Health Impacts of Smoking
Smoking is one of the leading preventable causes of disease and avoidable premature deaths, globally.
The risks of smoking tobacco are well documented[16].Through the process of combustion, more than 7,500 individual chemicals (150 chemicals known to be harmful and 60 chemicals known to be carcinogens) are produced in cigarette smoke. It is these chemicals produced through combustion that cause disease and death[11],[12],[13].
Smoking Attributable Diseases
Smoking can cause numerous diseases and cancers. According to the American Lung Association, the four major smoking-related diseases are chronic obstructive pulmonary disease (COPD), heart disease and stroke, which are cardiovascular diseases (CVD), and cancer (specifically lung)[17].
Chronic Obstructive Pulmonary Disease (COPD)
COPD is a collection of underlying conditions including chronic bronchitis and emphysema[18].
Chronic bronchitis is a persistent cough, occurring as a result of increased production of mucus in the airways. The condition is made worse by the loss of hair-like structures which normally transport dust and mucus out of the lungs. This is exacerbated due to swelling and constriction of the airways, further impacting on the ability of air to move freely in and out of the lungs.
Emphysema is a destructive disease affecting the alveoli (air sacs) within the lungs. These air sacs form the surface where oxygen enters the body. In emphysema, inflammatory processes lead to the destruction of the scaffolding of the lungs. As such, the air sacs, which usually resemble bunches of grapes, merge into larger structures. This dramatically reduces the lung surface area, rendering the individual patient unable to breathe well as more and more of the lung becomes affected.
Causes of COPD
COPD can be caused by chronic exposure to a lung irritant, smoke, dust, noxious gases, smoke from fires, and metal particles.
Cardiovascular Disease (CVD)
CVD is a condition affecting the blood vessels resulting in the reduction in blood flow to organs or tissues such as the limbs, brain, or the heart itself. The reduction in blood flow occurs due to narrowing and hardening of the oxygen carrying arteries[19].
The narrowing of the blood vessels or atherosclerosis occurs due to fat deposition. Irritation makes the vessels stickier to the white blood cells which enter the vessel walls to ingest the deposited fat. The narrower part of the blood vessel can become damaged as blood must pass more quickly through the smaller gap and a clot may form, further reducing blood flow.
Reduction in blood flow can prevent sufficient blood, and therefore oxygen, reaching an organ or tissue leading to pain, such as angina in the case of the heart. Severe blockage can occur suddenly if pieces of a clot are dislodged causing downstream blockages which can lead to heart attack or a stroke if the brain is affected.
Causes of CVD
Causes of CVD include smoking, diet, obesity, diabetes, physical inactivity, genetic susceptibility to high cholesterol, raised alcohol consumption and high blood pressure.
Cancer
Cancer is a term that describes a group of diseases that occur as the result of unregulated growth of abnormal cells, ultimately causing critical damage to the body’s tissues and organs[20]. The damage from a cancer is not limited to the initial site of growth, as it may move to elsewhere in the body. Normally, all cells within the body are strictly controlled by the instructions preserved in the DNA within our genes.
If these genes are changed by direct damage to DNA or other mechanisms, and those changes give the affected cells a selective advantage, these cells can grow and reproduce uncontrollably and give rise to a tumour. Damage to the DNA happens all the time at a low rate within our bodies because of exposure to environmental agents and due to endogenous processes. The cells in the body can usually identify and correct these mistakes or eliminate the damaged cells. Cancer can occur if damage to the DNA is too rapid to fix or if the correction process is prevented.
Causes of Cancer
Several environmental factors are strongly linked with various types of cancer. Risk factors for cancer include smoking, alcohol consumption, diet, physical inactivity, and exposure to environmental pollution and radiation.
Cigarette smoke is a source of chemicals which both directly damage the DNA within the cells of the body and also hamper its repair. Cigarette smoke enters the body via the mouth and lungs, and adult smokers have a highly elevated risk of developing lung cancer. The chemicals from the inhaled smoke are also carried around the body by the blood, and smoking has been associated with cancers in most organs of the body. Cancer Research UK states that smoking causes at least 15 different types of cancer[21].
Smoking Attributable Mortality
According to the World Health Organization (WHO), smoking is the leading preventable cause of premature death[22]. The prevalence of smoking is declining worldwide; however, the absolute number of adult smokers has increased over the past 30 years[23]. Quitting smoking reduces the relative risk of numerous smoking-related diseases and increases life expectancy for former adult smokers[24].
Sources
A full list of references for this page can be found in the section 11. References.
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