Common questions about smoking and cancer
On this page
- I know someone who smoked 'til old age and stayed healthy. Why didn't they get cancer?
- I know someone who never smoked but still got cancer. Why?
- Is there any point in giving up if I'm constantly surrounded by traffic fumes?
- Do roll-ups cause cancer?
- Can smoking cigars, pipes or bidis cause cancer?
- Does smokeless tobacco cause cancer?
- I know someone who smoked 'til old age and stayed healthy. Why didn't they get cancer?
- I know someone who never smoked but still got cancer. Why?
- Is there any point in giving up if I'm constantly surrounded by traffic fumes?
- Do roll-ups cause cancer?
- Can smoking cigars, pipes or bidis cause cancer?
- Does smokeless tobacco cause cancer?
Additives in cigarettes
The tobacco industry adds hundreds of additives to cigarettes to make easier to smoke and more appealing.
Cigarettes contain a wide range of additives, which vary by brand and can include chocolate, vanilla, menthol, peppermint, sugar, liquorice, herbs and spices.
They may not be harmful themselves but they help to overcome the initial off-putting taste that new smokers often experience.
The tobacco industry adds hundreds of additives to cigarettes to make easier to smoke and more appealing.
Cigarettes contain a wide range of additives, which vary by brand and can include chocolate, vanilla, menthol, peppermint, sugar, liquorice, herbs and spices.
They may not be harmful themselves but they help to overcome the initial off-putting taste that new smokers often experience.
Masking the sight and smell of smoke
Internal documents from the tobacco industry, made available on the internet thanks to legal action in the USA, also reveal that it used additives to make second-hand smoke less irritating.
Some additives have been used to make the smoke less visible, while others mask the smell, including vanilla, cinnamon, coffee extract and nutmeg oil.
While these may make cigarettes more ‘socially acceptable’, they are not actually any safer.
Internal documents from the tobacco industry, made available on the internet thanks to legal action in the USA, also reveal that it used additives to make second-hand smoke less irritating.
Some additives have been used to make the smoke less visible, while others mask the smell, including vanilla, cinnamon, coffee extract and nutmeg oil.
While these may make cigarettes more ‘socially acceptable’, they are not actually any safer.
Designing cigarettes for young people
In the 1970s, the tobacco industry began developing cigarettes specifically targeted at young people. These brands were designed to be less harsh and irritating.
Some companies used smoother tobacco at the filter end and stronger tobacco at the lit end. This gave a strong nicotine hit to start with but left the smoker with a ‘smoother’, more appealing taste.
The tobacco companies also added taste enhancers that make the cigarette seem smoother, including a combination of vanilla, chocolate and liquorice.
In the 1970s, the tobacco industry began developing cigarettes specifically targeted at young people. These brands were designed to be less harsh and irritating.
Some companies used smoother tobacco at the filter end and stronger tobacco at the lit end. This gave a strong nicotine hit to start with but left the smoker with a ‘smoother’, more appealing taste.
The tobacco companies also added taste enhancers that make the cigarette seem smoother, including a combination of vanilla, chocolate and liquorice.
I know someone who smoked 'til old age and stayed healthy. Why didn't they get cancer?
Smoking causes cancer. But this doesn't mean that all smokers will definitely get cancer or that all non-smokers won't. It means that smoking greatly increases the risk of this disease. Smokers are, on average, much more likely to get cancer than non-smokers.
In a similar way, we can say that eating sugary foods is a cause of tooth decay. This doesn't mean that all children who eat sugary foods will end up with decayed teeth. It means that, on average, children who eat lots of sugary foods are more likely to develop tooth decay than those who avoid such foods.
The fact is that half of all smokers eventually die from cancer, or other smoking-related illnesses. And a quarter of smokers die in middle age, between 35 and 69.
Smoking causes cancer. But this doesn't mean that all smokers will definitely get cancer or that all non-smokers won't. It means that smoking greatly increases the risk of this disease. Smokers are, on average, much more likely to get cancer than non-smokers.
In a similar way, we can say that eating sugary foods is a cause of tooth decay. This doesn't mean that all children who eat sugary foods will end up with decayed teeth. It means that, on average, children who eat lots of sugary foods are more likely to develop tooth decay than those who avoid such foods.
