Cigarette smoke contains about 4,000 different chemicals which can damage the cells and systems of the human body. At least 80 chemicals included can cause cancer. Most commonly found components in smoke include tar, arsenic, benzene, cadmium, formaldehyde, nicotine (a highly addictive chemical which inveigles a smoker into their habit) and hundreds of other poisons such as cyanide, carbon monoxide and ammonia.
Every time a smoker inhales, these chemicals are drawn into the body where they interfere with cell function and cause problems ranging from cell death to genetic changes which lead to cancer.
Tobacco smoking is probable cause for approximately 25 diseases. According to WHO figures, smoking is responsible for approximately five million deaths worldwide every year. It also contributes to many other diseases playing a major role in many more deaths.
Even the WHO states that its impact on world health isn't fully estimated. Smoking is a greater cause of death and disability than any single disease. By 2020, it is expected that the worldwide death toll will reach 10 million due to smoking. There are believed to be 1.1 billion smokers in the world, 800 million of them in developing countries.
Effects of smoking on the respiratory system
Smoking does excessive damage to the lungs as the poisons in smoke come into direct contact with lung tissue which increases the risk of lung cancer simultaneously. Studies have shown that men who smoke increase their chances of dying from the disease by more than 22 times. Women who smoke increase this risk by nearly 12 times [1]. Lung cancer is a difficult cancer to treat and long term survival rates are poor.
Chronic obstructive pulmonary disease or COPD is more common among smokers. This condition causes progressive and chronic airway inflammation and airspace remodelling resulting in irreversible lung damage, and makes it increasingly difficult for a person to breathe. Lung tissue from COPD patients displays oxidative DNA damage. Thousands of constituents, including several carcinogens, cytotoxic chemicals and potent oxidants in cigarette appear to target molecules and cellular pathways involved in cell death and lung inflammation leading to destructive alveolar remodelling in COPD [2].
Smokers those who may not have asthma are susceptible to wheezing similar to that experienced by asthma patients during an asthma attack due to the reaction to tobacco smoke.
And also, a smoker is likely to have a persistent cough from the time they start smoking.
Ciliated epithelium in the lung's airways move rhythmically to clear the mucus produced by the lungs to trap chemical and toxic substances. Tobacco smoke paralyzes these cilia, leading mucus accumulation in the lungs. Cigarette smoke also induces goblet cell growth increasing mucus production. Bronchospasm and increased phlegm production cause airway obstruction and decreased lung function resulting in poor physical performance [3].
Immediate1 and rapid effects on the cardiovascular system
Vasoconstriction
Nitric oxide (NO2) which is a vasodilator is reduced in smoking resulting vasoconstriction. It increases endothelin-1 which constricts vessels as well. Vasoconstriction may have immediate impact on patients whose blood vessels are already narrowed by plaques or partial blood clots, or in those who are in a hyper-coagulable state (in sickle cell disease). These individuals will be at an increased risk of stroke or heart attack [4].
Increased heart rate
The resting heart rate in a smoker is faster by two to three beats per minute than the resting heart rate of a non-smoker. Consumption of nicotine increases the heart rate, as soon as 30 minutes after smoking and also heart rate increases with increased nicotine consumption. Therefore, the heart of a smoker has to work harder than a non-smoker's heart. A heart that works hard can tire-out faster and may result in an early heart attack or stroke [5].
Increases blood pressure
Nicotine consumption increases blood pressure. Smokers have a higher systolic blood pressure than non-smokers [6]. Higher blood pressure requires the heart to pump harder in order to cope with the opposing pressure in the arteries wearing out the heart faster. The higher pressures also damage the kidneys where blood is filtered.
