E-cigarette aerosol

E-liquid is the mixture used in vapor products such as electronic cigarettes. The main ingredients in the e-liquid usually are propylene glycol, glycerin, nicotine, and flavorings. However, there are e-liquids sold without propylene glycol, nicotine, or flavors. The liquid typically contains 95% propylene glycol and glycerin. Propylene glycol and glycerine are used to produce the vapor while the flavoring provides the taste and aroma. The flavorings may be natural or artificial. About 8,000 flavors exist as of 2014. There are many e-liquids manufacturers in the USA and worldwide. While there are currently no US Food and Drug Administration (FDA) manufacturing standards for e-liquid, the FDA has proposed regulations that were expected to be finalized in late 2015. Industry standards have been created and published by the American E-liquid Manufacturing Standards Association (AEMSA).

The aerosol of electronic cigarettes is generated when the e-liquid reaches a temperature of roughly 100–250 °C within a chamber. The user inhales the aerosol, commonly called vapor, rather than cigarette smoke. The aerosol provides a flavor and feel similar to tobacco smoking. In physics, a vapor is a substance in the gas phase whereas an aerosol is a suspension of tiny particles of liquid, solid or both within a gas. Vapor from an electronic cigarette simulates tobacco smoke, but the process of burning tobacco does not occur. The aerosol is made-up of liquid sub-micron particles of condensed vapor, which mostly consist of propylene glycol, glycerol, water, flavorings, nicotine, and other chemicals. The various chemicals in the aerosol give rise to many issues concerning the safety of electronic cigarettes that have been much discussed. After a puff, inhalation of the aerosol travels from the device into the mouth and lungs. A 2014 review found that the particles emitted by e-cigarettes are comparable in size and number to particles in cigarette smoke, with the majority of them in the ultrafine range. The particles are of the ultrafine size which can go deep in the lungs and then into the systemic circulation. A 2014 review said local pulmonary toxicity may occur because metal nanoparticles can deposit in the lungs. Others show that the quantities of metals emitted are minimal and permissible by medicinal standards.

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