Is Second Hand Vapor Harmful to Breathe?

10 min read

The rise in the popularity of vaping is unsurprising. Globally, most health organizations now recognize vaping as a far safer alternative to smoking. Numerous studies have confirmed that vaping has a much lower risk of causing cancer. It is also highly probable that using e-cigarettes has a smaller negative impact on lung and cardiovascular function. Scientists and researchers have known about the dangers of exposure to secondhand smoke for years. Vaping does tend to produce much bigger clouds than smoking. With this in mind, many people may want to know – Is secondhand vapor harmful to breathe?

What is Secondhand Vapor

A plethora of different device types and styles are now available on the market. However, all of them require e-liquid to function. E-liquid consists of nicotine, flavorings, and a base to transport them.

Most e-cigarettes consist of a battery, or “mod” as well as a tank. The tank contains a coil of wire wrapped in a cotton wick, and some additional space to store the e-liquid. When activated, the coil heats the e-liquid, which turns into vapor that the user then inhales.

Secondhand vapor is vapor that has already been inhaled and exhaled by a user. This substance can linger in the air and could potentially be inhaled by other people. The dangers of secondhand smoke are well established, but what about secondhand vapor? As vaping is a new phenomenon, the research on “passive vaping” is scarce. However, the compounds in both vapor and smoke have been thoroughly studied by scientists, so predictions and comparisons between the two can be made.

The more research that is conducted into tobacco, the more harmful effects are uncovered. The smoke produced by burning tobacco contains all manner of nasty compounds. These include 69 chemicals known to cause cancer, and over 250 harmful substances in total. As well as tar, carcinogens and other nasties, combusted tobacco smoke contains large amounts of carbon monoxide. Carbon monoxide binds to red blood cells in place of oxygen, preventing this vital substance from reaching your organs.

Asides from cancer, smoke from tobacco can cause or contribute to many other health problems. One of the most serious of these is heart disease.

A chronic effect of smoking is damage to the blood vessels and cells. This can lead to fatty deposits called plaque accumulating in the arteries, narrowing them and reducing blood flow. Over time, these deposits can prevent an adequate supply of blood from reaching the heart, resulting in heart attack.

Secondhand smoke comes in two forms: Mainstream smoke, which is exhaled by the smoker, and sidestream smoke, which comes off the burning end of the cigarette. Long-term studies have shown that exposure to both forms of secondhand smoke can cause all of the same health issues as actually smoking. These include cancer, heart disease, stroke, and many more. Sidestream smoke is typically the far more toxic of the two. It contains higher levels of carcinogens than mainstream smoke, which has already been inhaled and filtered by the smoker’s respiratory system.

Exposure to secondhand smoke comes with some serious negative consequences. As well as lung cancer, there is evidence that secondhand smoke could cause diseases of the digestive tract, stomach, brain, breasts, and bladder. In children, exposure to secondhand smoke is also linked to other severe forms of cancer like leukemia and lymphoma.

Children are particularly vulnerable to the harmful effects of secondhand smoke. Studies have demonstrated that children of smokers are absent from school more frequently, have a higher rate of respiratory infection, and are more likely to suffer from a shortness of breath. Secondhand smoke has been demonstrated not only to trigger symptoms of asthma in sufferers of the disease, but also to create entirely new cases where no asthma had previously been diagnosed. Alarmingly, passive smoking has even been linked to cases of sudden infant death syndrome.

There is no safe level of exposure to secondhand smoke.

So What About Secondhand Vape?

Vaping involves heating a suspension of a liquid base (usually a propylene glycerol/vegetable glycerol blend), along with flavorings and nicotine, commonly known as e-liquid. To heat the eliquid, most vapers use a device known as an e-cigarette or “mod.” E-cigarettes consist of a battery, a wicked coil, and housing to hold it all together.

Most health bodies worldwide now recognize vaping to be a far safer alternative to smoking, but that’s not to say it is 100% without risk. Vapor produced by e-cigarettes does contain some harmful substances, but in tiny amounts compared to smoked tobacco. Any adverse health consequences from vapor are likely to be trivial compared to the combusted tobacco. The truth is that we don’t know if vaping has long term negative consequences and what those might be. However, we can make some educated guesses.

Is Second Hand Vapor Harmful to Breathe?

What is in Secondhand Vapor?

Unlike smoking, vaping doesn’t involve combustion. The vapor particles emitted by e-cigarettes are a liquid (technically an aerosol) rather than the solid particulates found in cigarette smoke. According to this study, vaping doesn’t seem to have any effect on air quality, whereas smoking (both tobacco and cannabis), frying food and even burning candles can affect the air quality (measured by total particle count).

Propylene glycol and vegetable glycerine comprise the base of almost all e-eliquids. Both of these substances have been approved for many, many years for use in food, cosmetic products, and pharmaceuticals. There is no known toxic dose for either PG or VG.

