Smoking and Cancer

Smoking And Cancer

Smoking is the most important preventable cause of cancer in the world.

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Smoking is the most important preventable cause of cancer in the world.

Cigarette smoking is harmful to the smoker and also nonsmokers who are exposed to the smoke. Smoking has negative health impacts on people at all stages of life. It harms unborn babies, infants, children, adolescents, adults and seniors.

Smoking harms almost every organ of the body and diminishes a person’s overall health. The chances of smokers being affected by cancer are very high. 

Several studies have shown that the various carcinogens in the cigarette smoke cause cancer. Cancers are most likely to occur in organs like lungs and oral cavity, which come into direct, contact with smoke. 

Cigarette smoke contains about 4,000 chemical agents, out of which 70 substances are carcinogenic. Some of these harmful substances are - carbon monoxide, tar, arsenic, cyanide, benzene, formaldehyde, methanol, acetylene, ammonia, lead etc.

When the carcinogens in cigarette smoke are absorbed and spread through the human body, smoking causes cancer at various distant sites. Smoking causes many types of cancer, including cancers of the lung, esophagus, larynx, mouth, throat, kidney, liver, bladder, pancreas, stomach, cervix, bowel and also acute myeloid leukemia. 

The risk of developing cancer is related to:
Number of cigarettes smokedDuration of smokingAge at which smoking is startedThe type of cigarettes smoked

Types of smoking:

Active smoking - Active smoking is the intentional inhalation of smoke using cigarettes and cigars.Passive smoking - Passive smoking is when a non-smoker breathes other people's smoke. It is also called as involuntary or secondhand smoking.

How Does Smoking Lead to Cancer?

Tobacco smoke contains about 70 carcinogenic (cancer causing) substances. Some of these harmful substances are - carbon monoxide, tar, arsenic, cyanide, benzene, formaldehyde, methanol, acetylene, ammonia, lead etc. The cancer-causing agents (carcinogens) in tobacco smoke enter the lungs on inhalation. From there they spread to the rest of the body and damage important genes. They mutate the DNA that controls the growth of cells, causing them to grow abnormally or to reproduce in a haphazard manner. The carcinogen carbon monoxide binds to hemoglobin in red blood cells. This prevents the affected RBCs from carrying a full load of oxygen. The carcinogen benzo[a]pyrene binds to cells in the airways and major organs of smokers. Smokers have lower levels of antioxidants in their blood, which prevents the damaged cells from repairing themselves. Smoking affects the function of the immune system and may increase the risk for respiratory and other infections.

Which Cancers are Caused due to Smoking?

Smoking harms almost every organ of the body and has negative health impacts on a person’s overall health at all stages of life. Smoking is the leading cause of cancer and causes many types of cancer. Cigarette smoking increases the risk of the cancer in the following organs - Lung cancer Larynx cancer Esophageal cancer Mouth or oral cancer Stomach cancer Pancreatic cancer Colorectal cancer Liver cancer Bladder cancer Kidney cancer Cervix cancer Breast cancer Non Hodgkin's tumors Blood cancers like Acute Myelogenous Leukemia (AML) Acute Lymphocytic Leukemia (ALL)

Passive Smoking

A non-smoker who breathes other people's smoke is called passive smoking. It is also called as involuntary or secondhand smoking. Passive smoking is particularly dangerous as the passive smoker inhales - The smoke from the burning tip of the cigarette (side stream smoke) The smoke that has been exhaled by the smoker (mainstream smoke) Passive smoking consists mainly of side stream smoke. Side stream smoke contains much higher levels of many of the poisons and cancer-causing chemicals in cigarettes and is about four times more toxic than mainstream smoke. Second hand smoke comprises of up to three times more carbon monoxide, five times more cadmium and about 15 times more benzene. The various chemicals and carcinogens in the cigarette smoke can cause smoking related diseases similar to ones acquired by actual smoking. Effects of passive smoking - Effects of passive smoking depend on the exposure levels and duration of exposures. It can be immediate or late effects. The chemicals in the cigarette smoke can cause irritation of the eyes, headache, cough, sore throat, and nausea. Studies have shown that in patients with asthma, exposure to smoke can reduce the lung function significantly and new cases of asthma can be induced in children who are exposed to cigarette smoke. A major review by the Government-appointed Scientific Committee on Tobacco and Health (SCOTH) stated that passive smoking is the cause of lung cancer and ischemic heart disease in adult non-smokers, and the cause of respiratory disease, cot death, middle ear disease and asthmatic attacks in children. Passive smoking increases the risk of getting frequent lower respiratory tract infections in children. Passive smoking during childhood predisposes children to develop cancer as adults. Exposure to passive smoking during pregnancy can lead to the birth of low birth weight babies.