有关“tobacco and society”的英语文章

有关“tobacco and society”的英语文章~

这里有一篇tobacco and society

Nowhere in the world has the issue of tobacco been so much debated as in our society. Nowadays, tobacco is more harmful than drug to people’s health, therefore many people think that smoking is legal that is a direct andprimary reason to induce this kind of problem. The above point is certainly true; this essay will outline three reasons.

The main reason is that tobacco is a silent killer to smokers. Tobacco is known to be the probable cause of some 25 different diseases, and for some,such as lung cancer, bronchitis and emphysema, it is the main cause. According to a WHO report four million people die yearly from tobacco-related diseases, that is one death every eight seconds. Tobacco is significantly becoming a greater cause of death and disability than any other single cause.

Another reason is that more and more young people are under 18 years old who smoke cigarette have been blinded by the deceit of tobacconists. Tobacco among adolescents remains stubbornly persistent. Smoking among adolescents rose in the 1990s in several developed countries，such as China,Vietnam and Thailand . While new markets are being opened by the tobacco industry actions, old markets have not been closed. Tobacco is a global threat.

Last but not the least reason is the increase in cigarette smuggling. Becauseof tobacco smuggling, the legal retailing and distribution systems are badly affected, and faced with increased lawlessness and heavy tax losses. This behavior severely affects the economy.

In conclusion, the tobacco should be considered illegal. Perhaps a pack of cigarettes is less harmful than another drug, but tobacco is actually the biggest killer of all the drugs.=================================================

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A computer is a machine that manipulates data according to a list of instructions.

The first devices that resemble modern computers date to the mid-20th century (around 1940 - 1945), although the computer concept and various machines similar to computers existed earlier. Early electronic computers were the size of a large room, consuming as much power as several hundred modern personal computers.[1] Modern computers are based on tiny integrated circuits and are millions to billions of times more capable while occupying a fraction of the space.[2] Today, simple computers may be made small enough to fit into a wristwatch and be powered from a watch battery. Personal computers, in various forms, are icons of the Information Age and are what most people think of as "a computer"; however, the most common form of computer in use today is the embedded computer. Embedded computers are small, simple devices that are used to control other devices — for example, they may be found in machines ranging from fighter aircraft to industrial robots, digital cameras, and children's toys.

The ability to store and execute lists of instructions called programs makes computers extremely versatile and distinguishes them from calculators. The Church–Turing thesis is a mathematical statement of this versatility: any computer with a certain minimum capability is, in principle, capable of performing the same tasks that any other computer can perform. Therefore, computers with capability and complexity ranging from that of a personal digital assistant to a supercomputer are all able to perform the same computational tasks given enough time and storage capacity.

It is difficult to identify any one device as the earliest computer, partly because the term "computer" has been subject to varying interpretations over time. Originally, the term "computer" referred to a person who performed numerical calculations (a human computer), often with the aid of a mechanical calculating device.

The history of the modern computer begins with two separate technologies - that of automated calculation and that of programmability.

Examples of early mechanical calculating devices included the abacus, the slide rule and arguably the astrolabe and the Antikythera mechanism (which dates from about 150-100 BC). Hero of Alexandria (c. 10–70 AD) built a mechanical theater which performed a play lasting 10 minutes and was operated by a complex system of ropes and drums that might be considered to be a means of deciding which parts of the mechanism performed which actions and when.[3] This is the essence of programmability.

The "castle clock", an astronomical clock invented by Al-Jazari in 1206, is considered to be the earliest programmable analog computer.[4] It displayed the zodiac, the solar and lunar orbits, a crescent moon-shaped pointer travelling across a gateway causing automatic doors to open every hour,[5][6] and five robotic musicians who play music when struck by levers operated by a camshaft attached to a water wheel. The length of day and night could be re-programmed every day in order to account for the changing lengths of day and night throughout the year.[4]

The end of the Middle Ages saw a re-invigoration of European mathematics and engineering, and Wilhelm Schickard's 1623 device was the first of a number of mechanical calculators constructed by European engineers. However, none of those devices fit the modern definition of a computer because they could not be programmed.