Long term effects on the Cardiovascular System
Excessive production and accumulation of low density lipo proteins in the blood vessels can cause narrowing of the vessels. Blood flow to the most vital organs, heart and brain can get impaired due to this causing them to fail. In smokers, nicotine increases the amount of LDL, triglycerides, cholesterol circulating in the blood vessels and decreases the amount of HDL available, increasing the risk for heart disease and stroke. Evidence suggests that smoking 1-5 cigarettes per day can implicate significant risk for a heart attack. Coronary heart disease (CHD) is one of the most important medical retributions of smoking. Unfortunately, sudden death will be the first sign of CHD and it is four times more likely to occur in young male cigarette smokers than in non-smokers. Women who use both cigarettes and oral contraceptives are at an increased risk of developing CHD by tenfold [7].
In atherosclerosis, fat and cholesterol form plaques which stick to the walls of an artery reducing the blood flow through it. Nicotine and other toxic substances from tobacco smoke damage the blood vessel walls, accelerating the formation of atherosclerotic plaques. It is found that, in atherosclerosis, the increased depositing of fat in the carotid artery depends on the duration of exposure to tobacco indicating that progression of atherosclerosis will be cumulative and irreversible, after some degree of exposure to smoke [8].
Cerebrovascular accident (CVA) or stroke causes brain damage leaving its victims with permanent disabilities. Smokers are twice as likely to have strokes and are almost a decade younger than non-smokers when they have them [9].
Smoking increases the risk of thrombosis in which a blood clot can get formed inside a blood vessel. In smokers, the rate of clot formation is dangerously high. Immediately after smoking, levels of thrombin, an enzyme that causes the blood to clot, are elevated in smokers which may lead to stroke. The role of fibrinogen, coagulation factors, and impaired fibrinolysis, possibly involve in thrombosis. Studies have implicated that smoking has an effect on various abnormalities of coagulation [10].
Effects on the brain
Nicotine directly affects on brain causing the smoker to addict into it. In addition to the chemical dependency, cigarette smokers suffer from higher rates of behavioural problems and stress. Smoking increases the stress. In contradictory to the general belief, smoking does not relieve stress. A smoker has a higher degree of stress than someone who does not smoke [11]. The feeling of relaxation that smokers experience while they are smoking is actually a return to the normal unstressed state that non-smokers experience all the time.
When compared to non-smokers, brain cells of smokers, specifically brain cell receptors have been shown to have less dopamine receptors [12]. Dopamine receptors are specific cell receptors found in the brain is believed to play an important role in addiction. Dopamine is naturally released in certain behaviours like eating, drinking and copulation. A feeling of relaxation is experienced when dopamine is released. One of the leading hypotheses regarding the mechanism of addiction theorizes that exposure to nicotine initially increases dopamine transmission, subsequently decreasing the function and number of dopamine receptors as well. The initial increase in dopamine activity due to nicotine results in the initial pleasant feelings for the smoker, but the subsequent decrease in dopamine leaves the smoker craving for more cigarettes. Long term smoking may continue to change brain chemistry decreasing dopamine receptors and thus yielding a more intense craving for cigarettes. These changes may be permanent. In addition it will affect other brain functions such as memory and intelligence because of the role played by these receptors in cognitive functions.
Studies have shown that smoking can lead to neuro inflammation, which can further lead to complications like multiple sclerosis. Neuro inflammation could occur due to NNK, a compound commonly found in all tobacco products. This compound which is a pro-carcinogen, becomes carcinogenic after it goes through metabolic processes in the body. It induces the white blood cells to attack brain cells, leading to significant neurological damage. Even though NNK does not seem to have a direct effect on the brain cells, it can lead to neuro inflammation [13].
Effects on the reproductive system
Use of tobacco affects every system involved in the reproductive process. Smoking remains a major cause of new-born deaths, early births and babies born with low birth weight even though smoking rates amongst pregnant women has fallen in recent years. Researchers have found that smoking is associated with:
5-8% premature births
13-19% cases of low birth weight in babies carried to full term
5-7% preterm-related deaths
23-34% deaths caused by sudden infant death syndrome (cot death)
In the UK, smoking in pregnancy causes up to 5,000 miscarriages, 300 perinatal deaths and around 2,200 premature births each year [14].
