Secondhand Marijuana Smoke Exposure
Secondhand Pot Smoke Risks and Drug Testing Implications
Sanja Jelic, MD, is board-certified in sleep medicine, critical care medicine, pulmonary disease, and internal medicine.
Secondhand marijuana smoke can negatively affect the health of exposed non-pot smokers
We have heard about secondhand tobacco smoke exposure for many years, but with the legalization of marijuana in some states, concerns have been raised about secondhand marijuana smoke exposure as well. These concerns come from two angles. One concerns health. Could secondhand marijuana smoke exposure have a negative effect on the health of exposed non-users? And, for those who do not smoke marijuana but hang out with marijuana smokers, could this exposure affect drug testing? Is secondhand marijuana smoke dangerous or could secondhand pot smoke mess up your drug testing at work? These are important questions to be asking.
Possible Health Risks
We know that personal use of marijuana carries some health risks but what about non-users who are exposed to secondhand marijuana smoke? Do adults or children who are exposed need to worry?
Limitations in Studying Health Risks
There are difficulties in evaluating potential hazards of secondhand marijuana smoke; not the least of which is that it is illegal in many areas, making studies difficult. Another is that the potency of marijuana has changed over time; the joints smoked by hippies in the 60’s aren’t the same as those smoked today. That said, several risks and potential risks have been identified.
In a study of 43 children, age 1 month to 2 years, who were admitted to hospitals in Colorado from 2013 to 2015 for bronchiolitis, urine samples tested for marijuana metabolites revealed that 16% of the children had a detectable level of exposure to secondhand marijuana smoke. Another study that provided a preliminary look at health outcomes of children living in homes where marijuana is used showed a “relatively strong. association. between indoor cannabis smoking and adverse health outcomes in children” indicating a significant need for further study.
Effect on Blood Vessels
Tobacco smoke (either in smokers or inhaled as secondhand smoke) can clearly damage blood vessels, with the risk of heart attacks and peripheral vascular disease in people who smoke or are exposed to secondhand smoke only a few examples. Research shared at the American Heart Associations (AHA) Scientific Meetings in 2014 suggested that secondhand marijuana smoke should likely be considered a public health problem.
A Significant Cause for Concern
Breathing secondhand marijuana smoke may cause as much damage to blood vessels as secondhand tobacco smoke.
This research looked at the effect of secondhand marijuana smoke on blood vessels, albeit in rodents. Rats that were exposed to secondhand marijuana smoke had a 70 percent reduction in blood vessel function. (These results were the same for rats exposed to marijuana smoke containing THC as those not, so it was considered likely that THC alone wasn’t the culprit.)
Of even more concern was that whereas blood vessel function returned to normal after 40 minutes for rats exposed to secondhand tobacco smoke, this wasn’t the case for the marijuana smoke group; in the rats exposed to secondhand marijuana smoke, blood vessel function remained affected after this interval.
While often we look at studies like this thinking that a lot of smoke over an extended period of time is to be most feared, a 2016 study made this approach questionable. It was found that even one minute of secondhand marijuana smoke could impair vascular endothelial function in rats. Even though we don’t know whether these results on rats reflect what happens in humans, knowing that vascular endothelial dysfunction underlies a leading killer in the U.S. (endothelial dysfunction leading to heart attacks), this information is worth investigating further.
Of course, the next step is determining the significance of reduced blood vessel function, something which has been linked to atherosclerosis and heart attacks.
Another concern surrounds the harmful chemicals in cigarette smoke. Tobacco smoke and marijuana are chemically alike, and therefore many of the harmful chemicals in cigarette smoke are likely to be found in marijuana smoke. We could make assumptions based on this evidence—that the cancer-causing chemicals in secondhand tobacco smoke which result in 34,000 deaths per year in the United States are also released in marijuana smoke—but until we have further studies, no one can say for sure.
In one study, levels of ammonia were 20 times higher in secondhand marijuana smoke than secondhand tobacco smoke. Levels of hydrogen cyanide and aromatic amines were three times to five times higher in secondhand marijuana smoke than secondhand tobacco smoke. And like tobacco smoke, marijuana contains a number of carcinogens (compounds known to cause cancer) such as benzene, cadmium, nickel, and more.
A final concern is not a risk related to marijuana smoke per se, but is a secondhand risk to those who are around those who smoke marijuana. Children and even dogs have suffered from the accidental ingestion of marijuana. From broken bongs that can cut, to the financial complications imposed on nearby nonusers (for example if a child has a parent who faces legal problems due to use), are all things that need to be considered by those who choose to smoke marijuana.
Effects of Secondhand Marijuana Smoke on Urine Drug Screens
Many people have questioned whether secondhand marijuana smoke in non-smokers can result in positive drug screens.
Though older studies seemed to say no, a 2015 study suggests that the answer is yes, in rare cases anyway. That said, the yes deserves an explanation. It’s wasn’t easy for a non-user to have a positive test. In the study that said “yes,” non-users were subjected to what was called “extreme exposure”—heavy exposure in poorly ventilated rooms—something that an individual would clearly be aware of. Even in this type of situation, the chance of a “false positive” result rapidly decreased with time; drug screens would be normal in a matter of minutes or hours.
The conclusion of one older study is that it would be improbable that people would unknowingly tolerate the nasty smoke conditions that would result in a positive test. What does this mean? If you are at risk of having a positive test, you’re probably hanging with the wrong crowd.
Public Health Impact
Certainly, the findings of changes in blood vessels with secondhand marijuana smoke raises concern about the public health impact of exposure, but a thorough understanding of risks, as well as preventive measures that should be taken, is lacking at the current time.
