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. Studies have found that 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.

Research shows 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 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?

Update: Read the blog post, “Two More Things We’ve Learned About Secondhand Marijuana Smoke.”

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.


If you take a hit of marijuana but blow it right back out of your nose instead of inhaling it into your lungs, will it get into your system to fail a drug test?
I think all the extra comments about if you like pot or not are your own choice and opinion. But I'm just trying to figue out if i could fail a drug test being around second hand smoke ?

It's unlikely.

I can be honest, my life is a living hell. My parents had been extreme marijuana advocates to the point where they would allow us to smoke it before 18. For myself I've quit marijuana but my brother smokes it on a daily basis. The hardest part is that I am trying to be an electrician but nothing is happening. My brother is a full blown addict who smokes it 24/7, he failed out of college and all he does is smokes it. My life seems almost impossible and sometimes I've thought about ending it. The struggle to stay clean in my own house is never ending due to the amount he smokes. I try to tell my mom but she just says she can't do anything about it. I wish so badly I had a parent who loved and cared for me enough to scream at my brother to stop or at least admit they did something wrong but it seems that my brother is unguidable at this point. It's not fair, it's just not fair. Sometimes I envy those kids who have evangelical parents because I know they are loved. I just cry every single night about it.

May we suggest you contact the Government’s National Helpline. It started as a suicide prevention helpline but now counselors are available 24-7 to discuss any issues of concern, including the kind you are facing. http://www.suicidepreventionlifeline.org/ Please keep us posted on how you are doing…you are in a tough spot and we admire your courage as you work to improve your life.

I just wish my mom wil believ me because i realy did not smoke
Hi I am also a second hand smoker of marijuana. I have been for 18 years now. I'm sick and tired of the constant disgusting smell. Every time I inhale for a long time my throat starts to hurt and my mood changes dramatically. As soon as I inhale a few times I get so pissed off. I live with a marijuana smoker who smokes on a regular basis and smells up the entire apartment. I just don't know how to get rid of the small and prevent it from coming into my room
my co worker smoke everyday and Im am a second hand and Im feel really sick of it : can't breath ,can't see ,headache ,..... really stuck because she is in the same room and got " high" 3-4 times a day ,ugh )-:
I'm stuck on. A city bus stuck with the sent from someone else. Hope my time to get off the bus comes fast .
I'm always around weed smokers and I have a medical examination to complete in the next 3days I haven't smoked before however, I drank weed tea more than 5 months ago. Will this be a factor for me not passing the medical examination?

While it's unlikely that secondhand smoke will show up on a drug test, without knowing exactly what you drank and what type of exam you're taking, we can't say whether the weed tea will show up on the exam.

The typos in these comments are ridiculous.
these people real life remedial its truly comical
I live in Southern California, Orange County to be exact, and the Sheriffs Department has said there is nothing they can do, and anyway it is a $100 fine which is nothing. I live in an apartment where I run TWO air purifiers 24/7 on TURBO and have 4 plug ins and all I smell is weed from two of my neighbors 24/7. I have complained twice to apartment management, but sadly nothing has been done. I cant afford to move, and I am miserable.
this page was amazing!!!! tysm for the information!!!1 im pretty sure my dog smokes so this really helps me......
I live in 2bed flat with one other 2bed flat in the same building above a shop.. My daughters room absolutely reeks of cannabis that seeps throughout the property. I have moved back into my parents to keep my daughter safe from effects.. But yet I'm still renting the flat due to all my property (sofas, units etc..) I have no clue what to do and is wondering would it harm my daughter in anyway if I moved back into the flat??...

We are sorry for your dilemma. Breathing in secondhand smoke is not good for your daughter. While it is unlikely she would get “high” from the smoke, there are many toxins in both marijuana and tobacco smoke. You might consider speaking with the landlord.

Do you think I could fail a probation drug test if people have been smoking around me for about 3 hrs

It's not likely that you could inhale enough secondhand marijuana smoke to fail a drug test.

I live in an apartment with two girls I don't even know but thats not the point. The two girls constantly smoke and the entire apartment smells horrible and disgusting. I'm straight edge, I've never tasted alcohol, smoked or anything but since I've moved in here I'm surrounded by it. Lately I've been getting the worse migraines I've ever experienced and they have become so aggressively bad I've started throwing up and getting physically sick. I went to the doctor and he had me do a breathing test, I was told I has copious amounts of smoke in my lungs and the doctor gave me a brochure on quitting smoking. I don't smoke but I'm constantly surrounded by it....idk what to do...
Move out move on ...
People I know that I'm always around smoke this and I'm scared how it can impact my life especially my health the smoke a good few joints a day and a good few fags I don't smoke and don't intend to and hate being around it and I also hate the smell and just everything about it can you please help

You may be able to talk to your friends and share your concerns about how their smoking is harming them and you. This post is about approaching friends about drug addiction, but a lot of the advice is good for starting a conversation about smoking as well: http://teens.drugabuse.gov/blog/post/real-teens-ask-how-can-i-help-my-fr... You can also share with them some of the information about smoking found on our Drug Facts page to help them understand why you're concerned: https://teens.drugabuse.gov/drug-facts Good luck!

I have spent 7 years living with somebody who reguarly smokes pot,I have since found out I am allergic to it so rather than nag the man to death have decided to end the realationship.For the past six months have suffered black outs be unaware of what happened to me the night before . I went to see a doctor and he did a few tests and asked if I was a regular smoker .I have never smoked . Therefore I have to make a brave desicion and it hurts but I have done it .
I go to my cousins house 2-4 nights a week for a few hours each time. He smokes medicinal marijuana heavily in a non ventilated room. I haven't smoked once with him while I've visited ever, and my hair tests just came back positive for marijuana, while my urine tests came back negative. Is there a way to fight this false positive to prove my innocence? I would love your feed back. Thanks

Hi Janet, for questions on drug testing, you can contact the Drug Free Workplace Helpline at 800-967 5752 or dwp@samhsa.hhs.gov.