The fact is that half of all smokers eventually die from cancer, or other smoking-related illnesses. And a quarter of smokers die in middle age, between 35 and 69.
I know someone who never smoked but still got cancer. Why?
Smoking is the most important cause of cancer but it is not the only one. Even for lung cancer. Although four in five cases are caused by smoking, the remainder are linked to other factors like asbestos and radon gas.
Our risk of cancer depends on a combination of our genes, our lifestyle choices and our environment. Because of this, no single action will completely guarantee to protect you against cancer. But avoiding smoking, or giving up, are the best things you can do to stack the odds in your favour.
Smoking is the most important cause of cancer but it is not the only one. Even for lung cancer. Although four in five cases are caused by smoking, the remainder are linked to other factors like asbestos and radon gas.
Our risk of cancer depends on a combination of our genes, our lifestyle choices and our environment. Because of this, no single action will completely guarantee to protect you against cancer. But avoiding smoking, or giving up, are the best things you can do to stack the odds in your favour.
Is there any point in giving up if I'm constantly surrounded by traffic fumes?
Yes. We know that both smoking and air pollution are linked to lung cancer, but the effect of smoking is considerably larger. The lung cancer risk from smoking is at least 25 times greater than that from air pollution.
In the UK, three out of every hundred cases of lung cancer are caused by air pollution. The rest are mostly caused by smoking. Giving up smoking is the best present you can give yourself.
Yes. We know that both smoking and air pollution are linked to lung cancer, but the effect of smoking is considerably larger. The lung cancer risk from smoking is at least 25 times greater than that from air pollution.
In the UK, three out of every hundred cases of lung cancer are caused by air pollution. The rest are mostly caused by smoking. Giving up smoking is the best present you can give yourself.
Do roll-ups cause cancer?
Yes, just like manufactured cigarettes, roll-ups can cause cancer. And some studies have found that they may be even worse for you. Roll-up tobacco contains the same cancer-causing chemicalsas manufactured cigarettes.
Yes, just like manufactured cigarettes, roll-ups can cause cancer. And some studies have found that they may be even worse for you. Roll-up tobacco contains the same cancer-causing chemicalsas manufactured cigarettes.
Can smoking cigars, pipes or bidis cause cancer?
Scientists have shown that smoking cigars and pipes increases the risk of cancers of the lung,mouth, food pipe (oesophagus), voice box (larynx) and more. Smoking these products is just as bad for you as smoking cigarettes.
Smoking bidis, the most common form of tobacco in south Asian communities, also causes the same types of cancer.
In short, there is no safe type of smoked tobacco.
Scientists have shown that smoking cigars and pipes increases the risk of cancers of the lung,mouth, food pipe (oesophagus), voice box (larynx) and more. Smoking these products is just as bad for you as smoking cigarettes.
Smoking bidis, the most common form of tobacco in south Asian communities, also causes the same types of cancer.
In short, there is no safe type of smoked tobacco.
Does smokeless tobacco cause cancer?
Almost all types of smokeless tobacco can cause mouth cancer. They could also increase your risk of pancreatic cancer, and other conditions including gum disease and heart disease. Some types or brands can be more dangerous than others. This is because different products can have very different levels of cancer-causing chemicals.
Most smokeless tobacco products in the UK are used by South Asian communities. In these communities, dry chewing tobacco is often used as part of a 'betel quid' or 'paan'. These consist of a mixture of betel nut (or areca nut), slaked lime and various herbs and spices, wrapped in a betel leaf. Betel nut itself can cause cancer, so chewing betel quids can cause mouth cancer even if no tobacco is added.
You can find out more information on our smokeless tobacco page.
Almost all types of smokeless tobacco can cause mouth cancer. They could also increase your risk of pancreatic cancer, and other conditions including gum disease and heart disease. Some types or brands can be more dangerous than others. This is because different products can have very different levels of cancer-causing chemicals.
Most smokeless tobacco products in the UK are used by South Asian communities. In these communities, dry chewing tobacco is often used as part of a 'betel quid' or 'paan'. These consist of a mixture of betel nut (or areca nut), slaked lime and various herbs and spices, wrapped in a betel leaf. Betel nut itself can cause cancer, so chewing betel quids can cause mouth cancer even if no tobacco is added.
You can find out more information on our smokeless tobacco page.
