| What is the nature of this substance which has | | | | carbon dioxide is that the former binds much more |
| caused so much controversy and is of such concern | | | | tightly to hemoglobin and is very slow to be removed. |
| to governments, religious bodies, and science? The | | | | Thus the blood can accumulate rather high levels of |
| tobacco plant is a member of the vegetable family | | | | carbon monoxide and slowly starve the body of |
| Solanaceae. The plant was named Nicotiana abacus in | | | | oxygen. When the cardiac system detects insufficient |
| honor of the French ambassador to Portugal in the | | | | levels of oxygen, the heart may begin to flutter and |
| 1850s, Jean Nicety, who believed the plant had | | | | operate inefficiently. In extreme cases heart attack |
| medicinal value and encouraged its cultivation. One | | | | may result. |
| chemical constituent of tobacco is nicotine. When | | | | Each cigarette causes a brief boost in the CO level |
| cultivated with various chemical fertilizers and | | | | which lasts for a few minutes and then declines until |
| insecticides, pro-cussed into cigarettes, and finally | | | | the next cigarette is smoked. |
| burned, many other physical constituents result. | | | | However, each cigarette adds slightly to the overall |
| Tobacco smoke contains thousands of elements. | | | | level. When people smoke normally, their CO levels are |
| Most are delivered in such minute amounts that they | | | | lowest in the morning and level off at their highest |
| are not usually considered in discussions of the medical | | | | values by midday. The typical twenty-per-day smoker |
| effects of cigarette smoking. In fact, there are so | | | | achieves levels averaging between 25 and 35 parts |
| many that it will take years of research to discover | | | | per million. However, even these "average" smokers |
| which constituents are harmful. Thereof undisputed | | | | may hit short-term levels of greater than 100 parts per |
| importance, however, are tar, carbon monoxide, and | | | | million. Firefighters are now routinely checked with |
| nicotine. | | | | portable CO analyzing machines while combating fires. |
| Troy is defined, rather arbitrarily, as the total particulate | | | | If their levels exceed 150 parts per million them may be |
| matter (TPM), minus water and nicotine, which is | | | | relieved and given oxygen, since even these generally |
| trapped by the Cambridge filter used in smoke | | | | healthy people run a risk of heart attacks. |
| collection machines. Persons who have used | | | | Nicotine is a drug that occurs naturally in the leaves of |
| ventilated-cigarette holders (for example, MD4) in an | | | | Nicotiana abacus. It is generally thought of as a |
| effort to give up smoking have probably noticed the | | | | stimulant since it provokes many nerve cells in the |
| accumulation in the filter of a thick, black material | | | | brain and height-ends arousal. However, its effects are |
| reminiscent of road tar. Tar, not present in unburned | | | | so complex that no simple label is completely accurate. |
| tobacco, is a product of organic matter being burned in | | | | For instance, by stimulating certain nerves in the spinal |
| the presence of air and water at a sufficiently high | | | | cord (Crenshaw cells), nicotine relaxes many of the |
| temperature. Tobacco products such as snuff and | | | | muscles of the body and can even depress knee |
| chewing tobacco do not deliver tar. | | | | reflexes. Its effects also vary depending on how much |
| Official figures for tar delivery of cigarettes in some | | | | is smoked. For example, nerve cells that are stimulated |
| countries printed on cigarette packets, do not reflect | | | | by the nicotine from a few cigarettes may be |
| tar contained in the tobacco or evening the smoke. | | | | depressed by smoking more cigarettes. |
| These estimates reflect the amount collected from the | | | | Nicotine closely resembles one of the substances that |
| standard cigarette-smoking machines. The levels may | | | | occur naturally in the body (acetylcholine), and the body |
| be useful for cigarette comparisons, but are otherwise | | | | has an efficient system to break nicotine down |
