Drugs & Health Blog

Secondhand Marijuana Smoke?

The NIDA Blog Team

In concerts, at house parties, even in the hallway of apartment buildings, you may have come into contact and been exposed to secondhand marijuana smoke.

In situations like these, people often worry how breathing someone else’s marijuana smoke affects them.  A couple of common questions and the answers may help you see through the fog of this smoky situation.

Can you get high from inhaling secondhand marijuana smoke?

Probably not. 

You may have heard the phrase “contact high,” about someone breathing secondhand marijuana smoke and feeling a buzz.    There have been studies that show in extreme conditions, with lots of smoke blown directly into your face, you can feel the high and it can even show up in a urine test. But this is not a normal circumstance.

Studies show that very little THC is exhaled back into the air when a smoker exhales. So little, in fact, that if you sat in a room while people exhaled the smoke of four marijuana cigarettes (sometimes called joints) in one hour, you wouldn’t get high.  You would have to be trapped in a room breathing the smoke of 16 burning joints before it you started to show signs of being high. 

Can you fail a drug test from inhaling secondhand marijuana smoke?

Again, probably not.

Since the amount of THC exhaled by marijuana smokers is so low, it would take a lot of secondhand exposure to fail a drug test. 

In a 2010 study, researchers measured the effect of secondhand marijuana smoke on non-marijuana smokers.  The non-smokers were placed in a well-ventilated space with people casually smoking marijuana for 3 hours.  The researchers then took blood and urine samples from the nonsmokers. They found that THC was present, but the amount was well below the level to needed to fail a drug test.  Another study found similar results: Testing positive is rare and limited to the hours directly following exposure.

What are the health effects of inhaling secondhand marijuana smoke?

Researchers are still working to figure this out. We still don’t know how a person is affected if they live with a regular marijuana smoker. We also don’t know how higher amounts of THC in today’s marijuana cigarettes affects secondhand smoke.

A recent study on rats suggests that secondhand marijuana smoke can do as much damage to your heart and blood vessels as secondhand tobacco smoke. But that study has not yet been done on humans.

We also know marijuana smoke contains harmful and cancer-causing chemicals, the same way tobacco smoke does. But we still don’t know how it affects a person’s health in the long run. Lots more research still needs to be done. 

Tell us in comments, what would you do if someone was smoking marijuana near you?

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.


