SMOKING: An Assault to YOUR Lung-Cells
....that smoking claims an average of 2950 lives every day, that nearly all Europeans know about the risks involved in tobacco use, and yet 100 million people still smoke (or chew tobacco). The cigarettes, cigars, pipe and chewing tobacco made from the tobacco plant seem to be uniquely addictive. This is because the nicotine in tobacco leaves causes a strong psychologically dependent on the taste and feel of tobacco.
Researchers are anticipating a future epidemic of lung, mouth, throat, and other cancers based on the smoking and chewing habits of woman and men of college age today. For this reason, it is worth examining the biological costs of tobacco use, focusing on the level of the cell, where the damage begins. You will then be better prepared to make personal decisions about smoking or chewing tobacco, to communicate to friends and family, and to vote on public issues such as cigarette taxes and smoking bans. Tobacco (Nicotiana tabacum) is a hardy C3 plant that grows up to 2m tall and produces very large leaves and spikes of pretty, usually pink, flowers. When Christopher Columbus arrived in the New World, he found Native Americans cultivating and smoking tobacco for what they believed to be medicinal properties. Columbus and other explorers carried tobacco to Europe and eventually the rest of the world. Today, 500 years later, the plant is still widely used. As a natural defense, tobacco leaves and stems produce various compounds that discourage insects and other predators. Among them is a bitter-tasting nitrogen-containing compound, the alkaloid called nicotine.
Smokers and chewers become physically hooked on this compound, which is toxic to the body but has profound and in some ways pleasant psychoactive properties. Researchers have found that after regular smoking or chewing for a year, a person has only one chance in five of quitting successfully on a given attempt. It takes most people three or four serious efforts to stop, and some are never able to. Nicotine addiction is only part of the problem of tobacco use. Analysis of smoke from burning tobacco reveals over 4000 separate compounds, including DDT, arsenic, nitrosamines, and formaldehyde, all known carcinogens. Similar tests of chewing tobacco reveals traces of three additional carcinogens: cadmium, uranium, polonium. One of the most damaging compounds in tobacco smoke is the poisonous gas carbon monoxide - the culprit when someone dies from fumes of a running car engine in a closed garage.
What do the free radicals, nicotine, and other tobacco compounds actually do to human cells?
|1. Paralyzed Cilia: Tobacco smoke can paralyze the cilia, the microscopic hairlike projections from cells lining the airways of the human respiratory tract. Without these continuously beating cilia, germs and particles of foreign matter can enter the lungs and cause irritation and infection. The lungs and respiratory passageways compensate by producing more mucus, which is expelled in a smoker's characteristic cough. Perennial coughing can weaken the lungs and lead to chronic bronchitis.|
2. Lung Cell Changes:
Cadmium, nitrogen dioxide, and other substances in cigarette
smoke can rupture cells in the lungs' tiny, ballonlike air sacs,
or alveoli. They can also prevent a cell's smooth endoplasmic
reticulum from producing normal amounts of surfactant. Both of
these changes can contribute to permanent shortness of breath
and to lung diseases such as emphysema.
3. Disturbed Mitochindria: Cell biologists have exposed eukaryotic cells to cigarette smoke, then viewed their mitochondrial membranes with an electron microscope. The smoke destroyed the mitochondria's normal internal structure, and with it, their ability to carry out the reactions of the Krebs cycle (an elementary process in cell respiration) and the electron transport chain. Thus the cell is starved for ATP (energy carrier within the cell) energy and eventually dies.
4. DNA Damage: Many of the toxic compounds in tobacco
can attack and damage DNA. Repair enzymes in the nucleus attempt
to fix these broken strands, and correct bungled base pairs. However,
continual exposure to the toxins can lead to an accumulation of
errors, which are implicated in the formation of cancerous tumors.
5. Nicotine and the Cell: Certain cells in the nervous and muscular system have receptor proteins in their membranes that bind nicotine. After binding the drug, these cells respond a bit differently to normal nerve signals, explaining how nicotine acts as a stimulant.
|6. Increased Carbon Monoxide: Smokers have elevated CO levels in their bloodstreams. When CO combines with hemoglobin, the pigment delivers less oxygen to the body's tissues, including the brain, and the person's ability to think clearly is reduced.|
|7. Immune Cell Changes: Researchers studying the white blood cells called macrophages that patrol and protect the airways and lungs have found an increase in the size and numbers of lysosomes within the cells and a decrease in protein synthesis. The cells are apparently so busy ingesting foreign particles and the debris of damaged cells that they can't grow and function properly. Immune cell disruption helps explain why smokers catch colds, flu, and pneumonia more easily than nonsmokers, as well as experience increased cancer rates.|
8. Immediate and Delayed Consequences:
Some cellular changes from smoking produce immediate effects.
After just a few days or weeks of smoking, most people have shortness
of breath and decreased ability to perform aerobic exercise. Tobacco
users have lowered resistance to colds and flu, and slower healing
of broken bones and other wounds. Female smokers tend to have
more miscarriages and babies of lower birth weight. Even in their
teens and twenties, tobacco users tend to develop periodontal
(gum) disease four times as often as nonusers. |
And many recent studies show that tobacco use interferes with complex tasks involving memory and reasoning, and addicts are more likely to have automobile or industrial accidents.
|Some of the more life-threatening health consequences of smoking and chewing include lung disease, heart disease, thyroid disease, and cancers of the mouth, throat, lungs, bladder, and other sites. These can take 20 or 30 years to develop - hence the factor of deferred disease in tobacco addiction. Users have twice the overall cancer risk of nonusers, 15 times the risk of oral and lung cancer, twice the probability of heart attack or stroke, and a much greater chance of lung damage. In all, smokers die an average of eight years earlier than nonsmokers, and are less healthy and less active during their intervening years.|
Also, the tars and gasses in cigarette smoke damage blood vessel
walls and increase one's chances of heart attack or stroke. Studies
show that 4 out of every 10 smokers - approximately 800,000 Europeans
each year - die as a direct result of their smoking habit. This
makes smoking by far the leading cause of preventable death each
Children raised around smokers are more likely to have respiratory
and bloodvessel problems. Adult nonsmokers who live with smokers
have a 30 percent higher risk of death from heart attacks, and
about 15,000 passive smokers in the US alone die of smoke induced
cancers each year.
While one quarter of European adults smoke (or chew tobacco),
the problem affects everyone. In 1993, physicians who looked at
nicotine levels in US-Americans' blood were surprised to report
that every person they screened had nicotine in their blood. Other
measures of the pervasiveness of tobacco smoke in the environment
are the statistics released in 1992 by the Environmental Protection
Agency. They blamed 2500 to 3300 lung cancer deaths each year
among nonsmoker5s on so-called second hand smoke (fumes exhaled
from smoker's lungs or rising from their burning smokes). The
EPA also attributed 150,000 t0 300,000 respiratory tract infections
per year among children to adult's smoking.
In an attempt to reduce the exposure of nonsmokers, many municipalities have officially banned smoking in restaurant, office buildings, and other public places. In addition, a US-based professional society of 9000 cancer specialists has called upon the federal government of the USA to levy an excise tax on cigarettes of about US$ 3 per pack, compared to the current 16 cents. They cite plummeting tobacco consumption in countries like Canada that have imposed such stiff taxes, and note that budget-conscious young people are among the first to quit when tobacco prices skyrocket.
We hope, in the name of good health, you will apply these findings on the cell biology of smoking to decisions you make about your own life or eventual ....