A hookah pen, also known as an e-hookah, is a compact, battery-powered electronic device designed to vaporize a flavored liquid for inhalation. It serves as a portable alternative to traditional water-pipe smoking. The device heats a solution to create an aerosol, which users inhale to experience the taste and sensation of shisha without burning charcoal or tobacco. Hookah pens are commonly disposable and marketed with a focus on the wide variety of sweet, fruity, and dessert-like flavors, often claiming to be nicotine-free.
The Primary Liquid Base
The liquid base is composed of two primary solvents: Propylene Glycol (PG) and Vegetable Glycerin (VG), which carry the flavorings and any nicotine. PG is a thin, colorless liquid that dissolves flavor compounds and delivers a “throat hit,” mimicking smoke inhalation. VG is a thicker, slightly sweet liquid derived from plant oils that produces the dense, visible vapor clouds. E-liquid formulations balance these components, with higher VG ratios yielding larger clouds and higher PG ratios enhancing flavor intensity.
Both PG and VG have a “Generally Recognized As Safe” (GRAS) status from the U.S. Food and Drug Administration, but this designation applies only to ingestion, not to repeated inhalation. Early research indicates that inhaling these heated and aerosolized solvents can cause adverse effects on bronchial cells and may lead to inflammation in the respiratory system.
Flavor Additives and Nicotine Variance
Flavor Additives
Beyond the solvent base, the liquid contains concentrated artificial flavorings, which are responsible for the product’s appeal, particularly the dessert and candy profiles. Many flavorants contain diketones, such as diacetyl and its substitute, acetyl propionyl, used to impart a creamy or buttery taste. While safe for consumption in food, inhaled diacetyl has been linked to bronchiolitis obliterans, a severe and irreversible lung disease commonly known as “popcorn lung.”
Nicotine Variance
A concern for consumers is the variance in nicotine content, as many hookah pens are explicitly advertised as “zero-nicotine.” Testing frequently reveals high rates of mislabeling, with a significant percentage of liquids containing nicotine levels inconsistent with the packaging. This lack of transparency can lead consumers to unknowingly develop a nicotine dependency, undermining the perception of the product as a safer, non-addictive option.
Toxic Byproducts Formed Upon Heating
Thermal Decomposition
The process of heating the liquid to create an aerosol, particularly when the atomizer coil overheats, causes the PG and VG solvents to break down into toxic carbonyl compounds. This thermal decomposition generates substances like formaldehyde, acetaldehyde, and acrolein, all of which are known respiratory irritants and potential carcinogens. Formaldehyde and acetaldehyde are produced from the degradation of both PG and VG, while acrolein is primarily a breakdown product of Vegetable Glycerin when exposed to high temperatures. The presence of these aldehydes in the aerosol poses a risk of oxidative stress and inflammation within the lungs.
Heavy Metal Contamination
Contamination in the aerosol also comes from the metallic components of the heating element itself. The coils are often made from metal alloys like Kanthal or Nichrome, which contain elements such as nickel, chromium, and lead. As the coil heats the liquid, microscopic particles of these heavy metals can leach into the e-liquid and become aerosolized. Studies show the aerosol can contain lead and nickel concentrations that exceed established safe limits for inhalation. Chronic exposure to these heavy metals is associated with a risk of damage to the lungs, liver, and central nervous system.