Tobacco Smoke

The World Health Organization (WHO) considers smoking to be a disease. Until the end of 19th century, tobacco was smoked almost exclusively by men and in pipes and cigars, involving little inhalation. Then manufacture of cigarettes began. Smoking cigarettes become fashionable for European men during First World War and in the 1940s women started smoking in large numbers too. In Pakistan, 40% of men and 12% of women smoke. Each day, 1200 young boys take up smoking, as well as many young girls.

The tobacco companies do not declare the ingredients in their products, but it is known by analysis that there are over 4000 different chemicals in cigarette smoke, many of which are toxic. Tobacco smoke is composed of ‘mainstream’ smoke (from the filter or mouth) and ‘side-stream’ smoke (from the burning tip). When a person smokes, about 85% of the smoke of that they release is side-stream smoke. Many of the toxic ingredients are in a higher concentration in side-stream than in the mainstream smoke and any other people in the vicinity are also exposed to them. Breathing someone else’s cigarette smoke is called passive smoking.

Three main components of smoke pose a threat to human health, damaging in particular either the gaseous exchange or cardiovascular system:

- Tar (a mixture of aromatic compounds) settles on the lining of the airways in the lungs and stimulates a series of changes that may lead to obstructive lung diseases and lung cancer. This connection was recognized in the 1950s.

- Carbon monoxide (incomplete combustion of carbon) diffuses across the walls of the alveoli and into the blood in the lungs. It diffuses into red blood cells where it combines with haemoglobin to form the stable compound carboxyhaemoglobin. This will reduce the oxygen that bind to haemoglobin, thus reduce the oxygen that carry by the red blood cells. The quantity of oxygen transported in the blood may be 5-10% smaller in smoker than in a non-smoker.

- Nicotine is the drug in tobacco. It is absorbed very readily by the blood and travels to the brain within a few seconds. It stimulates the nervous system to reduce the diameter of the arterioles and to release the hormone adrenaline from the adrenal glands. As a result, heart rate and blood pressure increase and there is a decrease in blood supply to the extremities of the body, such as hands and feet, reducing their supply of oxygen.