sprayed weed

Contaminated Cannabis and How To Detect it

Weed contamination is common, which is why it’s important for you to know how to spot it before it does any harm. Not only will it make cannabis safer for users, but also helps build trust in the burgeoning cannabis market.

Using cannabis has never been more popular. However, there have recently been reports of ever-increasing amounts of contaminated marijuana—something no user or self-respecting grower wants.

Well, good thing you’ve found this article as we’ll tell you everything you need to know about weed contamination. You’ll learn how weed gets contaminated, as well as a few friendly tips on how to spot contamination and how to avoid it.


Cannabis use is growing in popularity around the world. In fact, there are now a number of countries reforming cannabis for legal recreational and medical use. However, with every development comes change, and the amount of contaminated weed circulating is increasing.

You would think with increasing legalisation, that contamination would go down, due to regulation and testing. However, for home growers, there are no tests other than experience and knowledge. Contamination is very common in cannabis because it can happen during the growing, harvesting, and extracting process. Storage facilities might also contaminate cannabis, especially if these are stored for long periods of time.

Mildew or mold can easily be spotted with knowledge, but there are other contaminations that can only be discovered through chemical analysis.



Fungal growth is one of the most common causes of contamination, with mildew and grey mold being the usual suspects. If you happen to spot an unnatural looking white powder or a fuzzy skin texture, then that could be a sign that your cannabis has a fungal infection.

Rooms where cannabis is grown should have their own thermometer and hygrometer to ensure that the ideal temperature and humidity is maintained. The grower should conduct regular inspections to hunt for signs of contamination, and remove it as soon as it is seen.


Microbial contaminants are also common in cannabis because of the microbes’ strong adaptation build.

A recent study found in the Clinical Microbiology and Infection journal states that gram-negative bacilli are found in numerous dispensaries in Northern California. To make things worse, these bacteria contaminate medical cannabis which is used for medicinal purposes. Unfortunately, the only way to assure your weed is microbe-free is to have microbial testing.

Residual Solvents

Cannabis is often used to create extractions. While the process involved has a lot of benefits to the medical world, there’s still a huge chance that the process leaves behind solvent residue if not done correctly. Extreme care is needed when creating solvent based extractions.


Insects are one of the biggest problems a cannabis grower can face. Unfortunately, the most common thing they do to combat this is spray pesticides. Though this might drive away pests from damaging their cannabis plants, this process has serious negative effects on the end user.

Some pesticides remain in the plant even after harvest and curing. Inhaling these pesticide particles, with imidacloprid, spiromesifen, and etoxazole being the most common ones, is dangerous to one’s health.

Miscellaneous Contaminants

Contaminants are common in cannabis because of the processes involved in growing, harvesting, preparing, extracting, and eventually to packing its many products. As of now, it is not yet mandatory for cannabis to undergo contamination testing, even in countries where it is legal.

Because of this, the only way for you to know if your weed is contaminated is to check if the place where your cannabis is grown and packed answers to the safety precautionary measures. Or if you are growing yourself, by taking great care to ensure a clean and well maintained grow.



Before you smoke weed, always remember first to feel its texture. If it’s dry, then there is very little chance of mould contamination. But if it feels spongy and damp, it could be the case there is mould. Also be careful with cannabis that has a powdery texture because some dealers add crushed pills to enhance its aesthetic appeal—these are not always trichomes!


Speckled white discolorations or fuzzy greenish and grayish color on your weed is also another sign that there’s something wrong with it. These are usually the effects of mildew and mold contaminations.


Every cannabis strain has its own distinct scent. However, all share a musky sweet aroma. If it smells very sweet or has a gone-off scent, then it most likely is contaminated. Also be careful of weed that smells like fresh cut grass because this is a sign that it hasn’t been correctly cured or dried. Cannabis that has these characteristics usually get mouldy when in storage.

