What are the effects of secondhand exposure to tetrahydrocannabinol (THC) vapor from e-cigarettes (electronic cigarettes)?

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Last updated: April 18, 2025View editorial policy

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From the Guidelines

Secondhand exposure to THC vape smoke can potentially cause mild psychoactive effects in non-users, though typically less intense than direct use. The health risks associated with secondhand smoke exposure, including electronic nicotine delivery systems (ENDS), are a significant concern, as highlighted by the American Academy of Pediatrics 1. While the study focuses on ENDS, the principles of secondhand smoke exposure can be applied to THC vape smoke as well.

Key Considerations

  • The effects of secondhand THC vape exposure depend on several factors, including the concentration of THC in the vape product, the size and ventilation of the space, and duration of exposure.
  • Most people experiencing secondhand exposure might feel mild relaxation, slight cognitive changes, or no effects at all.
  • Those who are particularly sensitive, have no tolerance, or are exposed to heavy use in confined spaces could experience more noticeable effects.
  • Limited evidence suggests that extreme secondhand exposure could potentially cause a positive drug test result, though this is uncommon with typical casual exposure.

Recommendations

  • If you're concerned about exposure, the best approach is to avoid enclosed spaces where people are using THC vapes.
  • Request that others use their vapes outdoors or in well-ventilated areas away from you to minimize exposure.
  • Be aware of the potential risks and take steps to protect yourself, especially if you are sensitive or have concerns about drug testing.

From the Research

Second-Hand Smoke Exposure

  • Second-hand smoke exposure has been associated with an increased risk of respiratory symptoms, asthma, and chronic obstructive pulmonary disease (COPD) in adults 2, 3.
  • Studies have shown that individuals exposed to second-hand smoke may experience wheezing, severe dyspnea, cough on exertion, and asthma 2.
  • The population attributable fractions of asthma and COPD due to lifelong second-hand smoke exposure were found to be 4.3% and 2.9%, respectively 2.

Second-Hand Marijuana Smoke Exposure

  • Exposure to second-hand marijuana smoke has been shown to lead to cannabinoid metabolites in bodily fluids and psychoactive effects in individuals 4.
  • The health effects of long-term exposure to second-hand marijuana smoke are not well understood and require further research 4.
  • A study found that second-hand cannabis smoke exposure was associated with respiratory symptoms, particularly among cannabis users 5.

Protective Strategies

  • Alignment of tobacco and marijuana smoking bylaws may result in effective public policies to reduce second-hand smoke exposure 4.
  • Protective strategies, such as reducing exposure to second-hand smoke and third-hand smoke, can help mitigate the health effects of smoke exposure 6.
  • Further research is needed to understand the impact of exposure to third-hand smoke and the health effects of long-term exposure to second-hand smoke 4, 6.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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