Smoking is one of the major causes of deaths and disabilities, killing millions of people every year. Tobacco cigarettes, apart from nicotine, contains other toxins which are highly hazardous. Over the last decade or so, electronic cigarettes (e-cigarettes) have gained much attractiveness, mainly because of the nonexistence of tobacco and other toxic raw materials. Its usage has dramatically increased in USA and UK after bans on conventional smoking at public places.

E-cigarettes afford nicotine in aerosol form which is inhaled through mouth into the lungs. Pure nicotine along with some flavors, is present in solution form, usually in propylene glycol, vaporized by a heating filament, which is activated manually or through suction. Let’s first know what nicotine is.


Nicotine is an alkaloid, isolated from the leaves of Nicotiana tobaccum (tobacco). It is a potent stimulant and an acetylcholine receptor antagonist. The stimulant properties of this alkaloid make it an addictive drug. However, these properties of nicotine work at low doses. 50-60 mg of nicotine may prove fatal for human beings. Cigarettes contain 1-3 mg of nicotine and chain smokers often smoke a lot in one day, without being killed. The reason is that nicotine is not very stable and gets metabolized once it enters the body. The half-life of nicotine is 1-2 hours and is metabolized in the liver by CYP 2A6 enzyme to cotinine, a major metabolite of nicotine.

It has been studied that cotinine does not retain the nicotine side effects but enhances concentration, focus and memory in patients of Alzhiemer’s and schizophrenia. Nicotine crosses the blood brain barrier within seconds of inhalation and stimulates the release of acetylcholine, dopamine, β-endorphin, serotonin and other neurotransmitters which activate the brain. Nicotine has been associated with cardiovascular diseases and impaired fetal development in pregnant women. It has been thought of as a carcinogenic agent but has not shown any of such effects on human body.

From the discussion, it seems that nicotine or its metabolite, cotinine are not killers at all. Then what is the main cause of so many deaths due to smoking? The answer may be, the contaminants present in the cigarettes.

E-cigarettes are free from those contaminants but the flavors or other additives used may have some side effects. As far as the solvent is concerned, it has been observed to cause upper airway irritations. Other studies have revealed that the during vaping sessions, the particulate matter, metals, volatile organic compounds, and polyaromatic hydrocarbon contents increased indoor, which may be inhaled through passive vaping and cause health problems. FeNO levels have seen to be increased during vaping sessions. FeNO is an important biomarker for airway inflammation and asthma. The amount of nicotine in e-cigarrete claimed by the manufacturers may also vary and thus the smokers get an unusual quantity of nicotine.

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