Introduction
Smoking is an activity during which an individual inhales and exhales some fumes that are produced by burning different plant products. The most common plant products used for smoking around the world include tobacco, marijuana, hashish, etc. Cigarettes are the most commonly used tobacco product around the world. Other products that are used for smoking include e-cigarettes, pipes, cigars, chewing tobacco, etc.
Tobacco smoking has been practiced by Native Americans for ages. Columbus was the first person to introduce smoking in Europe. Later it spread to other areas of the world in no time. Smoking has now become a global epidemic. Millions of people use smoking products around the globe on a daily basis. According to the stats of the CDC, around 34 million people smoke tobacco cigarettes in the US alone. Smoking is not only limited to adults as it is also spreading among middle and high school students. E-cigarettes are becoming famous among younger adults.
Smoking is the leading cause of preventable diseases all over the world. Smoking harms nearly all organs in the body. Cigarette smoking is the most important culprit in causing a number of health problems. However, smokeless tobacco and other smoking products are also harmful to health. In this article, we will discuss some major health effects of smoking. So, keep reading.
Major Chemicals in Tobacco
As mentioned earlier, tobacco cigarettes are the most widely used smoking products around the world. A large amount of harmful chemicals is present in tobacco smoke. It has been identified that tobacco smoke contains around 2000 to 4000 different chemicals. More than 60 carcinogens have been identified to be present in tobacco smoke.
A brief detail of important chemicals present in tobacco smoke is given below.
Carcinogens
Carcinogens are chemicals that have the potential to cause different cancers in the human body. Due to a large proportion of carcinogens in tobacco smoke, smoking is associated with cancer of different organs. The important carcinogens include tar, polycyclic aromatic hydrocarbons, benzopyrene, and nitrosamine.
Nicotine
It is an alkaloid present in tobacco leaves and smoke. This substance is not directly associated with different diseases caused by smoking. However, it is a highly addictive chemical. It is responsible for the smoking addiction in smokers. If it were not present in tobacco, it would have been very easy for smokers to quit smoking.
In addition to the addictive effect, nicotine is also responsible for the acute effects of smoking such as an increase in heart rate, respiratory rate, and cardiac output. It does so by binding to nicotinic acetylcholine receptors in the brain. This activity stimulates the release of catecholamines from sympathetic neurons and is responsible for increased sympathetic activity associated with smoking.
In addition to this, nicotine is also responsible for the promotion of different tumors. However, this effect is not well understood.
Mucosal Irritants
Tobacco smoke contains some chemicals that irritate the respiratory mucosa. These include phenol, formaldehyde, and nitrous oxides, etc. They can cause toxicity to cilia and are responsible for various respiratory conditions associated with smoking.
Carbon Monoxide
Carbon monoxide is a notorious gas present in cigarette smoke. This gas decreases the oxygen-carrying capacity of hemoglobin. Carbon monoxide has two hundred times more affinity to hind to hemoglobin as compared to oxygen. Thus, it kicks oxygen molecules from hemoglobin and is responsible for impaired oxygen transport and utilization. In a room full of cigarette smoke, carbon monoxide can cause death due to suffocation.
After discussing the major ingredients present in cigarette smoke, we will now discuss the health problems caused by it.
Lung Cancer
Lung cancer is the second most common cancer worldwide. It is the number one cause of cancer-related death all around the world. Smoking is considered to be the single most important risk factor related to lung cancer. Cigarette smoking is responsible for 80% to 90% of lung cancer-related deaths in the US.
Lung cancer is a condition characterised by an uncontrolled division of cells in the lower respiratory tract. Different types of lung cancer have been identified based on the origin of the malignant cells and their histologic features. Smoking is a risk factor for all types of lung cancers.
Mechanism
Recall that cigarette smoke contains various mucosal irritants that cause irritation of the respiratory mucosa. It can cause inflammation and increased mucus production in the bronchial tree.
Cigarette smoke also contains potent carcinogen as described earlier. These carcinogens can produce thousands of mutations in the DNA of smokers. These mutations later lead to the uncontrolled division of cells in the bronchial tree.
Exposure to some other pollutants also increases the risk of lung cancer. However, it has been seen that smoking increases the risk of carcinogenic influences of other pollutants.
