Smoking is the single biggest cause of cancer in the world
Experts agree that smoking is the single biggest cause of cancer in the world. Smoking causes over a quarter of cancer deaths in developed countries and nearly one in five cancer cases.
Around half of current smokers will be killed by their habit if they continue to smoke. And 25-40% of smokers will die in middle age.
Smoking causes even more deaths from other respiratory diseases and heart conditions than from cancer. 2 If current trends continue, scientists estimate that tobacco will kill about one billion people in the twenty-first century.
Around half of current smokers will be killed by their habit if they continue to smoke. And 25-40% of smokers will die in middle age.
Smoking causes even more deaths from other respiratory diseases and heart conditions than from cancer. 2 If current trends continue, scientists estimate that tobacco will kill about one billion people in the twenty-first century.
Smoking greatly increases the risk of lung cancer
A 2011 study found that more than four in five lung cancers are caused by smoking. 5 In 2002, lung cancer killed around 33,600 people - about one person every 15 minutes. 9
Tobacco smoke was first shown to cause lung cancer in 1950. 10 This study found that people who smoked 15-24 cigarettes a day had 26 times the lung cancer risk of non-smokers. And people who smoked less than 15 cigarettes a day still had 8 times the lung cancer risk of non-smokers.
After these first results came out, UK scientists began a large study of smoking in British doctors, which Cancer Research UK has helped to fund. 11 This British Doctors’ Study has provided much of our current knowledge about the dangers of smoking.
Tobacco smoke was first shown to cause lung cancer in 1950. 10 This study found that people who smoked 15-24 cigarettes a day had 26 times the lung cancer risk of non-smokers. And people who smoked less than 15 cigarettes a day still had 8 times the lung cancer risk of non-smokers.
After these first results came out, UK scientists began a large study of smoking in British doctors, which Cancer Research UK has helped to fund. 11 This British Doctors’ Study has provided much of our current knowledge about the dangers of smoking.
- smoke the most cigarettes per day
- smoke over long periods of time, and
- start smoking young
The length of time spent smoking seems to be the more important of these two factors.
The British Doctors’ Study found that people who had smoked for 45 years had 100 times the lung cancer risk of people who had smoked for 15 years, regardless of whether they smoked heavily or moderately. And smoking one packet a day for 40 years is about 8 times more dangerous than smoking two packets a day for 20 years.
Even light or irregular smoking can increase the risk of cancer. One study found that even people who smoked 1-4 cigarettes a day had much greater risks of dying from lung cancer or heart disease, while another found that even people who smoke just 2 cigarettes a day are more likely to develop cancers of the mouth and oesophagus (food pipe).
And the EPIC study found that occasional smokers who have never smoked daily, still have higher risks of most cancers, and double the risk of bladder cancer.
Starting smoking at an early age increases the risk of cancer even more. One study found that young smokers are especially vulnerable to DNA damage caused by chemicals in cigarette smoke. And when they quit, they have higher levels of DNA damage than people who started smoking later in life.
Smoking also increases your risk of cancers of the bladder, cervix, kidney, larynx (voice box), pharynx (upper throat), nose, mouth, oesophagus (foodpipe), pancreas, stomach, liver and some types of leukaemia. And smokers are 7 times more likely to die of these cancer than non-smokers.
There is some evidence that smoking could also cause other cancers including bowel cancer and Hodgkin’s lymphoma.
There is some evidence that smoking could also cause other cancers including bowel cancer and Hodgkin’s lymphoma.
- Smoking is the most important preventable cause of bladder cancer and causes more than one in three cases in the UK. 5 It increases the risk of this disease by 3-5 times.
- Smoking doubles the risk of kidney cancer, and causes a quarter of cases in the UK.
- Smoking is the number one cause of mouth and oesophageal cancers, and together with alcohol, causes about three in four cases of these cancers in the UK. By the age of 75, a non-smoker has a 1 in 125 chance of developing these cancers, but a smoker’s odds are 1 in 16.
