The Effect of Secondhand Marijuana Smoke

Second-Hand Marijuana Smoke - Can You Get High? Does it Show up on a Drug Test? from CannabisNet on Vimeo.

Secondhand Smoke

Secondhand smoke (SHS) comprises the smoke released from the burning tip of a cigarette (typically tobacco, but in this case marijuana as well) between puffs and exhaled by the person smoking. It is also called ‘passive smoking,’ ‘environmental smoke,’ and ‘involuntary smoking.’ These terms suggest that active smoking may be acceptable while passive smoking is not. So why SHS faces such treatment?

Exposure to secondhand tobacco smoke is a serious public health threat worldwide, as many countries fail to protect their citizens, especially women and children. According to a research paper published by a group of scientists from The Institute for Health & Aging at the University of California, approximately 603,000 deaths are caused by secondhand tobacco smoke exposure every year.

Exposure to secondhand tobacco smoke takes a heavy death toll in developed countries as well. For example, the latest statistics provided by the Centers for Disease Control and Prevention suggest that exposure to SHS causes an estimated 41,000 deaths every year.

But what about secondhand marijuana smoke?

While some people believe that secondhand marijuana smoke is benign, there is some evidence suggesting otherwise. For example, a recent study published in the Journal of the American Heart Association found that one minute of exposure to cannabis SHS significantly impaired endothelial function in animals for at least 90 minutes, which is appreciably longer than the same treatment with tobacco SHS.

Does that mean that Marijuana SHS is More Dangerous than Tobacco SHS?

Clearly, more research is needed to determine if negative effect of marijuana SHS on health is the same in humans. Right now, though, it is apparent that non-smokers should avoid exposure to marijuana SHS to be completely safe. The same applies to tobacco SHS as well.

The current findings are a clear cause for concern, said Dr. Seth Ammerman from Stanford in a recent US News interview. “The notion that marijuana is natural and therefore safe is "misleading," he pointed out. ”Cyanide comes from a plant, as an example. There are many deadly poisons that also come from plants."

Can you get “Contact High” from Marijuana SHS?

A popular myth about marijuana smoking says that one can get high by inhaling secondhand smoke. Accordingly, you may feel the same effect even though you’re not smoking. While this sure sounds great for those who would like to believe in it, it is pretty much impossible to get the same effect, or get high, from inhaling marijuana SHS.

This statement is backed up by scholar evidence. A 2010 study completed by a group of Dutch researchers exposed eight healthy non-smokers to cannabis smoke in the everyday setting in one of the coffeeshops in a well-attended coffee shop in Maastricht, Netherlands. Every day, they were exposed to the smoke for three hours, and later blood and urine samples were collected to evaluate the exposure.

According to the results of this study, the participants’ samples showed minor traces of tetrahydrocannabinol (THC) in their blood. However, the concentration was so insignificant that every one of them would easily pass a standard drug test. Therefore, they concluded that even a significant exposure to marijuana SHS leads to an extremely small amount of THC in the system, so the person will not feel any effects, let alone get “contact high.”

So does that mean I can sit with My Weed-Smoking Buddies on the Couch and Don’t Worry about a Drug Test the Next Day?

Well, there’s the tricky part: you can’t. Until you make sure that the room is properly ventilated.

Yes, it was proven that a 3-hour exposure produced an incredibly small amount of THC in the blood. That study was conducted in an everyday setting of a well-ventilated coffee shop, which is very different from a poorly ventilated or unventilated environment. Every room in your house has a much poorer ventilation than in a coffeeshop in the Netherlands because the latter have to comply with extreme requirements of the government.

As it turns out, passive smoking can, in fact, cause you to fail a drug test. This unexpected finding was produced by a 2015 study conducted by the John Hopkins University. Smokers and non-smokers were placed in both unventilated and ventilated rooms to see if the exposure would be different.

Surprisingly, it was. In an unventilated environment, non-smokers obtained detectable THC levels in blood and urine, so they would not pass a standard drug test. The reason for this, as you already guessed, was the lack of ventilation. In addition to producing detectable THC levels, marijuana smoke also caused minor increases in heart rate, impaired performance on the digit symbol substitution task (DSST), and mild to moderate self-reported sedative effects.

Let’s wrap this up one last time: anyone exposed to marijuana smoke in an unventilated or poorly ventilated environment can fail a drug test. So, you can experience some of the effects of marijuana exposure. However, if you keep a window open, it would be almost impossible for you to inhale enough marijuana smoke to fail a drug test.

The Bottom Line

The known health risks of tobacco SHS raised questions about whether marijuana poses a similar threat. However, at this point, very little research has been conducted in this area. There is some evidence suggesting an even more harmful effect of secondhand marijuana, but no human studies have been registered so far.

In terms of drug testing, it is clear that a person exposed to marijuana SHS is safe if the environment is properly ventilated. Otherwise, the exposure may produce detectable levels of cannabinoids in blood and urine. Those saying that one can get “contact high” are likely to be wrong because one would feel effect from a lack of oxygen and the smoke content much faster.

So, even though many recreational marijuana users would love the “contact high” to be true, sorry, it is nearly impossible. This, however, should not stop vulnerable population such as women and children from taking precautions to avoid exposure to to marijuana SHS.

What Can Second Hand Cannabis Smoke Do To You?