Lung cancer is usually seen in workers who work in the asbestos industry, were exposed to asbestos in buildings, or uranium mines. It has been studied that the incidence of lung cancer among these workers who smoke is ten times higher as compared to those who do not smoke.
Similarly, smoking also increases the incidence of other cancers. It is due to the presence of a number of carcinogens in cigarette smoke. A brief detail of other cancers caused by cigarette smoke is discussed below.
Other Cancers
Lung cancer is not the only malignant condition caused by smoking. Rather, it can cause cancer in several other organs of the human body. Smoking is a major risk factor for cancers throughout the respiratory tract from the oral cavity to the alveoli.
Smoking can cause cancer of the oral cavity that can involve the mandible. It has a very low prognosis and death can occur in few years.
Smoking is a major risk factor for laryngeal carcinoma. Carcinoma of the larynx affects speech and deglutination. Cancer can arise in any part of the larynx.
Smoking can also cause carcinoma of the oesophagus. Carcinogens present in cigarette smoke enter the oesophagus and irritate the mucosa, thus causing cancer.
Pancreatic carcinoma can also arise due to cigarette smoking. In addition, carcinoma of the bladder can also arise in those who smoke.
The risk of developing cancer in the lungs and other organs is directly associated with the number of pack-years or the number of cigarettes smoked per day. As the number of cigarettes smoked increase, the risk of developing different cancers also increases.
In addition to cancers, smoking can cause other health problems that are mentioned below.
Respiratory Problems
The respiratory system is the most severely affected organ system due to smoking. It is because of the direct action of smoke on the respiratory mucosa. Different disease conditions of the respiratory system can arise in smokers. These include chronic bronchitis, emphysema, COPD, etc. A brief detail of these diseases is discussed below.
Chronic Bronchitis
It is a condition characterised by a productive cough that lasts for more than 3 months. It is highly associated with cigarette smoking.
Recall that cigarette smoke contains various mucosal irritants. In response to mucosal irritation, mucinous glands present in the bronchial mucosa undergo hypertrophy. This results in increased thickness of mucous glands relative to the overall thickness of the bronchial wall. The increased mucinous glands result in excessive mucus production.
The patient presents with an excessive productive cough due to increased mucus production. The patient also becomes cyanotic as carbon dioxide is trapped by mucus plugs within the airway. The partial pressure of oxygen in the airway decreases while the partial pressure of carbon dioxide is increased. The patient is at increased risk of infections.
One complication of chronic bronchitis is cor pulmonale. It is right-sided heart failure due to increased blood pressure in the pulmonary circuit. Hypoxia causes narrowing of pulmonary arteries and the pulmonary pressure increases. The right ventricle cannot pump against this increased pulmonary pressure. This leads to right-sided heart failure called cor pulmonale.
Emphysema
Emphysema is characterised by the irreversible widening of air spaces in the lungs. It occurs due to the destruction of walls between the alveoli. As the walls are destroyed, small air spaces coalesce to form large spaces that have decreased surface areas for gaseous exchange.
Cigarette smoke damages the lung parenchyma that results in the destruction of walls between the alveoli. The important factors responsible for the destruction of alveolar walls due to smoking are as follows.
- Protease-antiprotease Imbalance: Inflammation and irritation of lung parenchyma result in the release of protease enzymes from neutrophils and other inflammatory cells. These enzymes can damage the alveolar sacs. Alpha-1 antitrypsin is an anti-protease enzyme that neutralises the effect of proteases. Various chemicals in cigarette smoke lead to the increased production of proteases. The balance is disturbed leading to the destruction of alveolar air sacs.
- Oxidative Stress: Several substances in cigarette smoke are oxidants. These oxidants further enhance the damaging effects of smoke on parenchyma and contribute to the development of emphysema.
The patient with emphysema presents with dyspnea and cough with minimal sputum. Due to enlarged air spaces, the air is trapped in the respiratory tree. Patients have to make more effort to remove the trapped air. Thus, they have pursed lips due to prolonged expiration. The anteroposterior diameter of the chest also increases. It is referred to as barrel-chest. Weight loss is also seen in such patients. Cor pulmonale is a late complication of emphysema due to smoking.