Smoking can have a negative impact on female fertility. Women who smoke take longer to conceive than women who do not smoke. Tobacco consumption affects uterine receptivity reducing the chances of conceiving in a smoker fall by 10 to 40% per cycle. Women who smoke take a longer duration to conceive than non-smokers [15].
It has been found that smoking reduces the success rates of fertility treatment. In assisted reproductive treatments, women who smoke have demonstrated significant negative effects [16]. Furthermore in case of women undergoing in vitro fertilisation (IVF), exposure to second hand smoke can be as harmful as smoking itself.
Moreover, maternal smoking may have a negative impact on the fertility of the off-spring too. The number of germ cells and somatic cells has been shown to reduce in babies born to mothers who smoked during pregnancy [17].
Foetal growth and birth weight
Babies born to women who smoke are on average 200-250 grams lighter than babies born to non-smoking mothers. Research suggests that cigarettes can impede the blood flow in the placenta restricting the amount of nutrients that reach the foetus [18].
Other risks of smoking during pregnancy
Off springs of smokers are at a greater risk of congenital defects including an increased risk of oral clefts.
Maternal smoking and early childhood exposure to second hand smoke may cause emphysema in adulthood.
Babies born to mothers smoking during pregnancy have shown high foetal testosterone which can leads to autism, attention deficit hyperactivity disorder (ADHD), conduct disorder and antisocial behaviour.
The risk of psychiatric morbidity is significantly higher in the children of mothers who smoke during pregnancy. Maternal smoking has been associated with an increased risk of learning difficulties.
Smoking cigarettes may contribute to insufficient breast milk production. Milk production is reduced by more than 250 ml per day compared with non-smoking mothers.
Smoking is associated with early onset of menopause with the natural menopause occurring up to two years earlier in smokers.
Male fertility & sexual Impotence
Cigarette smoking affects male fertility. Males who smoke have a lower sperm count than non-smokers, and their semen contains a higher proportion of deformed sperms. Semen of smokers has been found to reduce the motility of sperms due to the by-products of nicotine present in smoke.
Evidence suggests that erectile dysfunction or impotence has a significant association with smoking. Nicotine and other vasoconstrictors present in smoke close down the blood vessels of the penis, leading to erectile dysfunction [19].
Immediate and Rapid Effects on the Gastrointestinal System
The gastrointestinal system which comprises from the mouth to the anus is easily affected by tobacco smoke.
Gastroesophageal Reflux Disease
Heartburn and acid regurgitation from the stomach are the symptoms of the disease. The body prevents these occurrences by secreting a basic medium to neutralize digestive acids under normal circumstances. But in smokers' the basic medium is less neutralizing than non-smokers as nicotine markedly reduces the secretion of water and bicarbonate providing a longer period of time to irritate the oesophagus by gastric acid [20]. Regular occurrence may cause ulcerations of the lower oesophagus, called Barrett's oesophagus which may develop into oesophageal cancer, and has a poor prognosis in most patients.
Peptic Ulcer Disease
Peptic ulcers are self-digested holes extending into the muscular layers of the oesophagus, stomach, and a portion of the small intestine. Excessive acid production and injuries to the inner protective layer is the cause for these ulcers. Mucus produced in the stomach protects the muscular layer from self-digesting. Cigarette smoke inhibits mucous production in the stomach unlike in the lungs. Smoking hinders gastrointestinal wound healing, resulting in peptic ulcer formation.
Periodontal Diseases
Smoking quickly changes the blood supply, immune response and healing mechanisms of the mouth allowing bacteria to form colonies in the mouth, resulting in the rapid initiation and progression of infections. Furthermore, gum inflammation and tooth decay take place due to the bacterial plaques formed. In addition, smoking increases tooth and bone loss accelerating deep gum pocket formation [21].
