Why Heavy Metals Testing in Cannabis is Important

By Apostol Todorovski

heavy-metals lead mercury cadmium arsenic

With the rapid growth in the production of inhalable cannabis products, many questions have been raised about the safety of acute and chronic exposure to aerosol mixtures of this kind. Heavy metals are chemical elements that are characterized by low biodegradability and by bioaccumulation in the human body can directly impact public health and wellness, particularly in the immunocompromised and pediatric patients, and these contaminants are needed to be minimalized in cannabis and cannabis-based products intended for human consumption.

With the rise of the demand for medicinal and recreational cannabis-based products containing tetrahydrocannabinol (THC) and cannabidiol (CBD) compounds, the cannabis industry is struggling to keep up accordingly. Regulating the industry to make sure products are safe for human consumption has been left to individual states since FDA (US Food and Drug Administration) has only been involved in the process of investigating in new drugs that have been submitted to conduct human clinical trials. Unfortunately, many states do not have the needed scientific background and experience to fully evaluate the safety, therapeutic efficacy, quality, and toxicological concerns regarding agricultural cultivation and production of cannabis-based products. Besides the focus on characterizing the potency (determination of CBD and THC), one of the most important contaminants to be measured is the level of heavy metals. Since cannabis and hemp will avidly accumulate trace elements in the cultivation process (from the soil, fertilizers, water, and pesticides) and furtherly from metallic equipment used for processing and preparation of concentrates and oils, it is critically important to monitor heavy metals to ensure the safety for human consumption.

“The big four”

Heavy metals in Cannabis Heavy metals in Cannabis source

Based on the likelihood of occurrence, toxicity and exposure, health authorities across the world are taking special notice of four chemical elements (arsenic, cadmium, lead, and mercury), widely known as “the big four”.

Arsenic (As)

Arsenic is a chemical element occurring naturally in the environment and can be released in larger quantities through volcanic activities, erosion of rocks, forest fires, and human activity. About 90% of the industrial arsenic in the U.S. is being used by the wood preserving industry. Arsenic can also be found in metals, drugs, soaps, semi–conductors, paints, dyes, etc. Certain fertilizers and pesticides can release high amounts of arsenic to the environment as can industry practices such as copper or lead smelting, mining, and coal burning. Arsenic is a tasteless and odorless compound and in its inorganic form is a well-known carcinogen that can cause cancer of the skin, lungs, liver, and bladder. Lower - level exposure can cause nausea and vomiting, decreased production of red and white blood cells, abnormal heart rhythm, damage to blood vessels, and sensation of “pins and needles” in hands and feet. Ingestion of high concentrations can possibly lead to death. Long term low - level exposure can cause darkening of the skin and appearance of small “corns” or “warts” on the palms, soles and torso. [2]

Cadmium (Cd)

Cadmium is a bluish - white very toxic metal found in soils, rocks, including coal and mineral fertilizers and used in batteries, pigments, metal coatings, plastics and electroplating. Cadmium is a known human carcinogen with a long biological half-life of 14 to 24 years that bioaccumulates in the human body when chronically exposed. Cadmium is generally found in higher levels in urine, blood, fat, and lung tissues. Smokers generally get exposed to significantly higher cadmium levels than non-smokers. Severe damage to the lungs may occur through breathing high levels of cadmium. Ingestion of high quantities of cadmium irritates the stomach, which leads to severe vomiting and diarrhea. Long-term exposure to lower levels leads to a buildup in the kidneys and possible kidney disease, lung damage and fragile bones. [2]

Lead (Pb)

