Tobacco


Composition

The burning of tobacco generates approximately 4000 compounds. The smoke can be separated into gas and particulate phases. The composition of the smoke delivered to the smoker depends on the composition of tobacco and how densely it is packed, the length of the column of tobacco, the characteristics of the filter and the paper, the temperature at which the tobacco is burned.

Among the gaseous phase components are carbon monoxide, carbon dioxide, nitrogen oxides, ammonia, volatile nitrosamines, hydrogen cyanide, volatile sulfur containing compounds, volatile hydrocarbons, alcohols and aldehydes and ketones. Some of these compounds inhibit ciliary movement in the lungs. Tar is the compound in tobacco that remains after the moisture and nicotine are subtracted and consists of polycyclic aromatic hydrocarbons, which are carcinogens. Non-volatile nitrosamines and aromatic amines play an etiologic role in bladder cancer. The actual content of nicotine in tobacco can vary from 0.2% to 5%.


Different forms of spit tobacco

Spit tobacco exists as: loose leaf tobacco which is placed in foil pouches and placed between cheek and lower gum where it is sucked and chewed; snuff, which is moist or dry powdered tobacco is sold in small round containers. The use of snuff is referred to as "dipping" which involves leaving a pinch of tobacco between the cheek and the lower gum. Chewing tobacco and snuff are two types of smokeless tobacco products that are commonly referred to as "spit tobacco." Compressed tobacco is used in pieces and each piece is called a "plug." The user bites off a small piece and places in the mouth. Nicotine gum is another form of oral nicotine intake mainly used by individuals who are trying to quit smoking.

Tobacco products compared with cigarettes

Taking a pinch of snuff has the same effects as smoking three or four cigarettes. The possibility of getting oral cancer increases significantly for individuals who use SLT on a daily basis for 3.5 years or longer. Continued use of SLT can cause cancer of the pharynx and esophagus. Long-term snuff users have a 50% greater risk of developing oral cancer than non-users. There is also severe inflammation of gum tissue, tooth decay, and tooth loss associated with the use of SLT. The Comprehensive Smokeless Tobacco Health Education Act of 1986 was enacted by the Congress and required the rotation of three health warnings on SLT packages and advertisements and bans SLT advertising on broadcasting media.

Chemical composition of nicotine

Nicotine is the most abundant of the volatile alkaloids in the tobacco leaf. Nicotine is a colorless, and volatile liquid alkaloid found in smoking and smokeless tobacco which turns brown and acquires the odor of tobacco upon exposure to air. The alkaloid is water-soluble and forms water-soluble salts.

Pharmacology of nicotine

Diverse effects of nicotine occur as a result of both stimulant and depressant actions on various central and peripheral nervous system pathways. This drug can increase the heart rate by excitation of the sympathetic nervous system, or by paralyzing the parasympathetic nervous system. Nicotine affects the medulla in the brain to increase heart rate. Nicotine causes a discharge of epinephrine from the adrenal medulla, which causes an increase in heart rate and raises blood pressure.

Physiological effects of nicotine

Briefly, nicotine can stimulate the brain at all levels, significantly increase breathing, lower HDL ( the good fats) levels, increase blood pressure and constrict peripheral blood vessels.

Some individuals experience nausea and vomiting, decreased urinary flow, increased free fatty acids. Nicotine increases the oxygen requirements of the heart muscle, but lowers oxygen supply, and this effect may lead to heart attacks. Nicotine initially stimulates the salivary and bronchial secretions and then inhibits them. Cigarette smoke causes the excessive saliva associated with smoking. Nicotine inhibits hunger and also causes a slight increase in blood sugar, and deadens the taste buds. Smokers often report weight gain and appetite increase after quitting smoking.

Psychological effects of nicotine

Nicotine is a highly addictive drug. More than 24 billion packages of cigarettes are purchased annually in the United States and approximately 400,000 deaths are attributed to cigarette smoking. Nicotine is so addictive that approximately 70% of smokers who want to quit smoking cannot and about 83% of smokers smoke every day. Smokers report that cigarettes help them to relax. Nicotine is a cholinergic agonist and stimulates the brain. Smokers experience withdrawal symptoms when trying to quit smoking.

Relationship between tobacco use and chronic illnesses

A dose response relationship exists between the number of cigarettes smoked per day and particular illnesses. Men who smoke two packs of cigarettes per day have a four time higher risk of developing chronic bronchitis or emphysema than nonsmokers.

In the long run lung tissue is damaged leading to emphysema. Cigarette smoking also increases the risk of cardiovascular disease and smoking is a major risk factor for heart attacks. The probability of heart attack is related to the amount smoked, which has a synergistic relationship to other risk factors such as obesity. Smoking is a major risk factor for arteriosclerotic disease and aneurysm.

A direct relationship (in men and women) has been found between amount of cigarettes smoked and the development of lung cancer

The risk for developing lung cancer increases:

* with the amount smoked
* duration of smoking
* age at which person started to smoke
* degree of inhalation
* tar and nicotine levels of the cigarettes.

A relationship also exists between smoking and cancers of the oral cavity, esophagus, urinary bladder, kidneys and pancreas. Cigarette smoking is the leading cause of bronchopulmonary disease. Respiratory infections are also more prevalent and more severe among smokers than nonsmokers. Lower birth weight and survival rate of infants born to women who smoke during pregnancy is a major concern. Infants born to mothers who smoke are more likely to die from sudden infant death syndrome (SIDS). Long term effects been observed in their physical growth, mental development and behavioral characteristics.

How is nicotine metabolized

Nicotine is absorbed from the respiratory tract, and through mouth tissue and skin. Approximately 80% to 90% of nicotine is metabolized in the liver, kidneys and lungs. The lungs metabolize a major portion of inhaled nicotine. The major metabolites of nicotine are cotinine and nicotine. The half-life of nicotine after inhalation or injection administration is about 2 hours. The kidney eliminates both nicotine and its by-pruducts. The rate of urinary excretion of nicotine is dependent on the pH (acidity) of the urine. Excretion is reduced when the urine is alkaline. Nicotine is also excreted in the milk of lactating women who smoke. Mammary milk of heavy smokers may contain 0.5 mg of nicotine per liter of milk.

Clinical uses of nicotine

Cigarettes, cigars and spit tobacco have no role in clinical medicine. Nicotine chewing gum (nicorette)may be useful for individuals who are trying to quit smoking.

Effects of nicotine on athletic performance

Athletes participating in an NCAA survey (2001) reported using spit tobacco for recreational or social purposes, to deal with the stresses of college athletics and to feel good. About 53% of the athletes who use spit tobacco reported using it 1-5 times daily. The use of nicotine in high doses is toxic and can cause nicotine poisoning.

Signs of nicotine poisoning are vomiting, sweating, mental confusion, diminished pulse rate, headache, breathing difficulty, respiratory failure caused by muscle paralysis and death. Impaired oxygen transport secondary to increases in carboxyhemoglobin. In many cases smoking will increase breathing rate during submaximal exercise, and this will reduce athletic performance.

Patterns of tobacco use in the United States

Every day 3000 young people become regular smokers. Every day 6000 teens under 18 smoke their first cigarette. Every day more than 1000 adults die prematurely as a result of an adolescent decision (USDHHS, 1996). Tobacco is considered a major gateway drug. The majority of heroin addicts initially begin using gateway drugs such as alcohol or tobacco products. The use of gateway drugs leads to the development of patterns of behavior that makes it easier for an individual to try other drugs. Cigarette smokers are more likely to use alcohol, marijuana, and cocaine than nonsmokers are.



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