Cannabis Made Clear

The Effects of Cannabis on the Lungs

Most people know smoking isn’t healthy, but is smoking cannabis better for you than smoking tobacco? How does smoking cannabis affect your lungs when compared with vaping cannabis?

x-ray of lungs

Ask anyone about inhaling cigarette smoke — your doctor, your family, your friends — and they’ll likely tell it to you straight: it’s not harmless. Ask them about inhaling cannabis, and you might get a different answer.

To be clear, smoking isn't the healthiest way to consume cannabis. But if you’ve ever wondered what the specific risks are, you’re in the right place. Want to know what the research says about smoking versus vaping cannabis? Looking for advice on how to mitigate the potential harms of inhaling cannabis smoke? Keep reading to learn more.

What is harm reduction?

Harm reduction refers to any program, policy or intervention that seeks to reduce or minimize the adverse health and social consequences associated with consuming a given substance, without requiring an individual to discontinue its use.

How does cannabis inhalation work?

Inhalation is the process of breathing in air, vapour or smoke through the mouth. Inhaling cannabis directs cannabinoids — active ingredients such as THC and CBD — into the lungs, where they’re absorbed by the bloodstream and travel to the brain.

The effects of inhaled cannabis can be felt almost immediately, usually peaking around 30 minutes after onset and lasting as long as six hours.

Cannabis is typically inhaled when it’s consumed in:

  • Joints or pre-rolls
  • Bongs
  • Pipes
  • Dab rigs
  • Dried flower vaporizers
  • Liquid or concentrate vapes, including pre-filled vape pens

What are the risks of inhaling cannabis smoke?

Both cannabis and tobacco smoke contain many of the same toxins, irritants and carcinogens that are known to be associated with heart and lung illnesses. Smoking cannabis with tobacco has a significantly negative impact on lung health. It is not recommended to combine the two.

When people who smoke cannabis — using a joint, a vaping device, a bong or a pipe — inhale deeply and keep the smoke in their lungs for a long time, they risk greater exposure to chemicals, which can provoke greater irritation of lung tissue and affect lung health. This can result in symptoms such as chronic coughing, phlegm production, wheezing, sore throat, hoarse voice and tightness in the chest. Smoking cannabis long term can worsen these symptoms and lead to chronic bronchitis.

Any form of smoke can irritate the respiratory tract, the section of the body that stretches from the outer nasal cavities through the throat and trachea and into the lungs and facilitates breathing.

Symptoms of an inflamed or irritated respiratory tract can include:

  • Shortness of breath
  • Wheezing
  • Coughing
  • Sore throat
  • Chest tightness
  • Bronchitis
  • Excess phlegm

Inhaling cannabis smoke can inhibit the immune system’s ability to protect the body from foreign pathogens, thus increasing susceptibility to infections, such as cold and flu.

Although we have learned some of the risks of inhaling cannabis, more studies are needed to understand how the risks stack up in real-world situations.

Many variables can affect a study’s validity, making it unclear exactly what the relative risk is of smoking cannabis. For instance, because population studies rely on participants’ assessments of their cannabis use and history, the studies can be unreliable. A daily cannabis smoker, for example, might be able to tell you what strain or cultivar they prefer and whether they use only one or like to mix it up, but it’s unlikely they know the detailed lab composition of their favourite products.

Another problem comes from the difficulty of parsing out what substance is causing harm. For example, cannabis from illegal sources can contain toxins, pesticides, chemicals and other contaminants that can strongly affect lung health. In addition, many studies don’t control for concurrent tobacco use, which can affect the studies’ results.

Vaping vs. smoking: Is one better than the other?

Not much more is known about the long-term pulmonary effects of inhaling a vaporized liquid than about the effects of inhaling plant material. Using a vaporizer with dried flower is believed to be the lowest-risk method of inhalation. Studies suggest reduced levels of toxic and carcinogenic substances in cannabis vapour when compared with cannabis smoke.

What are the risks associated with vaping?

Dried flower vaporizers are believed to be safer than joints, potentially producing fewer toxic by-products. And fewer is good, but it’s not none.

Researchers also wonder about the health risks of vape accessories themselves. Health Canada warns that the aerosol created by cannabis vaporizers can contain toxic substances. Heavy metals and other contaminants can leach into the cannabis and end up in the vapour, but it’s difficult to conclude if one type or brand of vape is safer.

