• Cancer develops following genetic damage to  DNA. This genetic damage affects the normal functions of the cell, including cell proliferation, programmed cell death and DNA repair. As more damage accumulates, the risk of cancer increases.

SMOKING

 

  In most people, lung cancer is related to cigarette smoking. Although some people who have never smoked get lung cancer, smoking causes more than 8 out of 10 cases (83%).

Here are some facts about smoking and lung cancer :

• 1.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

• 2. Starting smoking at a young age greatly increases the risk

• 3. 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

• 4. As soon as you stop smoking, your risk of lung cancer starts to go down

  5.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 smoke exposure to second hand smoke for non smokers .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 environmental tobacco smoke. 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, as 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.

OTHER FACTORS :

Asbestos can cause a variety of lung diseases, including lung cancer. There is a synergistic effect between tobacco smoking and asbestos in the formation of lung cancer.Asbestos can also cause cancer of the pleura, called mesothelioma (which is different from lung cancer).

Outdoor air pollution has a small effect on increasing the risk of lung cancer. Fine particulates (PM2.5) and sulfate aerosols, which may be released in traffic exhaust fumes, are associated with slightly increased risk. For nitrogen dioxide, an incremental increase of 10 parts per billion increases the risk of lung cancer by 14%. Outdoor air pollution is estimated to account for 1–2% of lung cancers.

Genetics
There is a genetic predisposition to lung cancer. In relatives of people with lung cancer, the risk is increased 2.4 times. This may be due to genetic polymorphisms.