| misleading to people who think that their intake of tar is | | | | (detoxification) and eliminate it in the urine (excretion). In |
| mainly determined by their brand of cigarettes. One | | | | fact, when given dose of nicotine is ingested, for |
| study showed that very low-tar cigarettes with official | | | | instance by smoking, about one-half is removed from |
| yields of only a few milligrams delivered 15 -20 | | | | the blood stream within 15to 30 minutes. The pattern of |
| milligrams when smoked the way a person might | | | | nicotine accumulation and elimination when cigarettes |
| actually smoke them. | | | | are smoked. Note that these patterns are similar to |
| Tar is one of the major health hazards in cigarette | | | | those observed for carbon monoxide. |
| smoking. It causes a variety of types of cancer in | | | | Another feature of nicotine is that it is well absorbed |
| laboratory animals. Also, the minute separate particles | | | | through the mucosa or the very thin skin of the nose |
| fill the tiny air holes in the lungs (the alveoli) and | | | | or mouth which is dense with capillaries. This is why |
| contribute to respiratory problems such as | | | | chewing tobacco and taking snuff are effective ways |
| emphysema. In the light of these facts many cigarette | | | | to ingest nicotine. In the form of cigarette smoke, |
| manufacturers have reduced the tar yields in their | | | | nicotine transfers directly from the alveoli of the lungs |
| cigarettes in an effort to provide "safer" cigarettes. | | | | into the arterial blood stream and rushes directly to the |
| Unfortunately, tar is important to the taste of the | | | | brain. It requires less than 10 seconds for inhaled |
| cigarette and the satisfaction derived from smoking. | | | | nicotine to reach the brain, so that even though the |
| Thus, when many people smoke low-tar cigarettes, to | | | | quantities are small, the effects may be strong. This is |
| get maximum enjoyment they inhale so deeply that | | | | even quicker than giving nicotine intravenously, since |
| they defeat the purpose of this type of cigarette. It is | | | | the venous blood supply must first pass through the |
| ironic that cigarettes engineered to deliver low-tar | | | | heart, then into the arterial stream of the lungs and, |
| yields when smoked by machines deliver higher yields | | | | finally, to the brain. |
| when smoked by people. | | | | Repeated exposure to nicotine, when it is smoked, |
| Carbon monoxide (CO) is a gas that results when | | | | re-salts in very rapid tolerance or diminished effect. |
| materials are burned. Carbon monoxide production is | | | | That is, during the day, as cigarettes are smoked, the |
| increased by restricting the oxygen supply, as is the | | | | smoker gets less and less of a psychological and |
| case in a cigarette. Carbon monoxide is also produced | | | | physical effect-even though toxins are building up in the |
| by internal combustion engines (as in cars) and even | | | | body. In fact, much of this tolerance is lost overnight. |
| by gas cookers and heaters. Like carbon dioxide | | | | As a result, cigarette smokers often report that their |
| (CO2), which also results from burning, carbon | | | | first cigarette of the day "tastes the best" or may |
| monoxide easily passes from the alveoli of the lungs | | | | even make them lightheaded if smoked too quickly. As |
| into the blood stream. There it combines with | | | | the day wears on and more cigarettes are smoked, |
| haemoglobin to form carboxyhaemoglobin (Cobh). | | | | people often smoke more out of habit or to avoid |
| Hemoglobin is that portion of the blood which normally | | | | disco-fort than for pleasure. |
| carries carbon dioxide out of the body (CO2 is | | | | Research to date on the hazards of cigarette smoking |
| produced by normal metabolic processes) and oxygen | | | | suggests that nicotine is not as hazardous as the tar |
| back into the body. When the hemoglobin is all bound | | | | and carbon monoxide in cigarette smoke. Its role is |
| up by either carbon monoxide or carbon dioxide, a | | | | more insidious, since people ingest these other |
| shortage of oxygen may result. | | | | substances (tar and CO) as bay-product of their |
| A critical difference between carbon monoxide and | | | | efforts to obtain nicotine. |