Halitosis
This is another word for bad breath. Bad breath, smelly hair and clothes, and yellow teeth are among the most immediate and offensive effects of smoking. The most immediate way that cigarettes cause bad breath is by leaving smoke particles in the throat and lungs
Effects on the kidneys
Glomerular filtration rate increases
Smoking increases heart rate and blood pressure, due to the effects of nicotine. Therefore, benefits of certain drugs for high blood pressure, such as beta blockers, are less in smokers. Smoking alters hemodynamic properties of the renal system. The increased blood pressure causes damage to the glomeruli, the filters in the kidney. As the glomerular filtration rate (GFR) increases, so does the amount of kidney damage. Smoking also affects the renal artery [22].
Tobacco chemicals and the kidneys
According to the researches carried out, over time, arsenic in cigarette smoke can lead to acute tubular necrosis with acute renal failure. Cells of the tubules carrying urine to the ureters begin to die due to deficit of oxygen leading to acute renal failure loosing kidney function. Inhaling the smoke allows chemicals to pass into their urine inducing formation of cancerous cells in the kidneys, leading to kidney cancer.
Immediate and Rapid Effects on the Immune System
Many components of cigarette smoke, including nicotine, might have immune modulatory effects. Nicotine is the main immune suppressive component in cigarette smoke, which inhibits both the innate and adaptive immune responses [23].
Otitis Media
The middle ear is very vulnerable to infection. Children who are exposed to environmental tobacco smoke are more prone to get ear infections than those are not. Continued exposure to tobacco smoke may result in persistent middle ear infections leading to hearing loss.
Sinusitis
The lining of the sinuses consists of finger-like hairs. These hairs clear mucus and foreign substances and prevent accumulation of mucus and infections. Cigarette smoke slows or stops the movement of these hairs, resulting in inflammation and infection.
Rhinitis
This is an inflammation of the inner lining of the nasal passages. In rhinitis, the same mechanism is involved as in sinusitis. Smoking causes immediate and long-lasting rhinitis.
Pneumonia
In pneumonia, fluid accumulates deep in the lung, making it an ideal place for bacteria to lodge. Smoking increases the body's susceptibility to the most common bacterial causes of pneumonia. If left untreated, it can lead to pus pocket formation, lung collapse, blood infection, and severe chest pain.
Immediate and Rapid Effects on the Metabolic System
Micronutrient Deficiencies
Smoking interferes with the absorption of a number of micronutrients, especially vitamins C, E, and folic acid resulting in deficiencies of these vitamins.
Oxidative Damage
Oxidants are active particles that are by products of normal chemical processes. These particles are usually destroyed by antioxidants, including vitamins C, E and A. When oxidation outruns anti-oxidation, oxidants directly damage cells and change genetic material, Smoking increases the number of circulating oxidants reducing the levels of antioxidants such as alpha-tocopherol, the active form of vitamin E, contributing to the development of cancer, heart disease, and cataracts [24].
Cancers associated with smoking
Smoking greatly increases the risk of cancers. Smokers are much more prone to get cancer than non-smokers. Tobacco smoke contains more than 70 different cancer-causing substances. When these chemicals enter the lungs they spread around the rest of the body damaging DNA and changing important genes causing cancer by making cells grow and multiply out of control.
Lung Cancer
A smoker is at an increased risk of developing lung cancer. Cigarette smoking is almost entirely responsible for small cell lung cancer, which is the most common type of lung cancer. This type of cancer quickly spreads to other organs, including bones and the brain. Wheezing, bloody phlegm, chest pain and coughing are common signs of lung cancer [25].
Pancreatic Cancer
Smoking is a risk factor for pancreatic cancer, which often has a poor prognosis. Usually it spreads quickly and is often not diagnosed until it has progressed significantly.
