There are more than 3000 chemical substances in tobacco's smoke. They are gas or liquid but they also exist as physical though microscopically small particles. The most important and the most harmful is nicotine. Among nicotine there are also tar, carbon monoxide, ammoniac, sulphur dioxide, methanol, phenols, and many others.

Tobacco's poisons ruins our body in different ways:
    - tar is harmful for mucous membrane of respiratory organs
    - nicotine weakens eyesight
    - nicotine influences on nervous system and makes sentiment of enjoyment
    - nicotine is harmful also for heart and circulation
    - nicotine lays on in liver and partly eliminates through kidneys
    - nicotine and other substances are harmful for mucous membrane of stomach and intestines
    - nicotine lames the function of sexual glands



As we can see above, the nicotine is the most important and also the most harmful substance in cigarettes and other tobacco products. Nicotine is also in use in farming, where it's used as an insecticide, and in veterinary medicine. Nicotine is one of the most dangerous nervous gases. Its effects can be compared to the effects of poisons, which are harmful as cyanide.
While smoking, nicotine passes on to blood, where it works on different parts of our body. Some of these effects can be seen very easily. For example, the temperature of skin lowers for about 5oC if only one cigarette is smoked. Also the beating of the heart is quite faster. Acute effects of poisoning are headache, vertigo, pallor, shaking of hands, vomiting, coughing up slimy scum and general weakness of smoker's body. If the poisoning is very, very effective the smokers could also die because the brain centre for breathing and heart beating can paralyse.
Consequences of chronicle poisoning with nicotine can be seen especially with many years' smokers. The effects of this poisoning are changes on veins and heart, loosing appetite and troubles in digestion, higher quantity of eliminated acids in stomach, stomach ulcer, menstrual problems, sterilisation or spontaneous abortion with women and impotence with men. Chronicle smokers often have insomnia, the sharpness of eyesight gets lower, some of smokers hardly distinguish colours and with some smokers nicotine-blindness appears.




Some of toxic substances in tobacco's smoke are in condense of the smoke, which is called tobacco's tar. If the cigarettes have filters, there is about 15 and 25 milligrams of tar in one cigarette but if they don't have filters, the contents of tar is quite bigger. If a smoker smoked about 10 cigarettes a day for ten years he would put on his mucous membrane in his throat, on his trachea and on his bronchi about 1kg of tobacco's tar. The bigger part of this tar eliminates with cough, which is quite characteristic for smokers. Slimy scum at coughing is called smoking catarrh. The other part of this tar stays in lungs, and increases the possibility for lung-cancer.




While smoking the smokers inhale also carbon monoxide. Carbon monoxide is gas, without smell and colour. It arises while the tobacco and cigarette paper are burning. There are about 5% of carbon monoxide in inhaled cigarettes' smoke. The quantity of carbon monoxide depends on how quick the cigarette is burning and on porosity of cigarettes' paper. Usually the quantity increases at the end of the cigarette.
The important thing is, that the smokers inhale it but they don't exhale it because it quickly passes by into the blood through lungs. In blood carbon monoxide blinds on oxygen conveyors, which usually are molecules of haemoglobin. Carbon monoxide forces the oxygen out, because the ability of conjunction with haemoglobin is at carbon monoxide about 300 times bigger than at oxygen. This is the main reason, which causes shortage of oxygen in tissues and body organs. This gas is also the main reason for failures and deaths of unborn children.