Putting aside the potential harms of inhaling toxins, vaping has other risks. For instance, it can take longer for vaporized cannabinoids to reach the bloodstream, which might trigger some consumers to think they’re not getting enough and to take bigger and longer puffs, ultimately inhaling more than intended and potentially having a negative experience.

Additionally, cannabis use disorder and over-intoxication is associated with high THC levels in products. Using vaping products (or any cannabis product) that has high levels of THC can increase the risk for cannabis use disorder and over-intoxication. Over-intoxication can cause severe anxiety, vomiting and paranoia. Further research is needed to understand the full effects of frequent and long-term cannabis vaping on brain, respiratory and cardiovascular functioning.

Learn more about the short- and long-term effects of cannabis consumption.

Vaping concentrates

Most research recommends vaping flower over smoking it, but less is known about the effects of vaping concentrates such as rosin, resin or distillate.

Whether buying a dried flower vaporizer or a pre-filled vape pen, purchase from a legal, regulated source, keep your device clean and avoid sharing with others to prevent spreading infection or disease.

It may be reassuring to know that the concentrates in regulated vape cartridges in Canada don’t contain the vitamin E acetate (as well as other pesticides and contaminants) associated with a 2019 outbreak of vaping-associated lung disease (VALI) in the United States.

What types of consumption methods may be safer than inhalation?

Ingesting edibles is believed to be safer from a lung-health perspective, posing no known risks to the respiratory system. Again, it’s not risk-free — consuming too many edibles can cause a range of adverse effects, such as paranoia, vomiting and delusion. Still, ingesting cannabis edibles is generally considered a lower-risk alternative to inhaling cannabis.

What are some ways to mitigate the risks of smoking?

Despite the risks associated with smoking, it’s still the most common way to consume cannabis, with the latest figures showing that 74% of Canadians who consume cannabis do so by smoking.

Harm-reduction tips for cannabis smokers

  • Avoid inhaling deeply, and don’t hold smoke in your lungs. Holding your breath after inhaling increases toxin absorption in your body. Small shallow puffs are best.
  • Don’t mix cannabis with tobacco. Smoking tobacco and cannabis together exposes you to inhalation risks from both substances. Nicotine, the primary psychoactive ingredient in tobacco, is one of the most addictive substances in the world. When you mix cannabis with tobacco, you risk nicotine addiction and increase the risk of cannabis dependence.
  • Buy legal, regulated cannabis. Health Canada requires Licensed Producers to test their cannabis products for contaminants, whereas illegal producers face no oversight regarding the safety of their products.
  • Limit how often you smoke. The Centre for Addiction and Mental Health (CAMH) recommends that if you do smoke cannabis, you should limit it to once a week or the weekends. The less you smoke, the lower your risk exposure.
  • Do not share joints, vaping devices or bongs. When you share with others, you risk spreading infection or disease.
  • Opt for products that contain no more than 100 mg/g (10%) THC content.
  • Speak to your health care provider before using cannabis. Cannabis can interact with your medications.

There’s no way around it: Smoking cannabis or any other substance can be dangerous to lung health. The suggestions above may help mitigate the potential harms, but they can’t eliminate them. Consuming cannabis using alternative methods to smoking, including vaporizing and ingesting edibles, is less harmful but is not risk-free.

Harm Reduction
National Institute on Drug Abuse
Why "Just Say No" Doesn't Work
Scientific American
The Cardiovascular Effects of Marijuana: Are the Potential Adverse Effects Worth the High?
Missouri Medicine
Marijuana linked to heart disease; supplement may mitigate risk, study reports
Stanford Medicine 
Heart Health
Centers for Disease Control and Prevention
Respiratory Tract
National Cancer Institute
A Guide to Cannabis for Older Adults
Canadian Centre on Substance Use and Addiction
Marijuana and Lung Health
American Lung Association
Health care use by frequent marijuana smokers who do not smoke tobacco
Western Journal of Medicine
The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research
National Library of Medicine
Are vaporizers a lower-risk alternative to smoking cannabis?
Canadian Journal of Public Health
Cannabis Use and Youth: A parent's guide
Here to help
Health Canada
Challenges and Barriers in Conducting Cannabis Research
National Library of Medicine
Vaping-associated lung illness
Health Canada
Alcohol and Drug Foundation
Mandatory cannabis testing for pesticide active ingredients - Requirements
Health Canada
10 Ways to Reduce Risks to Your Health When Using Cannabis
Using cannabis and tobacco together
My Health Alberta
Cannabis and
Heart Health
Cannabis and Heart Health
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