Does Passive Smoking Cause Cannabis to Show Up on Tests?

In 1998, Ross Rebagliati won the men’s giant slalom snowboarding gold medal at the Winter Olympic Games in Nagano, Japan. However, the day after his victory, he lost his medal due to a positive test result for cannabis. Rebagliati’s urine test showed 17.8 nanograms in his system, while the limit at that time was 15 nanograms.

Rebagliati claimed that the positive test result was due to passive inhalation of fumes he had been exposed to at a party the night before his departure to the games. The controversial appeal led to the reinstatement of his gold medal. Nevertheless, this event made many wonders: does passive smoking of cannabis intoxicate?

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Does Cannabis Vapor Cause Harm?

Research shows that secondhand smoke from burning cannabis poses two significant risks to non-smokers. Firstly, individuals who do not actively smoke but inhale secondhand cannabis smoke may experience mild THC intoxication. The second issue is that cannabis smoke contains hundreds of different chemicals and solid particles (microscopic matter particles) that can be toxic to those who inhale them, regardless of whether it is passive smoking or not.

Can You Get High From Secondhand Smoke?

In 2014, a group of researchers from Johns Hopkins conducted a study to learn more about the effects of inhaling cannabis fumes and smoke on non-smokers.

The researchers placed six cannabis smokers and six non-smokers in a small, enclosed room for three one-hour sessions.

In the first session, the room was unventilated, and the smokers were given joints containing 5.3% THC to smoke. In the second session, the room remained unventilated, and the smokers consumed joints with 11.3% THC. The final session allowed the use of fans in the room while the smokers again consumed joints with 11.3% THC.

The ventilation system was designed to simulate typical home air conditioning conditions based on HVAC standards. The study revealed two key factors: ventilation and THC potency both have an impact on whether non-smokers would test positive for cannabis.

In the first session, one of the non-smokers obtained a positive test result with a THC level of around 20 nanograms/mL (although this is well below the federal threshold for a positive result, which is 50 nanograms/mL). In the second session, four non-smokers had positive results up to 22 hours after exposure to the smoke.

None of the participants in the third session (the ventilated session) had positive test results for THC in their bodies, indicating that room ventilation plays a role in reducing smoke exposure. Further analysis showed that individuals passively inhaling smoke during the first two sessions experienced some mild cognitive impairment.

However, even the study authors acknowledge that the first two sessions of the study were quite unrealistic. One researcher described the conditions of those tests as the “worst-case scenario” because those conditions couldn’t “happen to someone without their knowledge.” In other words, the study examined the likelihood of intoxication through passive smoking by creating an extreme situation that is highly unlikely to occur in reality.

The study’s summary also admitted that under normal circumstances, positive test results among non-smokers would be unlikely, limited to the day after direct exposure, and would only occur when the exposure to secondhand smoke was extreme (e.g., in a closed room without ventilation). Therefore, the results of the third testing session are most relevant to reality: in a ventilated, air-conditioned room, individuals exposed to secondhand cannabis smoke would not test positive for THC.

Increase in Particulate Matter in the Air

A recent study from 2022 examined the effects of smoking from a bong and found that bong smoke significantly increases the amount of particulate matter – microscopic solid particles or liquid droplets – in the room’s air by up to 1000%.

In one of the sessions monitored 12 hours after smoking, the amount of particulate matter in the air was over ten times higher than before smoking. The researchers emphasized that even 15 minutes of bong smoke generated particulate matter concentrations over twice as high as the threshold for hazardous air quality set by the Environmental Protection Agency. Exposure to particulate matter above recommended guidelines is associated with reduced lung function and increased mortality from lung cancer and heart disease.

However, despite speculations about the impact of secondhand cannabis smoke on health, no studies have yet demonstrated a direct causal relationship between passive cannabis smoking and any specific disease or disorder.

Nevertheless, scientists have repeatedly shown that nearly constant exposure to air pollution in urban conditions is associated with higher risks of morbidity and mortality.

“It is hard to convincingly argue that the dangers of secondhand cannabis smoke pose a greater threat than the ubiquitous smoke and smog of modern urban life,” reads the research summary. “Whether secondhand cannabis smoke is significantly toxic or not – and the debate is justified and ongoing – it is likely just a drop in the bucket.”

Smoke From Cannabis vs. Tobacco Smoke

Many people believe that smoke from cannabis is not as harmful as tobacco smoke. As much as 27% of young adults consider passive cannabis smoking to be safe. However, evidence suggests that exposure to secondhand smoke from cannabis and tobacco can trigger asthma attacks, lung irritations, and respiratory infections.

Smoke from cannabis may also produce more particulate matter than tobacco smoke. In the aforementioned 2022 study on bong smoking, researchers found that bong smoke generated four times more particulate matter than cigarettes. They indicated that this level of air pollution could potentially contribute to various health problems for individuals exposed to passive cannabis smoking, not to mention the smokers themselves.

