The short-term effects of smoking cause the bronchioles (passages in the lungs) to constrict and the cilia lining air passage to stop beating. The smoke also makes the lining produce more mucus. Nicotine, the component which causes addiction in tobacco, produces an increase in the rate of the heart beat and a rise in blood pressure. It may, in some cases cause an erratic andirregular heart eat.
The long-term effects of smoking may take many years to develop but they are severe, disabling and often lethal.
Although all forms of air pollution are likely to increase the chances of lung cancer, many scientific studies show, beyond all reasonable doubt, that the vast increase in lung cancer (4000% in the last century) is almost entirely due to smoking.
Cigar and pipe smokers are probably at less risk because they often don't inhale. But notice that their death rate from lung cancer is still twice that of non-smokers.
There at least 17 substances in tobacco smoke known to cause cancer in experimental animals, and it is now thought that 90 percent of lung cancer is caused by smoking. There are 2 types of chemicals which cause cancer: initiators and promoters. Initiators cause the chemical mutations in DNA which produce cancer cells. Promoters help cancer cells to reproduce and grow but they don't cause cancer before an initiator is taken. Cigarettes have both initiators and promoters.
Emphysema is a breakdown of the alveoli (microscopic air sacs in the lungs which allow oxygen and carbon dioxide to get in and out of blood). The of one or more of the substances in tobacco smoke weakens the alveoli. The irritant substances in the smoke causes a "smoker's cough" and the coughing bursts some of the weakened alveoli. In time, the absorbing surface of the lungs is greatly reduced. Then the smokers cannot oxygenate their blood properly and the least exercise makes them breathless and exhausted.
The smoke stops the cilia ( hair ) in the air passage to stop beating and so the irritant substances in the smoke and the excess mucus collect in the bronchi. This leads to the inflammation known as bronchitis. Over 95% of people suffering from bronchitis are smokers and they have a 20 times greater chance of dying from bronchitis than non-smokers.
Coronary heart disease is the leading cause in most developed countries. It results from a blockage of coronary arteries by fatty deposits. This reduces the supply of oxygenated to the heart muscle and sooner or later leads to heart failure. High blood pressure, diets with too much animal fat, and lack of exercise are also thought to be causes of heart attack, but about a quarter of all deaths due to coronary heart disease are thought to be caused by smoking.
The nicotine and carbon monoxide from cigarette smoke increase the tendency for the blood to clot and so block the coronary arteries, already partly blocked by fatty deposits. The carbon monoxide increases the rate at which the fatty material is deposited in the arteries.
About 95% of patients with disease of the leg arteries are cigarette smokers and this condition is the most frequent case of leg amputations.
Strokes due to arterial disease in the brain are more frequent in smokers.
Cancer of the bladder, ulcers in the stomach and duodenum, tooth decay, gum disease and tuberculosis all occur more frequently in smokers.
Babies born to women who smoke during pregnancy are smaller average, probably as a result pf reduced oxygen supply caused by the carbon monoxide in the blood. In smokers, there is twice the frequency of miscarriages, a 50% higher still-birth rate and a 26% higher death rate of babies.
A recent estimate is that one in every 3 smokers will die as a result of their smoking habits. Those who don't die at an early age will probably be seriously disabled by one of the conditions described alone.
It is not only the smokers themselves who are harmed by tobacco smoke. Non-smokers in the same room are also affected. One study has shown that children whose both parents smoke, breathe in as much nicotine as if they were themselves smoking 80 cigarettes a year.