Electronic cigarettes (e-cigarettes) are alternative, non-combustible tobacco products that generate an inhalable aerosol containing nicotine, flavors, propylene glycol, and vegetable glycerin. Vaping is now a multibillion dollar industry that appeals to current smokers, former smokers, and young people who have never smoked. E-cigarettes reached the market without either extensive preclinical toxicology testing or long term safety trials that would be required of conventional therapeutics or medical devices. Their effectiveness as a smoking cessation intervention, บุหรี่ไฟฟ้า
their impact at a population level, and whether they are less harmful than combustible tobacco products are highly controversial. Here, we review the evidence on the effects of e-cigarettes on respiratory health. Studies show measurable adverse biologic effects on organ and cellular health in humans, in animals, and in vitro. The effects of e-cigarettes have similarities to and important differences from those of cigarettes. Decades of chronic smoking are needed for development of lung diseases such as lung cancer or chronic obstructive pulmonary disease, so the population effects of e-cigarette use may not be apparent until the middle of this century. We conclude that current knowledge of these effects is insufficient to determine whether the respiratory health effects of e-cigarette are less than those of combustible tobacco products.
The lungs are a physiologic marvel, transmitting the entire cardiac output through around 2000 km of capillaries with each heartbeat and performing gas exchange in 300 000 000 alveoli with a surface area of about 70 m2. With every breath, this highly adapted and delicate organ is exposed to infectious and inflammatory environmental stimuli. As a result of innate and acquired immunity, inspired air is cleaned and humidified before it reaches the alveoli. However, a failure of these processes leads to infection, inflammation, lung damage, and impaired gas exchange.
In considering the effects of electronic cigarettes (e-cigarettes) on lung health, we begin with a brief history of traditional cigarettes. Cigarette smoking accelerated in the late 19th and early 20th centuries in tandem with the growth of mass production technologies and advertising.1 However, it was not until the 1930s that statisticians noted increased cancer mortality rates and thoracic surgeons reported an increase in pneumonectomy to remove lung cancers.2 Three decades later the landmark 1964 US Surgeon General’s Report causally attributed lung cancer to cigarette smoking,3 and four decades after this the tobacco companies were defeated in the US court system on racketeering charges that they systematically deceived the public in the pursuit of profits. The lesson from smoking in the 20th “cigarette” century is that it took decades to show that addictive, heavily marketed inhaled tobacco products caused lung disease. It is therefore imperative that the scientific community uses all available modalities to define the health effects of novel tobacco products so that public health policy can be based on evidence.
E-cigarettes use a metal resistance coil to heat and aerosolize mixtures of vegetable glycerin, propylene glycol, nicotine, and flavoring agents. E-liquids are conducted from a tank to the coil by a wick made of cotton, silica, or ceramic, and the user activates electric current through the coil by depressing a button or by generating airflow through the device. Since their introduction 15 years ago, e-cigarettes have undergone major changes in design that allow the user greater control over e-liquid composition, nicotine concentration, and how the e-liquid is aerosolized/vaped.