In 1801, Joseph Marie Jacquard made an improvement to the textile loom that used a series of punched paper cards as a template to allow his loom to weave intricate patterns automatically. The resulting Jacquard loom was an important step in the development of computers because the use of punched cards to define woven patterns can be viewed as an early, albeit limited, form of programmability.

It was the fusion of automatic calculation with programmability that produced the first recognizable computers. In 1837, Charles Babbage was the first to conceptualize and design a fully programmable mechanical computer that he called "The Analytical Engine".[7] Due to limited finances, and an inability to resist tinkering with the design, Babbage never actually built his Analytical Engine.

Large-scale automated data processing of punched cards was performed for the U.S. Census in 1890 by tabulating machines designed by Herman Hollerith and manufactured by the Computing Tabulating Recording Corporation, which later became IBM. By the end of the 19th century a number of technologies that would later prove useful in the realization of practical computers had begun to appear: the punched card, Boolean algebra, the vacuum tube (thermionic valve) and the teleprinter.

During the first half of the 20th century, many scientific computing needs were met by increasingly sophisticated analog computers, which used a direct mechanical or electrical model of the problem as a basis for computation. However, these were not programmable and generally lacked the versatility and accuracy of modern digital computers.

Smoking: Effects of the habit and industry on society

Link Between Tobacco use and use of Illicit drugs.
Cigarettes along with alcohol and marijuana are considered a “gateway drug.” A 1994 report from the Center on Addiction and Substance Abuse at Columbia University states that there is a consistent relationship between the use of cigarettes and alcohol and the subsequent use of marijuana. Cigarettes, alcohol and marijuana use and the subsequent use of illicit drugs like cocaine is also linked, regardless of the age, sex, ethnicity or race of the individuals involved. Children 12 to 17 years old who smoke are nineteen times more likely to use cocaine. The 1994 report also found that the younger children are when they use these gateway drugs and the more often they use them, the more likely they are to use cocaine, heroin, hallucinogens and other illicit drugs. The report concludes that the data is already robust enough to make a strong case to step up efforts to prevent childhood use of cigarettes, alcohol and marijuana and to take firm steps to reduce children’s access to these gateway drugs.

People who abuse drugs are likely to be cigarette smokers also. More than two-thirds of drug abusers are regular tobacco smokers, a rate more than double of that in the general population. NIDA researchers have found that craving for nicotine also increases craving for illicit drugs among drug abusers who smoke tobacco, and this suggests that smokers in drug rehabilitation programs may be less successful than nonsmokers in staying off drugs.

Bodily functions and how they are affected
Tobacco smoke contains nicotine, a stimulant. Nicotine acts as an inhibitor (or block), that attaches to cholinergic receptors in the brain that are usually used to control respiration, heart rate, memory, alertness, and muscle movement. As such all are affected by smoking. Normally, acetylcholine (a similar, naturally present healthy neurochemical) would attach to the receptors, however nicotine interferes in this natural biological process and attaches to the receptors instead and blocks them.

Nicotine's effect in the body results in reduced acetylcholine production in the brain -- a physiological response to a perceived 'excess' of acetylcholine, an assumption by the body which is incorrect. This replacement of natural neurochemicals with nicotine is largely responsible for nicotine's addictive properties, because it creates a dependency for nicotine to continue fulfilling the role of acetylcholine and stop the body from becoming erratic. If a smoker stops smoking, lack of acetylcholine causes respiration, heart rate, memory, alertness, and muscle movement to be temporarily affected -- this can be so distressing it can be hard to continue cessation for some.

