The negative impact of passive, or second-hand, smoke from cigarettes is well documented. According to the CDC, approximately 2.5 million people have died from passive smoking since 1964. It caused over 7,000 deaths from lung cancer a year from 2005 to 2009 in non-smokers, and can also lead to other serious medical problems such as heart disease and respiratory bronchitis.
While tobacco smoke contains over 7,000 chemicals and dozens of carcinogens, marijuana is significantly better for your health. However, can passive smoke from marijuana cause medical problems of its own?
Some shocking claims are being made about the negative impact of second-hand marijuana smoke. For example, it could get you stoned, and it may also increase your risk of heart attack. Bizarrely, there is a suggestion that it is even worse than second-hand tobacco smoke in certain respects. Let’s see what scientific research has to say on the matter.
Does Passive Marijuana Smoke Get You Stoned?
The National Institute on Drug Abuse published some interesting studies on the subject, yet many of them have conflicting results or lack credibility. The first one was related to a study which involved second-hand exposure to marijuana in a well-ventilated room. After three hours, those who inhaled the smoke passively had elevated THC levels as one would expect. However, the level of the compound wasn’t high enough to fail a drug test.
In an additional study, conducted by Rohrich et al. exposed non-smokers to marijuana with a THC content of 11.3%. The subjects remained in an unventilated room for an hour until they were examined for THC levels. Researchers then performed a urine drug test on the subjects and their THC level was high enough to fail a drug test.
A similar test was performed by researchers at Johns Hopkins University in 2015 and was published in The Journal of Drug and Alcohol Dependence. It was a little different to the 2010 study insofar as it was conducted in ‘extreme’ conditions. Six smokers and six non-smokers were placed together in an unventilated 10-foot x 13-foot acrylic box. All 12 people sat side-by-side, and the smokers were given 10 high-potency joints to smoke.
When the non-smokers were tested after an hour, their urine displayed high levels of THC immediately, and for up to three hours afterward. While the findings were conclusive, to be fair, we find it hard to determine the merit of this particular study. Non-smokers were obviously going to be affected by ‘extreme’ conditions! If you sit beside someone smoking potent weed, you’re likely to feel a little stoned after an hour.
Is Second-Hand Weed Smoke More Dangerous Than Passive Tobacco Smoke?
The automatic answer to this question is ‘no,’ but a 2016 study published by the American Heart Association says something different. A group of rats was exposed to second-hand marijuana smoke for 60 seconds. Afterwards, their blood vessels took three times longer to recover full function than another group of rodents who were exposed to tobacco smoke. For reference, it took the cannabis inhaling rats 90 minutes to recover compared to 30 minutes for the rodents exposed to tobacco smoke.
Doctor Matthew Springer, the author of the study, said that our blood vessels can carry more blood if they sense that more is required to pass a greater level of blood to the tissues. Your vessels will dilate to ensure more blood gets through. However, exposure to any kind of smoke inhibits the process. Your risk of heart attack increases when your blood flow is impeded.
He continued by saying that while the effects are temporary for tobacco and marijuana smoke, you could suffer from long-term issues if exposure happens often enough. Over time, consistent exposure to second-hand smoke will increase the risk of developing clogged and hardened arteries.
While marijuana smoke was previously believed to be benign, it appears as if the burning of plant material is the cause of impaired blood vessels. In other words, it is the marijuana plant itself, and not its compounds, that is responsible.
This shocking discovery came hot on the heels of a 2014 study, also involving Springer, which also exposed rats to second-hand marijuana smoke. 40 minutes after exposure, the blood vessel function of the rats had returned to normal when exposed to tobacco smoke but not after marijuana smoke exposure.
Overall, blood vessel function dropped 70% after being exposed to marijuana smoke for half an hour.
This sounds like extremely bad news for marijuana lovers as well as their friends and family who may be exposed to the smoke on occasion. According to Springer, the blood vessel function of rats and humans is similar, so he believes human blood vessels will react in much the same manner.
Final Thoughts on Marijuana & Passive Smoke
Springer is adamant that second-hand marijuana smoke is bad for our health. He said that the reason most people believe passive weed smoke is harmless is due to the lack of evidence of its deleterious effects; evidence that is in abundance when it comes to tobacco smoke.
While he is confident of similar results in human studies, we haven’t actually seen the evidence yet. Although the blood vessel function of rats and humans is alike, it is not identical, and you have to take into account the enormous size difference between the species.
In reality, there is little evidence available to suggest that directly smoking cannabis is bad for the heart. A 2014 study published in the American Heart Association Journal showed that it is rare to suffer from a serious heart problem immediately after smoking pot. While another study claimed smoking marijuana made you five times more likely to suffer a heart attack within an hour, it is no greater a risk than if you have sex or engage in strenuous exercise.
Although these animal studies are a cause of concern, they are not proof that second-hand marijuana smoke is a potential killer. However, we recommend steering clear of passive weed smoke as it may be healthier to smoke it yourself!