Smoking tobacco greatly increases the risk of illness, disability and death from bronchitis, emphysema and lung cancer.

 1)      Bronchitis

Cigarette smoke stimulates the secretion of mucus by goblet cells in the trachea, but damages the cilia (tiny hairs which sweep the mucus away, trapping dirt and microorganisms).    This means that mucus accumulates in the bronchioles, and the irritation of the airways by the smoke is made worse because the cilia have lost their protective function.  This can lead to inflammation, called bronchitis.  The symptoms are recurring attacks of coughing and phlegm.  As the bronchioles narrow, breathing can become difficult.

 2)    Emphysema

Dust particles from tobacco smoke collect in the lungs, and this causes phagocytic cells of the immune system to increase in numbers.  These cells release an enzyme called elastase which can damage the delicate structures of the alveoli.  This reduces the area available for gas exchange, and leads to emphysema.  People with emphysema become very short of breath, and this can cause death from respiratory failure, heart failure or chest infection.

 3)    Lung cancer

Tobacco smoke contains carcinogenic chemicals which can cause tumour growth in the lungs.  These tumours can spread through the lungs, and on to other organs.

 4)    Smoking and pregnancy

Smoking while pregnant can decrease the availability of oxygen and nutrients to the foetus, because the nicotine and carbon monoxide reach the baby through the placenta.  It is estimated to account for 20 to 30 percent of low-birth weight babies, up to 14 percent of preterm deliveries, and some 10 percent of all infant deaths. The odds of developing asthma are twice as high among children whose mothers smoke more than 10 cigarettes a day.



Smoke content Effect on ventilation Effect on gas exchange Effect on pregnancy
Carbon monoxide Increases ventilation rate Reduces uptake of oxygen due to the formation of carboxy-haemoglobin Hypoxia reduces availability of oxygen to the foetus so reduces rate of growth
Nicotine Paralysis of cilia Accumulation of mucus in bronchioles.  Reduces gas exchange N/A
Tar Increases mucus production Tumours, emphysema, bronchitis reduce area for gas exchange N/A