Smoking and Vaping Cannabis: Respiratory and Other Risks

Breathing in cannabis, by smoking, vaping or "dabbing," sends THC and other substances straight into the lungs. This page covers what research and health agencies say about the breathing and related risks. It is education only. It does not rank methods or tell anyone how to use cannabis. If you are having trouble breathing right now, call 911.

How evidence is labeled here. Evidence of harm (association) means studies link a practice with a worse outcome. Mixed means studies disagree. Insufficient evidence means too little good research. Preclinical means cells or animals only.

What is in cannabis smoke

NIDA says smoke from cannabis products contains many of the same toxins, irritants and carcinogens as tobacco smoke and that smoking cannabis can harm lung tissue. [1] A review of the science says the carcinogens and respiratory toxins in cannabis and tobacco smoke are similar, but the way cannabis is smoked leads to higher per-puff exposure to tar and gases. [2] Poison Control adds that a cannabis cigarette gives as much as five times more inhaled carbon monoxide and three times more tar than a tobacco cigarette, because cannabis smokers inhale more deeply and hold the smoke longer. It notes that tobacco smokers use far more cigarettes. [3]

Cough, bronchitis and lung function

NIDA reports that long-term smoking is associated with large airway inflammation, increased airway resistance, lung hyperinflation and chronic bronchitis. It also says tobacco use among people who use cannabis makes the effect of cannabis alone hard to separate. [1] A 2018 systematic review of 22 studies found low-strength evidence that smoking marijuana is associated with cough, sputum production and wheezing. [4] It found insufficient evidence on lung function and obstructive lung disease. [4] Label: evidence of harm (association) for cough, phlegm and wheeze; insufficient evidence for lasting lung function loss and COPD. A 2019 review said effects on emphysema and obstructive disease are less clear than for tobacco and that solid conclusions are difficult because of limited research and confounding by tobacco. [2]

The American Lung Association states that smoking marijuana clearly damages the human lung and strongly cautions the public against smoking it. [5]

Cancer and heart questions

NIDA says research links cannabis use, particularly smoking, with a greater likelihood of head, neck or throat cancer. [1] For lung cancer, a 2024 review described the evidence as mixed and hard to interpret because many people also smoke tobacco. [6] Label: mixed (lung cancer); evidence of harm (association) (head and neck). For the heart, NIDA says cannabis can raise heart rate and blood pressure right after use and that some research links long-term use with stroke, heart attack and arrhythmias. It says it is not clear whether cannabis itself or other factors are involved. [1] See cardiovascular concerns.

Vaping: lung injury and unknowns

A 2024 review found that vaping may reduce exposure to some smoke toxins such as carbon monoxide, but that this is offset by vaping-associated lung injury, potentially more intense drug exposure and other not-yet-understood toxicities. [6] Vaping is not simply "smoke-free."

In 2019 the US saw an outbreak of e-cigarette or vaping product use-associated lung injury, called EVALI. Patients commonly had breathing difficulty, shortness of breath or chest pain, and some had vomiting, diarrhea, fever or fatigue. [7] The FDA says THC-containing vaping products, particularly from informal sources such as friends, family or in-person or online dealers, are linked to most EVALI cases, and that vitamin E acetate is strongly linked to the outbreak. [7] In the FDA's preliminary laboratory analysis, about half of the THC product samples contained vitamin E acetate as a diluent. [7] The FDA also says evidence is not sufficient to rule out other chemicals. [7] Cases peaked in September 2019 and declined afterward. [7] NCCIH records that the FDA has warned the public not to use vaping products that contain THC. [8] Label: evidence of harm (EVALI, with adulterated THC cartridges strongly implicated).

Heated liquids add their own concerns. A toxicology review explains that heating propylene glycol and glycerin can produce irritants and carbonyl compounds such as formaldehyde, that coils can release metals, and that the flavoring diacetyl can cause the lung disease bronchiolitis obliterans when inhaled. [9] That review is about e-cigarettes in general, not cannabis cartridges specifically. See vape liquids and cartridges and residual solvents in extracts.

Dabbing and concentrates

NIDA says smoking or vaporizing highly concentrated oils or extracts (wax, shatter) is called dabbing and can rapidly deliver large amounts of THC, which raises the risk of negative side effects. [1] More in concentrate potency and product-specific risks.

Young people

In a national US survey of 14,798 adolescents, cannabis use in nicotine vaping devices was associated with about double the odds of wheezing (adjusted odds ratio 1.81). The authors called this preliminary evidence. [10] See cannabis and adolescents.

Secondhand smoke

NIDA says secondhand smoke from cannabis contains many of the same toxins, irritants and carcinogens as secondhand tobacco smoke. [1] It also reports that secondhand exposure can produce positive urine drug tests, including in children exposed at home. [1] The American Lung Association says no one should be exposed to secondhand marijuana smoke. [5]

When to get urgent help

Persistent cough, shortness of breath, chest pain or wheezing after vaping are reasons to seek care. Poison Control lists them as signs of serious lung injury. [3] The FDA suggests contacting a health care provider or poison control at 1-800-222-1222 after a health concern from vaping. [7] See when to seek urgent help after cannabis.