Recent evidence has shown that smoking tobacco causes increases in dopamine levels in the brain, and lowers the levels of enzymes found in the brain that naturally stop the levels of dopamine becoming too high, this causes the promotion of abnormally high levels of dopamine similar to those experienced by heroin and cocaine addicts and users. Smokers have feelings of pleasure and reward when they smoke due to this chemical imbalance created.[18] One study found that smokers exhibit better reaction-time and memory performance as they tire, compared to non-smokers.[19]

Physical & Mental addiction
Nicotine, an element of tobacco smoke, is one of the most addictive substances that exists. When tobacco is smoked, most of the nicotine is pyrolyzed; however, a dose sufficient to cause mild somatic dependency and mild to strong psychological dependency remains. According to studies by Henningfield and Benowitz, nicotine is more addictive than marijuana and caffeine but of a lesser potential for somatic dependency than ethanol, cocaine and heroin. A study by Perrine concludes nicotine's potential for psychological dependency exceeds all other studied drugs[20] - even ethanol, an extremely physically addictive substance with a severe withdrawal that can be fatal. Many smokers use nicotine compulsively. About half of Canadians who currently smoke have tried to quit.[21] McGill University health professor Jennifer O'Loughlin stated that nicotine addiction can occur as soon as five months after the start of smoking.[22]

It can be difficult to quit smoking due to the withdrawal symptoms which include insomnia, irritability, anxiety, decreased heart rate, weight gain, and nicotine cravings. The relapse rate for quitters is high: about 60% relapse in three months. Also, nicotine users are sometimes reluctant to quit smoking because they do not see any short-term damages it may cause.

Smoking and depression
Data from multiple studies suggest that depression plays a role in cigarette smoking.[23] A history of regular smoking was observed more frequently among individuals who had experienced a major depressive disorder at some time in their lives than among individuals who had never experienced major depression or among individuals with no psychiatric diagnosis.[24] Another study found that the average lifetime daily cigarette consumption was strongly related to lifetime prevalence, and to prospectively assessed one year prevalence of major depression.[25] People with major depression are also much less likely to quit due to the increased risk of experiencing mild to severe states of depression, including a major depressive episode.[26] Depressed smokers appear to experience more withdrawal symptoms on quitting, are less likely to be successful at quitting, and are more likely to relapse.[27] The neurotransmitter systems affected by cigarette smoke mirror the neurotransmitter pathways that are thought to be involved in the biological mechanisms of depression, and the use of antidepressants as adjuvants to smoking-cessation treatment can enhance cessation success rates.[28]

Health benefits of smoking
Ulcerative colitis is twice as common in non-smokers as in smokers.[29] The nicotine in tobacco smoke acts as an anti-inflammatory agent.[30]

Also, it was thought that the risks of Parkinson's disease or Alzheimer's disease might be significantly lower for smokers than for non-smokers. Indeed, according to previous epidemiological studies, cigarette smokers were 50% less likely to have PD or AD than are age- and gender-matched nonsmokers.[31] One explanation given for this effect is the fact that nicotine allegedly decreases the levels of acetylcholine in the smoker's brain. Parkinson's disease consequently occurs when the effect of dopamine is less than that of acetylcholine. However, nicotine, a cholinergic stimulant, is the only substance in tobacco smoke which has those positive effects, and the consumption of pure nicotine would likely be more beneficial than smoking.

More recent evidence has however challenged the earlier epidemiological studies on methodological grounds.[32] A prospective Rotterdam Study found that the incidence of Alzheimer's disease is more than double for smokers as compared to non-smokers[33] and the Honolulu Heart Program (a longitudinal cohort study) also found more than twice the risk for Alzheimer's disease among medium and heavy smokers as compared to non-smokers.[34]

Passive smoking
Main article: Passive smoking

This photo illustrates smoke in a pub, a common complaint from those concerned with passive smokingPassive or involuntary smoking occurs when the exhaled and ambient smoke (otherwise known as environmental or secondhand smoke) from one person's cigarette is inhaled by other people. Passive smoking involves inhaling carcinogens, as well as other toxic components, that are present in secondhand tobacco smoke. Carcinogens that occur in secondhand tobacco smoke include benzene, 1,3-butadiene, benzo[a]pyrene, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, and many others.