However, research also suggests that tobacco smoke, whether firsthand or secondhand, is significantly more carcinogenic (cancer-causing) than cannabis smoke. Cannabis smoke has not been causally linked to tobacco-related cancers such as lung, colon, or rectal cancer.

One study speculates that adding cannabis to cigarettes may reduce the risk of cancer due to the beneficial effects of compounds present in the cannabis plant. The pharmacological properties of cannabinoids in cannabis may minimize the carcinogenic effects in several ways. For example, THC can inhibit the activity of certain enzymes required for the activation of carcinogenic components in smoke. However, large-scale comparative clinical studies involving cannabis and tobacco smokers are needed to learn more and confirm this theory.

Passive Cannabis Smoking vs. THC Testing

Passive smoking of cannabis, which refers to inhaling the smoke from burning cannabis by individuals in proximity, raises many questions. One of them is whether passive cannabis smoking can impact drug test results for the presence of THC.

In general, drug tests are designed to detect certain levels of THC (tetrahydrocannabinol) – the main psychoactive compound in cannabis. Drug tests, such as urine, blood, or hair tests, can detect THC even several days after the last use.

However, can passive cannabis smoking lead to a positive drug test result?

According to scientific research, the likelihood of that is very low. Although a person engaging in passive cannabis smoking may have trace amounts of THC in their body, these levels are usually much lower than the detection limit of drug tests. This means that in order for a test to yield a positive result, the person would have to be exposed to very high amounts of cannabis smoke over an extended period, which is unlikely in typical life situations.

In one study conducted by researchers from Johns Hopkins University, participants were exposed to cannabis smoke with varying concentrations of THC in a closed chamber. The results showed that even at the highest THC concentrations, only a few participants reached THC levels in their urine that exceeded the detection threshold of drug tests. Furthermore, in the case of those participants, the positive results lasted only for a short period after exposure.

In practice, the likelihood of obtaining a positive drug test result due to passive cannabis smoking is, therefore, very low. However, if there is a risk of being subjected to a drug test, it is always better to avoid situations where passive cannabis smoking could occur.

Is Passive Cannabis Vaporization Harmful?

Due to the popularity of vaporization, it is worth examining the data on the effects of passive inhalation of cannabis vapor. From the available evidence, it appears that passive inhalation of vapor can also pose certain risks.

In a recent study conducted in a well-ventilated point of sale and consumption location where vaporization was permitted, researchers found that the vaporizer produced concentrations of solid particles high enough to potentially affect cardiovascular health. The concentration of particles in the air was about 28 times higher when the lounge was open, and people were actively vaping compared to when the business was closed. The highest daily concentrations of particles correlated with the busiest hours.

“While vapor has fewer potential irritants than smoke, it can represent a much denser cloud of material,” said Caplan. However, Caplan also points out that vapor from cannabis is believed to produce fewer toxic compounds than cannabis smoke.

“Both smoke and vapor contain resinous substances, but they have different compositions,” Caplan explained. “Vapor is produced at lower temperatures than smoke, which means fewer chemical reactions and often fewer harmful compounds.”

Passive Smoking of Cannabis – Frequently Asked Questions

Can you be a passive cannabis smoker?

Yes, it is possible, especially when you are in a closed space with people actively smoking cannabis.

What is passive smoking?

Passive smoking refers to inhaling the smoke emitted by smokers. This includes both smoke directly from the cigarette and exhaled smoke from the smoker.

Can you get “high” from secondhand smoke?

Yes, although the likelihood is much lower than with active smoking. The concentration of THC in secondhand smoke is significantly lower.

Does passive cannabis smoking show up on tests?

It depends on various factors, such as the amount of smoke inhaled, the level of ventilation in the room, and the potency of THC in the cannabis used. In extreme conditions, it is possible but extremely rare.

What are the symptoms of passive cannabis smoking?

Symptoms may include a mild sense of intoxication, fatigue, dry mouth, red eyes, altered perception of time, or short-term memory problems.

Are cannabis fumes harmful?

Cannabis fumes, like smoke, can contain harmful compounds. Although they are generally less harmful than smoke, they can still pose a risk, especially with frequent exposure.

Is the smell of cannabis harmful to children?

The smell of cannabis itself is not harmful as it is produced by terpenes, which are naturally occurring aromatic compounds. However, children should not be exposed to cannabis smoke as it can lead to health problems.

Is inhaling the smell of cannabis harmful?

The smell of cannabis itself is not harmful. However, if the smell comes from cannabis smoke, it is possible that you are also inhaling harmful substances.

Is the smell of cannabis alone harmful?

No, the smell of cannabis alone is not harmful.

What are the effects of passive cannabis smoking?

Passive cannabis smoking can lead to symptoms similar to those experienced with active smoking, although they are usually milder. This may include a sense of intoxication, memory problems, or slowed reactions.

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(Featured image by Marek Piwnicki via Pexels)

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First published in Fakty Konopne, a third-party contributor translated and adapted the article from the original. In case of discrepancy, the original will prevail.

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