The risks of smoking moldy weed

This may sound obvious, but consuming moldy weed may present certain health hazards, particularly to the lungs. Less obvious is the fact that vapes and concentrates may pose some of the same dangers. Luckily, knowledge is the best preventative medicine. Here we'll cover how to assess the health risks of smoking moldy weed, how to tell if you've encountered moldy weed, and how to avoid smoking it at all.  

What are the risks of smoking moldy weed?

“The main concern is a reaction to the mold. Some people are more sensitive to mold than others. A mild reaction to inhaling mold might be coughing and throat irritation,” said Dr. Melanie Bone, board-certified OB-GYN and cannabis specialist.

Coughing and throat irritation, when moderate or severe, should be warning signs to scale back on smoking, whether mold is suspected or not. Mold is not the only factor that can cause these symptoms, so reduce your cannabis smoking if you find yourself experiencing a hacking cough or burning throat.

Other more serious symptoms may also arise from smoking moldy weed. “On the opposite end of the spectrum, those who are very sensitive or allergic to mold might experience significant problems with a fungal infection in the throat and lungs,” said Bone.

moldy marijuana plant
A review in the Journal of Allergy and Clinical Immunology found that 13 of 14 weed samples not purchased from dispensaries contained fungi.
Photo by: Gina Coleman/Weedmaps

A review in the Journal of Allergy and Clinical Immunology found that 13 of 14 weed samples not purchased from dispensaries contained fungi. Those findings are significant, since some people may develop dangerous lung infections from exposure to moldy weed. One 2016 study published on the CDC website showed that invasive fungal infections, including mold infections, are more prevalent among cannabis smokers than other individuals. The CDC recommends that organ transplant recipients and those who are otherwise immunocompromised refrain from smoking cannabis.

Another study, published in 2017 in the journal Respirology Case Reports, showed that long-term use of marijuana bongs could be detrimental to the lungs. The authors of the study wrote, “Compared to cigarette smoking, marijuana inhalation demonstrates greater damaging effect.” Notably, though, it was unclear in either the 2016 or 2017 study where the patients had obtained cannabis.

The easiest way to improve your odds of not getting moldy weed? Shop at a reputable, licensed dispensary.

How much moldy weed do you need to smoke to be adversely affected?

Just as the psychoactive effects of THC differ among individuals, so do the short and long-term effects of smoking moldy marijuana. “Some smokers will be affected right away, while others may not evidence any obvious untoward effects, even years later. It is unpredictable,” said Bone.

The unpredictability of moldy weed side effects means that consumers should exercise caution before lighting up. Fortunately, there are several key indicators that can help you identify and avoid moldy marijuana.

Can you tell if you have smoked moldy weed?

Before you smoke a joint or a blunt, there are ways you can tell if it is moldy. Odor, for example, is one of the surest ways to identify mold. “If it smells like old sneakers or your grandmother's attic, look carefully for evidence of mold,” Bone said.

weed smell
Odor is one of the surest ways to identify mold.
Photo by: Gina Coleman/Weedmaps

In addition, the closer the product is to its expiration date, the more likely it is to have acquired mold. If a cannabis product is past its expiration date, you should assume that it is moldy and unsafe to consume. Further, you may be at greater risk of ingesting mold or other hazardous substances if you smoke roach weed.  

If you do smoke moldy weed, the short-term symptoms of coughing and irritated throat are reliable clues. If you experience more severe symptoms, such as difficulty breathing, be sure to seek medical help.

How to avoid moldy weed

First and foremost, make your cannabis purchases through a licensed dispensary and be aware of the origin of every product you consume. Bone suggests knowing the provenance of products you buy and being sure it was checked for mold, which is white and powdery. Trichomes and mold can be confused but a closer look shows the latter is smaller.

Examining weed under a microscope or black light can help you distinguish between mold and trichomes. Black light in particular will reveal the telltale green glow on moldy weed. With the naked eye, you may be able to observe mold appearing as fuzz, spots, and slime.

If you have a batch of mold-free weed, there is no guarantee that it won't become moldy in the future. Proper storage of cannabis is crucial to keep it fresh and free of mold. Avoid exposure to excessive light and moisture and keep your weed sealed tightly in a container. Humidity is a foe of fresh cannabis, so do keep the weed stashed in a cool place, but do not refrigerate.  

Do I need to worry about old vapes or concentrates becoming moldy?

Old vapes and concentrates can also provide a hospitable environment (i.e., moist) for mold to grow, so be sure to apply the same caution with these cannabis products. As Dr. Bone said, “When in doubt, throw it out, because the long-term consequences of lung problems are just not worth it.”

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The information contained in this site is provided for informational purposes only, and should not be construed as medical or legal advice. This page was last updated on June 28, 2021.