Does smoking marijuana increase lung cancer risk?

By Aryan Shiari, M.D.

Marijuana laws are changing rapidly across many states, and researchers have found that legalization increases its use by about 20%. It's a widely used substance and the most commonly used federally illegal drug in the U.S. In 2019, about 49 million people age 12 and older in the U.S. used marijuana in the previous 12 months.

With more people smoking marijuana, it's important to consider how it can affect lung health. Here's what you need to know.

Chemicals in marijuana

People may wonder if smoking marijuana is less harmful than smoking cigarettes because cigarettes have more obvious cancer-causing substances. It's important to understand that marijuana isn't chemical-free. It contains a mixture of compounds and chemicals including tar, ammonia, polycyclic aromatic hydrocarbons, carbon monoxide, cyanide, benzene and many others.

Some of these chemicals and compounds have been linked to various types of lung diseases, including cancer.

Marijuana and lung cancer

Smoking marijuana may be associated with an increased risk of developing lung cancer. Additional research is needed to fully understand the long-term health effects of marijuana smoking and how it affects a person's risk for lung cancer.

However, researchers know that marijuana smoke contains many of the same harmful chemicals and compounds found in tobacco smoke. The issue is made more complex because many marijuana users also smoke tobacco, so it can be difficult to determine the cause of diseases they develop. For these reasons, physician researchers believe there still is cause for concern about smoking marijuana and lung health.

It's important to note that not all marijuana or tobacco users will develop lung cancer, and many factors, such as genetics and other lifestyle habits, can influence a person's risk.

Marijuana and lung irritants

Irritants in the lungs can cause harm to the delicate lung tissue. These irritants can be dust or pollen, but also chemicals or marijuana smoke. Smoking marijuana can lead to acute bronchospasm, which is a sudden constriction or narrowing of the airways. This can make breathing difficult, and cause coughing, wheezing and shortness of breath.

In addition to acute bronchospasm, smoking marijuana can increase the risk of developing chronic bronchitis, a long-term condition that occurs when the airways become inflamed, leading to increased mucus production, coughing and difficulty breathing. This can be a major concern for regular users of marijuana.

Smoking marijuana also can weaken the immune system, exposing users to more respiratory infections. Inhaling smoke from burning marijuana can irritate the lining of the lungs, making it easier for bacteria and viruses to cause infections.

Vaping marijuana

Some marijuana users prefer vaping over other methods. Vaping has been marketed as a safer alternative to smoking, but some research has shown that it can still cause harm to your health.

Vaping marijuana was tied to a 2019 outbreak of e-cigarette or vaping product use-associated lung injury, or EVALI. At that time, the Centers for Disease Control and Prevention cautioned people on using vaping projects containing marijuana, especially from informal sources like family, friends or acquaintances, due to EVALI outbreaks.

In addition, vaping often is associated with high-potency concentrates of marijuana, which can lead to a higher risk of mental and physical problems.

More research is needed to fully understand the risks associated with vaping marijuana, and it should not be considered a safe alternative to smoking. If you choose to use marijuana, be aware of the potential risks, and consider alternative methods of use that may be safer for your lungs, such as gummies or other edibles.

Learn more

Get more information on the risks associated with smoking marijuana from these reliable sources:

• Mayo Clinic
• Centers for Disease Control and Prevention
• National Institute on Drug Abuse
• American Lung Association

Learn more about lung cancer.

Also read these articles:

• "Reduce your risk of the 4 most common cancers"
• "Dear Mayo Clinic: How early should I be screened for lung cancer?"
• "Why lung cancer screening is important, especially for minorities"

Aryan Shiari, M.D., is a pulmonologist in Eau Claire, Wisconsin.

A version of this article was originally published on the Mayo Clinic Health System blog.