Is it okay if I just smoke light, mild or low-tar cigarettes?
No, low-tar cigarettes just as harmful as regular brands. The packs may show you lower tar and nicotine numbers. But these numbers are based on tests that use machines, not real people. When real people smoke 'low tar' cigarettes, they breathe in much harder to satisfy their nicotine cravings.
So even if the cigarettes taste weaker, they are still doing your body as much damage as 'stronger' brands. Besides, cigarettes contain many other harmful chemicals besides tar and nicotine.
It is a myth that some cigarette brands are safe to smoke. While different brands may vary in their ingredients, all of them are dangerous to your health.
Find out more in our What's in a cigarette? page.
No, low-tar cigarettes just as harmful as regular brands. The packs may show you lower tar and nicotine numbers. But these numbers are based on tests that use machines, not real people. When real people smoke 'low tar' cigarettes, they breathe in much harder to satisfy their nicotine cravings.
So even if the cigarettes taste weaker, they are still doing your body as much damage as 'stronger' brands. Besides, cigarettes contain many other harmful chemicals besides tar and nicotine.
It is a myth that some cigarette brands are safe to smoke. While different brands may vary in their ingredients, all of them are dangerous to your health.
Find out more in our What's in a cigarette? page.
Is it okay if I just smoke a few cigarettes a day?
The more cigarettes you smoke a day, the higher your risk of cancer. But you are increasing your cancer risk even if you only smoke a few cigarettes a day. Light smoking can still endanger your health.
Studies have shown that even people who smoke 1-4 cigarettes a day are still almost three times more likely to die of heart disease and lung cancer than non-smokers.
Some scientists have found that the number of years you spend smoking affects your cancer risk more strongly than the number of cigarettes you smoke a day. For example, smoking one pack a day for 40 years is much more dangerous than smoking two packs a day for 20 years.
The best way to reduce your risk of cancer is to give up smoking completely.
The more cigarettes you smoke a day, the higher your risk of cancer. But you are increasing your cancer risk even if you only smoke a few cigarettes a day. Light smoking can still endanger your health.
Studies have shown that even people who smoke 1-4 cigarettes a day are still almost three times more likely to die of heart disease and lung cancer than non-smokers.
Some scientists have found that the number of years you spend smoking affects your cancer risk more strongly than the number of cigarettes you smoke a day. For example, smoking one pack a day for 40 years is much more dangerous than smoking two packs a day for 20 years.
The best way to reduce your risk of cancer is to give up smoking completely.
Is it okay to smoke as long as I exercise and keep generally healthy?
Eating lots of fruit may reduce your risk of lung cancer. And some studies have found that getting moderate amounts of activity can also reduce your risk.
But these protective effects are very small compared to the damaging effects of smoking. If you are a smoker, then keeping fit and eating healthily is not going to cancel out your increased risk of cancer. Your best bet for reducing your risk is to give up smoking completely.
Eating lots of fruit may reduce your risk of lung cancer. And some studies have found that getting moderate amounts of activity can also reduce your risk.
But these protective effects are very small compared to the damaging effects of smoking. If you are a smoker, then keeping fit and eating healthily is not going to cancel out your increased risk of cancer. Your best bet for reducing your risk is to give up smoking completely.
Is it okay to smoke for just a few years?
Your risk of cancer increases with the number of years you spend as a smoker. While your risk of cancer will be low when you first start, bear in mind that tobacco contains nicotine, a highly addictive drug.
This is the reason why most smokers say they want to quit but find it so difficult. If you start smoking, you may find it very hard to eventually stop.
Your risk of cancer increases with the number of years you spend as a smoker. While your risk of cancer will be low when you first start, bear in mind that tobacco contains nicotine, a highly addictive drug.
This is the reason why most smokers say they want to quit but find it so difficult. If you start smoking, you may find it very hard to eventually stop.
Is it okay to smoke if I don't inhale?
No. Besides lung cancer, smoking can also increase the risk of cancers of the food pipe(oesophagus), throat and mouth. Even if you don't inhale, cancer-causing chemicals in tobacco smoke can be absorbed by the cells of your mouth.
Smoking and heavy drinking account for the majority of all mouth cancer cases in the UK.
No. Besides lung cancer, smoking can also increase the risk of cancers of the food pipe(oesophagus), throat and mouth. Even if you don't inhale, cancer-causing chemicals in tobacco smoke can be absorbed by the cells of your mouth.
