Committee Blog: Safety – Terpene Limits in Cannabis Manufacturing

by NCIA’s Cannabis Manufacturing Committee

From the taste of your fruits and vegetables to the aroma that travels from trees and flowers in bloom, terpenes are the organic compounds that play a vital role in the flavors and smells we experience daily. Terpenes are common ingredients that are used in many industries such as food, cosmetics, tobacco, and pharmaceuticals. Therefore, the information on the safety of terpenes in these industries can be used for determining the safe use of terpenes in a wide range of product applications.

Terpenes are currently being introduced into a variety of adult-use and medical cannabis preparations across the U.S. and hemp-CBD markets around the world for both flavor and functional purposes. Much research has been and still is being conducted on the therapeutic effects of terpenes and their synergistic effects when used in conjunction with cannabinoids. The strong research background supports the benefits of infusing terpenes into cannabis extracts, both in reference to endogenous terpenes found naturally in the plant and those terpenes that have been added back into preparations from other botanical sources. Therefore, almost every manufactured cannabis product contains a percentage of terpenes. However, the clear lack of understanding of the full potential of the terpene profiles, and misuse of these volatile, fragile compounds bring up various misconceptions regarding terpene safety versus their efficacy in creating an elevated user experience.

As terpenes make a significant contribution to the quality of cannabis products, which varies from one consumption method to the other, it is highly important to utilize the most advanced knowledge regarding terpenes in order to maximize their potential while maintaining product safety.

Inhalation

Bioavailability

Terpenes are a naturally occurring constituent in resin cannabis extracts. Terpenes have been incorporated into vaporizable formulations in the form of pre-filled cartridges. These terpene formulations are designed to produce specific effects based on the creator’s intentions, or the terpenes are simply reintroduced to mimic the source material since the extracts are often refined to the point that they have little or no taste (i.e., lost their original essence).

Inhalation of these volatile molecules leads to quick absorption of the compounds via the lungs and directly into the bloodstream. The high solubility of monoterpenes in the blood and hydrophobic medium suggests a high respiratory uptake and accumulation in fat tissues ( Falk 1990a). This was confirmed by recent studies of uptake and elimination of a-pinene and 3-carene in humans (Falk 1990b, Falk 1991b). The bioavailability range via inhalation of alpha pinene, camphor and menthol has been studied and reported to be 54-76% (Kohlert 2000) which is relatively high compared to oral bioavailability. Therefore, terpenes via inhalation are an efficient route of administration which allows low dosage of terpenes.

General Guidelines

When examining terpene infusion, the points below should be taken into consideration:

From accumulated knowledge within the cannabis industry and considering terpenes’ natural ratios in cannabis (1 – 5%) and data on safety, it is suggested not to exceed a concentration of 10% in the final product.
As terpenes are volatile molecules, the final terpene-infused product is recommended to be used only with adjustable temperature vaporizers such that the oil will not be heated to high temperatures to prevent unnecessary heat-derived toxin production.
Aerosol testing for the final product is recommended to test for heavy metals leaching into the vaporizable product.
Terpenes are recommended to be used within their defined expiration date labeled on the suppliers’ bottle. The final vaporizable product must be tested in a certified lab under the requirements of the authority having jurisdiction to make sure it meets all quality and regulatory requirements.

Terpene Limits

By using position papers such as the ANEC Position Paper on E-cigarettes and e-liquids, suggestions regarding terpene limits can be made for cannabis inhalable products. It is important to mention that the final decision on added terpene amounts and determination of product safety is the sole responsibility of the manufacturer based on their assessments, internal procedures, and local regulations.

The following numbers are the suggested infusion percentage of specific terpenes in E-liquid. This suggestion was calculated by using DNEL (Derived No Effect Level) levels in inhalation as well as frequency of puffs a day.

On average, E-liquid users take 500 puffs a day (ANEC position paper), whereas cannabis users take around 9 puffs a day. Therefore, the suggested terpene limit percentage in cannabis inhalables may be higher than E-liquid due to the lower daily usage.

Substance	Suggested Terpene Limit in E-liquid According to ANEC
Linalool	0.34%
Menthol	7.8%
Beta Pinene	0.7%
Alpha-Terpineol	1.1%
Geranyl Acetate	7.4%
Carvone	0.14%

Ingestion

Bioavailability

Terpene presence in foods of plant origin and in herbs with functional properties has led to further exploration of their bioavailability following oral consumption. The research on terpenes’ bioavailability is commonly done through medicinal plants since they are subjected to digestion within the mouth and stomach before accessing the small intestine. Bioavailability through oral ingestion is affected by mechanical actions, enzymatic actions, and different pH conditions, Transformations into usually more water-soluble and more readily excreted in the urine compounds affect this process as well. These transformations appear mainly in the liver, but also in the gastrointestinal tissue, lungs, kidneys, brain, and blood ( Furtado 2017) Several studies have shown that terpenes consumed orally are absorbed through the gastrointestinal tract and are bioavailable as soon as 0.5 h after intake, reaching their peaks between 2 and 4 h (Furtado 2017, Papada 2018).