Can someone please explain to me so I can tell my father that extreme conditions mean either blown in face when no air flow and tight space or through a kiss directly down your throat. He believes that someone can get high just by having weed blown in your face and that is what "extreme conditions" mean.

In the study referenced in the blog post, "extreme conditions" meant something like this: "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."

Unlikely isn't good enough. I could loose my career.
After reading some of these comments it's obvious some of you are smoking right now.
Being in the same room as someone else smoking it will give you a positive hair folical my girls just had one done and I am in co where its legal ...even if u don't smoke it if you are around it you will be hot
This article probably needs to be updated... a study came out in June 2015 showing that secondhand smoke in a unventilated area could result in a positive urine screen. http://www.sciencedirect.com/science/article/pii/S03768...

Thanks for the note. We do address the converse in this blog—that testing positive after exposure in a well ventilated area is rare, but can happen. However, we are in the process of updating our second hand marijuana smoke information and appreciate the link to the 2015 study.

My boyfriend smokes weed a lot and drinks up our apartment and I get chest pains a lot can it be caused my 2nd hand weed smoking
Thank you for reaching out to us. As a federal scientific research agency, we are unable to provide medical advice. However, it is important to listen to what your body is telling you, and seek medical help. There could be numerous things causing your discomfort, including stress. If you feel you are in crisis, please have someone drive you to the emergency room or call 911. You might be interested to know that there are animal studies linking second hand smoke to heart problems, but this has not been fully verified in human subjects.
tha fffffff
i have a problem with those that smell like they just smoked a joint and go to work to a job that needs your full attention it could kill your co-worker
yep, my co - worker , she is pot head ,she smoke everyday at work and got me " high " I was feeling horrible : headache , sleepy , dry mouth ,shaky ,can't do nothing after she is around me
I quit smoking pot almost 10 months ago . I have to get randomly Ua tested for a program I'm in. Yesterday my husband, his friend and his girlfriend, and I went on a road trip. We drove for about two hours each way. The guys smoke, I can't and his girlfriend didn't . The guys blazed blunt after blunt with the windows rolled up, the whole time . We didn't mind the smell, but upon reading many of these articles on Google, I'm very concerned I may test positive this week! Any new information? The car was poorly ventilated , and they smoked 2 hrs , and it was very good weed. Any feed back would be greatly appreciated! Please, no negative comments ! I'm just very curious and concerned ! Thanks in advance !!!
I work in an enviornment where grass is stored until destroyed. I sit at a desk across from the door that is continually opened and closed throughout the day, 6 hours, tues through fri. The smell is continually, sometimes strong and sometimes not but it is smelt for sure. Can this harm me, my lungs? I've not been able to find any documentation on this concern of mine. Thank you.
If the marijuana has not been burned, the smell is likely due to various volatile but not psychoactive compounds. We know of no research that suggests this can harm you; in fact, it is unclear if this has even been well researched. However, you can consider discussing your work environment with your employer.
"well-ventilated space" hardly any reading,how about an enclosed room?
Hahaha' How in the Hell can Marijuana have "Cancer Causing Chemicals" if it heals & cures A Lot of cancers & diseases? So dumb...
Hi Sarah, while the FDA has not approved the marijuana plant itself for medical use, NIH researchers are studying possible treatments derived from chemicals extracted from marijuana. These treatments are different from just smoking or ingesting the plant itself, however. You can read more here: https://www.drugabuse.gov/publications/drugfacts/mariju...
My 1 year old nephew laughs more than what I consider normal, people comment that he is so happy, but I believe it's the second hand smoke the father smokes out side the backyard and it filters into the house. The times I've been there, the smell of marijuana has been strongly undeniable. could he be getting high?
Thank you for reaching out to us. More research on secondhand marijuana smoke needs to be conducted. Contact highs are possible, but only in extreme conditions in unventilated rooms when smoke is repeatedly blown directly into the face. However, no research has been done on young children. It is important to note that exposure to any kind of smoke is not good for the lungs, especially in children. It is also important to note that if marijuana edibles are kept in the house that they be locked away from children. As a federal scientific research agency, we are unable to provide medical advice. However, when it comes to the health of a child, you do not want to take chances. I recommend a thorough medical checkup for the child, if possible. In addition, we offer a step-by-step guide that provides answers to common questions about treatment: https://www.drugabuse.gov/related-topics/treatment/what.... You might consider looking it over and seeing if it might be appropriate to approach the father about his drug use. To find treatment in your area, please call 1-800-662-4357 (toll-free) or visit this website and enter your location: https://findtreatment.samhsa.gov/. This free service is available 24/7/365. We wish you the best.
If someone blows weed smoke in your face would that affect your saliva drug test?
Probably not.
Oh yeah by the way please show me these negative effects I was a allstate athlete and honor student while in school and smoking never been sick from it the only person I ever met who had a bad reaction to it was allergic to thc and you know I know more people allergic to nuts granted everyone its different and still there is the best fact that nobody can name one person who was not allergic to thc that has died from it and someone please tell me the harm it does if you don't smoke out of tobacco ill wait :-P
I live in Miami, Florida. My neighbors smoke all the time and the disgusting smell reaches me through the vents. I want to call the cops, but don't know if Marihuana is legal or how to get the cops to go into their apartment. My building's management said that nor their security guards nor the police can just knock and ask if they are smoking. Don't know what to do. It gives me a really bad headache that persists even after sleeping it off throughout the night. Help! I am blind so this hurts my eyes, damaging them more. The headaches affect my eyes and health.


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