Contaminated cannabis: What is it and how do you spot it?

Despite being illegal in the UK for over five decades, cannabis remains widely used for both its medicinal and recreational properties. It is estimated that almost 10% of people aged 16 to 59 in the UK have used cannabis in the last 12 months – that’s more than 3 million people. But while prohibition may not impact consumer numbers, various considerations mean that it could affect consumer safety.

Advocates for prohibition as well as those in favour of reform often refer to the potential presence of contaminants in black market cannabis products. The unregulated cultivation of cannabis has indeed been associated with contamination with harmful chemicals and other substances designed to increase yields or simply the weight of the product.

For example, in recent years, reports of “grit weed” appear to have been on the rise in certain parts of the country. Consumers from every corner of the UK, from Cornwall to Glasgow, shared reports – some with photo evidence – of receiving contaminated weed.

This isn’t a new problem. As the Guardian noted in 2007, a rise in reports from the time indicated that grit weed – cannabis contaminated with tiny glass beads, sand, or other small particles – was being sold in almost every part of the country. The issue was eventually linked to illegally imported cannabis products from the Netherlands.

What is “grit weed”?

Grit weed is the name used to describe herbal cannabis products that have been contaminated with potentially harmful substances. Some black market cultivators spray their cannabis crops with tiny particles, which may be made of small glass beads, salt, sand, silicon, and even iron filings, in order to bump up the weight of the product. They are then able to sell smaller quantities of cannabis for an inflated rate.

Purchasing grit weed isn’t only leaving consumers out of pocket, it could also pose a risk to their health. For example, a case study of two individuals exposed to cannabis smoke containing glass or sand found that it can be associated with respiratory symptoms; however, spontaneous clinical improvements were observed shortly after cessation of the contaminated cannabis.

Back in 2007, an analysis carried out by the French Observatory of Drugs and Drug Addiction found that in many cases, glass particles found in grit weed are too large to be inhaled into the lungs. Instead, they are more likely to deposit in the mouth or throat where, though they may cause some discomfort, are likely to pass through the body causing little harm. Nonetheless, knowing what to look for could potentially save you some undesirable side effects.

How to spot grit weed

Unfortunately, grit weed isn’t always easy to spot. At first glance, the particles sprayed onto the leaves and flowers of the plant can resemble trichomes – the sticky, cannabinoid-rich appendages that cover the buds. Buds contaminated with glass beads, salt and other particles can even look like pretty high-quality stuff; however, if you can get a close enough look, there will likely be some tell-tale signs that things aren’t quite as they should be.

Grit Weed Alert! Contaminated cannabis on UK streets. We've had reports that this is in Wrexham, Oswestry, Coventry, Teesside, Manchester, London, Cheshire and Cornwall so far. Grit adds weight to increase profit, looks like THC to the untrained eye but causes harm! #regulatenow pic.twitter.com/rk0MLpxjaU

— UK Cannabis Social C (@UKCannabisClubs) November 8, 2023

Trichomes have a distinctive structure, appearing like tiny hairs with a globe at the end. If the frosty coating on your buds isn’t clearly distinguishable as these rounded hair-like structures – for example, if they are angular – you may want to investigate further or play it safe and toss the weed out right away.

Other potential cannabis contaminants

The sad truth is, for the vast majority of cannabis users in the UK (and other countries that continue to uphold prohibition), it is simply impossible to detect all potential contaminants – even if we have confirmed the trichomes are, in fact, trichomes.

There is also the risk of mould, pesticides, heavy metals, and more to contend with. Luckily, significant contamination with harmful substances is believed to be fairly rare – especially when purchasing from a trusted dealer (of which there are many). Nonetheless, it is essential to be aware of the potential harms associated with these contaminants.

Pesticides

A 2023 study of both legal and illegal cannabis products in Canada found that 92% of unregulated cannabis tested positive for numerous pesticides, compared to just 6% of regulated products. Similarly, a 2014 Luxembourg study detected pesticides (including fungicides, insecticides, and acaricides) in almost half of the seized cannabis samples tested, with 19 samples containing seven different products.

Another review notes that cannabis samples are often found to contain pesticides that are “classed as moderately hazardous by the World Health Organisation”. However, while some studies indicate that significant levels of pesticides may be transferred into cannabis smoke, there is currently little research into the harms associated with the consumption of pesticide-contaminated cannabis.

Mould

Mould is produced by some fungi and is an inconvenience that many of us will associate with damp or gone-off food. But it can also appear in more unexpected places – including our cannabis. This is most likely to happen if the buds aren’t cured quickly enough during processing, as mould forms best in damp conditions.

While mould might be easy to spot on an old loaf of bread, it can be harder to detect on plant matter. Unfortunately, when consumed – particularly when inhaled – it can have significant health implications. These can include irritation, allergic reactions, and fungal infections.

In recent years, there have been a number of reports of medical cannabis patients finding mould in their prescribed products. Some patients have told how they had difficulties reaching a resolution with their dispensary, despite attending hospital. While this is understandably a concern, particularly for those consuming cannabis for medicinal reasons, it is important to note that such cases are relatively rare.

For more information about possible contamination with mould, take a look at our recent article ‘Cannabis mould – what is it and how do you spot it?’

What about fake “cannabinoids”?

We’ve seen far too many news stories with sensationalist headlines referring to “cannabis” only to find on reading it that they are actually talking about synthetic cannabinoids, such as spice. These fake cannabinoids are often sprayed onto organic materials which are then smoked like cannabis; however, they are much more potent and can cause extreme reactions, including nausea, poor coordination, mental health issues, and even seizures.

Thankfully, it is relatively easy to distinguish these potentially dangerous products from real herbal cannabis. Unfortunately, the same isn’t always true of other products, such as vapes and e-liquds. Drug testing service WEDINOS frequently reports cheap e-liquids for refillable vapes sold as THC to contain synthetic cannabinoids and nicotine. While in Northern Ireland, a warning was issued in 2020 as a rise in vape products advertised as cannabis or THC, were found to contain spice.

And it’s not just synthetic cannabinoids that are being disguised as THC or CBD in vape products. A recent article by the Guardian reveals that so-called cannabis vape products containing xylazine – a powerful animal tranquiliser – may be on the rise in the UK. The drug, which can cause drug overdoses and skin ulcers – has also been found in counterfeit prescription drugs such as codeine, alprazolam (Xanax) and diazepam (Valium) in recent years.

Would cannabis legalisation help?

For many advocates of cannabis legalisation, greater regulation of cannabis products is the primary motivator. As has been made clear by decades of prohibition, people simply are not going to stop using cannabis, so would controlling its cultivation and distribution make it safer?

In theory, creating a legal supply chain of cannabis would allow for adequate testing of legal products. This would enable the detection of potentially harmful contaminants, from hazardous pesticides to dangerous drugs. However, with ongoing supply issues, including mould- and seed-infested cannabis, we have seen in the UK in recent years that things don’t always go as smoothly as they should.

Nonetheless, the only way to ensure consumers have access to the safest products possible is to regulate.