It is confirmed that, in adults, secondhand smoke causes lung cancer, nasal sinus cancer, breast cancer in younger women, heart disease, heart attacks, and asthma induction. Secondhand smoke is also known to harm children, infants and reproductive health through acute lower respiratory tract illness, asthma induction and exacerbation, chronic respiratory symptoms, middle ear infection, lower birth weight babies, and Sudden Infant Death Syndrome.[15]

In June 2006, US Surgeon General Richard H. Carmona called the evidence against passive smoke "indisputable" and said "The science is clear: secondhand smoke is not a mere annoyance, but a serious health hazard that causes premature death and disease in children and non-smoking adults.".[16] Passive smoking is one of the key issues that have lead to introduction of smoking bans, particularly in workplaces.

The composition of Environmental tobacco smoke (ETS) is similar to fossil fuel combustion products that contribute to air pollution, and has been shown to be responsible for indoor particulate matter (PM) levels far exceeding official outdoor limits.[17]
Health risks of smoking

Because of their nicotine addiction, many smokers find it difficult to cease smoking despite their knowledge of ill health effects.The health effects of tobacco smoking are related to direct tobacco smoking, as well as passive smoking, inhalation of environmental or secondhand tobacco smoke. A 50 year study of over thirty thousand British physicians showed that nonsmokers lived about 10 more years than the smokers. For those born between 1920 and 1929 the standardized mortality rate between the ages of 35 and 69 for nonsmokers was 15% and for smokers was 43% -- nearly three times greater.[10] Claims that personalities of smokers account for these differences are not convincing in light of the fact that the heavy smokers were about 25 times more likely to die of lung cancer or chronic obstructive pulmonary disease than the nonsmokers.[10]

Lung cancer rates are linked to the amount of people who smoke. It is noted that an increase in deaths from lung cancer appeared 20 years after an increase in cigarette consumption. The damage a continuing smoker does to their lungs can take up to 20 years before its physical manifestation in lung cancer. Women began smoking later than men, so the rise in death rate amongst women did not appear until later. More men than women smoke. More men than women die of lung cancer. The male lung cancer death rate decreased in 1975 -- roughly 20 years after the fall in cigarette consumption in men. Fall in consumption in women also began in 1975 but by 1991 had not manifested in a decrease in lung cancer related mortalities amongst women. [11]

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". Twenty-four percent of pregnant women in Indiana smoke cigarettes. If they didn’t smoke, it is estimated by one source that Indiana would reduce its infant mortality rate (12th highest in the country) by 9%. Tobacco smoke reduces the delivery of oxygen to the fetus through the presence of carbon monoxide, cyanide, and aromatic hydrocarbons. Nicotine and other substances in tobacco smoke cause reduction in placental blood flow, creating further reductions in oxygen delivery as well as reductions in nutrients to the unborn baby. Secondhand smoke exposure during pregnancy produces twice the risk of low birth weight babies. Smoking is the single largest modifiable risk factor in intrauterine growth retardation.

The main health risks in tobacco pertain to diseases of the cardiovascular system, in particular smoking being a major risk factor for a myocardial infarction (heart attack), diseases of the respiratory tract such as Chronic Obstructive Pulmonary Disease (COPD) and emphysema, and cancer, particularly lung cancer and cancers of the larynx and tongue. Prior to World War I, lung cancer was considered to be a rare disease, which most physicians would never see during their career. With the postwar rise in popularity of cigarette smoking, however, came a virtual epidemic of lung cancer.

The carcinogenity of tobacco smoke is not explained by nicotine, which is not carcinogenic or mutagenic. Rather, any partially burnt material, tobacco or not, contains polycyclic aromatic hydrocarbons, particularly benzopyrene. The mechanism of their carcinogenity is well-known: oxidation produces an epoxide, which binds to DNA covalently and permanently distorts it. DNA damage is the cause of cancer.

The incidence of lung cancer is highly correlated with smoking.A person's increased risk of contracting disease is directly proportional to the length of time that a person continues to smoke as well as the amount smoked. However, if someone stops smoking, then these chances gradually decrease as the damage to their body is repaired.

