The perception that smoking is the major cause of lung cancer has rightly sunk into the mind of people all over the world. 90% of lung cancer patients are smokers. The risk factors that result in primary lung cancer are:

• Tobacco
  Higher the number of cigarettes per day, higher the risk of lung cancer. The risk is calculated based on their smoking history – the number of pack of cigarettes per day multiplied by the years of smoking. Nitrosamines and polycyclic aromatic hydrocarbons are the two major carcinogens in cigarettes among about 7000 chemical compounds found in cigarettes, cause the maximum damage. People who have been smoking for more than 30 years are at the highest risk.
• Radon Gas exposure
  A colorless radioactive naturally occurring gas is found in soil and rocks. It can mix with water and also rise to the air. All of us can be exposed to Radon in your homes. Some places have more radon than others. Exposure to Radon gas is the second highest cause of lung cancer causing about 12,000 deaths a year.
• Second hand or passive smoking
  People who inhale the smoke from cigarettes even though they themselves are non-smokers are at high risk. Family members are the most affected. Out of the lung cancer deaths, more than 7,000 deaths are due to passive smoking.
• Air pollution
  Prolonged exposure to pollution from emissions from automobiles, factories, industries also increases the risk of lung cancer.
• Asbestos exposure
  About 6,000 people die annually due to lung cancer, particularly pleural mesothelioma. Most uses of asbestos are banned, but people who were exposed to it earlier, are at higher risk. Cancer can be latent for anywhere between 20 and 60 years. If those who are exposed to asbestos are also cigarette smokers, the risk is even higher.
• Medical history
  Persons who have been affected by any other lung diseases like lung fibrosis, pulmonary tuberculosis or chronic bronchitis at some stage in their lives fall under high risk.
• Other exposure
  People exposed to hazardous chemicals or minerals at work particularly steel, nickel, chrome, and coal gas have chances that they might be affected. Exposure to radiation, air pollution, and diesel particulate matter are all at high risk for primary cancer.

Old age and family history are also additional risks. All the above risk factors are compounded if the person is a smoker.

Prevention of lung cancer
Risk of lung cancer can only be reduced by avoiding or reducing exposure to one or many of the risk factors. Quitting cigarette smoking drastically cuts the risk, both for smokers as well as passive smokers. Being aware of carcinogens at home and workplace and avoiding exposure reduces risk further. Moderate to intense exercise, healthy diet, limited alcohol consumption, reducing dependence on artificial supplements contribute towards reducing the risk of lung cancer. Conducting radon tests once every two years and regular health screening for heavy smokers and people with previous lung diseases is recommended to rule out or detect signs of lung cancer in the initial stages itself. Lung cancer is completely curable if detected early.