General guidelines

Terpenes are commonly used as flavor ingredients and their usage guidelines are clear when used in foods, such as the FEMA values table below. However, when terpenes are used for therapeutic purposes, the suggested dose in food is not fully researched, and the balance between flavor and functionality is still yet to be determined. Basing the dosing according to flavor guidelines is a good place to start. Upper limits should be defined by safety limits such as the DNEL values table found below. It is important to use natural, Food Grade terpenes that are backed up with certificates of analysis and are safe to ingest.

Terpene Limits

The Flavor and Extract Manufacturers Association of the United States (FEMA) has developed an innovative program utilizing the GRAS concept to evaluate the safety of flavoring substances. The FEMA GRAS program began in 1959 with a survey of the flavor industry to identify flavor ingredients then in use and to provide estimates of the amounts of these substances used to manufacture flavors. This database provides information on all ingredients that have been determined to be “generally recognized as safe” under conditions of intended use as flavor ingredients. According to The FEMA GRAS assessment – aromatic terpenes used as flavor ingredients are ubiquitous throughout the food chain; and therefore, not surprising that they serve as effective flavoring ingredients.

The below table presents the average maximum usage levels of terpenes used as flavors in several product types as provided by FEMA.

Product	Lime Terpenes Average Max (ppm)	Orange Terpenes Average Max (ppm)	Grapefruit Terpenes Average Max (ppm)	Limonene Average Max (ppm)	Myrcene Average Max (ppm)	Linalool Average Max (ppm)
Beverages, Nonalcoholic	750	1,550	500	31	4.4	7
Beverages, Alcoholic	1,000	1,000	1,000	NA	NA	50
Chewing Gum	20,000	20,000	20,000	2300	NA	200
Hard Candy	5,000	5,000	5,000	49	13	400
Soft Candy	5,000	5,000	5,000	NA	NA	10

ppm is an abbreviation for “parts per million” and it also can be expressed as milligrams per liter (mg/L) or in a percentage where 10,000 ppm is 1%. For example, the maximum suggested infusion for orange terpenes in chewing gum is 2%, where the suggested infusion in hard candy is 0.5%.

*Point of thought*: Since terpenes in the cannabis industry are mostly infused in cannabis-based products, the frequency of usage of such products is lower than regular food products.

Additional safety data can be gathered from reviewing reports from governmental agencies such as European Chemicals Agency (ECHA). The following data about the DNEL (Derived No Effect Level) in the category of General Population was collected from ECHA website. These numbers may be used as a guideline for maximum daily intake via oral administration:

Substance	DNEL (Derived No Effect Level)	Calculated Daily DNEL for 70kg subject (mg/day)
Linalool	0.2 mg/kg bw/day	14
Menthol	4.7 mg/kg bw/day	329
Beta Pinene	0.3 mg/kg bw/day	21
Alpha-Terpineol	no hazard identified	no hazard identified
Geranyl Acetate	8.9 mg/kg bw/day	623
Carvone	69.4 µg/kg bw/day	4,858

For example, a 70 kg person consumes a 1g cookie that is infused with 1% Pineapple Express terpene formulation and Linalool constitutes 10% of the formulation, then there will be overall 10mg of terpene formulation in the cookie, out of the 10mg there is 0.1mg of Linalool which doesn’t exceed the DNEL level.

Topical

Bioavailability

Terpenes are lipophilic, small, and nonpolar molecules that are considered to be the largest group of natural fragrances. Terpenes can easily penetrate the skin and enhance transdermal delivery (Aqil 2007) and can potentially aid cannabinoid transdermal delivery. Terpenes are also known to have several dermal benefits including anti-inflammatory (Maurya 2014), wound healing (d’Alessio 2014) and anti-acne (Yuangang 2010). Terpene bioavailability via transdermal delivery ranges between 3-12% depending on the type of terpene, medium and application (Brain 2007, Gilpin 2010). Following topical application, maximum plasma levels of terpenes are reached within 10 minutes (Kohlert 2000).

