Secondhand Smoke from Marijuana More Dangerous than Tobacco


According to a new study from UC San Francisco researches, done on rats, a minute of exposure to secondhand smoke or SHS from marijuana has been observed to diminish the function of blood vessels to a level that is the same as SHS from tobacco. However, the negative cardiovascular effects last three times longer.

The professor of medicine and the senior author of the new study, UCSF’s Matthew Springer (Ph.D), said that arteries are urged to widen due to increased flow of blood in healthy animals. This is a process which is known as flow-medicated dilation or FMD. But SHS exposure compromises the FMD and the flow of blood is negatively affected. This increases the risk of atherosclerosis, heart attack, and other heart problems.  “Your blood vessels can carry more blood if they sense that they need to pass more blood to the tissues,” said Springer. “They dilate to allow more blood through. But that’s inhibited by exposure to smoke.”


The new research was published online in the Journal of American Heart Association. The study measured the FMD of rats, because it is similar to that in humans, before and after exposure to SHS from tobacco as well as marijuana. The results of the research showed that more than 50% of reduction in FMD was observed in rats that were exposed to SHS from marijuana for one minute.

These results were similar to the reduction of FMD seen in both humans and rats when exposed to tobacco SHS in studies performed previously. However, while rats were able to recover in less than 30 minutes after exposure to SHS from tobacco, the exposure to SHS from marijuana affected their internal system for 90 minutes. The SHS levels were kept approximately the same as one would find in restaurants where smoking is allowed.   


The new study has come forward with interesting results. The results are important due to marijuana studies being difficult to perform because of the substance’s illicit status, and the process of approval to be used in studies by the Drug Enforcement Agency and the FDA.

The National Institutes of Health’s National Institute on Drug Abuse, and the Elfenworks Foundation funded the study.

“The biggest reason that people believe marijuana secondhand smoke is harmless is because the public health community hasn’t had direct evidence of its harmful effects like it does with tobacco,” Springer said. “We hadn’t done the experiments, so I think there is definitely an underestimation of how harmful marijuana smoke is.”

Springer grew curious about the effects of marijuana SHS when he attended a concert in 2010 and saw a haze in the air due to numerous people smoking the drug. “It was really interesting to me, and distressing, because all these people in the stands would not tolerate it if the person next to them started smoking a cigarette” said Springer, “but they were fine with the marijuana.”


Springer presented his preliminary findings at the November 2014 American Heart Association Annual Scientific Sessions. This helped inspire the California Assembly Bill 2300. He believes that the new study will help the public become aware of the negative effects of marijuana SHS. “At this point, we’re saying that inhaling any smoke is detrimental to your health. I think that people should avoid inhaling smoke whether it’s from tobacco or marijuana cigarettes, forest fires, barbecues—just avoid smoke.”

Category: News

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Article by: Douglas Norman

Douglas writes all the latest health news for BodyFatLoss. He is very diligent about finding all the facts and sources of any new health and fitness findings.