Lead is a silver to dark gray, soft, malleable, corrosion resistant heavy metal and is one of the earliest metals discovered. As a result of human activities, such as fossil fuel burning, mining, and manufacturing, lead can be found in all parts of our environment: air, soil and water. Lead is used to produce batteries, ammunition and metal products like solder and pipes, and X-ray shielding devices. Lead is a highly toxic metal and, as a result of related health concerns, its use in several products like gasoline, paints, and pipe solder, has been drastically reduced in recent years. Today the most common sources of lead exposure are water pipes in old homes, drinking water, household dust, contaminated soil, lead in certain cosmetics and toys, and lead glazed pottery. Lead is considered a probable human carcinogen that affects every organ and system in the body. Lead has quite variable biological half-life from 30 days in the blood and up to 30 years deposited in the bones. Long term exposure of adults to lead can result in decreased performance in some tests that measure functionality of the nervous system, anemia, small increase in blood pressure, weakness in the fingers, wrists or ankles. Exposure to high levels of lead can severely damage the brain and kidneys and ultimately cause death. In pregnant women, high levels of exposure to lead may cause miscarriage, while in men high levels of lead exposure can damage the organs responsible for sperm production. [2]

Mercury (Hg)

Mercury is another hazardous heavy metal, silver in color, and usually combined with other elements and forms organic and inorganic mercury compounds. Metallic mercury is used for production of chlorine gas and caustic soda, and is also used in thermometers, dental fillings, switches, light bulbs and batteries. Coal-burning power plants are the largest human-caused source of mercury emissions to the air. Mercury in soil and water is usually converted by microorganisms to methylmercury, which is a known bioaccumulating toxin. After entering the human body, this chemical has a biological half – life of up to 80 days, but after crossing the blood-brain barrier, methylmercury can persist in the brain for decades. [2]

An additional concern regarding this contaminant is its ability to be absorbed 10 times more efficiently by the lungs than the gut. Chronic human exposure to mercury vapor largely results in neurological problems, restricted visual fields, tremors, and paranoia. Mercury chloride and methylmercury are known to be possible human carcinogens. The nervous system, generally, is very sensitive to any form of mercury. [2]

Exposure to high levels can damage the brain, kidneys, and developing fetuses. Effects on brain functioning may result in irritability, shyness, tremors, changes in vision or hearing, and memory problems. Short-term exposure to high levels of metallic mercury vapors may cause lung damage, nausea, vomiting, diarrhea, increases in blood pressure or heart rate, skin rashes, and eye irritation. [2]

Hyperaccumulation properties of the cannabis plant and other sources of contaminants

Cannabis plants have been shown to hyperaccumulate and incorporate heavy metals into tissues throughout the plant with the ability to bioremediate contaminated soils. Because of this, cannabis plants have been used to clean up toxic waste sites where other kinds of remediation attempts have failed. After the Chernobyl nuclear incident in Ukraine, 1986, industrial hemp was planted to clean up the radioactive isotopes that had leaked into the soil and ground waters. Even though this Chernobyl example of heavy metal and radionuclide contamination can be pointed to as extreme, as a result of normal anthropogenic activities over the past few decades, including mining, smelting, and the spread of pesticides, heavy metal pollution has become one of the most serious environmental problems today. There is no question that the current suite of four heavy metals being required by state - based regulators is totally inadequate to ensure cannabis products are safe for human consumption. According to evidence available in the public domain, there are about 15 heavy metals found in natural ecosystems and contamination from industrial activities that could be potential sources of contaminants in the plant (including nickel, vanadium, cobalt, copper, selenium, barium, silver, antimony, chromium, molybdenum, manganese, zinc and iron. It is worth mentioning that the chances of these elements ending up in the flowers and the final manufactured cannabis product are very high. Safety assessment of toxicity levels for these elements would need to be investigated further, but they could be the future basis of a federally regulated panel of elemental contaminants in cannabis and hemp. [1]