General guidelines

While some terpenes are known as dermal irritants, the severity of the irritation may depend on their concentration. These should not be used on any inflammatory or allergic skin condition and should always be appropriately diluted. The oxidation of terpenes can increase risk of causing skin reactions because the oxides and peroxides formed are more reactive. This can be seen with (+)-limonene, δ-3-carene and α-pinene and arise due to the formation of oxidation products, some of which are more sensitizing than the parent compound. For this reason, proper storage of terpenes is required to preserve their effectiveness and decrease the risk of adverse reactions.

The table below lists commonly known allergenic terpenes, and for this reason, should be declared on the packaging or in the information leaflet if the concentration of these allergenic fragrances is higher than the permissible concentration of 0.01% in shower gels and baths (rinse-off products) and higher than 0.001% in body oils, massage oils and creams (leave-on products)

Allergenic Terpenes

Citral

Citronellol

Eugenol

Farnesol

Geraniol

Isoeugenol

D-Limonene

Linalool

Terpene Limits

The International Fragrance Association (IFRA) defines which compounds represent a potential allergy risk and determines their maximum concentration to produce safe cosmetic products. IFRA also issues recommendations for the safe use of fragrance ingredients, which are published in the IFRA Code of Practice and its guidelines. In the below table, there can be found specific infusion recommendations for specific terpenes.

Substance Name	Restriction Limits in the Finished Product (%) according to IFRA:
Substance Name	Lip Products	Body Lotion, Cream & Oils	Hand Sanitizer & Hand Cream	Body Wash
Citronellol	2.20%	12.00%	3.20%	24.00%
Citral	0.11%	0.60%	0.15%	1.20%
Farnesol	0.21%	1.20%	0.29%	2.30%
Eugenol	0.45%	2.50%	0.64%	4.90%
Geraniol	0.85%	4.70%	1.20%	9.20%
Alpha Bisabolol	0.42%	2.40%	0.60%	4.60%

Testing of terpenes in dermal products can be achieved safely by making a sample product with terpene formulation infused at 0.5% to 5% concentrations in petrolatum. Patch testing can be a useful technique to detect and avoid skin reactions.

Committee Blog: Cannabis Classification and the Role of Terpenes

by NCIA’s Scientific Advisory Committee

From Indica/Sativa to Hybridization

Cannabis is thought to have originally been domesticated in the mountainous regions of Central Asia. As humans started exploring the world, they brought the plant with them, and the plant needed to adapt to the different climates in order to thrive. This gave rise to many of the cultivars (or “strains”) we deem as “landrace,” allowing some subspecies of the cannabis plant to naturally start propagating. Since plant breeding didn’t become en vogue for thousands of years until Gregor Mendel’s work with pea plants, these natural cultivars were able to gain great genetic fitness, as well as become genetically diverse from other landrace strains as they adapted to their specific, often isolated, environments analogously to the finches of the Galapagos Islands.

We are all familiar with indica and sativa. With growing popularity of plant breeding and creating crosses of indica-dominant and sativa-dominant strains, we have largely lost true landrace cultivars that are 100% one way or the other. Almost every strain sold in the modern market is a hybrid, featuring a mixture of indica-derived and sativa-derived genes. Did you know that indica and sativa designations focus more on the phenotype, or the observable characteristics (e.g. height, leaf shape/color, and branch formation), rather than genotype, the unique DNA sequence of an organism?

In cool and dry climates, the cannabis plant leaves are broader and there is less space between branches. This creates a shorter, more compact plant that is better able to retain heat and moisture. The broad leaves help maximize photosynthesis on the otherwise short-statured indica-dominant plants. If you instead look at a warmer climate, you will see the plants grow much taller and thinner. They grow up and out more so that they can easily dissipate the heat and moisture in these warmer regions. The branches of the sativa-dominant plants are also longer and the leaves have more nodes, though they are thinner than that of an indica plant. All of these characteristics may also help prevent mold growth on a sativa-dominant plant due to better air flow within the plant.

Since indica and sativa classifications are more likely to indicate landrace phenotypes and the climate in which the cannabis plant grew in, new methods of classification are being explored to better express to consumers and patients the effects of the cannabis or cannabis-infused product they are using. For example, Leafly launched a new way for their website to categorize cannabis strains that considers terpene profiles, rather than labeling them as indica, sativa, or hybrid. Since terpenes are produced in plants other than cannabis, a description based on terpene profiles is the most compelling option, as research can be done on the effects of terpenes produced by other sources. While the entourage effect in cannabis is likely important to its variable uses in medicine, more research is warranted to fully understand the effect.