Nicotine is a powerful, addictive stimulant and is one of the main factors leading to the continued tobacco smoking. Although the amount of nicotine inhaled with tobacco smoke is quite small (most of the substance is destroyed by the heat) it is still sufficient to cause physical and/or psychological dependence.

However, smokers usually ignore these facts and trade health risk for other qualities such as enjoyment and satisfied addictions. These smokers often think of the benefits of smoking rather than the downsides. Some smokers claim that the depressant effect of smoking allows them to "calm their nerves", often allowing for increased concentration. This, however, is only partly true. 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, whilst higher doses have stimulant effect."[12]

The health risks of smoking are not uniform across all smokers but vary according to amount of cigarettes smoked, with those who smoke more cigarettes at greater risk, although light smoking is still a health risk.

According to the Canadian Lung Association, tobacco kills between 40,000-45,000 Canadians per year, more than the total number of deaths from AIDS, traffic accidents, suicide, murder, fires and accidental poisoning.[13][14] However, the number of deaths related to smoking may be exaggerated because it is difficult to determine whether smoking actually caused the terminal illness.

shjspbml 也太没有创新能力了，完全抄我的。

Smoking: Effects of the habit and industry on society

Link Between Tobacco use and use of Illicit drugs.
Cigarettes along with alcohol and marijuana are considered a “gateway drug.” A 1994 report from the Center on Addiction and Substance Abuse at Columbia University states that there is a consistent relationship between the use of cigarettes and alcohol and the subsequent use of marijuana. Cigarettes, alcohol and marijuana use and the subsequent use of illicit drugs like cocaine is also linked, regardless of the age, sex, ethnicity or race of the individuals involved. Children 12 to 17 years old who smoke are nineteen times more likely to use cocaine. The 1994 report also found that the younger children are when they use these gateway drugs and the more often they use them, the more likely they are to use cocaine, heroin, hallucinogens and other illicit drugs. The report concludes that the data is already robust enough to make a strong case to step up efforts to prevent childhood use of cigarettes, alcohol and marijuana and to take firm steps to reduce children’s access to these gateway drugs.

People who abuse drugs are likely to be cigarette smokers also. More than two-thirds of drug abusers are regular tobacco smokers, a rate more than double of that in the general population. NIDA researchers have found that craving for nicotine also increases craving for illicit drugs among drug abusers who smoke tobacco, and this suggests that smokers in drug rehabilitation programs may be less successful than nonsmokers in staying off drugs.

Bodily functions and how they are affected
Tobacco smoke contains nicotine, a stimulant. Nicotine acts as an inhibitor (or block), that attaches to cholinergic receptors in the brain that are usually used to control respiration, heart rate, memory, alertness, and muscle movement. As such all are affected by smoking. Normally, acetylcholine (a similar, naturally present healthy neurochemical) would attach to the receptors, however nicotine interferes in this natural biological process and attaches to the receptors instead and blocks them.

Nicotine's effect in the body results in reduced acetylcholine production in the brain -- a physiological response to a perceived 'excess' of acetylcholine, an assumption by the body which is incorrect. This replacement of natural neurochemicals with nicotine is largely responsible for nicotine's addictive properties, because it creates a dependency for nicotine to continue fulfilling the role of acetylcholine and stop the body from becoming erratic. If a smoker stops smoking, lack of acetylcholine causes respiration, heart rate, memory, alertness, and muscle movement to be temporarily affected -- this can be so distressing it can be hard to continue cessation for some.

