E-cigarette liquids

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.

After the aerosol is inhaled, it is exhaled. Emissions from electronic cigarettes are not comparable to environmental pollution or cigarette smoke as their nature and chemical composition are completely different. The particles are larger, with the mean size being 600 nm in inhaled aerosol and 300 nm in exhaled vapor. Bystanders are exposed to these particles from exhaled e-cigarette vapor. There is a concern that some of the mainstream vapor exhaled by e-cigarette users can be inhaled by bystanders, particularly indoors, and have significant adverse effects. Since e-cigarettes involve an aerosolization process, it is suggested that no meaningful amounts of carbon monoxide are emitted. Thus, cardiocirculatory effects caused by carbon monoxide are not likely. E-cigarette use by an expectant parent might lead to inadvertent health risks to offspring. E-cigarettes pose many safety concerns to children. For example, indoor surfaces can accumulate nicotine where e-cigarettes were used, which may be inhaled by children, particularly youngsters, long after they were used.

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