Smoking and heavy drinking account for the majority of all mouth cancer cases in the UK.
Can smoking marijuana cause cancer?
Smoking and cancer
Thanks to years of research, the links between smoking and cancer are now very clear. Smoking is by far the most important preventable cause of cancer in the world. Smoking accounts for one in four UK cancer deaths, and nearly a fifth of all cancer cases.
In the UK, smoking kills five times more people than road accidents, overdoses, murder, suicide and HIV all put together.
Which cancers are caused by smoking?
Smoking causes more than four in five cases of lung cancer. Lung cancer has one of the lowest survival rates of all cancers, and is the most common cause of cancer death in the UK. The good news is that most of these deaths are preventable, by giving up smoking in time.
Smoking also increases the risk of over a dozen other cancers including cancers of the mouth, larynx(voice box), pharynx (upper throat), nose and sinuses, oesophagus (food pipe), liver, pancreas,stomach, kidney, bladder, cervix and bowel, as well as one type of ovarian cancer and some types ofleukaemia. There is also some evidence that smoking could increase the risk of breast cancer.
Not all smokers get cancer. Why?
You may know someone who smoked all their lives but lived to a ripe old age. Or you may know someone who never smoked but got cancer anyway. Does this mean that smoking doesn’t really cause cancer?
Not at all. Years of research have proven that smoking causes cancer. But this doesn’t mean that all smokers will definitely get cancer or that all non-smokers won’t. It means that smoking greatly increases the risk of this disease. Smokers are, on average, much more likely to get cancer than non-smokers.
In a similar way, we can say that eating sugary foods is a cause of tooth decay. This doesn’t mean that all children who eat sugary foods will end up with decayed teeth. It means that, on average, children who eat lots of sugary foods are more likely to develop tooth decay than those who avoid such foods.
The fact is that half of all smokers eventually die from cancer, or other smoking-related illnesses. Anda quarter of smokers die in middle age, between 35 and 69.
Our How do we know? page has more information on the evidence linking smoking to cancer.
How does smoking cause cancer?
Tobacco smoke contains more than 70 different cancer-causing substances. When you inhale smoke, these chemicals enter your lungs and spread around the rest of your body.
Scientists have shown that these chemicals can damage DNA and change important genes. This causes cancer by making your cells grow and multiply out of control.
Giving up makes a difference
Thanks to research, health campaigns and new policies, the number of smokers in the UK has halved in the last 50 years. Because of this, the number of people who die from lung cancer has also halved. Clearly, giving up smoking saves lives.
But there is still a long way to go. Lung cancer is still the second most common type of cancer in the UK and kills over 35,000 people every year. And there are signs that the number of people who are quitting is starting to match the number who are taking it up.
If you are a smoker, giving up smoking is the best present you can give yourself. There are many techniques you can try to help you join the increasing numbers of smokers who are quitting for good. You can find more advice on quitting in this section.
Finding it hard to quit? Get involved with Stoptober. Research shows that if you can stop smoking for 28 days, you are five times more likely to stay smokefree, and Stoptober leads smokers through a detailed step-by-step programme to help them achieve this goal.
Find out more about smoking
- The truth behind some smoking myths page, including the effects of roll-ups, light cigarettes, exercise, air pollution and more.
- The chemicals contained in cigarettes
- The scientific evidence linking smoking to cancer
- The effects that tobacco can have on children.
- The dangers of second-hand smoke and what Cancer Research UK is doing about it.
- The risks of smokeless and chewing tobacco.
- The reasons why people smoke and the addictive effects of nicotine.
- Good reasons to quit.
- Advice on quitting successfully, what help is available, and how to control withdrawal symptoms.
Smoking and cancer: What's in a cigarette?
A cigarette may look harmless enough - tobacco leaves covered in classic white paper. But when it burns, it releases a dangerous cocktail of about 4,000 chemicals including:- more than 70 cancer-causing chemicals
- hundreds of other poisons.
- nicotine, a highly addictive drug, and many additives designed to make cigarettes taste nicer and keep smokers hooked.
This page has more information on the various poisons in cigarette smoke. You can also read about where these come from and how concentrated they actually are.
