12.6.3 Additives that increase the attractiveness of tobacco products

Table 12.6.3.1 details many flavouring additives in cigarettes and roll-your-own tobacco in Europe. Of particular interest to regulators are ‘characterising flavours’ that predominantly influence the flavour and attractiveness of tobacco products.⁴ Examples of characterising flavours include diacetyl (which smells like butterscotch), geraniol (which smells like geranium and occurs in rose, citronella and many other essential oils), guaiacol (which smells like smoked ham, vanilla or cloves), fenugreek, fig extract, prune juice extract, rum and vanillin. Additives such as ammonium compounds and lactic acid may also modify the flavour of tobacco.⁴

Most tobacco contains high levels of sugars, which occur naturally in the plant and are added to tobacco after harvesting. Sugars add to the flavour of tobacco by undergoing chemical reaction processes called caramelisation and Maillard reactions that form volatile flavourants.^3,6,7 Sugars added to Australian tobacco products include white sugar/sucrose, invert sugar (a mix of glucose and fructose), sugar cane extract/syrup and high fructose corn syrup. The majority of tobacco companies that report added sugars designate these sugars as flavours.^8-10

Many of the flavouring additives are non-toxic, but they are converted into toxic substances after being modified during burning. For instance, heated sugars produce pyrolysis products, such as aldehydes and furans. Many of these are known toxicants and/or carcinogens.³

Liqueur/confectionery cigarettes are produced by diffusing volatile flavour essences throughout the cigarette or by a flavour pellet embedded in the filter.¹¹ As smoke is drawn through the filter, the casing of the pellet dissolves and the flavour essences are vaporised into the smoke.¹¹ Development of soluble pellet technology may explain the sudden appearance of liqueur/confectionery brands around the world in the early 2000s. Liqueur/confectionery flavour additives are believed to be part of ‘youth-oriented’ products (see Section 5.13), and likely to facilitate initiation among youth by masking the harshness of tobacco smoke in comparison with a 'full-flavour' cigarette.¹² The promotion and sale of fruit and confectionary flavoured cigarettes is now prohibited in all states and territories in Australia. See 10.8.4 for more details about flavoured cigarettes and tobacco in Australia.

Kreteks are cigarettes that originated in Indonesia, containing tobacco plus a significant amount of cloves (sun-dried flower buds of the clove tree). Kreteks also contain a ‘sauce’ that contributes to flavouring, with up to 100 ingredients.¹³ Information on the sauce ingredients is scarce, but it may include chemicals that give a chocolate, strawberry, liquorice and/or banana taste.¹⁴ Saccharin is added to the kretek wrapper to produce a sweet flavour.¹³ Eugenol (clove oil) is found in kreteks at up to 7% of the weight of the filler. Other chemicals from the cloves include eugenol acetate, caryophyllene, α-humulene, and methyl eugenol.¹⁵ The extent to which these contribute to the flavour of kreteks is poorly understood.

Bidis are hand-rolled, unfiltered cigarettes made in India and exported worldwide. They contain finely ground, sun dried tobacco rolled in a Tendu leaf (from the Tendu tree, native to India). Bidis are often high in added flavours, such as cherry, menthol, cinnamon, strawberry, vanilla, and raspberry.¹⁶

The tobacco used in waterpipes is usually highly flavoured and these flavours are a significant motivator for their use.^17-19 Fruity flavours are common. Benzyl alcohol, limonene, linalool and eugenol (clove oil) have also been detected in waterpipe tobacco.²⁰  

12.6.3.2 Reducing harshness and increasing smoothness

Reducing the harshness or increasing the smoothness of a product can improve the smoking experience, making it harder to quit and making young people more likely to take up smoking.^1,2  

Harshness has been carefully defined and measured by the tobacco industry; it is ‘a chemically induced physical effect associated with a roughness, rawness experience generally localised in the mouth and to a lesser degree in the upper reaches of the throat and the trachea due to inhalation of tobacco smoke.’¹ Nicotine, which is present in tobacco in substantial amounts, is one chemical that is responsible for the harshness of smoke.²¹ Lowering the amount of nicotine, particularly the ratio of nicotine to tar, can reduce the harshness of smoke. Propylene glycol (a humectant) has been found to reduce the delivery of nicotine whilst increasing tar levels, and may reduce harshness.^1,22 Added sugars, such as sucrose, glucose and fructose increase the acids in smoke, potentially lowering the ‘freebase’ nicotine (see Section 12.4.3.1), thereby reducing the harshness of the smoke on the mouth and throat.^1,3,23