- Smoking is the most important preventable cause of pancreatic cancer, one of the most dangerous types of cancer in the UK. It causes over a quarter of pancreatic cancer cases.
- Smoking is an important preventable cause of stomach cancer and causes over one in five cases in the UK.
Stopping smoking can reduce your risk
A large number of studies have shown that stopping smoking can greatly reduce the risk of smoking-related cancers. And the earlier you stop, the better. The last results from the Doctors’ Study show that stopping smoking at 50 halved the excess risk of cancer overall, while stopping at 30 avoided almost all of it.
However, it’s never too late to quit. One study found that even people who quit in their sixties can experience health benefits and gain valuable years of life.
The effects of stopping vary depending on the cancer. For example, ten years after stopping, a person’s risk of lung cancer falls to about half that of a smoker. And the increased oral and laryngeal cancer risks practically disappear within ten years of stopping. But the risks of bladder cancer are still higher than normal 20 years after stopping.
Cutting down the number of cigarettes you smoke slightly reduces your risk of lung cancer, but you’ll only experience the full health benefits if you stop altogether. One study found that even smokers who halved the number of cigarettes they smoked had similar risks of dying from heart disease and only slightly lower risks of dying from cancer.
However, it’s never too late to quit. One study found that even people who quit in their sixties can experience health benefits and gain valuable years of life.
The effects of stopping vary depending on the cancer. For example, ten years after stopping, a person’s risk of lung cancer falls to about half that of a smoker. And the increased oral and laryngeal cancer risks practically disappear within ten years of stopping. But the risks of bladder cancer are still higher than normal 20 years after stopping.
Cutting down the number of cigarettes you smoke slightly reduces your risk of lung cancer, but you’ll only experience the full health benefits if you stop altogether. One study found that even smokers who halved the number of cigarettes they smoked had similar risks of dying from heart disease and only slightly lower risks of dying from cancer.
Scientists have identified about 4,000 different chemicals in
tobacco smoke. According to the International Agency for Research into
Cancer, more than 70 of these chemicals could cause cancer. Many of the other thousands of chemicals are toxic and harmful to your health, including carbon monoxide, hydrogen cyanide and ammonia.
One study compared the amounts of cancer-causing chemicals in tobacco smoke with their ability to cause cancer. It concluded that the chemicals in smoke most likely to increase our risk of cancer include -butadiene, arsenic, benzene and cadmium.
Cigarettes contain at least 599 different additives including chocolate, vanilla, sugar, liquorice, herbs and spices. These are not toxic but they make cigarettes taste nicer and ensure that smokers want to continue smoking.
One study compared the amounts of cancer-causing chemicals in tobacco smoke with their ability to cause cancer. It concluded that the chemicals in smoke most likely to increase our risk of cancer include -butadiene, arsenic, benzene and cadmium.
Cigarettes contain at least 599 different additives including chocolate, vanilla, sugar, liquorice, herbs and spices. These are not toxic but they make cigarettes taste nicer and ensure that smokers want to continue smoking.
Carbon monoxide is the fourth most common chemical in tobacco smoke and can make up 3-5% of its volume. Many of the other toxins are present in lower amounts, but some can still cause major damage at low concentrations.
Even single poisons can lead to substantial cancer risks. For example, benzene is a known cause of leukaemia. One study estimated that the benzene in cigarettes is responsible for between 10-50% of the leukaemia deaths caused by smoking.
Some studies have suggested that radioactive polonium-210 could account for much of the lung cancer risk caused by smoking. Polonium-210 becomes concentrated in hotspots in smokers' airways, subjecting them to very high doses of high-energy alpha-radiation. One study estimated that smoking 1.5 packs a day leads to as much radiation exposure as having 300 chest X-rays a year.
Even single poisons can lead to substantial cancer risks. For example, benzene is a known cause of leukaemia. One study estimated that the benzene in cigarettes is responsible for between 10-50% of the leukaemia deaths caused by smoking.