Cancer-causing chemicals in tobacco smoke
- Tar - a mixture of dangerous chemicals
- Arsenic - used in wood preservatives
- Benzene - an industrial solvent, refined from crude oil
- Cadmium - used in batteries
- Formaldehyde - used in mortuaries and paint manufacturing
- Polonium-210 - a highly radioactive element
- Chromium - used to manufacture dye, paints and alloys
- 1,3-Butadiene - used in rubber manufacturing
- Polycyclic aromatic hydrocarbons - a group of dangerous DNA-damaging chemicals
- Nitrosamines - another group of DNA-damaging chemicals
- Acrolein - formerly used as a chemical weapon
- Other chemicals
Other poisons in cigarette smoke
- Hydrogen cyanide - used as an industrial pesticide
- Carbon monoxide - found in car exhausts and used in chemicals manufacturing
- Nitrogen oxides - a major component of smog
- Ammonia - used to make fertilisers and explosives
- More poisons
Tar is a term that describes a collection of solid particles that smokers inhale when they light a cigarette. It is a mixture of lots of chemicals, many of which can cause cancer. When it settles, tar forms a sticky, brown residue that can stain smokers’ teeth, fingers and lungs.
Because tar is listed on packs, it is easy to believe that it is the only harmful part of cigarettes. But some of the most dangerous chemicals in tobacco smoke are present as gases, and do not count as part of tar. This means that cigarettes with less tar still contain all the other toxic chemicals.
Arsenic is one of the most dangerous chemicals in cigarettes. It can cause cancer as well as damaging the heart and its blood vessels.
Small amounts of arsenic can accumulate in smokers’ bodies and build up to higher concentrations over months and years. As well as any direct effects, it can worsen the effect of other chemicals by interfering with our ability to repair our DNA.
Fish and seafood can be major sources of arsenic, but in a form that is less toxic and more readily removed from the body. In contrast, tobacco smoke contains arsenic in a more dangerous form.
Benzene is a solvent used to manufacture other chemicals, including petrol. It is well-established that benzene can cause cancer, particularly leukaemia. It could account for between a tenth and a half of the deaths from leukaemia caused by smoking.
Tobacco smoke contains large amounts of benzene and accounts for a big proportion of our exposure to this poison. The average smoker inhales about ten times more benzene than the average non-smoker.
And some studies have estimated that the amount of benzene that a person inhales through second-hand smoke over their lifetime could increase their risk of cancer.
Cadmium is a metal used mostly to make batteries. The majority of cadmium in our bodies comes from exposure to tobacco smoke. Smokers can have twice as much cadmium in their blood as non-smokers.
Studies have found that the amounts of cadmium present in tobacco smoke are capable of affecting our health. It is a known cause of cancer, and can also damage the kidneys and the linings of the arteries.
Our bodies have proteins that mop up harmful chemicals like cadmium, but the amounts in smoke can overload these proteins. Cadmium can also prevent our cells from repairing damaged DNA. Because of this, it can make the effects of other chemicals even worse.
Formaldehyde is a smelly chemical used to kill bacteria, preserve dead bodies and manufacture other chemicals. It is one of the substances in tobacco smoke most likely to cause diseases in our lungs and airways.
Formaldehyde is also a known cause of cancer. It is believed that even the small amounts in second-hand smoke could increase our lifetime risk of cancer.
Tobacco smoke is one of our major sources of formaldehyde exposure. Places where people smoke can have three times the normal levels of this poison.
Polonium is a rare, radioactive element and polonium-210 is its most common form. Polonium strongly emits a very damaging type of radiation called alpha-radiation that can usually be blocked by thin layers of skin.
But tobacco smoke contains traces of polonium, which become deposited inside their airways and deliver radiation directly to surrounding cells.
The lungs of smokers can be exposed to four times more polonium than those of non-smokers and specific parts may get a hundred times more radiation. One study estimated that someone smoking one and half packs a day receives the equivalent amount of radiation as someone having 300 chest X-rays a year.
Chromium is a metal used to make metallic alloys, dyes and paints and comes in different types. Chromium III or ‘trivalent chromium’ is most commonly used. It is available as dietary supplements and is harmless.
On the other hand, chromium VI or ‘hexavalent chromium’ is very toxic, is found in tobacco smoke, and is known to cause lung cancer. It allows other cancer-causing chemicals (such as polycyclic aromatic hydrocarbons) to stick more strongly to DNA and damage it.
