SMOKING AND LUNG CANCER:

Cigarette smoke contains over 60 known carcinogens, including radioisotopes from the radon decay sequence, nitrosamine, and benzopyrene. Additionally, nicotine appears to depress the immune response to cancerous growths in exposed tissue. It is not surprising then that smoking accounts for 80–90% of lung cancer cases.

Passive smoking – it is the inhalation of smoke resulting from another person smoking nearby. It is a known cause of lung cancer in non-smokers. A passive smoker can be classified as someone living or working with a smoker.

Those who live with smokers have a 20-30% higher risk while those in second hand smoke environment have 16-19% higher risk compared to non-smokers who are away from such environments.

RADON GAS AND LUNG CANCER:

Radon is a colourless and odourless gas generated by the breakdown of radioactive radium. The radiation decay products ionise genetic material, causing mutations that sometimes turn cancerous.

For every increase of radon concentration by 100 Becquerel per atomic mass, the risk increases 8-16%. Becquerel is a derived unit for measuring radioactivity.

ASBESTOS AND LUNG CANCER:

Asbestos can cause a variety of lung diseases, including lung cancer. Tobacco smoking and asbestos have a synergistic effect on the formation of lung cancer.

Asbestos can also cause cancer of the pleura (a thin lining between the lung and the chest wall). An aggressive cancer of the pleura is called mesothelioma which affects the lungs, heart or abdomen.

AIR POLLUTION AND LUNG CANCER:

Outdoor air pollution has a small effect on increasing the risk of lung cancer. Fine particulates (PM2.5) and Sulphate aerosols, which are released in traffic exhaust fumes, increase the risk of lung cancer.

An increment of 10 parts per billion of Nitrogen Dioxide increases the risk of lung cancer by 14%. Outdoor air pollution is estimated to account for 1–2% of lung cancers.

There is evidence to prove that an increased risk of lung cancer is attributed to air pollution such as burning of wood, charcoal, dung or crop residue for cooking and heating. Women who are exposed to indoor coal smoke have about twice the risk. Also, a number of by-products of burning biomass are known for suspected carcinogens.

GENETICS AND LUNG CANCER:

It is estimated that 8-14% of lung cancer is due to inherited factors. In relatives of people with lung cancer, the risk is increased 2.4 times. This is likely due to a combination of genes.

OTHER CAUSES:

Numerous other substances, occupations and environmental exposures have been linked to lung cancer which are:

• Production and mining of some metals and arsenic compounds

• By-products of combustion such as Carbon Monoxide, Sulphur Dioxide, Nitrogen Oxides & Lead.

• Ionising Radiation

• Toxic gases

• Rubber production and crystalline silica dust