Chest Pains

Take note that smoking weed shouldn’t cause chest pain. If you experience one after a smoking session, then that’s a tell-tale sign that you’ve just inhaled contaminated weed, or there is a more serious problem at play. Seek the help of a doctor as soon as possible.


If you’ve tried smoking cannabis before and haven’t felt any adverse reaction, then suddenly you do experience one, then that’s a strong sign that you’ve just smoked mouldy cannabis. This often leads to allergic reactions.


Smoking weed can be undoubtedly exciting. But this isn’t a reason for us to be irresponsible when using it. Take note that because of the growing demand for cannabis in the market, suppliers tend to speed up production, and in the process, risk contamination.

Always remember to make it a habit to inspect your weed before use. Check its physical appearance and search for whitish crystalline marks or unnatural looking stems.

You can also try rubbing a piece of stalk or bud on your fingers. If it feels very dry, chalky, or has abnormal features, then give it a second thought as these might have high amounts of contaminants. You don’t want to risk your health.

Weed contamination is common in cannabis plants, and if left unchecked, can lead to health problems. Here is how to deal with it.

Know Your Smoke – Grit, Spray and Flush.

Since 2007 there has been a worrying trend amongst large scale growers whereby they increase the weight of their yield by spraying the flowers with glass frosting spray, sugar or even micro contaminants. Whilst it is impossible to tell if micro contaminants have been used upon inspection; it is possible to check for glass frosting or sugar.

Cannabis coated in fine grit and falling off in the baggy.

When you get your bag of weed there are a couple of things you can do to check its quality. OK I know we all look for that wonderful frosty bud, however this can mean that you are getting something extra for your money that you definitely don’t want. If cannabis looks extremely frosty there are ways to check that it is ‘clean’ of unwanted additives. Run your finger round the plastic bag it came in or brush it across the flowers themselves (gently). Then place your finger in your mouth and rub the crystal around your teeth. If it is free of additives the crystal will just dissolve. If that happens nothing to worry about! Sit back and prepare your lovely (hopefully fairly weighed out) herb and think nothing more of it. If however you get a ‘snap crackle and pop’ sensation you can safely conclude that the deal is contaminated with glass. If it tastes overly sweet you have bought cannabis sprayed with sugar.

If unfortunately you have bought contaminated cannabis DO NOT SMOKE IT. I understand that getting a refund from a street dealer is nigh on impossible and lets face it not always safe, however the tight chest, headache, sore throat and other nasty side effects just aren’t worth it. Scientists are still unsure as to the long term effects of smoking ‘grit weed’ as the size of the glass particles varies which means in some cases this could cause damage to your lungs. As always the long term effects of pulmonary damage can take some time to manifest – in short it is a waiting game and one that is definitely not worth playing. It has been proven by scientists such as Tashkin et al that cannabis use, even when heavy and prolonged does little to no lung damage at all. However this ‘grit weed’ is not safe and was not featured in this research at all. Do you really want to be inhaling hot glass, iron or sand filings.

Purple Kush with dense trichome coverage.

One way to check for micro contaminants is to check the quality of the ash in your spliff or bong. I had cannabis once that was not something I would have classed as ‘grit weed’ as it passed all the above tests. However the ash left in the bong was greasy and would smear up your hand rather than just disintegrating. When tried in a joint the ash went solid and stuck to the end of the rizla failing to drop off the end into the ashtray as you would expect of high quality unadulterated flowers.

Please be careful, this cannabis is still in circulation and is still causing problems for people’s health. If you have any doubts –don’t smoke it. If you don’t feel safe to get a refund or even complain, vote with your feet. The more this sells the more unscrupulous growers will use glass and other contaminants to gain even more money from their yield than they already do. Alternatively follow the link below for guidance on growing your own for £4.20 a week.

By Beccy Gardham

White ash shows that the herb is well flushed of nutrients and is clean of any spray or sugar.

Know Your Smoke – Grit, Spray and Flush. Since 2007 there has been a worrying trend amongst large scale growers whereby they increase the weight of their yield by spraying the flowers with glass