By Matthew Tontonoz Friday, December 7, Among the 7, or so different chemicals in cigarette smoke, more than 70 are known to be carcinogens. Most carcinogens promote cancer by damaging DNA and causing mutations. Illustration by Wenjing Wu. That cigarettes cause cancer is no secret. Scientists have known that smoking causes cancer since at least the s, when epidemiological studies showed a clear link between smoking and lung cancer.
Experiments conducted in the s confirmed that the chemicals in cigarette smoke could cause cancer in mice. By the time the US Surgeon General issued his warning against smoking in , there was overwhelming evidence that cigarettes were deadly.
But in the years since, what have scientists learned about how cigarettes cause cancer? And does this knowledge open up new avenues for treatment and prevention? The first clues about how cigarette smoke causes cancer came in the s. Since DNA is the blueprint for life, anything that corrupts that blueprint is destined to cause trouble. The most well-studied of these is benzo[a]pyrene BP.
BP is one of several ring-shaped chemicals called polycyclic aromatic hydrocarbons that are produced when organic matter, such as a tobacco leaf, is burned. When it enters the body, BP becomes a powerful DNA disruptor, producing mutations that can lead to cancer. Like most foreign chemicals taken into the body, BP is processed by enzymes to make it water-soluble. This change allows the kidneys to excrete the foreign chemical in urine.
They form bulky attachments, or adducts, that bend DNA out of shape. Radioactive materials, like polonium and lead are found naturally in the soil and air. They are also found in the high-phosphate fertilizers that farmers use on their crops. Polonium and lead get into and onto tobacco leaves and remain there even after the tobacco has been processed. When a smoker lights a cigarette and inhales the tobacco smoke, the toxic and radioactive substances in the smoke enter the lungs where they can cause direct and immediate damage to the cells and tissues.
The same toxic and radioactive substances can also damage the lungs of people nearby. For more information on polonium, click here. Polonium and lead accumulate for decades in the lungs of smokers. Sticky tar in the tobacco builds up in the small air passageways in the lungs bronchioles and radioactive substances get trapped. Over time, these substances can lead to lung cancer.
Skip directly to site content Skip directly to page options Skip directly to A-Z link. Tobacco smoke contains many chemicals that are harmful to both smokers and nonsmokers. Breathing even a little tobacco smoke can be harmful 1 - 4. Of the more than 7, chemicals in tobacco smoke, at least are known to be harmful, including hydrogen cyanide , carbon monoxide , and ammonia 1 , 2 , 5. Among the known harmful chemicals in tobacco smoke, at least 69 can cause cancer.
These cancer-causing chemicals include the following 1 , 2 , 5 :. Smoking is the leading cause of premature, preventable death in this country. Cigarette smoking and exposure to tobacco smoke cause about , premature deaths each year in the United States 1.
Mortality rates among smokers are about three times higher than among people who have never smoked 6 , 7. Smoking causes cancers of the lung, esophagus, larynx, mouth, throat, kidney, bladder, liver, pancreas, stomach, cervix, colon, and rectum, as well as acute myeloid leukemia 1 — 3.
Smoking also causes heart disease, stroke, aortic aneurysm a balloon-like bulge in an artery in the chest , chronic obstructive pulmonary disease COPD chronic bronchitis and emphysema , diabetes , osteoporosis , rheumatoid arthritis, age-related macular degeneration , and cataracts , and worsens asthma symptoms in adults.
Smokers are at higher risk of developing pneumonia , tuberculosis , and other airway infections 1 — 3. In addition, smoking causes inflammation and impairs immune function 1. There have also been changes over time in the type of lung cancer smokers develop — a decline in squamous cell carcinomas but a dramatic increase in adenocarcinomas.
Both of these shifts may be due to changes in cigarette design and composition, in how tobacco leaves are cured, and in how deeply smokers inhale cigarette smoke and the toxicants it contains 1 , 8. Smoking makes it harder for a woman to get pregnant. Men who smoke are at greater risk of erectile dysfunction 1 , 9. But regardless of their age, smokers can substantially reduce their risk of disease, including cancer, by quitting. The U.
Environmental Protection Agency, the U. National Toxicology Program, the U. Surgeon General, and the International Agency for Research on Cancer have classified secondhand smoke as a known human carcinogen cancer-causing agent 5 , 11 , Inhaling secondhand smoke causes lung cancer in nonsmoking adults 1 , 2 , 4.
Approximately 7, lung cancer deaths occur each year among adult nonsmokers in the United States as a result of exposure to secondhand smoke 1. Secondhand smoke causes disease and premature death in nonsmoking adults and children 2 , 4. In the United States, exposure to secondhand smoke is estimated to cause about 34, deaths from heart disease each year 1.
Pregnant women exposed to secondhand smoke are at increased risk of having a baby with a small reduction in birth weight 1. Children exposed to secondhand smoke are at an increased risk of SIDS, ear infections, colds, pneumonia, and bronchitis. Secondhand smoke exposure can also increase the frequency and severity of asthma symptoms among children who have asthma. Smoking is highly addictive. The addiction to cigarettes and other tobacco products that nicotine causes is similar to the addiction produced by using drugs such as heroin and cocaine Nicotine is present naturally in the tobacco plant.
But tobacco companies intentionally design cigarettes to have enough nicotine to create and sustain addiction. The amount of nicotine that gets into the body is determined by the way a person smokes a tobacco product and by the nicotine content and design of the product.
Nicotine is absorbed into the bloodstream through the lining of the mouth and the lungs and travels to the brain in a matter of seconds. Taking more frequent and deeper puffs of tobacco smoke increases the amount of nicotine absorbed by the body. All forms of tobacco are harmful and addictive 4 , There is no safe tobacco product. In addition to cigarettes, other forms of tobacco include smokeless tobacco , cigars , pipes , hookahs waterpipes , bidis , and kreteks. There is no safe level of smoking.
Smoking even just one cigarette per day over a lifetime can cause smoking-related cancers lung, bladder, and pancreas and premature death 24 , Quitting smoking reduces the risk of cancer and many other diseases, such as heart disease and COPD , caused by smoking.
Data from the U. National Health Interview Survey show that people who quit smoking, regardless of their age, are less likely to die from smoking-related illness than those who continue to smoke. Regardless of their age, people who quit smoking have substantial gains in life expectancy, compared with those who continue to smoke. National Health Interview Survey also show that those who quit between the ages of 25 and 34 years live about 10 years longer; those who quit between ages 35 and 44 live about 9 years longer; those who quit between ages 45 and 54 live about 6 years longer; and those who quit between ages 55 and 64 live about 4 years longer 6.
Also, a study that followed a large group of people age 70 and older 7 found that even smokers who quit smoking in their 60s had a lower risk of mortality during follow-up than smokers who continued smoking. Quitting smoking reduces the risk of developing and dying from cancer and other diseases caused by smoking. Although it is never too late to benefit from quitting, the benefit is greatest among those who quit at a younger age 3.
The risk of premature death and the chances of developing and dying from a smoking-related cancer depend on many factors, including the number of years a person has smoked, the number of cigarettes smoked per day, and the age at which the person began smoking. Quitting smoking improves the prognosis of cancer patients. It also lowers the risk of pneumonia and respiratory failure 1 , 3 , In addition, quitting smoking may lower the risk that the cancer will recur, that a second cancer will develop, or that the person will die from the cancer or other causes 27 , 29 — Menu Contact Dictionary Search.
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