What are the causes and risk factors for lung cancer?

A risk factor is something that increases the chances of developing the disease. It could be a condition or substance. The chance of developing lung cancer increases with age. Smoking tobacco is known to be the most important risk factor in the case of lung cancer.

What are the common risk factors that can lead to lung cancer?

The most common risk factors for lung cancer are listed below:


Smoking cigarettes are known to be the main cause of developing lung cancer as the smoke from the cigarettes contain chemicals known as carcinogens. Carcinogens are chemicals that cause changes in the cells in the lungs which results in cancer.

The risk of developing lung cancer has many other factors involved like the age at which a person started smoking, the number of cigarettes smoked in a day and for how long the person has continued smoking.

Passive smoking

The inhaling of second-hand smoke is known as passive smoking and is one of the leading risk factors among non-smokers. The breathing in of secondhand smoke is as harmful as smoking a cigarette as the smoke from a burning cigarette contains the same amount of chemicals when inhaled.

Exposure to radiation

People who were exposed to atomic bomb explosions or nuclear accidents are at a greater risk of developing lung cancer. People who have also undergone radiation therapy for certain cancers like breast cancer also are at a higher risk of developing lung cancer.


Radon is a colourless odourless gas that comes from the breakdown of uranium in the soil and rocks. Outdoors the gas is diluted with fresh air so it is usually not a concern but Randon can seep into buildings through cracks in the foundation and dirty floors. The radon gas when breathed in can cause damage to the cells that line the lungs. Radon is known to be the leading cause of cancer in non- smokers. The risk of developing lung cancer depends on how much of the gas the person is exposed to and for how long.

Occupational exposure to certain chemicals

People who are exposed to certain carcinogens at work are at higher risk of developing lung cancer. An example of these carcinogens would be arsenic and inorganic arsenic compounds, silica dust, chromium, Cadmium, mustard gas etc.


The asbestos fibre is a silicate fibre that can last a lifetime in the lungs. The workplace is the most common area for exposure to asbestos fibres and this kind of an exposure is seen in industries that make both thermal and acoustic insulation materials. Research has linked the risk of developing lung cancer to the exposure to asbestos.

Air Pollution

A constant exposure to polluted air has been seen as the cause of lung cancer too as polluted air is seen to be as harmful as cigarette smoke and some lung cancer deaths have been attributed to the breathing in of polluted smoke.

Prior history of lung cancer

It is seen that people who have had lung cancer before are at higher risk of developing it again in comparison to the general population who have not had a history of lung cancer before. People who have had non-small cell lung cancer have an added risk of 1 to 2% per year and people who have had small cell lung cancer have an added risk of 6% per year.

Read more on the signs and symptoms of lung cancer

We find the best oncologists for you

Our cancer experts have an average in-field experience of 10+ years

Each of our oncologists has treated more than 10,000 cancer patients

Our doctors are trained at top cancer institutes such as Tata Memorial

Consult Our Doctor