1,3-butadiene or BDE is an industrial chemical used in rubber manufacture. Some scientists believe that of all the chemicals in tobacco smoke, BDE may present the greatest overall cancer risk. It may not be as good at causing cancer as some of the other chemicals listed here, but it is found in large amounts in tobacco smoke.
Polycyclic aromatic hydrocarbons or PAHs are a group of powerful cancer-causing chemicals that candamage DNA and set cells down the road to becoming tumours.
One of these chemicals - benzo(a)pyrene or BAP - is one of the most widely studied of all tobacco poisons. BAP directly damages p53, a gene that normally protects our bodies against cancer.
Nitrosamines are a group of chemicals that can directly damage DNA, like polycyclic aromatic hydrocarbons (PAHs).
They are found in small amounts in food. But tobacco products, including those that are chewed rather than smoked, are by far our largest source of exposure to these chemicals. Even though they are found in relatively small amounts in cigarettes, they are very strong cancer-causing chemicals.
Acrolein is a gas with an intensely irritating smell and is one of the most abundant chemicals in cigarette smoke. It belongs to the same group of chemicals as formaldehyde and acetaldehyde, both of which can cause cancer.
Until now, it wasn’t clear if acrolein causes cancer as well, but recent experiments suggest that it can. We now know that acrolein can cause DNA damage that is similar to the damage seen in lung cancer patients. Since smoke contains up to 1,000 times more acrolein than other DNA-damaging chemicals, it could be a major cause of lung cancer.
Acrolein also stops our cells from repairing DNA damage, like arsenic and cadmium. And like hydrogen cyanide, it kills the hairs that normally clean our lungs of other toxins.
Some of the other cancer-causing ingredients of tobacco smoke include:
- metals, such as nickel, lead, cobalt and beryllium. While you may be exposed to some of these metals through domestic items or food, inhaling them in tobacco smoke is worse, because they are easily absorbed by the lungs.
- acetaldehyde, which is also formed in your tissues when you drink alcohol - it is responsible for many nasty hangover symptoms
- hydrazine, a very toxic chemical used mainly in rocket fuel
Hydrogen cyanide is a poisonous gas. Of all the chemicals in tobacco smoke, it does the most damage to the heart and blood vessels.
Hydrogen cyanide does not cause cancer, but it increases the risk of other chemicals causing cancer by damaging cilia. These are tiny hairs lining the airways that help to clear toxins away. By killing cilia, hydrogen cyanide causes other dangerous chemicals to be stuck in the lungs and airways.
Carbon monoxide is a colourless gas with no smell. It is formed when we burn carbon-based fuels, such as gas in cookers or petrol in car engines. It can make up as much as 3-5% of tobacco smoke.
Carbon monoxide sticks to our red blood cells in place of oxygen. This lowers our blood’s ability to transport oxygen and deprives our tissues and organs of this vital gas.
Like hydrogen cyanide, it kills cilia and reduces our lungs’ ability to clear away toxins. This means that while carbon monoxide does not cause cancer directly, it makes it easier for other chemicals to do so.
Nitrogen oxide is a gas found in car exhaust and tobacco smoke.
Our bodies use it in very small amounts to carry signals between cells. But in large amounts, it is a major air pollutant. It directly damages lung tissue and causes inflammation in the lungs.
Normally, our bodies produce small amounts of nitrogen oxide, which causes our airways to expand. The large amount of nitrogen oxide in tobacco smoke changes things in two ways:
- When smokers are smoking, it expands their airways even further, making it easier for their lungs to absorb nicotine and other chemicals.
- When they are not smoking, it shuts off their internal nitrogen oxide production line, causing their airways to constrict. This is one reason why regular smokers often have difficulty breathing.
Ammonia is a gas with a strong, irritating smell, and is used in some toilet cleaners. Some studies have found that ammonia enhances the addictive power of nicotine. It changes nicotine into a gas that is more readily absorbed into the lungs, airways and bloodstream.
Like carbon monoxide and hydrogen cyanide, ammonia also kills cilia.
Tobacco smoke also contains many other poisons that produce harmful effects. These can be carried throughout the body via our blood vessels.