Scope of the Problem
It’s difficult to know how common secondhand marijuana smoke exposure is, most notably because it is illegal in many places. A 2015 study set out to examine this question by questioning people at two southeastern universities. Researchers found that:
- 14.5 percent of participants allowed cigarette smoking in the home
- 17 percent allowed marijuana smoking in the home
- 35.9 percent allowed cigarette smoking in cars
- 27.3 percent allowed marijuana smoking in cars
Of course, this study evaluated only a subset of people, but the take away message is that many people are likely exposed to secondhand marijuana smoke.
Exposure in Open-Air Stadiums
Again, it must be noted that studies looking at the potential impact of secondhand marijuana smoke are limited. A 2019 evaluation looked at the effect of secondhand marijuana smoke on the health of police officers working at open-air stadium events. Findings included detectable levels of THC in personal and area air samples, the presence of THC in the urine of 34 percent (but negative blood tests), and symptoms potentially attributable to the exposure including dry, red eyes, dry mouth, headache, and coughing. The officers, however, did not experience a “high” related to the exposure.
Accidental Ingestion in Children
While accidental ingestion of marijuana is a separate issue from secondhand smoke, we would be remiss to not mention it here. A 2017 systematic review published in the Journal of Pediatrics concluded that accidental ingestion of marijuana by children is a serious public health concern, and that physicians and the public should be aware of this concern in children who develop the sudden onset of lethargy or loss of coordination.
As more states legalize marijuana, issues regarding secondhand exposure are likely to be examined in more depth.
For Non-Users: Avoid secondhand marijuana smoke. If your loved ones use, ask them to use away from you, and certainly not in a poorly ventilated space.
For Users: Remember that legal doesn’t mean harmless. Consider the risk of secondhand smoke to non-smokers nearby, as well as the risk to children. Driving while under the influence of marijuana has the potential to result in injuries to both self, and other passengers in the car, as marijuana users are roughly 25 percent more likely to crash. And, keep in mind that long-term use of marijuana can result in addiction in some people.
A Word From Verywell
While many people use marijuana recreationally, we can’t dismiss its possible benefit to people suffering from medical conditions such as cancer. Hopefully, now that marijuana is legal in many places, studies can further define its possible benefit in comparison with potential risks. That said, priority should be given to protect non-smokers from the effects of exposure. Edibles may eliminate the concern over secondhand marijuana smoke exposure, but accidental ingestion remains a concern, and those who choose this route and are around children should take precautions recommended for any substance that could cause poisoning.
How does secondhand marijuana smoke exposure affect the health of nearby non-pot smokers, and what impact does this have on drug testing?
Cannabis Secondhand Smoke: Will It Show On A Drug Test?
A lot of people worry about how drug tests work concerning THC. Informing yourself about what you can or cannot do will be half the way to passing one successfully. Be sure you know how secondhand smoke from marijuana will affect your chances.
Cannabis has been associated with misconceptions and myths for a long time. Because of this, it’s no surprise that secondhand weed smoke would also be linked with dangerous consequences. Today, we’ll go through whether you can get high from secondhand smoke, and if this is enough to make you fail a drug test.
EFFECTS OF PASSIVE SMOKING
Whether in an intentional hotbox, an indoor sesh, or a cannabis coffeeshop environment, there will often be people present who don’t smoke. These are people that came for the friends and not for a few tokes of the dank. As such, these are also the people that worry researchers and government agencies; is secondhand smoke harming these individuals?
The inhalation of smoke will always be harmful. But if you’re worried about joining your friends on a smoke sesh every once in a while, don’t be. Especially if its cannabis smoke and not tobacco one. Secondhand smoke won’t kill you prematurely, nor will it create any health issues. Just don’t take your child to that environment. Although health consequences are a concern, you can’t really get high from a hotbox if you’re not smoking.
In order for your body to test positive for THC from a hotbox session, you’d have to be surrounded by smoke for hours. And furthermore, the reason hotbox highs are often more intense is mostly due to an abundance of CO₂ and slight oxygen deprivation. If you’re a past smoker or are on a tolerance break, it might also be your brain playing tricks on you. Your brain will link the weed smell to a feeling it remembers.
WILL I FAIL MY DRUG TEST FROM SECONDHAND SMOKE?
So, you were at a party having a conversation with a cool stoner. You inhaled a decent quantity of secondhand smoke and forgot you have that drug test in a couple of days. You obviously don’t want to lose your job. But before you dive into an insane detox to flush out the THC, we have good news for you. A 2004 paper concluded that “. the risk of positive oral fluid tests from passive cannabis smoke inhalation is limited to a period of approximately 30 min following exposure”. This seems fair enough. Just make sure you stay away from joints 30 minutes before your drug test.
A 2010 study also looked at cannabinoid concentrations in the blood and urine of people after being in a highly attended Amsterdam coffeeshop for 3 hours. The results showed that indeed the subject absorbed THC, but in miniscule quantities, not enough to get them high. In the blood, THC was only detectable for less than 6 hours. And this will probably be the closest to reality that a study can be on the subject.
This should be enough to relax you. But you should not take this to the extreme. It would still not be smart to hang around a lot of burning marijuana during the days, if not couple of weeks, leading up to a drug test. Research isn’t abundant on the subject, and there is still a lot for us to learn about cannabis. It will always depend on the THC contents of the weed your friends are smoking, how many are smoking, for how long, and where. All of this to say, you can and should be relaxed about this issue, but use your brain as well.
Find out if joining your friends for a smoke session will make you fail your next drug test, even if you're not partaking. The answer lies within!