Recent evidence has shown that smoking tobacco causes increases in dopamine levels in the brain, and lowers the levels of enzymes found in the brain that naturally stop the levels of dopamine becoming too high, this causes the promotion of abnormally high levels of dopamine similar to those experienced by heroin and cocaine addicts and users. Smokers have feelings of pleasure and reward when they smoke due to this chemical imbalance created.[18] One study found that smokers exhibit better reaction-time and memory performance as they tire, compared to non-smokers.[19]

Physical & Mental addiction
Nicotine, an element of tobacco smoke, is one of the most addictive substances that exists. When tobacco is smoked, most of the nicotine is pyrolyzed; however, a dose sufficient to cause mild somatic dependency and mild to strong psychological dependency remains. According to studies by Henningfield and Benowitz, nicotine is more addictive than marijuana and caffeine but of a lesser potential for somatic dependency than ethanol, cocaine and heroin. A study by Perrine concludes nicotine's potential for psychological dependency exceeds all other studied drugs[20] - even ethanol, an extremely physically addictive substance with a severe withdrawal that can be fatal. Many smokers use nicotine compulsively. About half of Canadians who currently smoke have tried to quit.[21] McGill University health professor Jennifer O'Loughlin stated that nicotine addiction can occur as soon as five months after the start of smoking.[22]

It can be difficult to quit smoking due to the withdrawal symptoms which include insomnia, irritability, anxiety, decreased heart rate, weight gain, and nicotine cravings. The relapse rate for quitters is high: about 60% relapse in three months. Also, nicotine users are sometimes reluctant to quit smoking because they do not see any short-term damages it may cause.

Smoking and depression
Data from multiple studies suggest that depression plays a role in cigarette smoking.[23] A history of regular smoking was observed more frequently among individuals who had experienced a major depressive disorder at some time in their lives than among individuals who had never experienced major depression or among individuals with no psychiatric diagnosis.[24] Another study found that the average lifetime daily cigarette consumption was strongly related to lifetime prevalence, and to prospectively assessed one year prevalence of major depression.[25] People with major depression are also much less likely to quit due to the increased risk of experiencing mild to severe states of depression, including a major depressive episode.[26] Depressed smokers appear to experience more withdrawal symptoms on quitting, are less likely to be successful at quitting, and are more likely to relapse.[27] The neurotransmitter systems affected by cigarette smoke mirror the neurotransmitter pathways that are thought to be involved in the biological mechanisms of depression, and the use of antidepressants as adjuvants to smoking-cessation treatment can enhance cessation success rates.[28]

Health benefits of smoking
Ulcerative colitis is twice as common in non-smokers as in smokers.[29] The nicotine in tobacco smoke acts as an anti-inflammatory agent.[30]

Also, it was thought that the risks of Parkinson's disease or Alzheimer's disease might be significantly lower for smokers than for non-smokers. Indeed, according to previous epidemiological studies, cigarette smokers were 50% less likely to have PD or AD than are age- and gender-matched nonsmokers.[31] One explanation given for this effect is the fact that nicotine allegedly decreases the levels of acetylcholine in the smoker's brain. Parkinson's disease consequently occurs when the effect of dopamine is less than that of acetylcholine. However, nicotine, a cholinergic stimulant, is the only substance in tobacco smoke which has those positive effects, and the consumption of pure nicotine would likely be more beneficial than smoking.

More recent evidence has however challenged the earlier epidemiological studies on methodological grounds.[32] A prospective Rotterdam Study found that the incidence of Alzheimer's disease is more than double for smokers as compared to non-smokers[33] and the Honolulu Heart Program (a longitudinal cohort study) also found more than twice the risk for Alzheimer's disease among medium and heavy smokers as compared to non-smokers.[34]

Passive smoking
Main article: Passive smoking

This photo illustrates smoke in a pub, a common complaint from those concerned with passive smokingPassive or involuntary smoking occurs when the exhaled and ambient smoke (otherwise known as environmental or secondhand smoke) from one person's cigarette is inhaled by other people. Passive smoking involves inhaling carcinogens, as well as other toxic components, that are present in secondhand tobacco smoke. Carcinogens that occur in secondhand tobacco smoke include benzene, 1,3-butadiene, benzo[a]pyrene, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, and many others.