Having considerations about where cannabis and hemp will grow is critically important because it could have serious implications on the level of heavy metals that are absorbed by the plant. Plant – based phytoremediation is emerging as a cost – effective technology to concentrate and remove elements and pollutants from the environment. The natural inclination of these types of plants to absorb heavy metals from the soil could potentially limit its commercial use for the production of medicinal cannabinoid-based compounds. Numerous studies provide convincing evidence that cannabis is an active accumulator of heavy metals such as lead, cadmium, arsenic, mercury, magnesium, copper, chromium, nickel, manganese, and cobalt. An additional complication is that cannabis and hemp not only absorb heavy metals from the soil, but also from the growing medium, fertilizers, nutrients, pesticides and growth enhancers. Cutting, grinding and preparing the cannabis/hemp flowers for extraction can often pick up elemental contaminants from the equipment itself. [1]

The cannabis industry can learn a lot from the pharmaceutical industry

Elemental toxicology guidelines to regulate the cannabis industry are being taken very loosely, compared to the regulations in the pharmaceutical, cosmetic, dietary supplements, and food industries. Today, there is very little understanding of what heavy metals contaminants are carried over into the cannabis-based products from the various purification steps including preparation, extraction, evaporation, concentration, and distillation. To better understand every potential source of heavy metal contamination in the production of cannabis-based products, the cannabis plant can be considered very similar to the raw materials used in the pharmaceutical industry. To reduce the amounts of elemental impurities in finished products, pharmaceutical manufacturers were required to characterize the entire production process. For that reason, the cannabis industry clearly has to better understand the entire production process, including cultivation steps in order to reduce the amounts of elemental impurities that end up in the final product. [1]

Even though there are numerous CBD-based products on the market intended for medicinal purposes, “Epidolex” is a CBD prescription drug manufactured by G.W. Pharmaceuticals, used for seizures in young children. Since it is a prescription drug, it is regulated by the FDA, according to USP Chapter 232/233 and ICH Q3D guidelines in the ROW for 24 elemental impurities Permitted Daily Exposure (PDE) limits for an orally – delivered drug. In compliance with these regulations, the manufacturer shows strong incentive to ensure that elemental contaminant levels are kept at low levels, since it is a drug prescribed for sick young children with compromised immune systems. [1]

With the lack of federal oversight regarding heavy metals testing in medicinal cannabis – based products and many inconsistencies with heavy metal limits in different states, ICH (International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use) guideline Q3D on elemental impurities is a place on which many state - regulatory agencies rely on.

As a result of the regulations imposed by the USP, Chapter <232> and Chapter <233> in collaboration with the ICH Q3D guidelines, the pharmaceutical industry was mandated to fully understand elemental pathways of the entire drug manufacturing process, including impurities derived from the raw materials, excipients, active ingredients, synthesis process, water quality, manufacturing equipment, containers, primary packaging, etc. To comply with these directives, companies have to show convincing evidence to the regulatory agency that elemental impurities of toxicological concern are below maximum permitted daily exposure (PDA) limits for different routes of delivery.

According to USP Chapter <232>, each of the elemental impurities has the potential to be present in differing oxidation or complexation states. Arsenic and mercury are of particular concern because of the differing toxicities depending on their inorganic and complex organic form. The toxicity of an elemental impurity is related to its extent of exposure (bioavailability). The extent of exposure is determined for each elemental impurity of interest for 3 routes of application: oral, parenteral, and inhalational. The limits are based on chronic exposure. [3]

Cannabis-based products are predominantly administered through oral and inhalation pathways.

Listed below in approximate order of relevance, are the factors considered in the safety assessment for establishing the Permitted Daily Exposure (PDE):

  • The likely oxidation state of the element in the product
  • Human exposure and safety data when it provided applicable information;
  • The most relevant animal study;
  • Route of administration;
  • The relevant endpoint(s).

