Drugs & Health Blog

Two More Things We’ve Learned About Secondhand Marijuana Smoke

The NIDA Blog Team

When we wrote about secondhand marijuana smoke in 2014, we still had many unanswered questions about its effects. Here’s what research since then has found:

  1. It’s hard to get “high” off of secondhand marijuana smoke. How much a room is ventilated could make the difference. A study found that if you’re in an unventilated room (the windows and doors are closed), and smoke is blown directly in your face for a while, it might make you feel a little sleepy and your thinking “fuzzy.” If the room is ventilated, this reaction probably won’t happen. But even if you feel normal, the smoke could get into your body and you could still fail a drug test.
  2. A study in rats indicates that secondhand marijuana smoke might harm your heart and blood vessels. In fact, when the rats inhaled the smoke for just one minute, their hearts and blood vessels didn’t function as well as normal for the next hour and a half! A study like this hasn’t been done in humans, but it’s troubling.

Researchers still have many unanswered questions, but the available evidence suggests that while inhaling secondhand marijuana smoke isn’t as bad for your health as smoking marijuana, it isn’t harmless, either.

Comments posted to the Drugs & Health Blog are from the general public and may contain inaccurate information. They do not represent the views of NIDA or any other federal government entity.


Smoke from anything is bad. No breaking new ground here. There are other ways of using marijuana as a medicine.
wrong medical marijuana helped a family member of mine out
Yes. Maybe medical marijuana may help but non-medical marijuana has proven towards this general result. Did your family member have a disease that was heart-related?
I disagree. I do not smoke marijuana but I am exposed to the smoke from neighbors who smoke it in our building. I do a monthly urine test for my doctor and every time marijuana shows up in my system. I never had this problem until we moved into the building
It amazes me how these studies underscore the I'll effects of burned marijuana. Just look at the used pipe they smoke out of after just one session. It's filthy and cached with tar. This has to be 10,000 times worse the cigarettes.
its not tar its resin which is just thc
Put some rats in a confined spaced full of smoke and they will react like there's danger from fire, they will hardly breathe and panic a little, then it's normal they have a faster heartbeat. Every breathing animal would have the same reaction, in the same setting, with any kind of smoke.
i personally applaud the creators of this website, how informational!!! my boyfriend does drugs and recently had a court order to quit, wish he saw this website first!
Thanks for such an excellent information.
Thanks for marvelous & informative article. Yes, Marijuana is the most illicit drug used all over the world. It is proved that marijuana causes brain damage, learning disabilities and reduce ones cognitive functions. Its legalization may produce many bad effects on student society and as well as others. We need more consciousness about it. Legalization may kick student lives of that state. So we needs to prevent it and establish proper treatment for addicted one. To treat the addicted one, At first we need to detect them and take him away from marijuana. One of the biggest hurdle to quit smoking weed is withdrawal symptoms like insomnia, anxiety and panic attack, vivid dreams and so many on. To get rid from it about 80-90% of people start again taking weed. From our 2 year experience about quitting weed, we recently published an article about “how to ease cannabis withdrawal symptoms” for them. Hopefully it help millions of people who are trying and trying to quit marijuana. Thanks
This was an amazing speech, i'm doing a research paper on weed, and you just helped a lot, thanks!
Thank you for your speech NIDA Blog Team! I was doing a research on Marijuana and it helped me a lot! This speech taught me so much stuff that I didn't know about Marijuana! Thanks a lot. I hope you have good luck on your other posts and speeches!
Is Marijuana is in all kinds of cigarettes? Thanks.

Traditional cigarettes contain dried tobacco leaves, and are legally sold to adults in all states. Marijuana cigarettes contain dried marijuana leaves and are not legally sold in most states (state laws vary). But because both kinds of cigarettes are smoked, they both contain toxic chemicals produced by burning the leaves. Like tobacco smoke, marijuana smoke is an irritant to the throat and lungs and can cause a heavy cough during use. It also contains levels of volatile chemicals and tar that are similar to tobacco smoke, raising concerns about risk for cancer and lung disease.

no,it is not. it's not in any.
Do you know if smoking Marijuana is more harmful than eating Marijuana? I need a lot of information to help with Marijuana. I need to write a research about it again. Thank you.

This depends. THC is the ingredient in marijuana that makes you “high.” Smoking marijuana gets
THC to your system more quickly, so you feel the “high” more quickly. Since people who eat food products containing marijuana have to wait longer to feel the “high” they often eat too much, and can end up feeling sick. However, uncomfortable side effects with all marijuana products containing THC are often related to how much THC is smoked or ingested. Health experts believe that more people are ending up in emergency rooms complaining of side effects because THC levels are higher than they used to be.

The first study is the only of its kind, with 19 participants (7 smokers, 12 non smokers). The thc levels in blood and urine were detectable, but only for a couple of hours. Very minimal effects and effects ameliorated with ventilation. I think it's a good thing to research but I don't this it's appropriate to make such a claim--there's very limited evidence-base for this claim. Also had no comparison groups.

We do say in this blog that we still have many unanswered questions. Interestingly, we get a lot of inquiries from people who live in the same home or even the same apartment building with a marijuana smoker and have to involuntarily smell it. They ask us if it is safe. So, we agree it is worthwhile research and when more research findings emerge, we will keep you informed though this blog.

So if I am in a car and they are smoking with their windows down can I get high still would that come out on my UA

It is unlikely your urine screen would come out positive for marijuana but it can happen. It usually happens when you are in a closed room, or car, for a long period of time and people are blowing the smoke close to you. A bigger question is---is the driver smoking? Because if he is, you should probably get out of the car. Smoking marijuana can impair driving, and it is not safe.

can you get sick from being in a closed truck for say about two hrs with some one who smokes high grade marijuana iget real nausuea and some times actuly throw up when I get home

We recommend you seek the advice of a health care professional to answer your specific questions about this.

A neighbor ling 2 floors under me smokes weed. It seeps into my bedroom. I wake up with headache and dnizziess which could be dangerous as I am a senior with balance problems!
If you walk by someone in public and he/she is exhaling marijunia smoke, and you breath it in, can you become high?

It’s very unlikely you can get high from secondhand marijuana smoke. To learn more, check out “Are there effects of inhaling secondhand marijuana smoke?” on https://www.drugabuse.gov/publications/drugfacts/marijuana.

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