Monday, November 8, 2010

What does the tobacco smoke contain?

The combustion of tobacco produces a type of smoke that contains more than 4000 substances and chemicals, which are made up of particles and gases that can be inhaled and absorbed into the body. Most of the components 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.

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The International Cancer Investigation Agency however has identified over 50 carcinogenic substances in tobacco smoke. 11 of the substances are proven to cause cancer in humans, 7 probably cause cancer in humans and 49 of the substances cause cancer in animals but have not yet been proven to in humans.

Other substances found in environmental tobacco smoke are certainly poisonous and most definitely none are beneficial to a person's health.

The U.S. Environmental Protection Agency (EPA) has classified environmental tobacco smoke as a Group A carcinogen. This means that there is more than enough evidence to prove that tobacco smoke, whether it is inhaled by the smoker or the non-smoker, can cause cancer in humans.

Mainstream and sidestream smoke both contain a huge number of toxic, poisonous and carcinogenic substances.

Surprisingly, sidestream smoke (smoke that escapes the end of a burning cigarette) contains much higher concentrations of many of the chemical compounds.

What's more is that the particles that make up sidestream smoke are much smaller than those of mainstream smoke. This means that these smaller particles that float in the air, will be inhaled much deeper into the lungs and will be able to reach the furthest and deepest corners within a person's respiratory system and therefore causing much more damage.

For example, cadmium, a known lung cancer causing substance, is found in concentrations that are six times higher in the smoke that is inhaled by passive smokers as opposed to the smoke that is inhaled directly by the smoker through the cigarette.

Even so, although 85% of the smoke that is present in a smoke-filled room is made up of sidestream smoke, passive smokers still have a lesser risk of suffering the effects of the harmful substances contained in tobacco smoke.

Three of the main components of environmental tobacco smoke are:
  • Nicotine - an addictive drug as powerful as cocaine or heroin. It alters the brain as well as a person's behavior and mood. It is also used in insecticides.
  • Tar - a cancer causing substance that damages the lungs.
  • Carbon monoxide - a gas that replaces some of the oxygen in the body that is needed for the lungs to function properly. Carbon monoxide is a poisonous gas, which is also found in car exhaust fumes.
Some of the carcinogenic substances found in tobacco smoke are:
  • Tar - used to tarmac roads.
  • Arsenic - very potent deadly poison.
  • Cadmium and nickel - used in batteries.
  • Vinyl chloride - used to make vinyl products. Short-term exposure causes dizziness, headaches and tiredness. Long-term exposure can lead to cancer and liver damage.
  • Creosote - a component of tar. If inhaled it can cause irritation of the respiratory tract.
  • Formaldehyde - a preservative substance used in forensic labs. It causes cancer in humans and in animals.
  • Polonium 210 - a radioactive substance that requires special handling techniques when studied in labs. It can cause cancer of the liver and bladder, stomach ulcers, leukemia amongst other diseases.
Other irritant toxins that are found in cigarette smoke are:
  • Ammonia - a pungent colorless gas used in many cleaning products such as window or glass cleaner.
  • Acetone - the main component of nail varnish remover.
  • Acrolein - an extremely toxic substance used to manufacture acrylic acid. It is considered a possible human carcinogen and it irritates the lungs and is the cause of emphysema.
  • Hydrogen cyanide - deadly toxic poison used to kill rats. If breathed in in small doses, it can cause headaches, dizziness and weakness.
  • Carbon monoxide - a deadly gas if inhaled in enclosed spaces. Faulty and leaking gas heaters, boilers, stoves and tobacco smoke all produce this gas.
  • Toluene - used to manufacture paint, paint thinners, nail varnish and adhesives. Low - moderate levels can provoke tiredness, weakness, loss of appetite and memory loss.
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It was undoubtedly identified that the 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 withhaemoglobin 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.

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 15 to 30 minutes.

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.

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