As well as hydrogen cyanide and ammonia, gases like sulphur dioxide also kill cilia (protective hairs) in our lungs. This stops them from being able to clear away other harmful chemicals.
Chemicals like hydrogen sulphide and pyridine irritate our airways.
Toluene can damage brain cells and interfere with their development
Concentration of chemicals in cigarettes
Most of the harmful substances in tobacco smoke are found at low levels in a single cigarette. But over months and years, many of them can build up to high levels in our bodies. And they are even more dangerous when mixed together.
This is why a smoker’s risk of cancer and other diseases increases the more cigarettes they smoke a day, and the more years they spend smoking.
Compared to non-smokers, the breath and blood of smokers can have:
- twice as much cadmium,
- four times as much radioactive polonium-210
- ten times as much benzene
- ten times as much arsenic
A major source of poisons
Due to strict regulations, we are mostly protected from exposure to the poisons in smoke in the environment.
So for most of us, a large part of our exposure to cancer-causing chemicals like benzene,formaldehyde and cadmium comes from breathing in tobacco smoke. And a few poisons, such as some nitrosamines, are unique to tobacco.
Some chemicals, such as arsenic and cadmium, are also found in some types of food but for various reasons, this is less of a problem:
- Chemicals that we inhale are more problematic than those we eat, because our lungs are better than our guts at absorbing them. For example, our guts absorb about 6% of cadmium in our food, but our lungs absorb 60% of any inhaled cadmium.
- Some chemicals, such as arsenic and chromium, are found in less harmful forms in food than in tobacco smoke.
Why do poisons build up?
Our cells have special cleaner proteins called ‘detoxification enzymes’ that mop up harmful chemicals and convert them into harmless ones. But the chemicals in smoke, such as cadmium, can either damage or overwhelm these cleaners. Because of this, it can take decades for your body to remove any cadmium that gets inside it.
Other chemicals such as formaldehyde, ammonia and hydrogen cyanide kill cilia, the small hairs that clean toxins from your airways.
This means that the poisons in smoke accumulate in our lungs, blood and other organs over time.
A cocktail effect
Individual chemicals in smoke can be even more dangerous when mixed together. They can interact with each other to increase our risk of cancer and other diseases even more.
For example, some chemicals in tobacco smoke can directly damage part of our DNA, including key genes that protects us against cancer. These chemicals include benzo(a)pyrene, polonium-210,benzene, acrolein and nitrosamines.
This is already bad news, but it’s made worse by other chemicals. Chromium makes poisons likebenzo(a)pyrene stick more strongly to DNA increasing the chances of serious damage.
Arsenic, cadmium and nickel interfere with our bodies’ defence systems and prevent them from repairing damaged DNA. This makes it even more likely that damaged cells will eventually turn cancerous.
Source of the chemicals in cigarettes
The chemicals in cigarette smoke come from the tobacco plant itself, its surroundings, the manufacturing process, and burning the cigarette.The tobacco plant itself
Nicotine is found naturally in the tobacco plant. It is a neurotoxin (a poison that kills nerve cells) and the plant uses it to stop animals from eating it.
The soil
Tobacco plants absorb various chemicals from the soil and fertilisers. These become stored in the leaves and are released when the leaves are burned. These chemicals include metals like cadmium, arsenic and chromium.
The air
Tobacco plants have large leaves with sticky hairs called trichomes. These hairs can capture chemicals such as radioactive polonium-210 from the atmosphere, building up higher concentrations than other plants.
The leaves can also absorb and concentrate chemicals used in fertilisers and pesticides.
Processing
Some dangerous chemicals are formed when tobacco leaves are processed and cigarettes are manufactured.
For example, when tobacco is cured to remove moisture from the leaves, bacteria produce nitrites that react with chemicals in the leaves. This produces most of the nitrosamines in the final product. Many of these chemicals are unique to tobacco and not found in other plants.
Burning
Most of the dangerous chemicals in tobacco smoke are formed through the many chemical reactions that occur as the cigarette burns.
Burning organic material such as tobacco leaves produces polycyclic aromatic hydrocarbons. And sugars that are added to cigarettes produce formaldehyde when burned.
Additives
Hundreds of chemicals are added to cigarettes in order to make them taste nicer and easier to smoke. This include the irritating gas, ammonia, which can increase the addictive power of nicotine.
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