Some studies have suggested that radioactive polonium-210 could account for much of the lung cancer risk caused by smoking. Polonium-210 becomes concentrated in hotspots in smokers' airways, subjecting them to very high doses of high-energy alpha-radiation. One study estimated that smoking 1.5 packs a day leads to as much radiation exposure as having 300 chest X-rays a year.
Chemicals in tobacco smoke can build up to harmful amounts
Many tobacco poisons disable the cleaning systems that our bodies use to remove toxins. Cadmium overwhelms cleaner enzymes that mop up toxins and convert them into more harmless forms. And many gases such as hydrogen cyanide and ammonia kill cilia, tiny hairs in our airways that help to clear away toxins.
So over time, tobacco poisons can build up to high levels in our blood, substantially increasing our risks of cancer and other diseases. By comparing the levels of toxins in smokers and non-smokers, some studies have found that smokers can have:
So over time, tobacco poisons can build up to high levels in our blood, substantially increasing our risks of cancer and other diseases. By comparing the levels of toxins in smokers and non-smokers, some studies have found that smokers can have:
- twice as much cadmium in their blood
- four times as much polonium-210 in their lungs
- ten times as much benzene in their breath.
- ten times as much arsenic in their blood.
The cocktail of chemicals in tobacco smoke is even more dangerous as a mix.
Chemicals such as nitrosamines, benzo(a)pyrene, benzene, acrolein, cadmium and polonium-210 can damage DNA. Studies have shown that benzo[a]pyrene damages a gene called p53 that normally protects our cells from cancer.
One study found that chromium makes PAHs stick more strongly to DNA increasing the chances of serious DNA damage. Others have found that chemicals like arsenic, cadmium and nickel stop our cells from repairing DNA damage. This worsens the effects of chemicals like benzo(a)pyrene and makes it even more likely that damaged cells will eventually turn cancerous.
Chemicals such as nitrosamines, benzo(a)pyrene, benzene, acrolein, cadmium and polonium-210 can damage DNA. Studies have shown that benzo[a]pyrene damages a gene called p53 that normally protects our cells from cancer.
One study found that chromium makes PAHs stick more strongly to DNA increasing the chances of serious DNA damage. Others have found that chemicals like arsenic, cadmium and nickel stop our cells from repairing DNA damage. This worsens the effects of chemicals like benzo(a)pyrene and makes it even more likely that damaged cells will eventually turn cancerous.
The poisons in cigarettes can affect almost every organ in the body
The many toxins in tobacco smoke can harm many different parts of your body.
Many tobacco poisons can damage your heart and its blood vessels. By comparing the amounts and strengths of different chemicals, one study found that hydrogen cyanide and arsenic alone can cause major damage to our bodies’ blood network.
Acrolein, acetaldehyde and formaldehyde are most likely to cause diseases in our lungs and airways. Gases like hydrogen sulphide and pyridine can also irritate our airways, radioactive polonium-210 deposits damage surrounding cells, and nitrogen oxide constricts the airways, making breathing more difficult.
A protein called haemoglobin carries oxygen round our bloodstream. But carbon monoxide and nitrogen oxide stick more strongly to haemoglobin than oxygen, and reduces the levels of oxygen in our blood. This starves our organs of this vital gas.
Toluene can interfere with the development of brain cells. It also disrupts the insulating sheath that surround nerve cells, making them less efficient at carrying signals.
Many tobacco poisons can damage your heart and its blood vessels. By comparing the amounts and strengths of different chemicals, one study found that hydrogen cyanide and arsenic alone can cause major damage to our bodies’ blood network.
Acrolein, acetaldehyde and formaldehyde are most likely to cause diseases in our lungs and airways. Gases like hydrogen sulphide and pyridine can also irritate our airways, radioactive polonium-210 deposits damage surrounding cells, and nitrogen oxide constricts the airways, making breathing more difficult.