An alternative approach is to increase the smoothness of smoke using additives that mask the harshness, without reducing delivery of nicotine. Chemicals that mask the harshness of smoke may do this by reducing the feeling of irritation felt in the mouth or throat when smoking.¹ Menthol and thymol are such additives, due to their local anaesthetic effect, see Section 12.7.2. Levulinic acid and levulinates are additives that can mask the harshness of smoke whilst maintaining or increasing nicotine delivery.^1,24 Glycyrrhizin (found in liquoric) and other additives that make the taste sweeter can also mask the harshness of smoke.^1,25 Eugenol (clove oil), which comprises up to 7% of the weight of kreteks, has local anaesthetic properties and may act to increase smoothness of these Indonesian cigarettes.²⁶

Synthetic cooling agents such as WS-3 and WS-23 are chemicals that can mask the harshness of tobacco using a similar mechanism to menthol.²⁷ They do not have a characteristic flavour, and therefore may be considered to be non-flavourants that have a cooling effect. After menthol bans in some jurisdictions in the US, the presence of the synthetic coolant WS-3 has been detected in some cigarettes labelled as ‘non-menthol’ but with similar packaging and colours as used for menthol cigarettes.^{27 ,28} WS-3 has also been found in oral nicotine pouches.²⁹

Humectants are chemicals that promote the retention of moisture in the tobacco (increase the humidity). Tobacco that becomes too dry has a harsh taste and feel, which can be improved with the addition of humectants.² Humectants commonly added to tobacco products include glycerol, propylene glycol and sorbitol.¹ By quantity per cigarette, humectants are one of the most common additives. In Australia, roll-your-own tobacco products have higher amounts of humectants (glycerol and propylene glycol) and higher moisture levels than factory-made cigarettes.³⁰

12.6.3.3 Improving the look and aroma of smoke

Many flavourings additives and added sugars produce appealing aromas when smoked. Improving the smell and appeal of the smoke may reduce the annoyance of the smoke to other people and therefore may improve the user experience of smoking.¹ Acetylpyrazine, anethole and limonene are additives that reduce the smell of sidestream smoke. Chemicals added to the wrapper, including magnesium oxide, magnesium carbonate, sodium acetate, sodium citrate and calcium carbonate can reduce the visibility of smoke.³¹ These chemicals are predicted to reduce the harshness of taste and make the tobacco look ‘fresher’.³¹

12.6.3.4 Improving the look of tobacco products

Relatively high levels of humectants (glycerol and propylene glycol) in Australian roll-your-own tobacco are predicted to make the tobacco look more moist and ‘fresh’. This may contribute to false perceptions that roll-your-own tobacco is more natural and has fewer additives than tobacco in factory-made cigarettes.³¹

Colouring agents such as pigments are added to tobacco products to modify their appearance. Any colouring or other chemicals added to the cigarette paper forms part of the smoke that is inhaled as mainstream or sidestream smoke. These include chemicals that modify the burn rate, discussed in Section 12.6.4. Chemicals added to the filter may be inhaled, but those added to the tipping paper (around the filter) would not be. In some countries, pigments are added to the cigarette paper or tipping paper to make cigarettes of varying colours,²⁶ which can make them more appealing, particularly to younger users.³² Pigments are also used to print branding on the cigarette paper and tipping paper. Titanium dioxide is often added to the cigarette filter as a whitening agent.³³

12.6.3.5 Creating the impression of health benefits

Additives in tobacco products have been used in some countries to create the impression, through brand naming, that these products have health benefits or reduced health hazards. Examples of these additives are vitamin C, vitamin E, fruit and vegetables extracts, amino acids such as cysteine and tryptophan, essential fatty acids such as omega-3 and omega-6,^26,34 and charcoal in filters.³⁵