COPD
Chronic obstructive lung diseases are a group of respiratory disorders that are characterized by blockage of air in the respiratory system. Air is trapped in the airways and cannot be expired easily. It may be due to mucus plugging of the airways, decreased elasticity, destruction of air sacs, or thickened and inflamed airways.
Smoking is one of the leading causes of COPD.
Cardiac Problems
Smoking has devastating effects on the cardiovascular system. Multiple studies show a direct association between smoking and coronary artery diseases. Smoking is a major risk factor for atherosclerosis that can later lead to myocardial infarction and stroke.
A brief detail of some major cardiac problems associated with smoking is discussed below.
Atherosclerosis
It is a disease in which blood vessels become narrowed due to a plaque resting on the tunica intima. A plaque is formed on the innermost layer of the blood vessels that protrudes into the lumen. In this way, it obstructs the blood flow and can lead to the hypoxic injury of the organ involved. Atherosclerosis usually involves large and medium-sized blood vessels.
Smoking is the major risk factor for the development of atherosclerotic plaque. Chemicals in cigarette smoke get absorbed into the blood during gaseous exchange within the lungs. They cause an injury to the vascular endothelium. Lipids from the blood leak into the endothelium and are oxidized here. These are taken up by the macrophages that lead to the formation of foam cells. Further inflammation and healing lead to the formation of atherosclerotic plaque having a lipid core and fibrovascular cap. Smooth muscle proliferation also occurs at the site of injury.
Complications of atherosclerosis include angina, myocardial infarction, stroke, pulmonary embolus, etc.
Myocardial Infarction
Myocardial infarction is characterized by permanent injury to cardiac myocytes and cell death. It occurs when the blood supply to one of the walls of the heart is completely cut. Hypoxia causes cell death in the cardiac tissues.
The most common cause of myocardial infarction is the rupture of an atherosclerotic plaque that leads to the formation of a thrombus within the coronary arteries. A thrombus is a blood clot that is formed within a blood vessel. When a thrombus is formed in one of the cardiac blood vessels, it causes complete occlusion of the involved artery. Blood cannot reach the tissues supplied by that artery leading to the death of cells in the involved region.
Smoking is one of the major causes of myocardial infarction worldwide. It is due to the fact that chemicals present in smoke cause endothelial injury leading to the formation of atherosclerotic plaque.
The patient presents with chest pain that radiates to the left jaw, left shoulder and arm, cold sweats, and shortness of breath. These symptoms are not relieved with rest. Myocardial infarction is a leading cause of non-cancer deaths around the world.
Stroke
Stroke is characterized by regional ischemic injury to the brain that results in focal defects. The neurologic symptoms depend on the part of the brain involved.
A stroke occurs when blood supply to one of the areas of the brain is suddenly stopped. Reduced or interrupted blood supply results in the death of brain cells.
Stroke can occur due to multiple causes, one being atherosclerosis. Smoking is a major modifiable risk factor for the development of stroke. Smokers are at a much higher risk of developing stroke as compared to those who do not smoke.
The patient of stroke presents an emergency with troubled speech, numbness of one side of the face, arms or legs, trouble walking, and decreased vision. A stroke is a medical emergency that must be managed immediately to save the patient from permanent impairment.
Gangrene
Another important health problem caused by smoking is gangrene. Gangrene is defined as the death of tissues due to lack of blood flow to the involved organs. Smoking can cause gangrene of the extremities that might need amputation for patient relief.
Gangrene occurs due to an interruption in blood supply. Recall that chemicals inhaled while smoking is toxic to blood vessels. They can cause endothelial injury leading to the formation of clots within the blood vessels. If a thrombus is formed in an artery supplying the extremities, interruption in blood supply causes tissues death and necrosis leading to gangrene.
An important vascular disease associated with smoking is Buerger disease. It is a disease in which vessels supplying the digits undergo vasculitis (inflammation of the vessel wall) that ultimately leads to necrosis. The patient presents with ulceration of the fingers and toes that causes gangrene. It finally results in the amputation of fingers and toes. This disease has a strong association with smoking and is treated by smoking cessation. Smoking cessation will not reverse the gangrene/amputation that has already occurred, but it will prevent the spread of the disease to the surrounding digits.
Pregnancy
Smoking has a huge impact on the health of both the mother and the baby. The harmful chemicals present in cigarette smoke increase the risk of complications during pregnancy. They can even put the life of the mother and fetus at risk. Some chemicals in smoke are teratogens that can cause developmental abnormalities in the developing fetus.
