Vegetable glycerin (VG) is a clear, odorless, and sweet-tasting liquid commonly derived from vegetable fats such as soybean, coconut, or palm oils. This versatile compound finds widespread use across various industries, including food, cosmetics, and pharmaceuticals, where it acts as a sweetener, moisturizer, or solvent. In products designed for inhalation, such as e-cigarettes, VG serves as a primary component in e-liquids, producing visible vapor and contributing a mild, sweet taste.
How Vegetable Glycerin Reaches the Lungs
The primary way vegetable glycerin interacts with the respiratory system is through inhalation, particularly when heated and aerosolized in devices like e-cigarettes. When e-liquids containing VG are heated, they transform into an aerosol, a fine mist of particles suspended in the air. These aerosolized particles are then drawn into the respiratory tract.
Upon inhalation, particle size dictates how deeply they penetrate the lungs. Larger particles tend to deposit in the upper airways, including the mouth, nose, and throat. Smaller, submicron particles can travel much further, reaching deeper pulmonary regions where gas exchange occurs. Once inside the moist environment of the lungs, VG, a hygroscopic substance, absorbs water, causing the inhaled particles to expand.
Immediate and Short-Term Lung Reactions
Inhaling aerosolized vegetable glycerin can trigger immediate and short-term reactions within the lungs and airways. Common initial responses include throat irritation, a dry cough, and general discomfort. This irritation is partly attributed to VG’s hygroscopic nature, meaning it attracts and absorbs moisture. As VG particles draw water from the delicate mucous membranes lining the airways, it can lead to sensations of dryness and dehydration.
Beyond dryness, some individuals may experience transient inflammatory responses in the airways shortly after exposure. Studies indicate inhaled VG can increase inflammatory markers within the lungs. This can manifest as mild swelling in the airways, possibly causing coughing or wheezing. While these acute effects are often temporary and resolve quickly once exposure ceases, they represent the body’s immediate response to an inhaled substance.
Long-Term Pulmonary Considerations
Repeated and prolonged inhalation of vegetable glycerin raises concerns about long-term impacts on lung tissue and function. Continuous exposure to VG aerosol can lead to sustained inflammation within the lungs. This chronic inflammation may alter lung cell structure over time. Some research indicates VG can leave a residue of fat globules in the lungs.
The persistent presence of VG and resulting inflammation are being investigated for their links to more chronic respiratory conditions. Long-term inhalation of VG has been associated with an increased risk of chronic cough, bronchitis, and reduced overall lung function. Concerns also exist regarding impaired immune responses within the airways, potentially making the lungs more susceptible to infections. In rare instances, lipoid pneumonia has been reported in individuals inhaling VG, leading to inflammation that impedes breathing.
Scientific Understanding and Ongoing Research
The scientific understanding of vegetable glycerin’s full impact on lung health, particularly from chronic inhalation, is still developing. Research into the safety of inhaled VG remains an ongoing area of study. A significant limitation stems from the relatively recent widespread use of VG in inhalation products, limiting comprehensive long-term human studies.
It is often challenging to isolate the specific effects of VG from other substances commonly found in inhaled products, such as nicotine and flavorings. Therefore, ongoing research employs various methodologies, including in vitro studies on human cells, animal models, and epidemiological observations, to better understand these complex interactions. While some concerns regarding VG inhalation have emerged, definitive conclusions about its long-term safety are still being established.