Tobacco is extracted from around 65 known species of the tobacco plant of which the one that is grown commercially and widely as a source of tobacco is Nicotiana tobaccum. The growing use of tobacco is a cause of great concern around the world due to its serious effects on health.

Non-communicable diseases (NCDs) like ischemic heart diseases, cancers, diabetes, chronic respiratory diseases are the leading causes of death globally and associated with tobacco use. Available data from WHO demonstrate that thirty-eight million people die each year from NCDs, of which nearly 85% of NCD deaths occur in low- and middle-income countries.

Composition of Tobacco

Tobacco products contains around 5000 toxic substances. Most important and dangerous constituents are:

  1. Nicotine
  2. Carbon Monoxide
  3. Tar

Nicotine is the major cause of the predominant behavioral effects of tobacco. It is a poisonous substance leads to addiction. Nicotine influences and reinforces all tobacco-use behavior. After absorption, nicotine travels rapidly to the brain, in a matter of seconds, therefore, the psycho-active rewards associated with smoking occur quickly and these rewards are highly reinforced. Nicotine binds to the receptors in the brain where it influences the cerebral metabolism. Nicotine is then distributed throughout the body, mostly to skeletal muscles. Development of tolerance to its own actions is similar to that produced by other addictive drugs.

Carbon mono-oxide reduces the amount of oxygen blood can carry and causes shortness of breath.

Tar is a sticky residue which contains benzopyrene, one of the deadliest cancer causing agents known.

Other compounds are carbon dioxide, nitrogen oxides, ammonia, volatile nitrosamines, hydrogen cyanide, volatile sulfur containing compounds, volatile hydrocarbons, alcohols, aldehydes and ketones. Some of these compounds are known to cause cancers of various organs of the body.

Mechanism of action

Nicotine has structural similarity to a body neuro-transmitter acetylcholine (Ach) which conveys information from one neuron to another. Acetylcholine is an important neurotransmitter involved in systems concerned with mental and physical arousal, learning and memory, and several aspects of emotion. There are also other receptors for acetylcholine in the body, apart from the ones at synapses. They are also found at the junction of nerve and muscles and nerves and certain glands. Acetylcholine receptors throughout the body are traditionally classified as nicotine receptors (those that respond to nicotine) and muscarine receptors (those that respond to muscarine). The ability of nicotine to combine with acetylcholine-receptors means that it can exert actions like acetylcholine at all synapses where nicotine acetylcholine-receptors (nAChRs) are present and can trigger impulses.

Forms of tobacco intake

  1. Cigarette – Most common and most harmful
  2. Bidi – most commonly used form in India
  3. Cigar –
  4. Hookah (Hubble bubble)
  5. Sheesha
  6. Tobacco chewing
  7. Kreteks (clove cigarettes)
  8. Snuff – Moist & Dry
  9. E-cigarette – recent intruder in the list

When non-smokers are exposed to smoke containing nicotine and toxic chemicals emitted by smokers it is called passive smoking or exposure to second hand smoke.

Risk factors for tobacco initiation

Following factors influence the predilection for tobacco use:

1.Biological:

  • Developmental aspects of adolescent age group include (a) establishing independence and autonomy, (b) forming a coherent self-identity and (c) adjusting to psycho-social changes associated with physical maturation.
  • Gender: tobacco use is more common among males in India.

2.Psychological:

Low emotional stability and risk taking behavior are more common in tobacco users. Existence of some mental disorders also increases the risk of tobacco use.

3.Social and Environmental:

Parental influence, lower education status, attraction towards role models, cultural practices, etc.

Consequences of tobacco use
Various effects of tobacco use are as follows:

  1. Economic loss
  2. Health loss
  3. Environmental loss

Tobacco is considered as a major behavioral risk factor for non-communicable diseases one of the leading causes of death. Treatment of cardiovascular diseases and cancer imposes maximum financial burden on the individual and family. For cultivation of tobacco crop forests are destroyed. Burning of tobacco produces number of toxicants in environment. Manufacturing, packaging and transportation also cause environmental pollution.

Cancers associated with tobacco
Tobacco is also associated with cancer of respiratory tract, lung, upper gastrointestinal tract, liver, pancreas, kidney, urinary bladder, oral cavity, nasal cavity, cervix, etc. Smokeless tobacco (chew tobacco, snuff etc.) is a major cause of cancer of the oral cavity.
Risk of developing cancer increases with:

  1. Duration of use of tobacco
  2. Number of tobacco product use per day
  3. Degree of inhalation

Cardiovascular diseases

  1. Stroke is vascular disease of the brain where tobacco causes either constrict of blood vessels or rupture leading to loss of consciousness and paralysis.
  2. Tobacco affects coronary vessels of the heart leading decrease of blood supply or death of heart muscles which is known as ischemic or coronary heart disease. This in turn causes cardiac arrest.
  3. Smoking acts synergistically with other risk factors like high cholesterol and blood pressure to increase the risk of Coronary Heart Diseases (CHD).

Respiratory Diseases

  1. Chronic Obstructive Pulmonary Disease: It includes chronic bronchitis and emphysema
  2. Asthma: Smoking is associated with acute attacks of asthma
  3. Tuberculosis

Effect on pregnancy and its outcome

  1. Bleeding during pregnancy
  2. Ectopic pregnancy
  3. Miscarriage/abortion
  4. Premature delivery of baby
  5. Stillbirth
  6. Abnormalities of the placenta

Effects on newborns and childhood
Maternal tobacco use during pregnancy and exposure of child to second hand smoke in childhood is known to be a risk factor for following conditions:

  1. Maternal smoking is associated with congenital malformations in baby like orofacial clefts, clubfoot and atrial-septal defects.
  2. Increased risk of allergies
  3. Higher blood pressure in childhood
  4. Increased likelihood of obesity
  5. Stunted growth
  6. Poorer lung function
  7. Increased likelihood of developing asthma

Miscellaneous

Following conditions are known to worsen if case of tobacco use:

  1. Rheumatologic conditions: Rheumatoid arthritis
  2. Kidney damage
  3. Eye Disease: Age-Related Macular Degeneration
  4. Dental Disease like caries
  5. Diabetes
  6. Inflammatory bowel diseases
  7. Erectile dysfunction

References

  1. WHO. Non-communicable Diseases Country Profiles.  2014. Available from  http://apps.who.int/iris/bitstream/10665/128038/1/9789241507509_eng.pdf.
  2. WHO. NCDs country profile. 2010. Available from http://www.who.int/nmh/countries/ind_en.pdf.
  3. WHO. Available from http://who.int/mediacentre/factsheets/fs339/en/.
  4. Talhout R, Schulz T, Florek E , Benthem J, Wester P, Opperhuizen A. Hazardous Compounds in Tobacco Smoke. Int. J. Environ. Res. Public Health 2011;8:613-28.
  5. Department of Health and Human Services. The Health Consequences of Smoking—50 Years of Progress: A Report of the Surgeon General. 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, 2014

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