Is Secondhand Cannabis Smoke A Real Thing?

February 19, 2024
Is Secondhand Cannabis Smoke A Real Thing?
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Sharing a joint is extremely common with cannabis users and it sends off acrid smoke as it gets “puffed, puffed, and passed” around the room. Even if you only get one or two puffs before the joint goes out, you may have inhaled a considerable amount of smoke and wondered, “can I get high with just the smoke?” You might also wonder if the idea of a secondhand high (or contact high) from just the smoke is a real thing, and you’re not alone. In this article, we’ll be going into greater detail on the idea of secondhand cannabis smoke, along with other questions like possibly failing a drug test or getting high from the smoke without ever taking a puff. We’ll start off by looking at exactly how inhaled THC works within your body.

How THC In The Air Works

Cannabis product types like vape carts, pre-rolls, and flower are intended to be lit or fired in order for the aerated THC to be inhaled (thus the term “inhalables”). As you inhale, the THC is absorbed into the lungs where it enters the bloodstream, effectively bypassing the digestive system completely. The total amount of THC inhaled depends on a variety of factors like how deep a pull was inhaled, how long the smoke/vapor was held, how many pulls were taken, and the strength of the THC. There’s not a clear answer to how much THC is absorbed via inhalation, but researchers in a 1999 study and a 2005 study estimate the amount to be between 30-50%. This amount gives us an idea of how great the bioavailability of inhalables for the initial consumer is; while not full, it is indeed substantial compared to other product types. But what about the lost 50%-70% that was exhaled? Can that amount really affect passersby who haven’t taken a single puff? Before we answer that, let’s see how THC works within your bloodstream.

How THC In The Bloodstream Works

The theory of secondhand smoke being a real thing isn’t a new concept; studies as far back as the 1980s have looked into the validity of such claims. However, cannabis has evolved since then and so have the studies. Cannabis today has the potential to be considerably stronger which leads others to wonder if the potential for secondhand highs is also greater. In a 2015 study, a group of researchers decided to look into the exposure and effects of non-smokers to cannabis smoke. The study involved a dozen people, half being smokers and the other half nonsmokers. All participants were led into a small unventilated room, where the smokers proceeded to light up and smoke 10 joints that contained 11.3% THC each (essentially to hotbox). After an hour, everyone was ushered out to change protective clothing and wash up to finalize the study. The experiment was then repeated, with a small change: now the room was ventilated.

The study concluded some interesting results: with the non-ventilated room, the non-smokers tested and confirmed to have traces of THC in both their blood and urine. Additionally, the non-smokers experienced mild to moderate increases in heart rate, subjective drug effects, and some level of impairment in both behavior and cognition. When compared to the ventilated room, there were no trace amounts of THC found in the blood or urine nor were there any changes in behavior, cognition, or heart rate. The study concluded that while a secondhand high from inhaled smoke is possible, it must be done in extreme conditions (hotboxing in non-ventilated areas).

So…Is Secondhand Cannabis Smoke A Real Thing?

In 1998, Olympic snowboarder Ross Rebagliat won gold in the men’s slalom event. Yet his medal was stripped upon learning that the Canadian snowboarder failed a drug test by a 2.8ng/mL margin, with the test showing a 17.8 ng/mL on a 15ng/ML threshold. Rebagliati successfully appealed the court decision, citing that while he had indeed used cannabis six months ago, he had been exposed to secondhand cannabis smoke and that’s what caused the failed drug test. Is it possible that this was correct, or did the courts not fully understand how secondhand exposure works and were effectively hoodwinked? As one famous movie quote says, “It’s not what you know; it’s about what you can prove in court!”

As far as passing a drug test goes, it’s a stretch that you’d fail one strictly from being in a room with smokers. Plausible? Sure. But possible? Most likely not. Again, you’d have to be in an unventilated space with very large quantities of THC smoke to have even trace amounts of THC in your blood or urine.

From a strictly scientific perspective, yes, secondhand cannabis smoke is real. But only if you hotbox with an unreasonably potent amount of THC smoke. If you’re outside or in a room with windows and people start to smoke a joint or two, you most likely won’t feel any effects (i.e., you won’t get high). Yet in a THC-smoke-filled room with zero ventilation? You just might get a little buzzed.

Final Thoughts

The argument of secondhand cannabis smoke being a real thing has been troubling non-smokers for quite some time. The evidence of more recent studies suggests that while it is indeed possible, extreme measures must be taken (i.e., many potent joints in an unventilated room in a short period of time). Hotboxing is still a common practice, whether it be in a car, a windowless basement, etc. If you’re worried about being exposed to secondhand smoke, chances are you won’t experience any effects or fail a drug test. If you’re an avid cannabis smoker, try to be mindful of those around you. While the legality of cannabis use in the US is rapidly changing, the stigma still remains.

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