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!
are all of you cracy nobodys gonna kill over some weed
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!!!
So true. Potheads can't smell. So that's why it doesn't bother them.
True true, even cigarette smokers lose their sense of smell. My dad smoked cigarettes and weed for years and years ayears and said when he stopped both that his sense of smell and taste where extremely better.
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.
Untrue in fact it has been repeatedly proven to delay and halt the forming of the adult brain.....
It paralyzes them instead! Not much better. I have loved ones who smoke everyday, multiple times a day, and some who smoke a few times a week. They all show signs that their thought process, and memory are majorly effected. I smoked pot last year 1 time for the 1st time in like 10 years. I was noticably effected for about 3 days after smoking!
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.
Amen!!! Worry about the real problem-prescription drugs, meth, etc.
How something disconnecting your brain could be good for you!? I don't believe you're not a smoker for saying this. Haven't met that one sober person with fully functioning brain who would say this...
Hell no Lola. I will not just agree to let folks do what they want when it comes to smoking. If you have a 15 yr old son who is not doing well academically and has started to hang out with those who have no job and smoke weed in cars, Hell no i'm not just going to say.....ok 15 yr old do whatever you want to do because you love it. That's not how this parents thinks or how this household is run.
Ugh. I'm dealing with this right now. My neighbors have been smoking pot pretty much all day, and I was trying to do my Algebra review for a test, and I have a massive headache now. My apartment also smells like a skunk lives in my closet too..
Skunk smells very differently from weed! I love the smell of certain weed, but I don't smoke as I don't like the affect it has on me; I use salves and lotions derived from weed for my ailments throughout my body and it helps immensely!
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
It makes my stomach turn. Worse than cigarette smell.
If one is not a smoker of anything, one's sense of smell tends to be more acute.
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.
Yes I deal with this all day my boss, dad, mom, sister, friends everywhere I go I'm around it and I don't like it but I can't tell my boss to stop or I'll be fired and ect with family
right ! i swear people just tend to overreact to such dumb stuff it's completely idiotic to me in my opinion !


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