Rates of cigarette smoking have been declining in recent decades due to increased awareness of the dangers of smoking. Quitting smoking can be very challenging due to the addictive nature of nicotine, so some people transition to electronic or e-cigarettes, which provide nicotine but theoretically reduce exposure to the thousands of toxic chemicals found in conventional cigarettes. The perceived safety of e-cigarettes, also called vapes, has led to their use by people who never smoked conventional cigarettes, especially teens and young adults. However, recent studies indicate that e-cigarettes can also expose users to a range of toxic substances, several of which are known to harm the brain [1].
E-cigarettes consist of three major parts, a liquid, a battery, and a heating coil. The process of vaping involves heating the liquid to the point of vaporization, which is when it becomes an inhalable aerosol.
Heating coils are made of metal. Two of the most common metal alloys used in the coils are Kanthal, a combination of iron, chromium, and aluminum, and Nichrome, an alloy of nickel and chromium [2]. Lead-containing copper alloys are often used for electrical connections and solder joints. These toxic metals can be transferred to the liquid when it comes in contact with the heated coil [2].
Nicotine salts in the liquid can increase the leaching of metals from the coils, while some artificial sweeteners used in flavorants, such as ethyl maltol, may enhance the ability of the leached metals in the vape to be taken up into the cells of the body [3]. In addition to the nicotine and flavoring, the e-cigarette liquid contains a solvent, typically a mixture of propylene glycol and glycerin. When heated, the solvent breaks down, leading to the release of well-established carcinogens, such as formaldehyde and acrolein [4].
The rate of exposure to these toxins is not uniform from puff to puff, but rather, levels increase over time [1; 4]. The voltage settings also influence toxin emissions. Higher voltages result in higher coil temperatures and greater toxin production [2; 4].
The levels of several of the toxic metals found in e-cigarette aerosols exceed the threshold for cancer risk [1]. Concerningly, the aerosols from many of these vaping products contain lead, a known neurotoxin [1; 2]. There is no safe level of lead exposure.
A comprehensive analysis of the impacts of short and long-term e-cigarette use on brain health has not yet been conducted, but the research conducted to date indicate the potential for harm, particularly in adolescents [5].
The short-term impact to cognition appears negligible for cigarette smokers transitioning to e-cigarettes, though the long-term impact remains unclear [5].
The adolescent brain is still developing and is negatively impacted by nicotine exposure [6]. Adolescents are also at higher risk for vaping-related brain fog, attention deficits, and mood disorders. A study in college students found that students who vaped showed worse performance on cognitive tests [7]. This may be related to reduced blood flow to the brain and increased stress to brain cells.
Second-hand exposure to the toxins contained in the vaping aerosols can also cause harm [8]. When used indoors, levels of these aerosols can build up in the air and eventually make their way onto surfaces, such as clothing and furniture. Studies in animal models find that this type of exposure can induce neuroinflammation, which may negatively impact cognitive function [9].
While exposure to some of the toxins found in conventional cigarettes may be reduced by the use of e-cigarettes, this option should not be considered safe. Exposure to certain toxins, particularly heavy metals, may be higher with e-cigarettes, which could increase the risk for long-term damage to the lungs and brain.
References
Betsy Mills, PhD, is a member of the ADDF's Aging and Alzheimer's Prevention program. She critically evaluates the scientific evidence regarding prospective therapies to promote brain health and/or prevent Alzheimer's disease, and contributes to CognitiveVitality.org. Dr. Mills came to the ADDF from the University of Michigan, where she served as the grant writing manager for a clinical laboratory specializing in neuroautoimmune diseases. She also completed a Postdoctoral fellowship at the University of Michigan, where she worked to uncover genes that could promote retina regeneration. She earned her doctorate in neuroscience at Johns Hopkins University School of Medicine, where she studied the role of glial cells in the optic nerve, and their contribution to neurodegeneration in glaucoma. She obtained her bachelor's degree in biology from the College of the Holy Cross. Dr. Mills has a strong passion for community outreach, and has served as program presenter with the Michigan Great Lakes Chapter of the Alzheimer's Association to promote dementia awareness.
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