body of the world

Smoking 
Tobacco smoking is the practice where tobacco is burned and the vapors either tasted or inhaled. The practice began as early as 5000–3000 BCE. Many civilizations burned incense during religious rituals, which was later adopted for pleasure or as a social tool.Tobacco was introduced to Eurasia in the late 16th century where it followed common trade routes. The substance was met with frequent criticism but became popular, nonetheless.
German scientists formally identified the link between smoking and lung cancer in the late 1920s. Their studies led to the first anti-smoking campaign in modern history. The campaign failed to reach across enemy lines during the Second World War and quickly became unpopular, thereafter. In 1950, health authorities again began to suggest a relationship between smoking and cancer. Scientific evidence continued to mount in the 1980s, which prompted political action against the practice. Rates of consumption since 1965 in the developed world have either peaked or declined. However, they continue to climb in the developing world.
Smoking is the most common method of consuming tobacco, and tobacco is the most common substance smoked. The agricultural product is often mixed with additive^. and then pyrolyzed. The resulting vapors are then inhaled and the active substances absorbed through the alveoli in the lungs. The active substances trigger chemical reactions in nerve endings, which heighten heart rate, memory, alertness, and reaction time. Dopamine and endorphins are released, which are often associated with pleasure.As of 2000, smoking is practiced by approximately 1.22 billion people. Men are more likely to smoke than are women, though the gender gap declines with the younger age.
Many smokers begin during adolescence or early adulthood. Usually, during the early stages, smoking provides pleasurable sensations and serves as a source of positive reinforcement. After an individual has smoked for many years, the avoidance of withdrawal symptoms and negative reinforcement become the key motivations to continue.

Persistence

The reasons given by smokers for this activity are broadly categorized as addictive smoking, pleasure from smoking, tension reduction/relaxation, social smoking,stimulation, habit/automatism, and handling. There are gender differences in how much each of these reasons contribute, with females more likely than males to cite tension reduction/relaxation, stimulation and social smoking.
Some smokers argue that the depressant effect of smoking allows them to calm their nerves, often allowing for increased concentration. However, according to the Imperial College London, "Nicotine seems to provide both a stimulant and a depressant effect, and it is likely that the effect it has at any time is determined by the mood of the user, the environment and the circumstances of use. Studies have suggested that low doses have a depressant effect, while higher doses have stimulant effect."

Patterns

A number of studies have established that cigarette sales and smoking follow distinct time-related patterns. For example, cigarette sales in the United States of America have been shown to follow a strongly seasonal pattern, with the high months being the months of summer, and the low months being the winter months.
Similarly, smoking has been shown to follow distinct circadian patterns during the waking day—with the high point usually occurring shortly after waking in the morning, and shortly before going to sleep at night.

Health

Tobacco use leads most commonly to diseases affecting the heart and lungs, with smoking being a major risk factor for heart attacks, strokes, chronic obstructive pulmonary disease (COPD), emphysema, and cancer (particularly lung cancer, cancers of the larynx and mouth, and pancreatic cancer). Cigarette smoking increases the risk of Crohn's disease as well as the severity of the course of the disease. It is also the number one cause of bladder cancer.
The World Health Organization estimate that tobacco caused 5.4 million deaths in 2004and 100 million deaths over the course of the 20th century. Similarly, the United States Centers for Disease Control and Prevention describes tobacco use as "the single most important preventable risk to human health in developed countries and an important cause of premature death worldwide."

Social

Famous smokers of the past used cigarettes or pipes as part of their image, such as Jean Paul Sartre's Gauloises-brand cigarettes; Albert Einstein's, Kiana Lee Rosch's, Douglas MacArthur's, Bertrand Russell's, and Bing Crosby's pipes; or the news broadcaster Edward R. Murrow's cigarette. Writers in particular seem to be known for smoking, for example, Cornell Professor Richard Klein's book Cigarettes are Sublime for the analysis, by this professor of French literature, of the role smoking plays in 19th and 20th century letters. The popular author Kurt Vonnegut addressed his addiction to cigarettes within his novels. British Prime Minister Harold Wilson was well known for smoking a pipe in public as was Winston Churchill for his cigars. Sherlock Holmes, the fictional detective created by Sir Arthur Conan Doyle smoked a pipe, cigarettes, and cigars, besides injecting himself with cocaine, "to keep his overactive brain occupied during the dull London days, when nothing happened". The DC Vertigo comic book character, John Constantine, created by Alan Moore, is synonymous with smoking, so much so that the first storyline by Preacher creator, Garth Ennis, centered around John Constantine contracting lung cancer. Professional wrestler James Fullington, while in character as "The Sandman", is a chronic smoker in order to appear "tough".
The problem of smoking at home is particularly difficult for women in many cultures especially Arab cultures where it may not be acceptable for a woman to ask her husband not to smoke at home or in the presence of her children. Studies has shown that pollution levels in door places are higher than levels found on busy roadways, in closed motor garages, and during fire storms. Furthermore, smoke can spread from one room to another, even if doors to the smoking area are closed.