A brief detail of smoking-related pregnancy complications and developmental abnormalities is given below.
Fertility Problems
Smoking is known to decrease fertility in both males and females. Certain studies show that smokers are likely to have double the risk of developing fertility-related problems as compared to non-smokers. Cessation of smoking is advised by doctors to couples who are having trouble getting pregnant.
Ectopic Pregnancy
If an embryo implants in a place other than the uterus, it is termed an ectopic pregnancy. Nicotine present in cigarette smoke can cause ectopic pregnancy. Nicotine is a stimulant neurotransmitter that can cause contractions of the fallopian tubes. These contractions prevent the movement of the embryo into the uterus. Thus, it is implanted at a site other than the uterus. Fallopian tubes are the most common site of ectopic pregnancy. Ectopic pregnancy always ends in a miscarriage and can even put the life of the mother at risk.
Miscarriage and Stillbirth
Miscarriage is defined as the unexpected loss of a pregnancy during the first trimester. If it occurs after 20 weeks of gestation, it is called a stillbirth. If the mother is a smoker, chemicals present in smoke are considered to be the cause of miscarriage or stillbirth if any other obvious reason is not present.
Abruption of Placenta
The placenta is the only connection between the foetus and mother for the supply of oxygen and nutrition. Abruption of the placenta is a condition in which the placenta gets separated from the uterus and causes massive bleeding. It results in miscarriage or stillbirth and can even cause the death of the mother.
Developmental Abnormalities
Smoking during pregnancy can cause a number of developmental abnormalities and birth defects. It is due to the fact that certain chemicals present in smoke are teratogens that affect the development of tissues in the developing fetus. They can cause developmental delay, cerebral palsy, hearing and vision impairments, congenital heart defects, abnormal structure of the heart, cleft lip and palate, etc. Doctors strongly discourage smoking during pregnancy.
Summary
Smoking has become a habit of a large population in the world nowadays. Smoking is the number one risk factor for a number of diseases that can lead to the death of a person. Out of all the different forms of smoking that exist, cigarette smoking has the most devastating effects on human health.
Cigarette smoke contains a number of chemicals that are harmful to human health.
It contains carcinogens that can cause a number of cancers in the body.
Nicotine present in cigarette smoke causes addictive effects.
Mucosal irritants present in the smoke can cause respiratory problems.
Carbon monoxide decreases the oxygen-carrying capacity and can even cause death due to suffocation.
Smoking is the number one cause of lung cancer worldwide. Carcinogens present in the smoke cause DNA mutations that can lead to lung cancer.
Carcinogens in cigarette smoke can also cause cancer of other organs such as the oral cavity, bladder, pancreas, etc.
Cigarette smoke contains mucosal irritants that are harmful to the respiratory system due to their direct action on respiratory mucosa.
Chronic bronchitis is characterized by a prolonged productive cough that can cause dyspnea, blue bloaters, and even cyanosis.
Emphysema characterized by the destruction of alveolar walls is also seen in most smokers.
Smoking can also cause different cardiac problems. All these problems are due to atherosclerosis that involves the formation of plaque within the blood vessels. Atherosclerotic plaque later can lead to myocardial infarction, stroke, or gangrene.
Smoking during pregnancy has health impacts on the mother as well as the fetus. It can cause fertility problems, developmental abnormalities, ectopic pregnancy, placental abruption and much more.
References
- U.S. Department of Health and Human Services. A Report of the Surgeon General: How Tobacco Smoke Causes Disease: What It Means to You. Atlanta: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2010 [accessed 2012 May 10].
- U.S. Department of Health and Human Services. A Report of the Surgeon General: Highlights: Overview of Finding Regarding Reproductive Healthpdf icon. [PDF–542 KB]. Atlanta: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2010 [accessed 2012 May 10].
- U.S. Department of Health and Human Services. The Health Consequences of Involuntary Exposure to Tobacco Smoke: A Report of the Surgeon General: Secondhand Smoke: What It Means To You. Atlanta: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2006 [accessed 2012 May 10].
- U.S. Department of Health and Human Services. The Health Consequences of Smoking: What It Means to You. Atlanta: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2004 [accessed 2012 June 15].