get da heck out of there
It was in my dorm room, nothing i can do about it
SAME!!!!!! literally RIP
If you have a problem with Marijuana smokers in a dorm room or an apartment building do what I have done and call the police and have them arrested. It's still against the law even under your own roof if it effects others. I cleaned out my entire apartment building. I have kids so I do not want the exposed to it especially on a normal basis. I even Remember there is always something that you can do nothing is beyond your power if you want it or want to accomplish something.
What state is this?? I leave in L.A and police keeps saying that there's little they can do. I have a 3year old son.
Be careful with that. That's good but understand there are people that will kill you and your family for calling the cops. You may think your helping but in all reality your putting you and you family in dangerm
That's true but how would they know who called? I am sure it was anonymous!
I doubt shes afraid of a bunch of potheads. They'll light up and forget the cops were ever there.
Snitch its jus weed!! Why do so many people hate the smell.
Because it smells like a skunk landed right in front of you....that's why!!!
It ruins your clothes, distracts you from doing studies, it stinks, gives people that don't smoke a headache and I'm paying rent and don't want to be exposed to it. Oh and it kills your brain Ella.
It doesn't kill brain cells. That's a myth that has been dispelled.
I absolutely agree with you. I am severely allergic to cigarette smoke and my body reacts to this the same. I pay rent as well and should not walk in from work to this smell in my space or in my blood.
It only ruins your clothes if you dont wash them and take care of them not because of marijuana. Go hang out with people like you. Hence.. Not in this country bud
Yes! Thank you...my neighbor smokes enormous amounts and it stinks so bad. I was wondering why I had a headache this morning...
Yes it does gives you headache and sometimes sick to the stomach
I use to smoke it. Now it stinks to me worse than somebody having a cigarette and I smoke cigarettes but have had to go for 3 days without smoking and when I was around cigarette smell I got sick so had one. Weed smell is alot different and people need to have respect for others and not do it where they live. Weed is still illegal with federal law. State law might make it okay but Federal can come in and take every single one of y'all to jail for smoking
Cigarette smoke is worse my head spins off when I smell that mess but weed don't effect me like that in fact to get of that headache....join them
I don't smoke and I totally believe it has many medical properties that help sick people. Our society has been brainwashed over the years to believe that it is bad for us. Alcohol, cigarettes, sugar, fatty fast food is something we should worry about. Its time to chill and let people enjoy what they love.
I agree. I cheef daily
Some people have good job
Typical selfish dumb comment weed when smoked stinks and offends others that don't smoke weed
Some people (not a dorm situation ) have to worry about DOT drug rests
You're a snitch lol
Kids duh. They don't choose to smoke. It affects their brains. You should now
You should know* not now. Just an FYI. You need to save every brain cell you have
Omg your wasting tax payers money and wasting police time, cause of a smell... to be fair earth made the weed plant and cause we decide its harmfull you think it is. Whys is booze man made but not against the law but it cause more harm then cannabis dose. Infact they proven it to medically help you. Its from the earth its self not man made. I dont get this world.
Weed today is not natural. You think Marijuana naturally has 15% or more THC? And besides, something being natural means very little. Cobra venom is natural, that must mean it's not bad for you. At any rate though, marijuana has not been shown to cause any negative effects outside of smoke inhalation damage to the lungs, and diminished brain development in individuals under the age of 25. And you can remove the first one if you vape THC instead.
So are you going to come to my house and shove a vitamen down my throat because its "good for me." Everyones missing the main point here, NO ONE has a right to force someone to smoke secondhand marajuana smoke. And yes just because its not getting people high does not mean that the 1. psychoactive substance THC and 2. any other substances and pesticides in the marajuana smoke are not entering their bodies. What gives anyone the right to force me to put a psychoactive drug in my body that I don't like. I don't care how "good" you think it is for me.
I am around 50.. I agree with those who is against the smell and possibly the effects- not all people react the same to medication, for those that are stating it is medicine - I am prescribed medication for pain if my blood, cheeks, or urine showed up positive :I would be screwed. I am asthmatic now and I never smoked a cigarette. As a teenager, I tried smoking pot; but, I had an adverse reaction. Later, to find that I am schizoid affective. Not everyone is the same ,if we were we wouldn't need a variety of meds. Instead of thinking just about you- you may consider the person next to you.
Thank you Linda for posting this as its relevance includes people of all ages! I actually had the same situation occur to me. Bc my neighbors smoke weed in the apartment next door (and they have parties each night and despite closing my windows I can still smell their smoke and the apt is always so full of smoke like the cloud is so dense you can't even see through it!) and so at my pain management drs office not too long ago they did the usual routine blood work and urine tests and they found evidence of pot use. I was so confused bc since I have asthma I have never smoked a cigarette or pot even once (I go into anaphylaxis) Bc it may be legal in some states doesn't mean there aren't still people who are banned from having contact with pot, like individuals with chronic pain who are on pain contracts with their Drs and basically almost all of them state that if pot is found in your urine you can be spontaneously kicked out of the clinic therefore causing a great deal of pain and stress to another person. Thankfully my doc was understanding about my neighbors abnormal behavior but it scared me to death! I think it boils down to where you use pot that is if it's even legal in your state. I mean if you have close neighbors like in an apartment building generally a person wouldn't turn their tv up all the way just bc they prefer it loud. Because they live in a close quarters community, they have to consider the lives of their neighbors just as their neighbors do as well- it's called being an adult. Where as if someone who owns a farm likes to smoke pot occasionally and their nearest neighbor is a few miles away I feel that there is a difference in that situation bc what they are doing won't affect their neighbors (assuming the individual lives alone). Plus scientific studies have proven that both Tobacco and pot smoke is bad for dogs and cats, so if you don't care about neighbors at least consider your pets and their well being! I find it so incredibly concerning that some people are so self centered that they don't even care about how something they do might affect their neighbor! What's happened to getting to know your neighbors? So sad.
