Just One Minute of Marijuana Secondhand Smoke Impaired Blood Vessel Function for 90 Minutes | Research

The takeaway

A single minute of exposure to marijuana secondhand smoke impaired blood vessel function in rats for at least 90 minutes, substantially longer than comparable impairment from tobacco secondhand smoke, and the effect did not require cannabinoids.

Read this if you are exposed to marijuana secondhand smoke or are interested in the cardiovascular effects of cannabis.

1 minute of marijuana SHS impaired blood vessel function for 90+ minutes, longer than tobacco SHS.

What the researchers found

Researchers exposed rats to marijuana secondhand smoke at levels comparable to real-world tobacco secondhand smoke conditions and measured blood vessel function using femoral artery flow-mediated dilation (FMD), a standard measure of endothelial health.

Just one minute of marijuana smoke exposure impaired FMD to a comparable extent as tobacco smoke. However, the recovery time was dramatically different: tobacco smoke impairment resolved relatively quickly, while marijuana smoke impairment persisted for at least 90 minutes.

Critically, the impairment occurred even when the marijuana had no cannabinoids (THC, CBD removed) and when the rolling paper was removed (burning marijuana plant only). This means the vascular damage was caused by the combustion products themselves, not by any specific component of cannabis or rolling paper.

Endothelium-independent vasodilation (tested with nitroglycerin) was not affected, confirming the damage was specific to the endothelial cells lining blood vessels.

Why it matters

As marijuana legalization expands, the assumption that marijuana secondhand smoke is harmless is increasingly relevant. This study demonstrates that marijuana smoke impairs blood vessel function through the same mechanism as tobacco smoke but with longer-lasting effects, challenging the notion that marijuana SHS is benign.

The numbers in context

1 minute of marijuana SHS impaired FMD comparably to tobacco SHS. Marijuana SHS impairment lasted at least 90 minutes, longer than tobacco. Effect occurred without cannabinoids and without rolling paper. Endothelium-independent dilation was not affected.

How the study worked

Rats had femoral artery FMD measured before and at multiple time points after exposure to marijuana secondhand smoke at concentrations matching real-world tobacco SHS conditions. Multiple conditions were tested: regular marijuana, cannabinoid-free marijuana, marijuana without rolling paper, tobacco, and chamber air (control). FMD and nitroglycerin-mediated dilation were used to distinguish endothelium-dependent from independent effects.

What this study cannot tell us

This was a rat study, and the vascular response may differ in humans. The exposure was acute (one minute), and chronic effects were not studied. FMD is a marker of endothelial function, and the link between acute FMD impairment and long-term cardiovascular disease requires further investigation. The concentrations used matched tobacco SHS conditions but may not represent all marijuana smoke exposure scenarios.

How to read the evidence

Moderate evidence from a well-designed animal study with multiple control conditions, published in the Journal of the American Heart Association.

When this study was published

Published in 2016. The cardiovascular effects of marijuana smoke continue to be studied as legalization expands.

The bigger picture

Public health debates about whether smoke-free laws should include marijuana often assume that marijuana smoke is fundamentally different from tobacco smoke. This study shows they cause the same type of cardiovascular damage through combustion products, and that marijuana smoke may actually be worse in terms of recovery time.

Questions still open

Does chronic exposure to marijuana secondhand smoke increase cardiovascular disease risk? Would vaporized cannabis have the same vascular effects? Why does marijuana smoke impairment last longer than tobacco smoke impairment? Should smoke-free laws explicitly include marijuana?

Common questions

Is marijuana secondhand smoke harmful?

This study found that just one minute of marijuana secondhand smoke impaired blood vessel function for at least 90 minutes in rats, longer than comparable tobacco exposure. The damage was caused by combustion products, not by THC or CBD, meaning any smoked substance can cause this harm.

Is marijuana smoke as bad as tobacco smoke?

For acute blood vessel damage, this study found marijuana smoke was at least as harmful as tobacco smoke and the effects lasted longer. However, the long-term cardiovascular consequences of chronic marijuana smoke exposure have not been as well studied as tobacco.

Read the original research

One Minute of Marijuana Secondhand Smoke Exposure Substantially Impairs Vascular Endothelial Function.

Journal of the American Heart Association, 5(8)

View on PubMed ↗Publisher’s paper ↗

Citation

Wang, Xiaoyin; Derakhshandeh, Ronak; Liu, Jiangtao; Narayan, Shilpa; Nabavizadeh, Pooneh; Le, Stephenie; Danforth, Olivia M; Pinnamaneni, Kranthi; Rodriguez, Hilda J; Luu, Emmy; Sievers, Richard E; Schick, Suzaynn F; Glantz, Stanton A; Springer, Matthew L. (2016). One Minute of Marijuana Secondhand Smoke Exposure Substantially Impairs Vascular Endothelial Function.. Journal of the American Heart Association, 5(8). https://doi.org/10.1161/JAHA.116.003858