Terpenes and Terpenoids

Terpenes are plant constituents that impart olfactory, gustatory, and medicinal properties to plants. These Volatile Organic Compounds (VOCs) are “Generally Recognized as Safe” by the FDA and are composed of repeating isoprene units arranged head-to-tail to create the over 200 terpenes known to be produced in the cannabis plant. These terpenes are found in other plants as well. Terpenes generally come in three varieties depending on how many isoprene units are used to construct them: monoterpenes are composed of two isoprene units, sesquiterpenes of three units, and diterpenes of four units.

The term “terpenoid” is often used interchangeably with the term “terpene.” The difference is terpenoids are modified terpenes that contain oxygen, while terpenes are hydrocarbons containing only hydrogen and carbon. This modification usually occurs through either the movement or loss of a methyl (-CH3) group or, more commonly in cannabis, through its interaction with oxygen during the drying/curing process. As such, “terpenoids” are more correctly used to describe smokable flower, whereas “terpene” is more accurate when describing the compounds when they are being produced by the living plant.

Terpenes have three main purposes: environmental adaptation, the repulsion and destruction of predators, and the attraction of pollinators. Monoterpenes, such as limonene and α-pinene, tend to predominate in the flower portion of plants and have been shown to repel herbivorous insects in Arabidopsis thaliana, often used as a model organism of the cannabis plant, due to their volatile aromatic properties. Sesquiterpenes, on the other hand, have a bitter taste and deter larger plant-eating organisms, due to their predominance in the leaves of a plant. The sticky nature of terpenes also helps to trap bugs as they move around on the plant. From the perspective of cannabis, humans have shown to be excellent pollinators as illustrated by the diverse cannabis strains available at your local dispensary.

Terpenes are strongly inherited from parent plants and are not often affected by environmental factors over the short term. Terpene profiles, therefore, can be used to help distinguish between indica-dominant and sativa-dominant classifications due to the ratio of individual terpenes’ stimulating or sedating properties. Below are descriptions of some of the most common and best-researched terpenes. The summation of sedating and stimulating terpenes produced by the plant will determine whether the net effect of consumption will have more “indica” properties or more “sativa” properties.

α-pinene is one of the most common terpenes found in nature occurring in pine trees as well as many common spices such as rosemary, basil, and dill. Along with its role as an insect repellant, it has also been shown to have anti-inflammatory properties. It has the ability to cross the blood-brain barrier and inhibits the breakdown of acetylcholine, a neurotransmitter which can stimulate cognitive functions. This will cause α-pinene to have more of a stimulating effect.

Limonene is another common terpene found in citrus fruits. It has been shown to help with anxiety and depression by increasing dopamine and serotonin levels in the brains of mammals. Limonene has also been shown to increase alertness as well as help with weight loss and relief of gastric distress.

β-myrcene is one of the most common terpenes found in cannabis, though it is also found in hops and mangos. It gives off an earthy aroma of cloves and has been shown to have pain-relieving and anti-inflammatory properties in mice. Due to its sedating effects, it was thought to be a reliable indicator of indica strains; however, recent studies have shown that this terpene is equally present in both indica and sativa strains. The sedating properties are responsible for the ”couch-lock” effect some people experience when consuming certain cannabis strains.

β-caryophyllene has a dual use in protecting plants from grazing species since it both attracts insect predators as well as repels grazing insects. It is commonly found in spices such as black pepper and oregano and has a spicy flavor. It can act as a gastro-protective agent and is helpful in fighting stomach ulcers. It has also been shown to help combat symptoms of opioid addiction, through a process called opioid sparing. β-caryophyllene selectively activates CB2 receptors, the cannabinoid receptor primarily found in muscle tissue as opposed to brain tissue which is generally high in CB1 receptors. Due to this, it has more physically sedating properties making it a common terpene found in more indica-leaning strains.

Linalool is a terpenoid alcohol commonly found in lavender. It is a highly sedating phytochemical that is coveted for its anti-anxiety properties. It also helps as an antidepressant since it assists in serotonin-receptor transmission. As an anti-epileptic, it helps to modulate motor movements, presumably due to its sedating properties. When applied topically, it has been shown to help heal skin burns as well as treat acne.

Through a combination of these terpenes and the other 200+ terpenes found in the cannabis plant, we get a balancing act between sedating and stimulating properties. And since everything is technically a hybrid now, the cannabis industry should strongly consider other ways to categorize different cultivars, rather than just indica or sativa, to better educate the consumer on its effects.

The Scientific Advisory Committee is comprised of practicing chemists and other scientific field professionals to advise other NCIA committees as they work to develop standards and guidelines for the various sectors of our industry, ensuring that any formal recommendations produced by other NCIA committees are scientifically sound, sustainable, and legitimate.