounts of major ingredients such as sucrose, propylene glycol or cocoa are disclosed to the public. Furthermore, only 22 of the 50 most-used ingredients have been specified by name. In the reports for the general public the tobacco industry does not reveal the nature of all flavourings, colours, or adhesives used. Quantitatively, sugars and humectants (e.g. glycerol, propylene glycol) are the dominant additives in cigarettes. Furthermore, compounds which influence the taste of the cigarette are used in many brands; relevant substances are cocoa (incl. cocoa powder, cocoa extracts, shells of cocoa bean etc.) and liquorice (incl. liquorice extract). Other ingredients are part of the cigarette paper, the filter, or are used as glue. Even if the tobacco companies are secretive about the exact amount of flavours used in each brand, some information is available on the websites of the tobacco companies (e.g. BAT 10 ). Most of the tobacco companies disclose only the highest amount of ingredients used in their brands (i.e. Quantity Not Exceeded (QNE)). Therefore, it is not possible to draw conclusions about the average amount added or about the percentage of brands that contain a particular ingredient. As an example the information on the Philip Morris website 11 for German cigarettes has been evaluated. In the compilation the maximum use levels are given, i.e. Philip Morris only discloses the highest amount used in its brands. Most of the flavours are added in very small amounts. On the other hand, menthol and lactic acid are flavours used in milligram amounts per cigarette (see table 3). For the calculation it was assumed that each cigarette contains about 700 mg of tobacco. Table 3 Ingredients added to the tobacco based on a table presented by Philip Morris International (PMI) on cigarettes manufactured for sale in Germany11
|Ingredient||Maximal use level(w/w%)||Maximal use level(mg/cigarette (700 mg))|
|benzoic acid sodium salt||0.3||2.1|
|carob bean and/or extract||0.2||1.4|
|cocoa and cocoa products||0.2||1.4|
|orange oil, sweet||0.005||0.035|
|orris root extract||0.001||0.007|
|valerian root extract||0.001||0.007|
8 According to the Council Directive 2010/12/EU of 16 February 2010, the following shall be deemed to be cigars or cigarillos if they can be and, given their properties and normal consumer expectations, are exclusively intended to be smoked as they are: (a) rolls of tobacco with an outer wrapper of natural tobacco; (b) rolls of tobacco with a threshed blend filler and with an outer wrapper of the normal colour of a cigar, of reconstituted tobacco, covering the product in full, including, where appropriate, the filter but not, in the case of tipped cigars, the tip, where the unit weight, not including filter or mouthpiece, is not less than 2,3 g and not more than 10 g, and the circumference over at least one third of the length is not less than 34 mm.
Les additifs du tabac 2. What goes into tobacco products? 2.1 What are the main tobacco products? The SCENIHR opinion states: A wide variety of tobacco products are available