Secondhand Marijuana Smoke May Be As Bad For You As Tobacco

Matthew L. Springer, Ph.D.  Associate Professor of Medicine Division of Cardiology Cardiovascular Research Institute Broad Center of Regeneration Medicine and Stem Cell Research Center for Tobacco Control Research & Education Helen Diller Family Comprehensive Cancer Center University of California, San Francisco   MedicalResearch.com Interview with:
Matthew L. Springer, Ph.D
.
Associate Professor of Medicine
Division of Cardiology
Cardiovascular Research Institute
Broad Center of Regeneration Medicine and Stem Cell Research
Center for Tobacco Control Research & Education
Helen Diller Family Comprehensive Cancer Center
University of California, San Francisco    

Medical Research: What is the background for this study? What are the main findings?

Dr. Springer: The general public is aware that cigarette secondhand smoke is harmful. However, many people who actively avoid tobacco secondhand smoke don’t feel the need to avoid marijuana secondhand smoke; they don’t consider it harmful because there’s no nicotine and because we who tell them to avoid tobacco smoke don’t tell them to avoid marijuana smoke.  However, secondhand smoke from tobacco and marijuana is very similar in chemical composition (4000-7000 chemicals depending on whom you ask), aside from the nicotine and the THC (the psychoactive drug in marijuana).

We and others have shown that brief exposure to tobacco secondhand smoke, such as 30 minutes, at real-world levels impairs vascular function in humans.  We developed a way to study vascular function (measured as arterial flow-mediated dilation; FMD) in living rats, and recently published that even one minute of sidestream smoke from the burning tips of tobacco cigarettes, a well-accepted model for secondhand smoke, is enough to start detecting impairment of FMD.  The main findings of the current study are that in laboratory rats, FMD was substantially impaired by a 30 minute exposure to marijuana secondhand smoke, when measured 10 minutes after the end of exposure.  Impairment was comparable to that resulting from exposure to tobacco sidestream smoke, although whereas impairment from tobacco smoke was temporary and had normalized by 40 minutes later, FMD was still impaired 40 minutes after the end of exposure to marijuana smoke.  Smoke from marijuana lacking THC still impaired FMD, showing that  is not required for this effect. Similarly, the impairment of FMD by marijuana secondhand smoke confirms that nicotine is not required for smoke to cause this effect.

A limitation is that we tested at levels that approximated real-world tobacco secondhand smoke conditions (due to lack of information about ambient levels of marijuana secondhand smoke in social situations).  However, these results support the concept that “smoke is smoke,” and it is notable that we have already published that even one minute of exposure to tobacco smoke at those levels leads to detectable impairment of FMD.

Medical Research: What should clinicians and patients take away from your report?

Dr. Springer: The impact on clinicians is that they should be aware that at least some deleterious cardiovascular effects of tobacco secondhand smoke exposure are caused by marijuana secondhand smoke as well, so physicians should consider advising their patients to avoid exposure to any smoke, regardless of whether the source is tobacco or marijuana.

Additional impact for individuals is that they should be aware that exposure to marijuana secondhand smoke may be as harmful to their vascular health as exposure to tobacco secondhand smoke, and that especially as marijuana is increasingly legalized, regulations that protect the public from secondhand smoke exposure should be written broadly enough to include marijuana secondhand smoke.

Bottom line: public exposure to secondhand smoke should be avoided whether the source is tobacco or marijuana.

Citation:

AHA14 abstract:

Secondhand marijuana smoke may damage blood vessels as much as tobacco smoke

 

 

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