Secondhand cannabis smoke can affect the lungs and heart, and it can cause intoxicating effects in people who breathe it. The health impacts of secondhand cannabis smoke are greatest for children, pregnant people, older adults, and anyone with asthma, COPD, or heart disease. No safe level of secondhand smoke exposure has been established.
Secondhand Cannabis Smoke Inhalation: What Nonsmokers Breathe
What Is Secondhand Cannabis Smoke?
Secondhand cannabis smoke is a mix of the smoke exhaled by a person using cannabis and the smoke released from the burning tip of a joint, blunt, pipe, or bong. This side-stream smoke may contain higher concentrations of some combustion byproducts than the smoke that is inhaled.
Like tobacco smoke, cannabis smoke contains fine particulate matter, carbon monoxide, volatile organic compounds, polycyclic aromatic hydrocarbons, and other irritants. It also contains THC, the compound that causes intoxication.
Secondhand Cannabis Smoke Effects
Short-Term Health Effects
Breathing secondhand cannabis smoke can cause immediate irritation and, in some cases, intoxication.
Exposure to Secondhand Cannabis Smoke: A Practical Buying Guide for Cleaner Indoor Air
- Eye, nose, and throat irritation
- Coughing, wheezing, or shortness of breath
- Headache, dizziness, or nausea
- Increased heart rate and changes in blood pressure
- Dry mouth, red eyes, or coordination problems
- Anxiety, paranoia, or confusion, mainly with heavier exposure
Children exposed to secondhand cannabis smoke may become sleepy, irritable, or clumsy. These effects can be mistaken for other problems, so parents and caregivers should be aware of the source.
Long-Term and Cardiovascular Risks
Regular exposure to secondhand cannabis smoke may harm the respiratory system. People who live or work in spaces where cannabis is smoked often report chronic cough, phlegm, and bronchitis symptoms.
The cardiovascular system can also be affected. Smoke exposure can trigger inflammation, blood vessel dysfunction, and changes in blood clotting. For people with existing heart disease, this can raise the risk of a heart attack or stroke.
Cannabis smoke contains known carcinogens. The evidence linking secondhand cannabis smoke to cancer is not as strong as the evidence for tobacco smoke, but avoiding exposure is still the cautious choice.
Who Is Most at Risk?
Some groups face higher risks from secondhand cannabis smoke.
- Children and teens: Their lungs and brains are still developing. Secondhand THC can affect attention, memory, and mood.
- Pregnant people: THC can cross the placenta. Exposure has been linked to low birth weight and possible developmental effects in some studies.
- Older adults: They are more likely to have heart or lung conditions that smoke can worsen.
- People with asthma, COPD, or allergies: Smoke is a common trigger for flare-ups.
- Anyone who cannot consent: Infants, pets, and people in shared housing have no control over the air they breathe.
How It Compares to Secondhand Tobacco Smoke
Secondhand cannabis smoke and secondhand tobacco smoke share many of the same harmful components. Both produce fine particles and toxic gases that can irritate the airways and stress the heart.
One key difference is THC. Cannabis smoke can intoxicate bystanders, while tobacco smoke delivers nicotine. Cannabis is often smoked unfiltered, which may increase exposure to tar and other combustion products. Neither type of smoke is safe to breathe.
Does CBD Protect Against Secondhand Cannabis Smoke?
No. CBD is not a shield against the health impacts of secondhand cannabis smoke. CBD products are not approved to prevent lung damage, counteract THC intoxication, or treat heart or respiratory disease.
Some people use CBD for general wellness, but it does not replace clean air. If you are concerned about smoke exposure, focus on reducing the smoke itself, not on taking a supplement afterward.
How to Reduce Exposure
You can lower secondhand cannabis smoke exposure with a few practical steps.
- Smoke outdoors, away from doors, windows, and vents.
- Do not smoke in a car, especially with children or non-smokers present.
- Use air purifiers with HEPA and carbon filters, but know they do not remove all smoke particles.
- Open windows and use exhaust fans. Ventilation helps but does not make indoor smoking safe.
- Choose smoke-free forms of cannabis, such as edibles or tinctures, if you use cannabis.
- Set clear rules for your home and vehicle.
- Support anyone who wants to quit or switch to a smoke-free option.
When to Talk to a Doctor
Seek medical advice if you or a family member has chest pain, heart palpitations, trouble breathing, or frequent respiratory infections after smoke exposure. Children with asthma or ongoing cough should be evaluated.
Tell your doctor about any regular exposure to secondhand cannabis smoke, including at home, work, or in social settings. This helps them assess your risk and recommend the right steps.
Bottom Line
Secondhand cannabis smoke is not harmless. It can irritate the lungs, affect the heart, and cause intoxication in bystanders. The best protection is to keep smoke out of shared air, especially around children, pregnant people, and anyone with heart or lung conditions.