It is confirmed that, in adults, secondhand smoke causes lung cancer, nasal sinus cancer, breast cancer in younger women, heart disease, heart attacks, and asthma induction. Secondhand smoke is also known to harm children, infants and reproductive health through acute lower respiratory tract illness, asthma induction and exacerbation, chronic respiratory symptoms, middle ear infection, lower birth weight babies, and Sudden Infant Death Syndrome.[15]

In June 2006, US Surgeon General Richard H. Carmona called the evidence against passive smoke "indisputable" and said "The science is clear: secondhand smoke is not a mere annoyance, but a serious health hazard that causes premature death and disease in children and non-smoking adults.".[16] Passive smoking is one of the key issues that have lead to introduction of smoking bans, particularly in workplaces.

The composition of Environmental tobacco smoke (ETS) is similar to fossil fuel combustion products that contribute to air pollution, and has been shown to be responsible for indoor particulate matter (PM) levels far exceeding official outdoor limits.[17]
Health risks of smoking

Because of their nicotine addiction, many smokers find it difficult to cease smoking despite their knowledge of ill health effects.The health effects of tobacco smoking are related to direct tobacco smoking, as well as passive smoking, inhalation of environmental or secondhand tobacco smoke. A 50 year study of over thirty thousand British physicians showed that nonsmokers lived about 10 more years than the smokers. For those born between 1920 and 1929 the standardized mortality rate between the ages of 35 and 69 for nonsmokers was 15% and for smokers was 43% -- nearly three times greater.[10] Claims that personalities of smokers account for these differences are not convincing in light of the fact that the heavy smokers were about 25 times more likely to die of lung cancer or chronic obstructive pulmonary disease than the nonsmokers.[10]

Lung cancer rates are linked to the amount of people who smoke. It is noted that an increase in deaths from lung cancer appeared 20 years after an increase in cigarette consumption. The damage a continuing smoker does to their lungs can take up to 20 years before its physical manifestation in lung cancer. Women began smoking later than men, so the rise in death rate amongst women did not appear until later. More men than women smoke. More men than women die of lung cancer. The male lung cancer death rate decreased in 1975 -- roughly 20 years after the fall in cigarette consumption in men. Fall in consumption in women also began in 1975 but by 1991 had not manifested in a decrease in lung cancer related mortalities amongst women. [11]

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". Twenty-four percent of pregnant women in Indiana smoke cigarettes. If they didn’t smoke, it is estimated by one source that Indiana would reduce its infant mortality rate (12th highest in the country) by 9%. Tobacco smoke reduces the delivery of oxygen to the fetus through the presence of carbon monoxide, cyanide, and aromatic hydrocarbons. Nicotine and other substances in tobacco smoke cause reduction in placental blood flow, creating further reductions in oxygen delivery as well as reductions in nutrients to the unborn baby. Secondhand smoke exposure during pregnancy produces twice the risk of low birth weight babies. Smoking is the single largest modifiable risk factor in intrauterine growth retardation.

The main health risks in tobacco pertain to diseases of the cardiovascular system, in particular smoking being a major risk factor for a myocardial infarction (heart attack), diseases of the respiratory tract such as Chronic Obstructive Pulmonary Disease (COPD) and emphysema, and cancer, particularly lung cancer and cancers of the larynx and tongue. Prior to World War I, lung cancer was considered to be a rare disease, which most physicians would never see during their career. With the postwar rise in popularity of cigarette smoking, however, came a virtual epidemic of lung cancer.

The carcinogenity of tobacco smoke is not explained by nicotine, which is not carcinogenic or mutagenic. Rather, any partially burnt material, tobacco or not, contains polycyclic aromatic hydrocarbons, particularly benzopyrene. The mechanism of their carcinogenity is well-known: oxidation produces an epoxide, which binds to DNA covalently and permanently distorts it. DNA damage is the cause of cancer.

The incidence of lung cancer is highly correlated with smoking.A person's increased risk of contracting disease is directly proportional to the length of time that a person continues to smoke as well as the amount smoked. However, if someone stops smoking, then these chances gradually decrease as the damage to their body is repaired.

Nicotine is a powerful, addictive stimulant and is one of the main factors leading to the continued tobacco smoking. Although the amount of nicotine inhaled with tobacco smoke is quite small (most of the substance is destroyed by the heat) it is still sufficient to cause physical and/or psychological dependence.

