Lung cancer risks and causes
This page tells you about risks and causes of lung cancer. You can find information about
Lung cancer risks and causes
Lung cancer is the 2nd most common cancer in the UK. It is one of the few cancers where there is a clear cause in many cases.
Smoking and lung cancer
In most people, lung cancer is related to cigarette smoking. Although some people who have never smoked get lung cancer, smoking causes nearly 9 out of 10 cases (86%).
The more cigarettes you smoke, the more likely you are to get lung cancer. But the length of time you have been a smoker is also important. Starting smoking at a young age also greatly increases the risk. Cigarette smoking is the main cause of lung cancer. But pipe and cigar smokers are still much more likely to get lung cancer than non smokers. Passive smoking (breathing in other people's cigarette smoke) increases the risk of lung cancer, but it is still much less than if you smoke yourself.
As soon as you stop smoking, your risk of lung cancer starts to go down. However long you have been smoking, it is always worth giving up.
Other risk factors
The second most important risk factor for lung cancer is exposure to radon gas. Radon is a naturally occurring radioactive gas that can seep out of the soil. Other risk factors include exposure to certain chemicals, air pollution, previous lung disease, a family history of lung cancer, past cancer treatment and having poor immunity. In some people who get lung cancer there is no obvious risk factor.
Protecting against lung cancer
Changes to lifestyle such as eating more fruit and vegetables and being more active may reduce your risk of lung cancer.
You can view and print the quick guides for all the pages in the About lung cancer section.
Lung cancer is the second most common cancer in the United Kingdom (excluding non melanoma skin cancer). Around 41,400 people are diagnosed in the UK each year.
In most people, lung cancer is related to cigarette smoking. Smoking causes nearly 9 out of 10 cases (86%). A further 3% of cases of lung cancer are caused by exposure to second hand smoke in non smokers (passive smoking).
Here are some facts about smoking and lung cancer
- The more you smoke, the more likely you are to get lung cancer but it is the length of time you have been a smoker that is most important
- Starting smoking at a young age greatly increases the risk
- Filtered and low tar cigarettes might not increase your risk quite so much, but most smokers cancel this out by taking more, deeper puffs or smoking more cigarettes
- As soon as you stop smoking your risk of lung cancer starts to go down
- Passive smoking (breathing in other people's cigarette smoke) increases the risk of lung cancer, but it is still much less than if you smoke yourself
It is almost impossible to work out the risk of occasional passive smoking. We know that the risk of lung cancer for passive smokers goes up the more cigarette smoke they are exposed to. Overall, people exposed to environmental tobacco smoke at work or at home have their risk of lung cancer increased by about a quarter compared to people who are not exposed to it. Heavy exposure to environmental tobacco smoke at work has been shown to double the risk of lung cancer.
Cigarette smoking is the main cause of lung cancer. But pipe and cigar smokers are still much more likely to get lung cancer than non smokers. They are also much more likely to get cancer of the mouth or lip.
In the past, lung cancer has always been more common in men than women. Now, because more women smoke, it is almost as common in women.
However long you have been smoking, it is always worth giving it up. Talk to your GP or practice nurse. They will be able to help and support you while you are giving up.
We have information about organisations that help you give up smoking.
Some other things increase lung cancer risk, but they increase the risk far less than smoking. They are
- Exposure to radon gas
- Exposure to certain chemicals
- Air pollution
- Previous lung disease
- A family history of lung cancer
- Past cancer treatment
- Previous smoking related cancers
- Lowered immunity
Radon gas is a naturally occurring radioactive gas which comes from tiny amounts of uranium present in all rocks and soils. The radon gas can build up in homes and other buildings. The highest levels have been found in south west England, but higher than average levels may be found in many other parts of the UK.
Radon is the second biggest cause of lung cancer after smoking. The risk from radon increases the risk from smoking. Smokers with high indoor levels of radon have a particularly high risk of getting lung cancer. If you are worried about this, the Health Protection Agency Radiation Protection Division has information on how to check radon levels in your house.
A number of substances that occur in the workplace may cause lung cancer. In particular, these include asbestos, silica, and diesel exhaust. Exposure to asbestos in the construction industry and shipbuilding is now much lower than in the 1960s. But asbestos is still a cause of lung cancer and the risk is increased amongst smokers. Silica which is used in glass making, may cause a condition known as silicosis. This condition increases the risk of lung cancer.
People at the highest risk of lung cancer caused by diesel fumes are miners and professional drivers. Information about other workplace chemicals that have a very small risk of causing lung cancer can be found in the statistics area of our News and Resources section.
Air pollution may cause lung cancer. We know this from studies on people exposed to large amounts of diesel exhaust fumes at work for many years. This type of long term occupational exposure may increase lung cancer risk by up to 47% (that is the average risk of lung cancer, plus half again). One study has shown that people living in areas with high levels of nitrogen oxides (mainly from cars and other vehicles) have their lung cancer risk increased by about a third.