A protein called haemoglobin carries oxygen round our bloodstream. But carbon monoxide and nitrogen oxide stick more strongly to haemoglobin than oxygen, and reduces the levels of oxygen in our blood. This starves our organs of this vital gas.
Toluene can interfere with the development of brain cells. It also disrupts the insulating sheath that surround nerve cells, making them less efficient at carrying signals.
Nicotine is a very addictive drug
The Royal College of Physicians compared nicotine
to other supposedly ‘harder’ drugs such as heroin and cocaine. They
looked at many things including how these drugs cause addiction, how
difficult it is to stop using them, and how many deaths they caused.
The panel concluded that nicotine causes addiction in much the same way as heroin or cocaine and is just as addictive, if not more so, than these ‘harder’ drugs.
Smokers associate smoking with feeling good because nicotine makes the brain release dopamine - a chemical linked to feelings of pleasure. Smokers can also make mental links between abstract things like the taste of cigarettes or the feeling of smoking. These behaviours can become just as addictive as the nicotine itself.
The panel concluded that nicotine causes addiction in much the same way as heroin or cocaine and is just as addictive, if not more so, than these ‘harder’ drugs.
Smokers associate smoking with feeling good because nicotine makes the brain release dopamine - a chemical linked to feelings of pleasure. Smokers can also make mental links between abstract things like the taste of cigarettes or the feeling of smoking. These behaviours can become just as addictive as the nicotine itself.
Smokers are still exposed to dangerous chemicals if they smoke filtered or ‘low-tar’ cigarettes
Filters do not block out the many toxic gases in smoke, such as hydrogen cyanide, ammonia and carbon monoxide. They also do nothing to reduce levels of sidestream smoke from the burning end of the cigarette.
Some of the most dangerous chemicals in tobacco smoke, like hydrogen cyanide, are present as gases, and do not count as part of tar.
This means that cigarettes with less tar are not necessarily any less dangerous.
Besides, researchers have found that people who smoked low-tar brands smoked harder and more frequently to satisfy their nicotine cravings. For example, in one study, low-tar smokers inhaled 40% more smoke per cigarette and ended up with similar nicotine levels as smokers who use normal brands.
And some smokers block filters with fingers or saliva. One Canadian study showed that over half of discarded cigarette butts showed blocked filters.
According to one study, low-tar smokers ended up inhaling about 80% more smoke, and had similar levels of cancer-causing chemicals in their blood. They can also inhale over twice as much tar and nicotine as smokers of normal brands.
Some of the most dangerous chemicals in tobacco smoke, like hydrogen cyanide, are present as gases, and do not count as part of tar.
This means that cigarettes with less tar are not necessarily any less dangerous.
Besides, researchers have found that people who smoked low-tar brands smoked harder and more frequently to satisfy their nicotine cravings. For example, in one study, low-tar smokers inhaled 40% more smoke per cigarette and ended up with similar nicotine levels as smokers who use normal brands.
And some smokers block filters with fingers or saliva. One Canadian study showed that over half of discarded cigarette butts showed blocked filters.
According to one study, low-tar smokers ended up inhaling about 80% more smoke, and had similar levels of cancer-causing chemicals in their blood. They can also inhale over twice as much tar and nicotine as smokers of normal brands.
Tobacco, as well as alcohol, can cause mouth, oesophageal and liver cancers. Scientists have also found that together, their effects are much worse. And while alcohol does not cause stomach cancer, it can worsen the risk of this disease in smokers.
One study found that together, smoking and drinking increased liver cancer risk by ten times. And a Spanish team found that people who smoke and drink heavily could increase their risk of oesophageal cancer by up to 50 times.
This problem is made even worse because heavy drinkers and smokers often have poor diets.
Smoking also interacts with many other cancer risk factors and worsens their effects. For example the lung cancer risk due to exposure to high levels of radon gas is 25 times higher in smokers than in non-smokers.
