second hand marijuana

What Are the Side Effects of Secondhand Marijuana Smoke?

Marijuana smoke is created whenever someone burns the leaves, flowers, stems, or seeds of the cannabis plant. Marijuana is used by an average of 26 million Americans per month. It’s been studied for some medical uses.

But despite marijuana’s prevalence, its safety is sometimes in dispute. Smoking it, or being near someone else who is smoking it, does cause side effects.

Marijuana contains a chemical called THC, which can block pain and bring on a feeling of relaxation to people who breathe it in or consume it. Smoking weed has depressant, hallucinogenic, and stimulant effects. Inhaling THC can also impair your ability to concentrate and to operate a car.

Whenever you’re breathing in THC, it’s possible to get high. Effects of THC vary from person to person, as well as how much of the chemical you’re exposed to.

Drug test results can differ for people who are exposed to secondhand marijuana smoke and people who smoked marijuana.

In 2015, a small study of six smokers and six nonsmokers showed that marijuana smoked in highly concentrated quantities could trigger a positive urine drug test among people who were simply exposed to the smoke in an unventilated room.

However, ventilation during marijuana exposure, as well as how often exposure occurred, were critical factors in what the drug test result would be.

For example, smelling marijuana smoke in passing once in a while is a lot different from living with a habitual marijuana smoker who uses marijuana in your presence regularly.

Another small study attempted to mimic a more true-to-life example.

Rather than stick nonsmokers in a closed, unventilated room for long smoking sessions, these study participants spent three hours in a coffee shop where other patrons were smoking marijuana cigarettes.

After their exposure to secondhand marijuana smoke, participants were tested for THC. While a trace amount of THC did show up in their blood and urine, it wasn’t enough to trigger a positive drug test result.

It was unlikely that any contact high was passed during this study.

With that being said, getting a contact high is possible.

Being near marijuana smoke often and in poorly ventilated areas (like a car with the windows rolled up or a small bedroom without a fan) may result in feeling a limited amount of the effects that the person smoking experiences.

But catching a whiff of marijuana fragrance through your apartment window or entering a room where people were smoking several hours ago is very unlikely (maybe even impossible) to affect you at all.

There isn’t much by way of clinical data to understand if secondhand marijuana smoke is as bad for your health as tobacco smoke.

According to the American Lung Association, regularly smoking marijuana yourself can damage your lungs and weaken your immune system.

And a 2016 study on rats showed that just one minute of secondhand marijuana smoke impaired lung function for at least 90 minutes — which is longer than the lungs are affected by tobacco secondhand smoke.

Secondhand marijuana smoke exposes you to many of the same toxic chemicals as smoking it directly does. Because of this, the American Lung association recommends that people avoid exposure to secondhand marijuana smoke.

Contact high may be less common than we think, but it’s possible. Here are some of the other side effects and symptoms of secondhand marijuana smoke exposure.

Delayed reflexes

Smoking weed can slow your reaction time when you’re on the road. If you have high levels of THC in your blood from secondhand marijuana smoke, it might have the same effect.


If you’re around marijuana smoke for a long period of time, you may begin to feel lightheaded or dizzy.


One effect of the THC in marijuana is the feeling of calmness it gives some users. For others, this calmness can take the form of feeling tired or lethargic.


Researchers are still trying to understand the connection between excessive marijuana exposure and mental health. It appears that marijuana use can trigger or worsen some mental health conditions, including depression.

No link has been established between secondhand smoke marijuana exposure and depression.

The legal and medical use of marijuana is changing rapidly, but that doesn't mean it's safe for everyone to be exposed to it. Here's what you need to know.

Exposure to Secondhand Smoke from Marijuana is Dangerous

September 11, 2020


Call it what you want: marijuana, pot, weed, herb, ganja or cannabis. Regardless of the name, secondhand smoke from marijuana is dangerous for people exposed to it, especially children. 1 2

In November 2016, marijuana became legal for recreational use by adults 21 and older in California. While there is a lot of research underway about marijuana and potential health benefits and harms, one thing is very clear: marijuana secondhand smoke is harmful to people around it.

Marijuana secondhand smoke is dangerous, containing many of the same cancer-causing chemicals and toxic chemicals as cigarette secondhand smoke.

It has significantly higher amounts of toxic chemicals such as tar and ammonia, and more than twice the amount of hydrogen cyanide, an extremely poisonous chemical. 3 4 When you inhale the smoke, you are inhaling into your lungs some of the same hazardous fine particulates found in cigarette smoke. 3

While they are different products, both marijuana and cigarettes produce harmful and toxic secondhand smoke associated with adverse cardiovascular effects like hardening and narrowing of the arteries which could lead to heart attack and stroke. 5 And, unlike traditional tobacco products, research confirms that exposure to secondhand marijuana smoke produces a secondhand high. 6

Studies have also shown that: Nonsmokers exposed to secondhand marijuana smoke report feeling the effects of a secondhand high, or “contact high,” 6 with detectable levels tetrahydrocannabinol (THC) – the psychoactive ingredient in marijuana– found in their blood and urine. 7

Nonsmokers exposed to marijuana secondhand smoke in a room without ventilation tested positive for THC for up to three hours following exposure. 8 Marijuana secondhand high effect is particularly troubling when considering the potential impact to children exposed to marijuana smoke.

Unfortunately, reports of marijuana secondhand smoke exposure are on the increase in California. A 2018 statewide survey found that adult exposure to marijuana secondhand smoke often occurs in public spaces, including sidewalks, parks, and shopping areas as well as private homes. In addition, 40% of adult Californians reported recent exposure to marijuana secondhand smoke in 2018, almost doubling in just two years. 9 The potential harm from marijuana secondhand smoke exposure highlights the importance of understanding marijuana use law in California:

  1. First, while it is legal to consume marijuana on private property, you cannot consume, smoke, or vape cannabis in public places or in any location where smoking tobacco is prohibited. This may also include apartments. 10 11
  2. Property owners and landlords have the right to prohibit smoking of marijuana on their properties. 11 12
  3. Even though it is legal under California law, you cannot consume or possess cannabis on federal lands such as national parks, even if the park is in California. 13
  4. It is illegal to take marijuana across state lines, even if you are traveling to another state where it is legal. 14 15

Visit Let’s Talk Cannabis to understand the facts about marijuana use.

Secondhand marijuana smoke is not safe. Learn about the facts here, including the dangers related to secondhand marijuana smoke you might not know about.