However, smokers usually ignore these facts and trade health risk for other qualities such as enjoyment and satisfied addictions. These smokers often think of the benefits of smoking rather than the downsides. Some smokers claim that the depressant effect of smoking allows them to "calm their nerves", often allowing for increased concentration. This, however, is only partly true. 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, whilst higher doses have stimulant effect."[12]

The health risks of smoking are not uniform across all smokers but vary according to amount of cigarettes smoked, with those who smoke more cigarettes at greater risk, although light smoking is still a health risk.

According to the Canadian Lung Association, tobacco kills between 40,000-45,000 Canadians per year, more than the total number of deaths from AIDS, traffic accidents, suicide, murder, fires and accidental poisoning.[13][14] However, the number of deaths related to smoking may be exaggerated because it is difficult to determine whether smoking actually caused the terminal illness.

我建议你看这几个网址，应该会有你所想要的：
http://www.answers.com/topic/smoking
http://www.answers.com/main/ntquery?s=tobacco&gwp=8

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宁化县19278664432： tobacco究竟是可数名词还是不可数 - ？
度界车前： 你好, tobacco是不可数名词,如 许多烟草Many tobacco You can buy all kinds of tobacco from this shop.你可以从这家商店购买各种烟草.

宁化县19278664432： 古巴雪茄英文介绍 - ？
度界车前： All the world to know the cigars experts agree that only Cuba fertile clay, give birth to the world's best tobacco, and from the hand of the Cuban cigar system, but also go global cigar gourmet. Cuban cigars acme flavor by special technology is made....

宁化县19278664432： 写一篇有关保持健康,远离吸烟80词左右英语作文 - ？
度界车前： 您好:there many people addicted to smoking .They take it for granted that smoking is a symbol of a successful man,ther think they just smoke for pleasure and to kill time,but as far as smoking is concerned It's no aggression to say that the ...

宁化县19278664432： 请问tobacco前面可以加a 吗?可不可以说a tobacco,如果用some的话该怎么加? - ？
度界车前： tobacco是不可数名词,前面不能a或者an,some直接加就好,some tobacco 谢谢!

宁化县19278664432： tobacco什么意思？
度界车前： tobacco [tə'bækəu] n.烟草, 烟叶 This shop is licensed to sell tobacco. 这家商店获准经销烟草商品.

宁化县19278664432： tobacco(烟草)是不可数名词吗? - ？
度界车前： 不可数名词 1)物质名词(不可数): 烟叶;烟草(制品) Try to do without tobacco and alcohol...尽量不要抽烟喝酒. 2) (不可数)烟草植株 Tobacco is the plant from which tobacco is obtained.

宁化县19278664432： 烟叶的英语翻译 烟叶用英语怎么说 - ？
度界车前： 你好!烟叶 tobacco 英[təˈbækəʊ] 美[təˈbækoʊ] n. 卷烟; 烟草,烟叶; 烟草制品; 纸烟; [例句]Try to do without tobacco and alcohol 尽量不要抽烟喝酒.

宁化县19278664432： 有关早餐与健康的英语作文 字数100左右 - ？
度界车前： No Breakfast, No Good Now a lot of students go to school in a hurry so that they have no time to have breakfast. But not having breakfast will do harm to their health and their study. Having no breakfast will throw the normal work of our digestive ...

宁化县19278664432： 高一关于吸烟的英语作文,100到120字？
度界车前： Tobacco smoke is killing thousands of people every year and injuring hundreds of thousands more every day like children. Federal officials released a massive report that is sparking renewed efforts to ban smoking in public places. Secondhand ...

宁化县19278664432： tobacco的中文意思？
度界车前： tobacco [tə'bæko] [词典释义] n. 1. 烟草;烟叶 2. 烟草制品 3. 抽烟 [网络释义] tobacco 1.烟草,烟叶 2.咽草 Tobacco 1.烟草