Electronic cigarettes, or vapes, are battery-operated devices that heat a liquid solution into an aerosol for inhalation. These devices come in various shapes and sizes, sometimes resembling traditional cigarettes, pens, or USB drives. Their growing popularity has led to extensive discussion about their safety and potential health effects on users and bystanders, given the distinct nature of the substances they deliver compared to traditional tobacco products.
E-Liquid and Aerosol Composition
The liquid used in e-cigarettes, known as e-liquid, contains primary ingredients: propylene glycol (PG), vegetable glycerin (VG), nicotine, and various flavorings. Propylene glycol is a clear, nearly tasteless liquid that serves as an effective carrier for flavorings and nicotine, while vegetable glycerin is a thicker, slightly sweet fluid that contributes to visible aerosol production. Nicotine, derived from tobacco, is the addictive substance in most e-liquids, though some formulations are nicotine-free. Flavorings provide a wide range of tastes, from tobacco and menthol to fruits and desserts.
When the e-liquid is heated by the device’s coil, it transforms into an aerosol, not simply water vapor. This heating can lead to the formation of new chemical compounds through thermal decomposition. For instance, propylene glycol can degrade to produce acetaldehyde and formaldehyde, while vegetable glycerin can form acrolein and formaldehyde. These aldehydes are volatile organic compounds present in the aerosol.
Beyond e-liquid components, the heating coil and other metal parts also contribute to the aerosol’s composition. Studies have detected various heavy metals in e-cigarette aerosols, including nickel, tin, and lead. Other metals like chromium, iron, copper, manganese, arsenic, and zinc are also identified, often leaching from components like nichrome wire or solder joints. Concentrations vary by device type, power settings, and e-liquid flavor.
Known Health Implications of Vaping
Vaping can have several physiological effects, impacting the respiratory and cardiovascular systems. In the lungs, inhaled particles and chemicals can cause inflammation and irritation, potentially leading to lung damage and scarring. Conditions like bronchiolitis obliterans, often called “popcorn lung,” have been associated with diacetyl, a flavoring chemical sometimes used in e-liquids that can cause scarring in the tiny airways of the lungs. While diacetyl has been banned in UK-regulated e-liquids, it has been found in many e-cigarette brands in other regions.
A serious acute lung injury, known as e-cigarette or vaping use-associated lung injury (EVALI), emerged as an outbreak in 2019, causing thousands of hospitalizations and deaths. EVALI symptoms include shortness of breath, cough, chest pain, fever, and gastrointestinal issues. While vitamin E acetate, often found in THC-containing vape products, was strongly linked to the EVALI outbreak, other e-cigarette substances may also contribute. This illness can severely damage the lungs and may require intensive care.
Vaping also affects cardiovascular health. E-cigarette use can immediately increase heart rate and blood pressure. Regular nicotine exposure from vaping can worsen heart rate variability and constrict arteries. These changes suggest an increased risk for cardiovascular disease. Research indicates the cardiovascular impact on vapers can be similar to that seen in traditional cigarette smokers, even in younger individuals.
Nicotine is highly addictive, especially for adolescents. The adolescent brain continues to develop until around age 25, and nicotine exposure during this period can harm brain development. This affects circuits controlling attention, learning, mood, and impulse control. Adolescents may quickly develop nicotine addiction, and early exposure can increase vulnerability to other substance addictions later in life.
Secondhand Aerosol Exposure
The exhaled aerosol from e-cigarettes is not harmless water vapor and poses risks to bystanders. This secondhand aerosol contains various substances that can be inhaled by non-users. Among its components are nicotine, ultrafine particles, and low levels of harmful chemicals present in the primary aerosol.
Ultrafine particles can be inhaled deeply, potentially exacerbating respiratory conditions like asthma and contributing to cardiovascular issues. Non-smokers exposed to secondhand vape aerosol can absorb nicotine at levels comparable to those exposed to secondhand cigarette smoke. Additionally, the exhaled aerosol can contain trace amounts of formaldehyde, acetaldehyde, and heavy metals like lead, nickel, and chromium, which are known carcinogens or toxins. Concentration and specific chemicals vary based on device type, operation, and e-liquid.
Physical Device Hazards
Beyond inhalation risks, e-cigarettes present physical dangers from the devices themselves. A primary concern is the lithium-ion batteries that power them. These batteries, similar to those in cell phones, can malfunction, overheat, and lead to fires or explosions. Incidents have resulted in severe injuries, including burns, particularly to the face, hands, and groin, sometimes leading to permanent disfigurement.
Battery failures can occur due to various factors, such as manufacturing defects, overcharging, or external damage like punctures or contact with metal objects (e.g., keys or coins) when carried in a pocket. The cylindrical shape of many e-cigarettes can make them prone to behaving like “flaming rockets” if a battery fails, intensifying the danger. Users should follow manufacturer instructions for charging and avoid incompatible chargers or damaged batteries to reduce these risks.
Another significant physical hazard is the risk of poisoning from accidental ingestion or skin exposure to concentrated nicotine in e-liquids. Flavored e-liquids are tempting to young children and pets. Even small amounts of concentrated nicotine, if swallowed or absorbed through the skin, can cause severe poisoning, leading to symptoms like nausea, vomiting, dizziness, tremors, rapid heart rate, and in severe cases, seizures, respiratory arrest, coma, or even death. Poison control centers receive thousands of calls related to e-liquid exposures, with a majority involving children under five years old.