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