The causes of lung cancer

The number 1 reason people get lung cancer is cigarettes – at least 85 per cent of new cases are related to smoking. Of the 4,000 chemicals in cigarette smoke, experts believe at least 50 can cause cancer.

Toxins in cigarette smoke can kill cilia, the protective hairs lining the bronchus, which are the main airways in the lungs. With the cilia no longer able to sweep out unwanted particles, the toxins can become embedded in the lung lining and cause cells to develop abnormally.

Although people who smoke have three to 17 times more chance of getting lung cancer than non-smokers, according to Health Canada, quitting has immediate benefits:

• After 72 hours: lung capacity increases.
• After three months: lung function increases by as much as 30 per cent
• After 10 years: chances of getting lung cancer decrease by half.

Other inhaled pollutants linked to lung cancer are: asbestos fibres, insulation used in older buildings; chromium, a chemical used in paints and dyes; and radon, a carcinogenic gas found naturally in the environment that can build up in homes.

Symptoms

Any combination of the following could be a sign of lung cancer:

• Repetitive cough: This is the body's way of trying to clean out dust and dirt from the normally sterile respiratory passages.
• Coughing up mucous, blood: As the hair-like cilia in the lungs are killed, a thicker layer of mucous forms in the airways. “Smokers’ cough” is the only way the body has left to get rid of foreign particles. As well, people with a tumour in their airways may be trying to cough up the tumour.
• Chest pain: A tumour can grow into the chest wall, causing pain.
• Droopy eyelid, sunken eye: A tumour can grow into nerves in the neck, causing these symptoms.
• Shortness of breath, wheezing, or hoarseness: Blocked or inflamed lungs can cause these.
• Recurrent respiratory infections: Repeated cases of bronchitis or pneumonia could be a sign of lung cancer.

A biopsy, in which a sample of the tissue is removed from the lung for testing, is the only definitive way to determine whether someone has lung cancer. Doctors can also collect sputum samples to check for malignant cells, or order a CT scan, a detailed series of X-rays, of the lungs.