Your kids are gonna smoke it anyway
Dude savage
Unfortunately I live in Colorado! My daughter who is a child with Down Syndrome and a congenital heart defect is being effected poorly from our neighbors below. It literally smells as if I have been smoking it in my own apartment sometimes. They live below us, so the smoke travels up. Both my daughter and I get headaches and stomachaches from the smell. However, my daughter has a lot of ear, nose and throat problems and it makes her eyes water and her nose run a lot. I keep cleaning and it doesn't help! Though the neighbors below have complained about the noise I make cleaning all of the time. They must smoke in their room,because the odor is strongest on my daughters bedroom. She can't sleep because of how it effects her. This is just awful, and there is nothing I can do about it in this state.
Run to the cops snitch you act like people doing herion or something
The fact the you are using the words "not likely" and "not normally" in this article it is very clear that you ar defending marihuana and being very bias instead of just providing facts about the subject
i agree with baker if you would experience effect of 2nd hand cannabis smoke like some people are - me included you would look at it differently.
I was a cdl holder until a few days ago when i tested marijuana.the dot has an exceptable level of thc in urine at 15 nano grams per milliliter thats 15 billionths of a gram per millionths of a liter volume by weight.i was in a parking lot and smelled weed in the air the next day my sister inlaw sparked up near me about six feet away.i moved away into the garage where i unknowingly walked into where she had just been smoking.took a test two days later and tested positive for thc well above 50ng per mL
I do not smoke weed & I'm on probation & I could get sent to jail if I smoke so heck no I don't, I went for a job & had to take a drug test & I nearly failed, by some miracle the line I mean barley showed color, put it this way the Lady must have either been a pit smoker or was just in a good mood that day, I sat in smoke daily I never would dream this could happen!
Mickey moose you are obviously lying. If you arent a habitual user the thc from directly smoking pot will ne out m of your system in ad little as 12 hours.
That's because you smoked, silly. There's no way you tested that high for not actually smoking. Second hand smoke won't peek levels above 5 nano-grams, and that's if you're sitting right beside a pot smoker. Just admit to everyone on this forum thst you actually smoke and lost your job because of your own actions. Feeding untruth across the Internet is a political tactic to control the masses. Are you being paid to spread this false statement? Please be honest.
A mililiter is 1/1000 of a liter
the fact that your attacking the article that clearly states "MARIJUANA HAS NOT EVER BEEN LINKED TO HEALTH PROBLEMS IN HUMANS" air quotes don't lie. claiming the person is being bias is just you trying to belittle some one because of your own shortcomings about the topic. if you dislike the article, write your own, but i doubt yours will pop up as the top 5 sites for this search. I dealt with acid reflux since i was 12, it would get soo bad i'd suffer for hours at times due to the pain it caused in my stomach as if i had food poisoning, without the vomiting or other end of it, I tried marijuana when i was 24, and am a Legal user, i smoke each evening, but if i had to i could go a few days at a time before the beneficial effects ware off, Yes for a short time before bed i do feel high, but the following day I wish i was the kid who hung out behind the bleachers because i would have been able to be a normal not-in-pain kid and teen. Go ahead, call me bias because i do use it, do i abuse it? nope, but i do live a much easier life thanks to it. IF some one was bias, they would slander the tobacco industry, this person is stating known facts, not his/her problem if you can't read it correctly for what it is.
I read your post. Granted this is a year late. I also have severe acid reflux, ever since I was a little kid. It is so bad that I have choked several times in my sleep and woke up choking. My throat feels like it is on fire and the taste would not go away and I have to stay up for several hours in the middle of the night until I can safely go back to sleep. Also I do not know why you smoke weed to solve the problem. If it is because of the pain then it is not acid reflux. Acid reflux is something that is caused from a combination of different things. Such as the position of your body and what you eat as well as the activity you are performing. To have constant pain does not constitute Acid Reflux. You either have an issue in your stomach lining or ulcers. So with that said I do not know why you were given medical marijuana when that will not do anything for acid reflux. Any sensible doctor would have prescribed you Omeperazole. This is a medication that helps greatly with acid reflux. He would have also suggested a change in diet as well as different sleeping positions. So with that said you are mistaking it, or are lying about the whole situation. Since I actually have acid reflux, this is very offensive and I wish you would not use the disease as an excuse to smoke weed. Again I would consult a specialist as I have and find out what is causing your constant pain in your stomach. Because somewhere along the line either the medication or you are doing something very wrong to keep causing this pain you are experiencing. Also I have every right to be biased when it comes to making sure people don't have to be exposed to inhaling others' smoke from marijuana use. Do you know why? It is because of the medication that I am on as well as my conditions. So even a chance of second hand smoke can cause very negative and unknown side effect in my health. I suffer from Tourette Syndrome, ADHD, OCD, Depression, Anxiety and am on a various assortment of medication due to all of these medical conditions. Also keep in mind not just the effects of my conditions and the medication, but the side effects of the medication as well. So when I am exposed to second hand smoke, I do not complain just because it smells bad. People should be more respectful of others and do not know what smoking a medication near someone else can do to their health. Also I am very aware of the medical effects of Marijuana and the dosage it take to actually have an affect of the human body. So don't think that a little bit isn't going to affect someone. Also this article is absolutely ridiculous. I have yet to see a medical or scientific fact stated. This is basically a blog for someone to defend weed. Marijuana has side effects that are not all that good. And a lot of people smoke it and abuse the law just so that they can get high. You need to see where people who do not smoke are coming from. Be more respectful and realize things for what they really are. Thank you for reading this comment and I hope you are able to get a better diagnosis for whatever ails you. Have a wonderful day NinjaGrowPwnz
What about if you had a friend you visited 2 - 3 days a week over a period of 2 yrs in a small room unventilated. I don't smoke it but my drug test came back positive - I got fired!


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