Based on a large European study, researchers think that 5 to 7% of lung cancers in non smokers are due to outdoor air pollution. In China and India, the use of coal for cooking and for heating the home, and a high level of smokiness in the home, has been shown to increase lung cancer risk. But levels of smoke in UK homes are generally much lower than in China and India.
Having had a disease that caused scarring in the lungs may be a risk factor for a type of lung cancer called adenocarcinoma of the lung. Tuberculosis (TB) can make scar tissue form in the lungs. A recent study in China showed that people who have had TB have double the risk of lung cancer. This risk continues for more than 20 years.
Chlamydia pneumoniae is a type of bacteria that can cause chest infections. Some studies have shown that people with antibodies to chlamydia pneumoniae have an increased risk of lung cancer. The risk is greater for people who smoke.
Researchers are looking into the impact of family history on lung cancer. It is likely that there is at least one faulty lung cancer gene that can be passed down in families (inherited). If you have a first degree relative with lung cancer your risk of lung cancer is increased by 51%. The risk is even greater if a brother or sister has lung cancer. This risk is regardless of whether or not you smoke. But families of smokers will all be exposed to cigarette smoke and so have an increased risk of lung cancer whether they have inherited a faulty gene or not.
There is some evidence that particular cancer treatments might increase your risk of lung cancer. A review of lung cancer after treatment for breast cancer shows that ways of giving radiotherapy for breast cancer in the past increased the risk of developing lung cancer. But the most up to date methods of giving radiotherapy to treat breast cancer do not seem to increase the risk of primary lung cancer.
Researchers in Sweden found that lung cancer may occur up to 20 years after treatment for breast cancer. The research showed that the women who went on to develop lung cancer were almost all smokers at the time of their breast cancer treatment. Recent research shows that women who have oestrogen receptor negative breast cancer may be at increased risk of developing lung cancer.
Treatment for other types of cancer has also been linked to a slightly increased risk of lung cancer some years later. People may have an increased risk of lung cancer if they have had treatment for
- Hodgkin lymphoma
- Some types of non Hodgkin lymphoma
- Testicular cancer
- A type of cancer of the womb
But it is important to remember that having no treatment for these cancers is a much greater risk to your health than the slight increase in risk from treatment. It is most important to get the treatment you need at the time. In some of this research, lung cancer risk seems to be increased even more in smokers, so if you have had radiotherapy to your chest it is very important not to smoke.
People who have had a head and neck cancer, oesophageal cancer or cervical cancer have an increased risk of lung cancer. This may be explained by the fact that the risk of these cancers is higher in smokers. But it could also be a result of radiotherapy treatment.
HIV and AIDS lower immunity and so do drugs that people take after organ transplants. An overview of research studies shows that people with HIV or AIDS have a risk of lung cancer that is 3 times higher than people who do not have HIV or AIDS. People who take drugs to suppress their immunity after an organ transplant have double the usual risk of lung cancer.
There is also in increased risk of lung cancer in people who have some auto immune conditions. For example research shows that systemic lupus erythematosus (SLE) may double the risk of lung cancer.
The following factors may help to protect against lung cancer.
Researchers have recently been looking into links between vitamins and lung cancer. Fresh fruit and vegetables may help to prevent cancer because they contain chemicals that can prevent cell damage. The antioxidant vitamins A, C and E were thought to help reduce the risk of lung cancer, but the evidence for this is not clear. But there is now strong evidence that flavonoids, found in many fruits and vegetables, do help to reduce lung cancer risk. But changing your diet won't reduce your risk of lung cancer much if you carry on smoking. The most important thing by far is to stop smoking.
Researchers have looked into whether taking extra vitamin E and beta carotene may help stop smokers getting lung cancer. The body uses beta carotene to make vitamin A. Early results suggest that vitamin supplements do not help to prevent lung cancer. They may even be harmful in smokers or people who have been exposed to asbestos in the past. Another similar substance to beta carotene, called beta cryptoxanthin, is found in fruits such as oranges and mangoes. It may lower lung cancer risk, but we don't know how it affects smokers yet.
Studies show that higher levels of physical activity may lead to a 20 to 40% reduction in lung cancer risk. This includes activity at work, in the household, and leisure activity, such as walking or golf. One study has shown that that more vigorous exercise such as workouts, cycling or jogging may be more helpful in reducing lung cancer risk. Not all studies have measured the impact of smoking but it seems that the benefit of physical activity is greater for smokers. Research into this area is continuing.
In 2010, a review of the randomised trials looking into whether aspirin can protect people from a number of health conditions found that taking aspirin everyday for at least 5 years reduced the risk of dying from lung cancer. You should not take aspirin regularly without checking with your doctor first though. Drugs like aspirin can damage the lining of your stomach and may cause bleeding.
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