There are already known daily intake standards for some of the elemental impurities that exist for food, water, air and occupational exposure. Some of the standards, where appropriate, are considered in the safety assessment and establishment of the Permitted daily exposure. Inhalation studies using soluble salts (when available) were performed over studies using particulates for inhalation safety assessment and derivation of the inhalation PDEs. Inhalation PDEs are generally based on either local (the respiratory system) or systematic toxicity. [4]


Chemical elements that are included in ICH guideline Q3D are placed into three classes based on their toxicity (permitted daily exposure) and the likelihood of occurrence in the product. The chances of occurrence are derived from the probability of use in the manufacturing process, the probability of being a co-isolated impurity with other elemental impurities in materials used in the manufacturing process, and also the observed natural abundance and environmental distribution of the element. This classification is intended to focus the risk assessment on those elements that are the most toxic but also have a reasonable probability of inclusion in the final product.

Class 1

The chemical elements Arsenic (As), Cadmium (Cd), Mercury (Hg), and Lead (Pb), commonly known as “the big four” are human toxicants that have limited or no intended use in the manufacturing process of cannabis products. Beyond coming from natural sources and agricultural methods, they can infiltrate cannabis-based products during the processing of cannabis as well. The presence of these types of chemical elements in cannabis-based products typically comes from commonly used materials (mined excipients).

Class 2

Elements are generally considered route-dependent human toxicants. This class is furtherly divided into two sub–classes (2A and 2B), based on their relative likelihood of occurrence in the drug product.

Class 2A elements are characterized by a relatively high probability of occurrence in the product, while Class 2B elements have a reduced probability of occurrence in the product.

Class 3

Elements in this class have relatively low toxicities by the oral route of administration. However, these elements may require consideration in risk assessment for inhalation and parenteral routes.

Generally, the risk assessment process is described in three simple steps:

  1. Identifying known and potential sources of elemental impurities that may find their way into the product
  2. Evaluating the presence of a particular elemental impurity
  3. Summary and documentation of the risk assessment process.

In many cases, previously mentioned steps are occurring simultaneously and the outcome is always focused on developing an approach to ensure that potential elemental impurities do not exceed the permitted daily exposure limits.

As long as there is compelling strong evidence showing that elemental impurity should be excluded from testing, the risk assessment strategy is allowed by global pharmacopeias, described in ICH Q3D guidelines. [4]

With this approach, the pharmaceutical industry is required not only to understand the many potential sources of heavy metals in raw materials but also to know how the manufacturing process contributes to the presence of elemental impurities in the finished product. It makes sense that to some degree there is a transfer of contaminants from the raw material to the finished product, but how do manufacturing processes have an impact on the amount carried over?

Even though the manufacturing process of cannabis-based products might be seen as very similar to the manufacturing process of drugs and herbal medicines, cannabis-based products are being used differently in very different quantities by consumers. Primary packaging and its delivery mechanisms used for these products (such as inhalers and vaporizers) can be an additional source of exposure to elemental contaminants. [4]

Accreditation programs

Cannabis testing laboratories currently are not covered by the FDA and they are guided by state regulators. Implementation of ISO/IEC 17025:2017 laboratory competence certification accreditation system (standards for calibration and testing laboratories that ensure technical competence for producing precise and accurate test and calibration data) together with ISO/IEC 17043:2010 (standards that specifies general requirements for the competence of providers to develop and operate proficiency testing schemes using well-established interlaboratory comparison studies) are some of the recent approaches by the state regulatory authorities to provide confidence to cannabis consumers that testing is being performed according to universally accepted standards. To qualify for such accreditations, cannabis laboratories must conform to all ISO standard areas, including analytical procedures, calibration of instruments and equipment, properly trained personnel who meet specific academic credentials, etc. [1]

Analytical methods used in testing cannabis and cannabis-based products for heavy metals

Herbal medicinal products are currently not included in the scope of the ICH Q3D Guideline on Elemental Impurities. However, the European Pharmacopoeia, General Monograph 2.4.27: Heavy metals in herbal drugs and herbal drug preparations, describes methods for determination of heavy metals in herbal drugs and fatty oils. These methods cover lead, cadmium, and mercury as well as arsenic, copper, iron, nickel, and zinc.