Mouth, Oesophageal, Larynx and Throat Cancer
Mouth, oesophageal, larynx and throat cancer are all caused by smoking. Weight loss, trouble eating, sore throat, abnormal breathing sounds, open sores, tumorous growths and fatigue are all symptoms of these types of cancers.
Stomach cancer
Nicotine and other chemicals in tobacco smoke changes production and composition of gastric secretions important to stomach function leading to stomach cancer.
Kidney and bladder cancers
The chemicals in tobacco smoke are excreted from the body via urine once metabolized. Urine of smokers show increased mutagenic activity due to these metabolized products. Therefore, when they come into contact with cells lining the organs and structures, have the potential to alter the DNA of these cells.
Cervical cancer
Cervical cancer is the third most common cancer in women worldwide. Persistence of high-risk Human Papilloma Virus (HPV) infection is the strongest risk factor for cervical cancer and it is thought that smoking might interact with the HPV by increasing the risk for persistent infection, or by increasing the rate at which malignancy develops [26].
Acute myeloid leukemia
Cigarette smoking is associated with an approximately 50% increase in leukemia risk. In acute myeloid leukaemia, an excessive number of cancerous white blood cells are formed diminishing normal blood cell activity. Contents of tobacco smoke including benzene, the radioactive metals polonium-210 and lead-210 are known to causes for leukaemia in humans. These radioactive metals emit ionising radiation causing changes in the genetic matter. Smokers have a 30-50% higher risk of developing acute myeloid leukaemia than non-smokers [27].
Liver cancer
Liver is the main organ where the contents of tobacco smoke are metabolised. These products include various carcinogens which could possibly lead to cellular damage and eventual development of cancer. Carcinogens may directly act on the genes of the hepatocytes.
Colorectal (bowel) cancer
Smoking may be one of the avoidable risk factors that cause colorectal cancer. Tobacco carcinogens are known to affect DNA in the cell lining of the colon.
Second hand smoke
Second hand smoke (SHS) or environmental tobacco smoke includes a mixture of air diluted smoke from the burning tip of a cigarette & the exhaled 'mainstream' smoke, exhaled by the smoker. Inhaling SHS is an unavoidable consequence of being in a smoke filled environment.
Health effects of exposure to second hand smoke
Children are specially vulnerable to SHS as they breathe more rapidly & they inhale more pollutants per pound of weight. Children exposed to SHS have an increased risk of having below mentioned health effects.
Asthma
Lower respiratory infection
Bronchitis
Middle ear disease
Bacterial meningitis
Sudden infant death syndrome (SIDS)
General reduced respiratory function (cough wheeze)
This also affects children's mental development. Children even at low levels of smoke exposure have deficiencies in reading and reasoning skills. Evidence suggest that exposure to SHS can lead to increased school absenteeism. Considering the risk of having lung cancers, children who are exposed to SHS on a daily basis grow up with more than triple risk of having lung cancers in later life.
There is a major risk of developing emphysema in adulthood as the lungs may not recover completely from the effects of early life exposure to passive smoking.
Parental exposure to second hand smoke tends to have adverse impacts on the health of the foetus resulting following consequences
Low birth weight
Premature birth
Spontaneous abortion
Still birth [28]
Conclusion
Tobacco use imposes enormous public health and financial costs, costs that are completely avoidable. Cigarettes are responsible for approximately one in every five deaths around the world.
This report illustrates the harmful impact of smoking on nearly every organ in the body. It emphasizes the necessity of being vigilant in prevention of smoking. People have made significant progress in their fight against smoking, but we still have much more work to do.
Smoking causes cancers in almost all parts of the body. Smoking diminishes health generally and adverse health effects begin before birth and pursue across the life span. The believing we do something when we do nothing is the first illusion of tobacco. So, it is easier to stay out of it than struggling to get out.
Acknowledgement
I am deeply indebted to Dr. R. S. J. Lenora for the advice and guidance received from him in completing this work.
