Medical experts praise e-cigarettes or vaping as the best alternative for people who want to quit smoking.However, some governments disagree on the use of the vaping fluid, a liquid chemical that usually consists of nicotine, propylene glycol, and flavorings.Not all vaping fluid contains nicotine, though.

In Australia, the government banned the use and purchase of vaping fluid because it contains liquid nicotine, and liquid nicotine is classified as a poison by the country's Therapeutic Goods Administration.However, tobacco smoking remains legal in the country.

"For those smokers who won't or can't quit, the next best thing would be to switch to vaping.While the long-term risks are not entirely clear, there is broad consensus now that they are much less harmful than tobacco cigarettes.This [vaping] might offer another option to get to a smoke-free life.You do want policy measures encouraging people to move away from traditional smoking and you want to protect those that don't smoke, like young people." said Hayden McRobbie, a professor at Queen Mary University.

Advocates of smoking alternatives expressed the larger point of vaping - a harm reduction tool to help smokers quit.But the use of e-cigarettes or vaping has been subjected to regulations reviewed in many countries.

- In Austria, e-cigarettes and cartridges containing liquid nicotine are classified as medical devices and medicinal products, respectively.

- In Belgium, a royal decree legalized the sale of cartridges that contain nicotine, provided that cartridges are not more than 2 ml and liquid nicotine should not exceed the 20 mg per milliliter limit.The sale is prohibited to minors under the age of 16 years old.

- In Croatia, a law has been passed that classified e-cigarettes as tobacco products.Vaping is prohibited in all public enclosed facilities and public buildings.Advertising of such product is also prohibited by the law.

- In Hong Kong, nicotine-based e-cigarettes are classified as Type I Poison under the Pharmacy and Poisons Ordinance.The sale or possession of such materials is punishable by law with up to two years of imprisonment.

- In Singapore, e-cigarettes are prohibited under the Section 16 (1) of the Tobacco (Control Advertisements and Sale) Act.

- In Japan, e-cigarettes that contain nicotine have been banned since 2010.E-cigarettes that are nicotine-free are sold to minors and adults because no regulation exists for it.

- In South Korea, a heavy tax is imposed on the sale and use of e-cigarettes.

Health Dangers of Vaping

Whether or not the e-cigarette cartridge contains nicotine, the other chemical that makes up the vaping fluid can still endanger the user's health.Based on a study conducted by researchers at the University of Carolina at Chapel Hill School of Medicine, e-cigarettes can trigger the same potentially dangerous immune responses that normal tobacco products do.The immune response occurs when you puff on a real cigarette or an electronic one.Once the smoke or vapor reaches your lungs, the chemicals will be detected as foreign substances by your body.As a reaction, cells from the immune system will arrive in parts of your lungs to clean up the substances, but the immune cells may also attack the area, thinking it needs to be removed from the body.This also occurs even if you are smoking pure water.

"The effect of the smoke from a cigarette irritates your airway, causing it to produce its own markers that invite your body's immune systems cells which identify that signal as a potential threat to your body.Once you have your immune system cells come to the lungs they will attack that area thinking it needs to be destroyed.Over time, that process can destroy your lung, which is when you develop lung diseases," said Dr.Pushan Jani, a pulmonologist at Memorial Hermann-Texas Medical Center.It also means that vaping can lead to inflammation of the lungs.

Other chemicals that make up the vaping fluid contain a solvent and it produces an aerosol when heated.The primary substance in the fluid is called propylene glycol and it becomes propylene oxide when heated -- a chemical considered as a human carcinogen.The liquid acrolein can irritate the upper respiratory tract and increase the airway resistance that leads to asthma.Tin, one of the metals used to heat the vaping fluid, is poisonous to lung cells.The metal nanoparticles can also deposit in the lungs, leading to toxicity, and these particles can enter the bloodstream.

The flavorings in the vaping fluid of e-cigarettes attract young people.Flavorings are chemicals that are known to be reasonably safe for ingestion but can be quite dangerous to breathe in, according to Dr.Robert Jackler, chair of otolaryngology and a professor of otorhinolaryngology at Stanford University.

Health professionals still recommend non-smoking methods, such as nicotine patches, gums, and lozenges to quit smoking.Nicotine dosage in nicotine replacement therapy is calculated and monitored to reduce the harmful effect on the patient.