The following apparatus that is described in this section is considered essential in testing of heavy metals in herbal drugs and herbal drug preparations and consists of the following:

  • Digestion flasks, polytetrafluoroethylene, perfluoroalkoxy polymer, quartz or glass flasks with a volume of 20-150 mL, fitted with an airtight closure, a valve to adjust the pressure inside the container, and a polytetrafluoroethylene tube to allow the release of gas;
  • A system to make flasks airtight, using the same torsional force for each of them;
  • A programmable microwave oven (e.g. with a magnetron frequency of 2450 MHz, with a selectable output from 0 to 1500 ± 70 W in 1 percent increments), a polytetrafluoroethylene-coated microwave cavity with a variable speed exhaust fan, a rotating turntable drive system and exhaust tubing to vent fumes;
  • An atomic absorption spectrometer, an inductively coupled plasma-atomic emission spectrometer, or an inductively coupled plasma-mass spectrometer. [5]

The most commonly used analytical technique for tracing elemental impurities is considered to be inductively coupled plasma mass spectrometry (ICP-MS), emphasizing its superior sensitivity over other atomic spectroscopic approaches. It is a very sophisticated multi-element analytical technique that can easily measure down to parts per trillion (ppt) detection levels. It requires an analytical chemist with a high degree of expertise in trace–elemental analysis to generate and evaluate these types of results. Analytical method development and validation, collecting a representative sample, use of reference materials, interference corrections, calibration routines, sample preparation, and digestion techniques, are few of the many skills needed to perfectly execute this technique. For that reason, the pharmaceutical industry abandoned the old USP Chapter 231 – sulfide precipitation colorimetric test and wrote two brand new methods: USP Chapter 232 (defining 24 elemental impurities of toxicological concern) and USP Chapter 233 (addressing most suitable analytical procedures including plasma spectroscopic techniques, sample digestion procedures, and robust validation protocols using standardized spike recovery testing procedures).

Other widely known techniques used in cannabis heavy metal testing are ICP-OES (Optical emission Spectrometry), FAA (Flame atomic absorption), electrothermal atomization atomic absorption (ETAA), and atomic fluorescence (AF). Any of these techniques is adequate as long as its detection capability is sufficient for detecting the maximum limits that are defined by the regulatory authorities. [5]

Sample preparation for cannabis heavy metal testing

Specific sample preparation protocols, microwave digestion conditions, and ICP Mass Spectrometry (ICP-MS) methodology are developed and employed to offer a robust method for all cannabis sample types. Typically, sample preparation consists of homogenization followed by microwave digestion to break down the complex matrix and extract the heavy metals. The dried cannabis plant generally is a very inhomogeneous matter that consists of leaves, buds including resin, stems of various thicknesses, and seeds. Every part of this plant accumulates heavy metals to a different extent. Because of this, when preparing the samples for heavy metals content in cannabis, the material needs to be thoroughly homogenized through a robust sample preparation scheme before sample analysis. There are numerous known techniques for sample homogenization, but the most recommended process for this type of sample breakdown is grinding. Depending on the technical complexity of the process, there are various milling techniques: mills (rotor, cutting, knife, ball mill), mortar and pestle, and rolling pin. Differing in feed quantity, milling speed, and final sample fineness, sometimes the best result can be achieved by combining a few or more of these techniques. Because of the sticky and smearing appearance of cannabis resin, it is always recommended to freeze cannabis samples before milling. Freezing can be accomplished by placing the samples in a – 20°C freezer, or by using cooling agents like dry ice (- 78°C) or liquid nitrogen (- 196°C). Depending on the target analytes in the testing, specific grinding tools are allowed or forbidden to be used in the process of sample preparation. When analysis of arsenic, cadmium, lead, and mercury are being conducted, stainless tools can be used no matter what type of grinder is more suitable for the grinding process. [6]

