What is ‘Irradiated’ Cannabis?

And why does it matter?

by Ruby Deevoy

When you hear the word ‘radiation’, it probably doesn’t conjure up the best images. We know that at certain doses, exposure to radiation can damage DNA in our cells, cause cancer and even kill you. But we’re all exposed to unavoidable low level radiation every day. There are radioactive materials and radiation in the earth, in space, in lightning, in the air and in our food. 

There’s also radioactive fallout all around us from historical nuclear testing and nuclear accidents, at levels that are deemed safe by the experts. Many people are understandably concerned about the radiation most prescribed cannabis products have been exposed to – a process called ‘irradiation’ that’s commonly used to meet strict EU-GMP safety standards regarding microbial contamination.

To help cannabis patients make informed choices about the products they consume, this article will answer some of the most frequently asked questions about cannabis irradiation

  • Is irradiated cannabis safe to consume?
  • Does irradiation affect the therapeutic benefits of cannabis? 
  • Why do producers irradiate cannabis in the first place?


What is irradiation?

First thing’s first – if we’re going to discuss the pros and cons of irradiated cannabis, we’d better understand what irradiation actually is.

irradiation noun

ir·​ra·​di·​a·​tion | \ i-ˌrā-dē-ˈā-shən  \

Definition of irradiation

1: exposure to radiation (such as X-rays or alpha particles)

2: the application of radiation (such as X-rays or gamma rays) for therapeutic purposes or for sterilization (as of food)also : partial or complete sterilization by irradiation


There are three types of radiation:

Alpha: Alpha radiation is extremely harmful (the most harmful type of radiation there is), however, it lacks the energy to penetrate most things. It can’t penetrate human skin. It can however cause severe damage and death when inhaled or swallowed. Cannabis is never irradiated using this type of radiation.

Beta: Beta radiation is more penetrating than alpha particles, but less damaging to living tissue. It can penetrate human skin and cause burns, but are most dangerous when inhaled or swallowed. If an eBeam is used to irradiate cannabis, this is the equivalent of Beta radiation, but generated using electrons not a radioactive source. 

Gamma: Gamma rays are electromagnetic radiation, like X-rays. They have tremendous penetrating power, easily penetrating skin, clothes and can only be blocked by several inches of lead or a few feet of concrete. If exposed to a high blast of gamma rays, this radiation is deadly. 

However, it has a very short half-life, only taking seconds to disappear, and so is commonly used to treat many consumable products including fruit, vegetables, cereals, bulbs and tubers, dried aromatic herbs, spices and vegetable seasonings, fish, shellfish, poultry and cannabis.


Why is medical cannabis irradiated?

As an organic product, cannabis will never be naturally sterile. Microbes and spores will inevitably be present on every single bud of cannabis. For most people, this isn’t such a big deal – a load of the bacteria will be eradicated by heating if you smoke or vape anyway, and even if it doesn’t, your immune system is likely strong enough to fight anything nasty off. 

But for some, who are chronically ill or immune compromised, inhaling potentially harmful spores could be fatal. The irradiation process is supposed to kill off any microbes, thus making a decontaminating the flower and extending its shelf life.

You could argue that humans have been consuming non-irradiated cannabis safely for thousands of years, and it’s only very recently that we’ve felt the need to introduce this process to make cannabis eligible as a medical product in the UK. But the possible dangers of using contaminated cannabis are well established in scientific literature (Llamas et al., 1978; Sutton et al., 1986; Marks et al., 1996; Szyper-Kravitz et al., 2001; Kouevidjin et al., 2003; Cescon et al., 2008; Bal et al., 2010; Ruchlemer et al., 2015). For those with compromised immune systems, such lung diseases could be even fatal (Hamadeh et al., 1988). 

Aspergillus spores pose one of the greatest risks to cannabis patients which, unlike cannabis itself, has killed people. This perhaps highlights one of the greatest risks of patients being forced to buy cannabis in an unregulated, illegal market.

Worryingly, studies have found irradiated Aspergillus (using 2 kGy) produced levels of mycotoxins two times greater than those produced by control strains. This study found that gamma radiation decreased fungal populations significantly.

However, doses of 5 and 10 kGy (10 being the maximum dose as advised by the Food and Agriculture Organization, International Atomic Energy Agency, World Health Organization, and European Commission) were ‘insufficient to completely eliminate the viability of some A. flavus strains.’ It also finds that ‘Irradiation did not change toxigenicity and triggered surviving toxigenic strains to produce aflatoxin B1’’.

Other studies show Gamma radiation to be effective at reducing Aspergillus flavus and aflatoxins (poisonous carcinogens and mutagens that are produced by certain moulds, particularly Aspergillus species). This study shows a maximum degradation rate of 83.36% (at dose of 6 kGy).