One study found that together, smoking and drinking increased liver cancer risk by ten times. And a Spanish team found that people who smoke and drink heavily could increase their risk of oesophageal cancer by up to 50 times.
This problem is made even worse because heavy drinkers and smokers often have poor diets.
Smoking also interacts with many other cancer risk factors and worsens their effects. For example the lung cancer risk due to exposure to high levels of radon gas is 25 times higher in smokers than in non-smokers.
Several studies have shown that breathing in other people’s smoke causes cancer in non-smokers. Second-hand smoke contains several cancer causing chemicals. Many of these chemicals are present in higher concentrations than in the smoke inhaled by the smoker themselves.
One study analysed 55 studies from around the world found that non-smoking spouses of people who smoke at home have 27% higher risks of lung cancer. And a review of 22 studies found that people exposed to second-hand smoke in the workplace have 24% higher risks of lung cancer.
Those who were exposed to the highest levels of second-hand smoke at work had twice the risks of lung cancer.
One study estimates that passive smoking may kill over 11,000 people every year in the UK from cancer, heart disease, strokes and other diseases.
Second-hand smoking also causes other health problems in non-smokers including asthma and heart disease. One study showed that even 30 minutes of exposure to second-hand smoke can reduce blood flow in a non-smoker’s heart.
One study analysed 55 studies from around the world found that non-smoking spouses of people who smoke at home have 27% higher risks of lung cancer. And a review of 22 studies found that people exposed to second-hand smoke in the workplace have 24% higher risks of lung cancer.
Those who were exposed to the highest levels of second-hand smoke at work had twice the risks of lung cancer.
One study estimates that passive smoking may kill over 11,000 people every year in the UK from cancer, heart disease, strokes and other diseases.
Second-hand smoking also causes other health problems in non-smokers including asthma and heart disease. One study showed that even 30 minutes of exposure to second-hand smoke can reduce blood flow in a non-smoker’s heart.
Children
are particularly at risk because they breathe faster than adults and
have underdeveloped immune systems. A study by the Royal College of
Physicians showed that about 17,000 children in the UK are admitted to
hospital every year because of illnesses caused by second-hand smoke.
A large study of over 300,000 people found that children who were frequently exposed to cigarette smoke at home had a higher risks of lung cancer as adults. Another study found that children in households where both parents smoke have a 72% higher risk of respiratory diseases.
And the EPIC study found that exposing children to second-hand smoke increases the risk of bladder cancer later on in life by a third.
Childhood exposure to second-hand smoke had also been linked to a wide range of other conditions including asthma, Sudden Infant Death Syndrome (or cot death) 80, childhood meningitis 81 and mental disabilities.
A large study of over 300,000 people found that children who were frequently exposed to cigarette smoke at home had a higher risks of lung cancer as adults. Another study found that children in households where both parents smoke have a 72% higher risk of respiratory diseases.
And the EPIC study found that exposing children to second-hand smoke increases the risk of bladder cancer later on in life by a third.
Childhood exposure to second-hand smoke had also been linked to a wide range of other conditions including asthma, Sudden Infant Death Syndrome (or cot death) 80, childhood meningitis 81 and mental disabilities.
Smoking during pregnancy hinders the blood flow to the placenta, which reduces the amount of nutrients that reach the baby. Because of this, women who smoke while pregnant have lighter babies than those who don’t smoke. And low birth weight can lead to higher risks of diseases and death in infancy and early childhood.
There is also evidence that women exposed to second-hand smoke during pregnancy also have lighter babies.
Smoking during pregnancy has also been linked to other pregnancy complications including miscarriage, stillbirth, ectopic pregnancy and cot death. It may also have consequences for the physical and mental development of the child.
There is also evidence that women exposed to second-hand smoke during pregnancy also have lighter babies.
Smoking during pregnancy has also been linked to other pregnancy complications including miscarriage, stillbirth, ectopic pregnancy and cot death. It may also have consequences for the physical and mental development of the child.
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