Does nicotine cause cancer?
Hands up if you thought nicotine caused cancer? There are many people who still believe it’s the nicotine in cigarettes that causes lung cancer and the many other smoking related diseases. If you ask family or friends you can guarantee the majority will have the perception of nicotine as the cancer causing chemical present in cigarettes. This is the first charge against nicotine that needs to be addressed. Nicotine does not cause cancer or any smoking related disease. Of the three main causes of death from smoking, lung cancer arises from direct exposure of the lungs to the carcinogens in tobacco smoke, chronic obstructive pulmonary disease (COPD) from the irritant effects of smoke, and cardiovascular disease from the effects of smoke on blood vessel walls. To all intents and purposes, smokers smoke for nicotine but are killed by tar. So we can agree that nicotine is innocent of the charge that it causes disease.
Is Nicotine a Lethal Poison?
The second charge that nicotine stands accused of is that it’s a lethal poison. Recently, the Managing Director of Totally Wicked was engaged in a radio show debate in which a medical doctor claimed if a bottle of e-liquid was spilt on a baby’s foot it would be fatal! This type of horror story from a medical doctor reinforces the scaremongering of nicotine toxicity in the public perception, and directly influenced the nonsensical TPD regulation of limiting e-liquid bottle sizes and maximum nicotine strengths. Although pure nicotine is a toxic compound to be handled with caution, the common claim that 30-60 milligrams of nicotine causes death has been debunked and traced back to a dubious source from the 19th century! Reports of non-fatal suicide attempts or accidents involving nicotine ingestion on the scale of up to 1500mg confirm the lethality of nicotine has been grossly exaggerated for over a century! Nicotine from tobacco, nicotine replacement therapies (NRT patches, gums, sprays), and e-liquids is consumed by millions of people per day, and any reported poisoning is exceptionally rare. Overdosing on nicotine products used as directly is almost impossible, given the ability of the user to titrate dose and the short half-life of nicotine (i.e. nicotine is quickly metabolised and cleared from the body, hence the urge of a smoker to light up first thing in the morning). So for the charge that nicotine is a lethal poison, I think any judge would agree, it’s a trumped-up charge which needs to be downgraded to a misdemeanour. Pure nicotine is toxic and must be handled with care. But remember in toxicology the dose makes the poison, and the dose needed to make nicotine a lethal poison is vastly higher than any of us have been led to believe.
How addictive is Nicotine?
The third charge covers the addictiveness of nicotine, or more specifically, the addictiveness of nicotine in cigarettes compared to NRT’s and e-liquid. To make a judgement, we need to know a little bit more about combustion chemistry and the pharmacology of nicotine.
Nicotine is a naturally occurring alkaloid present in the leaves of the tobacco plant, and is the major psychoactive compound and mediator of addiction to tobacco use. Nicotine absorption across cell membranes, and its ability to reach the brain, is pH dependent. Only non-ionised nicotine can be rapidly absorbed into the bloodstream. Smoke is a relatively acidic medium, so a significant amount of nicotine in cigarettes cannot be rapidly absorbed by the smoker. The speed of nicotine delivery is very important for smoker satisfaction and addiction potential. Tobacco scientists have been manipulating the pH of smoke for many years to increase the proportion of non-ionised nicotine (the psychoactive form) by the addition of alkaline additives (e.g. ammonia) and tobacco curing methods to optimise nicotine delivery. The speed of pulmonary (lung) absorption of nicotine from cigarettes is very rapid, hence the importance for smoker satisfaction and addiction potential. Even cigarette design, such as ventilation holes, maximise the rate of nicotine lung absorption by forcing the smoker to compensate nicotine dose by deeper inhalations and more frequent puffs. Contrast this with NRTs and e-cigarettes. NRTs have low addictive potential due to the method of administration and slower absorption. You don’t hear of many never-smokers becoming addicted to nicotine patches? The same can be said for e-cigarette users, the rate of never-smokers becoming vapers has been shown to be minuscule. New generation e-cigarette devices have improved the rate of nicotine delivery to the user, but it is still shown to be significantly slower than for cigarettes. Again, all evidence shows never-smokers who have tried modern e-cigarettes are not becoming addicted vapers. E-cigarette users also report they feel less dependent on them compared with tobacco cigarettes. Is there another aspect to the re-enforcement of nicotine addictiveness in cigarette smoke?
The addictive potential of cigarettes is not only influenced by their nicotine content. When a smoker lights up a cigarette the smoke produced contains over 5000 chemicals. Scientific studies have provided a link between certain chemicals in smoke and their ability to reinforce the addictive properties of nicotine. Monoamine oxidase inhibitors (MAOI’s) are a class of chemicals present in tobacco smoke. They increase the levels of neurochemicals in the brain such as dopamine and serotonin. In rodent lab experiments, MAOI’s have been shown to facilitate nicotine self-administration and enhance its motivational properties. Without MAOI’s the animals would not self-administer nicotine. These findings contribute to the strong re-enforcing properties of nicotine in cigarettes. Data indicates that MAOI’s present in tobacco smoke act in synergy with nicotine to enhance its rewarding effects.
Sugars are naturally occurring tobacco components, and can also be added to tobacco during the manufacturing process (up to 20 wt %). Burning of the sugar in tobacco releases significant amounts of a chemical called acetaldehyde (approx. 1500 microgram per cigarette). In animal experiments, it has been demonstrated that acetaldehyde has addictive properties and acts synergistically with nicotine. Laboratory experiments also highlight the reluctance of test animals to self-administer only nicotine, unlike other addictive drugs such as heroin, cocaine, and alcohol. Alkaline additives, such as ammonia, also increase the addictive properties of nicotine (for reasons previously discussed).
So we have discussed just a few of the chemicals present in tobacco smoke, and their potential to enhance the addictive properties of nicotine in cigarettes. The TPD forces manufacturers to label e-liquid products with the health warning “this product contains nicotine which is a highly addictive substance”. The case has been proven that nicotine is a highly addictive substance in cigarette smoke. Its addictiveness as a standalone chemical is a matter of considerable debate, with good evidence to suggest nicotine-only addiction is a much less significant issue in the harm reduction debate.
Has nicotine received a fair trial in the court of public opinion and are we missing a great opportunity for harm reduction policy? Trial by media is certainly not fair, especially the perpetuation of such myths in our media that nicotine equates to cigarette smoke.