Terpenes are a large class of aromatic organic compounds produced by various plants, including citrus, pine, and especially cannabis. These volatile molecules are responsible for the distinctive scents and flavors in these botanical sources. These molecules are hydrocarbons composed primarily of hydrogen and carbon atoms. The rising popularity of concentrated extracts has led many to question the practicality of inhaling these compounds in isolation and the potential health consequences of doing so.
The Role of Terpenes in Plants and Products
Terpenes serve multiple purposes for the plants that produce them, acting as natural defense mechanisms against grazing animals and insects due to their often strong, bitter flavors. Conversely, their appealing aromas work to attract pollinators, facilitating plant reproduction. In commercial products, terpenes are primarily used to provide flavor and fragrance, forming the basis of essential oils and various food flavorings.
In the context of cannabis, these compounds are theorized to work with cannabinoids like THC and CBD to influence the overall effect experienced by the user. This concept, often called the “entourage effect,” suggests that the combined action of the plant’s compounds is greater than the effect of any single component. The presence of terpenes is what gives different cannabis varieties their unique profiles, ranging from earthy and musky to bright and citrusy.
Common Methods of Inhalation
Direct inhalation of concentrated terpenes is typically accomplished through high-heat methods like dabbing or vaporization. Dabbing involves placing a concentrated form of the terpene—either alone or mixed with other extracts—onto a heated surface, called a nail, which is often heated to temperatures between 400°F and 600°F. Electronic vaporizers, or vape pens, are another common method, where the terpene-containing liquid is heated within a cartridge.
These devices often heat the material to temperatures between 350°F and 450°F, depending on the user’s setting. Terpenes are frequently added back into cannabis extracts, such as distillates, primarily to restore the flavor and aroma lost during the high-purification extraction process. Many common terpenes, such as myrcene, have boiling points as low as 334°F, meaning they are easily volatilized even at the lower end of these typical consumption temperatures.
Chemical Risks of High-Temperature Inhalation
The primary concern regarding terpene inhalation stems from thermal decomposition, which occurs when the compounds are heated above their vaporization points. This process can produce toxic byproducts that are not present in the original plant matter or extract. For instance, heating terpenes can lead to the formation of methacrolein, a strong respiratory irritant, and benzene, a known human carcinogen.
The oxidative liability of terpenes means that their chemical structure is prone to reaction when heated in the presence of air, contributing to the formation of these hazardous substances. The risk is compounded because many users do not precisely control the temperature of the heating element, especially in traditional dabbing methods. This often pushes the heat well past the point where decomposition products begin to form.
Purity and Source Material Differences
Terpenes used in consumer products vary significantly based on their source, which affects their purity and potential safety profile. Naturally-derived terpenes are extracted directly from the cannabis plant, while botanical terpenes are extracted from non-cannabis sources like lavender or citrus rinds. A third category, synthetic terpenes, are manufactured in a laboratory, sometimes using petrochemical derivatives. The purity of the final product is also compromised by the use of diluents, or cutting agents, which are often added to reduce the viscosity of thick cannabis oils for use in vape cartridges.
Common diluents like Propylene Glycol (PG), Vegetable Glycerin (VG), and Medium-Chain Triglyceride (MCT) oil have been linked to the formation of hazardous compounds when heated. Heating these carrier oils can produce toxic aldehydes, such as formaldehyde and acetaldehyde, which are known irritants. Additionally, residual solvents like butane or propane can remain in the final product if post-extraction purging is inadequate, posing an unknown risk due to lack of standardized regulation.