Tobacco smoking

Tobacco smoking is the practice where tobacco is burned and the vapors either tasted or inhaled. The practice dates to 5000 BC in shamanistic rituals.[1][2] Many civilizations burnt incense during religious rituals, which was later adopted for pleasure or as a social tool.[3] Tobacco was introduced to the old world in the late 1500s where it followed common trade routes. The substance was met with frequent criticism, but became popular nonetheless.[4] The industrialization of tobacco production compounded with increased health awareness during the late 1920s prompted a strong anti-smoking political agenda. This movement was centered in Nazi Germany. However, following the Second World War, the movement quickly became unfavorable.[5] It was not until the late 1950s that health authorities once again began suggest the relationship between smoking and cancer.[6] These suggestions were confirmed in the 1980s, which prompted political action against the practice. Rates of consumption from 1965 onward in the developed world have either peaked or declined.[7] They however continue to climb in the developing world.[8]
Smoking is the most common method of consuming tobacco, and tobacco is the most common substance smoked. The argicultural product is often mixed with other additives[9] and then pyrolyzed. The resulting vapors are then inhaled and the active substances absorbed through the alveoli in the lungs.[10] The active substances trigger chemical reactions in nerve endings which hightens heart rate, memory, altertness,[11] and reaction time.[12] Dopamine and later endorphins are released, which are often assoicated with reward and pleasure.[13] As of 2000, smoking is practiced by some 1.22 billion people, and men are more likely to smoke than women
source;http://en.wikipedia.org/wiki/Tobacco_smoking