Ways to reduce errors that occur from sampling and testing

  • It seems obvious, but representative sampling at the very beginning of every quality control test is crucial for a successful analysis.
  • Cleanliness of the sampling rooms, specially designed sampling tools, tidy surface area where testing is performed, and correct handling of samples are things to address seriously
  • ICP-MS offers extreme sensitivity with low detection limits and because of this, any potential source of elemental contaminants needs to be eliminated from the operating rooms where analysis is being conducted. Fluctuations in air temperatures can lead to signal drift, so rooms with controlled temperature, airflow, pressure, and humidity should be considered where ICP-MS testing is intended to take place. Consider installing the instrument in ISO 6 or ISO 7 classrooms. An operator that smokes can elevate background levels, particularly for cadmium.
  • Metallic grinding equipment when preparing the samples for digestion should be avoided.
  • Digestion of samples in inadequate containers and vessels can be a major source of contamination. Make sure that analysis blanks are clean and free of elemental contaminants.
  • All chemicals, acids, analytical reagents, reference calibration standards, and deionized water should be of high-grade purity for the intended use.
  • Understanding uncertainty and errors involved in analytical methodology (analytical balances, calibration standards, reference materials, sample preparation techniques and precision, etc.) [1]

Product recalls

There is clear evidence that in today’s market commercially available cannabis-based products are not completely free from heavy metal contaminants and some of the products are being recalled for high levels of heavy metals.

In June 2019, Medical cannabis regulators in Maryland warned the public about the risk of possible lead contamination in popular vaping devices. They issued an advisory to notify patients and stakeholders of potential lead contamination of cannabis liquids in vape cartridges following exposure to heat.

Since the beginning of the medical program in 2017, state-licensed cannabis growers have been required to test for heavy metals. Additionally, regulations for quality control testing on the final vape cartridges were proposed as an additional safeguard, in the interest of public safety. According to the Maryland Medical Cannabis Commission advisory, even though results indicate that lead is not present in Maryland vape cartridges at the time of product testing, there is a possibility that lead may leach into the cannabis liquid from exposure to the heating coils with use, over time. At that time, Maryland was among the few states that required two steps of testing for heavy metals in cannabis: one at the growing stage and one at the processing stage when the raw flower is infused into the product.

Today’s challenge regarding cannabis heavy metals testing is the lack of standardization across different testing facilities. In the examples presented above, it is very clear that manufacturers claiming their products have traces of heavy metals within limits, often receive divergent results for their products from third-party laboratories and regulatory authorities. These are a few of many examples where wildly inconsistent test results are being generated across laboratories, showing the need for regulated and standardized protocols for equipment, operating procedures, and qualification and certification documents for lab personnel. With time, state regulators are gaining more experience and are attempting to implement basic accreditation measures for cannabis laboratories.

The majority of the states that allow for medicinal cannabis are only focused on the regulation of Pb, As, Cd, and Hg. But, there are numerous publicly available documents showing that there are probably another 10 to 15 heavy metals to be assessed as potential contaminants in cannabis and cannabis-based products. [7]

