Tobacco products, most commonly cigarettes, have come to include more and more additives in recent decades. They include agents to retain moisture and preservatives, as well as a large range of flavourings and other chemicals which modify the properties of tobacco or the experience of smoking.
Some of these additives may make addiction to tobacco as a source of nicotine more likely. They may affect addictiveness of the product or simply make smoking more attractive.
The number of additives is so large, and the chemical mixtures produced by cigarettes so complex, that measuring effects of individual additives is difficult, and expensive. Much of the research is confined to the industry.
How can we evaluate tobacco additives, how good are current methods, and what is currently known about their effects?
An assessment by the European Commission Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR).
Questions on Tobacco Additives
- Introduction
- What goes into tobacco products?
- How can tobacco products and their ingredients be assessed?
- Does development of nicotine addiction depend on the dose?
- Do additives make tobacco more addictive?
- What else can enhance the addictiveness of tobacco products?
- Do additives make tobacco more attractive?
- What further research might be needed?
The answers to these questions are a faithful summary of the scientific opinion produced in 2010 by "The Scientific Committee on Emerging and Newly Identified Health Risks" (SCENIHR):
"Addictiveness and Attractiveness of Tobacco Additives" Learn more...
1. Introduction
Tobacco use is both addictive and harmful. EU directives provide for regulation of tobacco products to protect public health. This includes the possibility of banning additives. Some additives may increase the addictiveness of tobacco products
This report investigates criteria for evaluating additives, the role of additives in tobacco products, and how the design of such products can affect attractiveness and addictiveness.
2. What goes into tobacco products?
The majority of smokers use cigarettes. A manufactured cigarette is a carefully designed device for delivering nicotine. Cured and processed tobacco is packed and wrapped to create a standardised product. The characteristics of each brand depend on the tobacco type and blend, how it is cured, the additives used and other technical characteristics of the cigarette. These may affect for example the content of different substances in the smoke, burning characteristics nicotine release and the size of smoke particles.
In recent decades, more and more additives have been introduced, and current cigarettes may contain up to 10 per cent additives by weight. Nearly 600 different additives have been documented. They also affect smoke characteristics, such as colour, harshness, odour and flavour.
The main tobacco additives are sugars, which are also present naturally, and moisturising agents. Others include preservatives and numerous flavourings, including cocoa, liquorice, menthol and lactic acid.
Roll-your-own cigarettes, cigars, waterpipes and smokeless tobacco products, which may also contain additives, all account for small portions of the total market.
3. How can tobacco products and their ingredients be assessed?
Tobacco products are addictive and have higher addictive potential than pure nicotine. Methods are needed to compare the addictiveness of tobacco with and without additives. However, it is experimentally difficult to distinguish the possible effects of additives from those of chemicals normally present in tobacco smoke.
Both animal and human studies are considered in the assessment of additives. While human studies may relate to both addictiveness and attractiveness, animal studies are restricted to the former.
Animal studies usually involve self-administration of nicotine, and are believed to rely on the same neurobiological mechanisms as human drug dependence. Human studies measure both objective effects of tobacco products – such as rate of consumption and chemical absorption – and subjective effects – such as reported pleasure in smoking.
Systematic experiments in which specific additives are present or absent are difficult to carry out. Human testing of different tobacco products for addictiveness faces severe ethical problems, especially if information is sought about effects on children or non-smokers. For these reasons, current methods for the assessment of additives are not adequate.
4. Does development of nicotine addiction depend on the dose?
Nicotine addiction has been extensively studied, from investigations of the absorption and metabolism of nicotine in smoke to its wide range of effects on neurotransmitter chemicals in the brain. Animal studies indicate that pure nicotine is only weakly addictive but data on human drug use indicate that the addictive potential of tobacco is very high.
Individual responses vary widely, but nicotine dependence is correlated with the number of cigarettes smoked daily.
Animal studies show that the response to nicotine depends on the dose, rising as the dose increases and then falling off again – so the curve of dose-dependence is an upside-down U-shape. This is similar to other drugs.
5. Do additives make tobacco more addictive?
Additives could enhance addictiveness by:
- Enhancing nicotine content directly
- Increasing the bioavailability of nicotine – so the body reacts more strongly
- Making it easier to inhale tobacco smoke
- Producing substances in the smoke which increase addictiveness of nicotine
- Altering the properties of tobacco smoke, such as the size of the smoke particles.
No tobacco additives have been identified which are addictive by themselves. Some may influence nicotine addiction. There is most evidence about sugars, which are added to many tobacco products but are also naturally present in tobacco leaves.
Burning sugar produces chemicals called aldehydes, including acetaldehyde. This is thought to increase levels of one class of neurotransmitters by inhibiting the enzyme which usually clears them from the system. However, there is no proof that aldehydes in smoke increase the levels of these chemicals in the blood.
Ammonia and its compounds are added to some tobacco products to reduce the acidity of the smoke. It was thought that this would increase nicotine absorption, which is inhibited in acidic media. However, this probably only affects nicotine intake via the mouth, and smokers take in most of the nicotine via the lungs. Ammonia-laced tobacco products do not appear to significantly increase blood nicotine levels.
6. What else can enhance the addictiveness of tobacco products?
Additives aside, the way cigarettes are made affects smoke composition, including tar, carbon-monoxide and nicotine levels, and the size of smoke particles.
Particle size can affect nicotine exposure because smaller particles pass further into the lungs. Mixing more air with the smoke by designing a better ventilated cigarette can reduce nicotine intake by diluting the smoke.
However, smokers tend to smoke enough to get the dose of nicotine they crave whatever the composition of the smoke. If it delivers less nicotine, they puff harder and more often.
7. Do additives make tobacco more attractive?
Additives can make smoke look more attractive – for other people as well as the smoker – and reduce lingering odours, as well as mask the smell of smoke. They can make it easier to start smoking by making the smoke, cooler, sweeter, and less harsh to the throat. Harshness can be altered by changing the ratio of nicotine to tar, and also by adding flavourings which give the impression a particular cigarette brand is “smooth”.
It is very difficult to identify the role of individual substances in enhancing attractiveness. There is most information about menthol, used in cigarette brands which are popular in the USA. Menthol reduces harshness and may encourage deeper inhalation of smoke. In the USA a much higher proportion of African Americans than European Americans smoke mentholated cigarettes.
The available data do not allow drawing any conclusion on the overall effect of additives on the use of tobacco products. The prevalence of smoking (i.e. the number of smokers) is stable or in decline in most EU Member States. 2006 figures indicate that 27.5 per cent of adults smoked in the EU – 33.2 per cent of men and 21.8 per cent of women – roughly the same levels as in 2002. Smoking is more common, on average in Eastern European Member States.
Flavourings may be used to target young people, and there is evidence that younger smokers are more likely to use flavoured cigarettes. However, UK data suggest that brand preferences of child and adult smokers are quite similar. There are also indications in the UK market, which is dominated by domestic brands, that cigarettes marketed as “additive free” may become popular.
8. What further research might be needed?
More research is needed on a number of aspects of additives, addiction and attractiveness of tobacco products. Useful investigations would include:
- Composition of smoke from tobacco products other than cigarettes.
- The neurophysiology of tobacco addiction.
- The role of sugars in the addictiveness of tobacco products.
- Measures of the attractiveness of tobacco products and additives.
- Studies on brands preferred by new smokers and reasons for brand choice.
Such studies could be pursued through European collaborative projects, or even by the creation of a European Institute for research on drugs of abuse.
The GreenFacts Three-Level Structure used to communicate this SCENIHR Opinion is copyrighted by Cogeneris SPRL.