There are also studies to suggest the process of irradiation doesn’t get rid of certain microbes (like E. coli and Salmonella) for good, like heat does. One study found that an eBeam caused extensive DNA damage within E. coli cells (as noted in many other studies), but they remained metabolically active up to 9 days post-irradiation.

In a study examining gamma radiation, it was found that almost all microbes were resuscitated 2 months after irradiation.

There’s no denying that some patients need their cannabis to be microbe free (or at least containing safe levels), but is irradiation the best technique? Furthermore, is irradiation safe?

Is irradiation safe?

A large amount of our food is irradiated for the same reason as cannabis, and it’s been this way since the 1950s. According the Food Standards Agency (FSA), decades of research has deemed this process to be perfectly safe, stating that ‘irradiated food has been exposed to radiation but does not become radioactive itself’.

Gamma radiation, which is commonly used to decontaminate produce, decays in a matter of seconds. So while you might not want to be standing in the room with the rays, it doesn’t stick around long. 

eBeam radiation is also deemed to be safe (perhaps even safer as it’s not from a radioactive source), and has been used around the world for many years as a sterilization process.

Of course, it’s not only a question over the safety of ingesting (or inhaling) an irradiated product that bothers a large number of cannabis patients. It’s how the process might impact the composition of the flower – the cannabinoids, terpenes and flavonoids – and therefore the therapeutic effects.

Is irradiated cannabis good or bad?

Patients who try irradiated cannabis often remark on the poor flavour, smell and dry appearance and smoke of the product, suggesting a detrimental effect on water content and terpenes – the aromatic compounds, which do possess important therapeutic value, but are present in very small amounts. Some experts believe they play a huge role in the pharmacological actions of cannabis, whereas others don’t.

The only single peer-reviewed paper that demonstrates the effect of radiation on cannabis flowers (by Bedrocan BV, the licensed company that provided the medicinal grade cannabis tested) has shown these decreases. But only in amounts that are unlikely to make any difference to medicinal effects.

The researchers evaluated the cannabinoid, terpene and water content of cannabis flowers before and after irradiation. The results showed a measurable effect on terpenes, which in general was between 10 and 20%, but for some components as much as 38%. 

Although this may seem like a lot it’s actually comparable to the effect that short term storage in a paper bag had on cannabis samples, in a study performed by (Ross and ElSohly, 1996). Water content was also shown to be reduced as a result of irradiation, while CBD and THC remained the same.

However another 2020 study performed by researchers with no links to the cannabis industry found that the level of THC significantly increases as a result of irradiation. 

It also noted evidence that irradiation using gamma rays induced degradation and detoxification of phenolic compound 2-nitrophenol (2-NP), generating several volatile products (Alsager et al., 2018); change in colour, taste and flavour (of peanuts); decreases in the overall level of volatile components (in sage seeds), substantially affecting β-pinene and limonene (Yalcin et al., 2011); decreases anti-oxidant activity; and an increase total phenolic content. This increase was also seen in a study performed in 2000, on citrus fruits.

Research into how irradiation affects minor cannabinoids is still lacking.

Is irradiated cannabis right for me?

Given how dangerous microbe contamination can be for some patients, it’s clear that there is a need for some sort of process that can make cannabis products unequivocally safe for consumption. Whether irradiation is the best option is another question, and it certainly seems as though there is room for further research and an alternative solution.

However not all patients require a decontaminated product and, if only for a more pleasurable experience in terms of smoothness of smoke, taste and smell, would prefer access to a non-irradiated product. This, compounded with the fact that more research is evidently still needed to determine the full effects of irradiation on cannabis, is enough to suggest that in an ideal world, both options should be available. 

Patients should be informed as to whether a product is irradiated or not and be given a full certificate of analysis for any prescribed cannabis product as standard – including microbial, heavy metal, terpene and cannabinoid content, so that they can make an informed decision. 

If non-irradiated cannabis products would be your preference, it is possible to be prescribed these. Currently there are two ranges that meet EU-GMP microbial requirements in other ways. It’s also possible to choose between gamma irradiation and eBeam irradiation. You can view a list of options here, but to be absolutely sure, make sure to ask your prescribing clinician. 


This article has been fact-checked by:

Professor Mike Barnes, chairman of the Medical Cannabis Clinicians Society and the Cannabis Industry Council

Tristan Castillo, Head of Extraction & Formulation for True North Labs, Switzerland

Dr Callie Seaman, PhD Chemist and director of Aqualabs

Ruby Deevoy is a U.K. cannabis journalist with years of experience covering CBD and cannabis in mainstream publications such as The Independent, The Mirror, The National, Elle, Red, Top Sante and Natural Health magazine. She’s also the U.K’s only CBD columnist, writing monthly for Top Sante magazine, cannabis agony aunt for Leafie, writes the Indybest CBD product lists, is founder of The CBD Consultancy and is the primary press member for The Cannabis Industry Council. Tweets @RDeevoy.

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