Heavy metals testing in cannabis vaping aerosols

Historically, most recreational consumers are using cannabis by inhalation. The chemistry behind this process has been predominantly investigated in tobacco products and many studies have highlighted the similarity in carcinogenic properties of chemicals found in tobacco and cannabis cigarettes. Vaping sticks, carts, and pens are today’s common way of inhaling cannabis products. The demand for these devices has skyrocketed, which attracts manufacturers with very little regard for safety. In today’s market, there are thousands of these devices where the cannabis extract or oil is heated up to 200°C and formed aerosols are consumed by the consumer very much like a medical device used by asthma patients. The concern about these devices arises from the fact that most of the components inside the vaping devices are typically metal, including mouthpiece, coil, liquid tank, battery terminals, etc. These parts are usually made from elements such as Fe, Cr, Cu, Ni, Pb, Sb, Sn, Zn. Taking into consideration the temperatures that reach near 200°C and the potential presence of dissolved metals in vaping devices, it can be almost certainly concluded that some fine metallic particles will end up in the consumer’s air pathways. With the increased popularity of cannabis vaping in the United States, new regulations have risen in the state of Colorado regarding the testing of heavy metal contaminants in emitted aerosol, using electronic cannabis delivery systems (ECDS). With this Colorado became the first proactive state in this field to require testing cannabinoid vaping aerosols for heavy metal contaminants. The Colorado directive specifically emphasizes the characterization of the vaping aerosol for heavy metals, not just the liquid. The main reason behind this regulation is mainly due to the many different materials used inside ECDS and cannabis vaporizer single-use cartridges. Cannabis psychoactive and therapeutic components reach their volatile state when cannabis extract is heated and tiny airborne droplets form an aerosol. The aerosol (called a vapor) is inhaled by the end-user. The transport of the metal particles in vaping aerosol is not clear, but they vary depending on the elemental composition of the vaping device and their physical and chemical properties. Most of the metals used in the composition of vaping devices are not volatile at temperatures of 200-300°C, therefore metal volatility is not the mechanism of transport in the aerosol. [8]

Sampling the aerosol without contaminating the sample is quite a challenge, due to the mechanism of aerosolization at temperatures around 200 – 300°C. Once the aerosol has been generated, there must be a way to collect the very same aerosol sample in order to be measured by inductively coupled plasma mass spectrometry (ICP-MS). On the other hand, sampling the vaping liquid from the refillable pod or vaping device tank is quite simple and straightforward. What types of solvents will be used for dilution will be determined from the diluents used in the device. In electronic nicotine delivery systems (ENDS), typically used diluents are hydrophilic compounds (water-soluble) like propylene glycol or vegetable glycerin. However, vaping devices used for cannabinoids are harder to sample because diluents might also include some oils which are not water-soluble (hydrophobic), in addition to the cannabinoid extract itself, which is hydrophobic. In this case, the liquid needs to be extracted and dissolved with an organic solvent, and organic solvents present problems to the ICP-MS instrument unless an optimized sample introduction system is used. This is usually achieved by rinsing the initial tubing with diethylene glycol monoethyl ether (DEGMEE). This solvent is characterized by low volatility, excellent hydrophobic properties, and high water solubility. [8]

The most commonly used method for trapping and collecting vapor from vaping devices is with an aerosol-generating machine, which is similar to the traditional smoking machines used to measure contaminants in tobacco products. These types of machines work extremely well for measuring organic analytes, but when it comes to the evaluation of inorganic pollutants, limitations arise. It is mostly because many of the components of the vaping device are not made of high purity materials. Because of this, researchers are usually forced to customize the aerosol generation machines when used for testing heavy metals.

There are two known available and scientifically valid methods used in the collection of vaping aerosols:

  • ISO Standard – Method 20768:2018, a specifically developed test routine of cannabinoid vapor products with analytical vaping machines.
  • CORESTA Method 81, a method that defines the requirements for generating and collecting aerosol samples from e-cigarettes for analytical testing purposes.

Both of these methods have similar specifications and they both are similar in functionality, even though the CORESTA method is more widely known to be used with tobacco and nicotine vaping products. [8]


Today’s global demands on cannabis and cannabis-based products are moving so fast that the scientific community is really struggling to keep up with them. On the other hand, global industrialization leaves our environment severely polluted by heavy metals, which brings an enormous burden to the cannabis industry in the process of producing safe, effective, and high-quality cannabis-based products. It is very clear that currently, heavy metals testing on cannabis and cannabis-based products is very challenging for both testing laboratories and regulatory authorities. For this reason, it is critically important that every potential source of heavy metal contaminants in cannabis and cannabis-based products will be thoroughly assessed and at the same time, adequate controlling data over these contaminants will be demonstrated.

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