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Is vaping cannabis safe? What we know (and what we don’t)

Vaporisation is one of the most common cannabis consumption methods, but what do we know about the potential risks?



Vaping is widely believed to be a safer alternative to smoking when it comes to cannabis consumption, but what do we know about the potential risks and long-term effects?

Vaporisation is one of the most common cannabis consumption methods, particularly when a flower-based product is prescribed for a medical condition.

It works by heating the flower or extract to a temperature at which it decarboxylates the raw acid forms of cannabinoids (THCA and CBDA) and converts them into the active cannabinoids, commonly known as CBD and THC, which are then inhaled through vapour. 

Vaping usually occurs at a temperature below 200°C, and many believe it to be a safer method of consumption than smoking, which occurs at higher temperatures and releases toxins and carcinogens during the combustion process which are then absorbed into the lungs. 

Many people vape cannabis, as opposed to taking oils or edibles, because they prefer how it makes them feel or because its effects can be felt faster, and, as a result, this may provide more effective relief for patients experiencing chronic pain or acute anxiety. 

However, we still know relatively little about the potential negative effects of vaping cannabis.

There are some concerns around microbial contamination in inhaled cannabis, particularly for individuals with weakened immune systems who may be more at risk from infection. The issue is particularly prevalent due to a lack of consistency and standardisation when it comes to testing cannabis products. 

Cannabis is a plant, and so it naturally contains – and is exposed to – potentially harmful organisms including bacteria and fungi, as well as mycotoxins they produce and pesticides from the growing process. These bacteria and fungi, along with other toxins, are known as the ‘microbial burden’ or ‘bioburden’.

While heating to temperatures above 60°C is known to kill bacteria and fungi, how effective this is can depend on exposure time and temperature. Microbes also thrive with increasing temperatures and start to multiply up to a certain temperature at which they die.  

Some of the fungi found in cannabis are usually not considered harmful for healthy individuals, but can cause serious infections in people with compromised immune systems.

Meanwhile, bacteria present which may be cause for concern include Clostridium, which can cause diarrhoea, Streptococcus (also known as Strep A), Salmonella and certain Escherichia, or E.coli.

READ MORE: How to clean your cannabis vaporiser

New research raises potential concerns

A recent study found that vaporising cannabis flower may not reduce the microbial load, posing potential risks for immunocompromised patients. 

Researchers at the National Center for Toxicological Research used cannabis plant material supplied by the National Institute on Drug Abuse (NIDA) to assess the impact of heating using a commercial vaporiser, the Volcano Digit by Storz & Bickel.

A cannabis placebo, ‘low THC potency’ (1.9%) cannabis and ‘high THC potency’ cannabis (6.5%) were then exposed to either no heat or heating for up to 70 seconds at 190°C using the vaporising device.

The researchers found that heating cannabis to the standard commercial vaporiser temperature of 190°C for 70 seconds did not significantly reduce the ‘microbial bioburden’ in the cannabis.

The authors concluded: “Overall, the study demonstrated that heating of the cannabis materials at 190°C in the vaporiser for 70 seconds (settings suggested by the manufacturer to volatize the bioactive compounds) did not lead to significant reductions in microorganisms present in the cannabis materials, and, in some cases, the heating seemed to enhance the numbers of organisms recovered.”

They go on to say that this final observation could be due to residual compounds ‘sticking’ microorganisms to the plant material. 

What does this mean for cannabis consumers?

While it is important that all patients – and prescribers – are aware of the potential risks of vaporising, this is most concerning for those who may be more vulnerable to infection. 

Vaping with electrical devices is a relatively new phenomenon, with commercial vaporisers only becoming widely available in the last decade. As a result, there is limited data on the long-term effects of it.

Some of the fungi identified, including members of the ‘Aspergillus genus’, have been known to cause allergic reactions and/or infections in ‘highly immunocompromised’ patients. This includes those with conditions that weaken the immune system, such as HIV or other immune disorders, and patients taking immunosuppressant medications.

Dr Callie Seaman, a cannabis scientist who has worked in the hydroponics industry for the last 20 years, helped us break down these findings.

“This is mostly a concern for those people who have pulmonary problems or are immunocompromised,” she explained.

“This is where we have got to warn patients about these risks so that they can consider what the best mode of administration is for them. Like any medication, you need to know about the risks that come with it. It would be irresponsible of us to think that there are no risks associated with consuming cannabis.”

Most of the cannabis products that are available on prescription in the UK have undergone a process known as irradiation, which helps to kill microbes and further reduce the microbial load, although it doesn’t completely eliminate the risk.

“Through irradiation you are reducing the risk of these microbes being there, but while it will kill the actual colonies – or anything living – it doesn’t get rid of the mycotoxins that they produce,” Dr Seaman continued.

“Inhaling anything can be problematic in my view, particularly if your immune system is compromised to the point where something like pneumonia could become a serious problem. 

“You wouldn’t want to be vaporising but looking at other methods of consumption where there is less chance of exposure [to microbes], such as oils or tinctures.”

What do cannabis prescribers know about the risks?

The Medical Cannabis Clinicians Society (MCCS) delivers regular training for UK doctors who are interested in prescribing cannabis.

The president of the MCCS, Professor Mike Barnes, told Cannabis Health that there is awareness of the risks of microbial load in certain patient groups among prescribers.

While the society doesn’t have any written guidance, the potential risks of vaping are taught as part of its training programmes. 

Professor Barnes commented: “When prescribed in the UK, cannabis flower must be consumed via a vaporiser, which studies have shown to be safer than smoking. However, there are always going to be risks that come with any medication, and it’s important that patients are informed of them.

“The MCCS makes new and ongoing prescribers aware of the risks of vaporising, particularly for those populations who may be more vulnerable to adverse effects, and these are covered as part of our ongoing teaching programme.”

This article was reviewed for accuracy by Dr Callie Seaman and Professor Mike Barnes. 

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Sarah Sinclair is a respected cannabis journalist writing on subjects related to science, medicine, research, health and wellness. She is managing editor of Cannabis Health, the UK’s leading title covering medical cannabis and CBD, and sister titles, Cannabis Wealth and Psychedelic Health. Sarah has an NCTJ journalism qualification and an MA in Journalism from the University of Sunderland. Sarah has over six years experience working on newspapers, magazines and digital-first titles, the last two of which have been in the cannabis sector. She has also completed training through the Medical Cannabis Clinicians Society securing a certificate in Medical Cannabis Explained. She is a member of PLEA’s (Patient-Led Engagement for Access) advisory board, has hosted several webinars on cannabis and women's health and has moderated at industry events such as Cannabis Europa. Sarah Sinclair is the editor of Cannabis Health. Got a story? Email / Follow us on Twitter: @CannabisHNews / Instagram: @cannabishealthmag


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