Asides from PG and VG, what’s in secondhand vapor? The truth, according to this study, is not much. Once the vapor has been breathed in and circulated throughout the user’s lungs, there is almost nothing left. The only things remaining are trace amounts of ingredients, such as flavorings.

The Case of Diacetyl

A few years ago, there were some concerns that a particular flavoring used in many e-liquids could cause lung damage. Diacetyl, the flavoring in question, imparts a buttery taste to food products, and was once used to flavor popcorn.

Back in the early 2000s, some workers at popcorn factories developed a previously unknown illness. The disease is called bronchiolitis obliterans, and is more commonly known as popcorn lung. Significant exposure to diacetyl was found to be the cause of this disease, hence its name.

There have been no reported cases of popcorn lung being caused by vaping, and it’s easy to see why. This study shows that a pack of cigarettes contains about 6718 mcg of diacetyl. Research into diacetyl in e-liquid has shown a cartridge contains about 9mcg – 750 times less than the cigarettes!

If popcorn lung were a potential risk of vaping, you would expect to have seen previous cases caused by smoking. There is currently no strong evidence that shows that vaping can cause popcorn lung, so personally, I wouldn’t worry too much about it.

Another difference between cigarette smoke and vapor is that there is no “sidestream” effect with vaping. In contrast to cigarettes, all secondhand vapor has already passed through the user’s lungs. The respiratory system acts as a filter, and most of the substances in vapor are absorbed by the user and, therefore, not present once they exhale.

Is Second Hand Vapor Harmful to Breathe?

Can You Vape Indoors?

Smoking indoors rapidly leads to high levels of pollutants in the air. The toxic substances from cigarette smoke can remain in place for a long time, and up to 80% of them are invisible to the naked eye. Vapor from e-cigarettes does not seem to have the same effects. One study found that the air inside vape shops where 13 people had been using their devices (in a confined space!) had levels of flavoring and formaldehyde far below legal limits.

Does Secondhand Vapor Contain Nicotine?

As mentioned, the main constituents of secondhand vapor are PG, VG, and small amounts of nicotine. When vaping indoors, the exhaled clouds eventually fall to the ground. Some people may be concerned that nicotine could accumulate on surfaces or the floor, where pets and children could be exposed. The good news is that this is probably a mislaid fear – This study showed that nearly 94 percent of the nicotine in vapor from e-cigarettes is absorbed by the user, with only tiny amounts left over. Another study has supported this. The paper claims that “thirdhand” absorption of nicotine from surfaces that had been in contact with vapor is not possible by any known means.

Does Vaping Leave a Residue?

With smoking tobacco, residual compounds from the smoke, also known as thirdhand smoke (THS), can combine with other naturally occurring gases and form carcinogens that then settle onto carpets and furniture. Although the dangers from exposure to these substances are unclear, some studies have shown that these particles can persist for many months. In theory, pets or young children who spend a lot of time in close contact with the floor could disturb these particulates and inhale them.

One potential drawback to vaping indoors is that it can leave a residue on windows – I’ve certainly noticed a build-up on my car windshield before. While this can be a pain in the backside to remove, it isn’t harmful. The oily residue that some vapers notice is almost entirely leftover from vegetable glycerine, so if this bothers you, you can just switch to vaping e-liquids with a higher concentration of PG.

Is Secondhand Vapor Dangerous?

Vaping is an entirely new human activity, so making definitive statements about its safety, especially in the long-term, isn’t really possible. However, all of the research conducted so far suggests that not only is secondhand vaper safer than secondhand smoke, but that it doesn’t seem to pose any health risks whatsoever.

The conclusion of this recent study into the effects of secondhand vapor was that “exposure experienced by bystanders is clearly very low compared to the exposure of vapers, and thus there is no reason to expect it would have any health effects.” Based on the current research, and until science says otherwise, it doesn’t seem that exposure to secondhand vape should be a concern.

Secondhand Vaping - More a Question of Manners

Just because secondhand vapor itself isn’t harmful, that doesn’t mean you should start choking unsuspecting members of the public with fat clouds from your sub-ohm beast. People are unlikely to appreciate having an aerosol blown all over them from inside someone else’s body.

Though the substances in vapor are benign, some doctors think the vapor itself could act as a transmission vector for some airborne diseases, including SARS-CoV-2, which causes the coronavirus. More research will have to be done in this field, but at present it would be wise (and conscientious) not to expose people to any unnecessary risks.

In general, it’s best to avoid vaping in public indoor spaces – Not only is it inconsiderate, but many states and countries have laws against it. If vaping outside, try and keep away or downwind from other people. If in doubt, merely asking anyone in your proximity if they mind you vaping is all it takes to avoid being an inconsiderate person.
The last thing vaping needs in any more controversy – One poor mannered vaper makes us all look bad.


Secondhand smoke, and potentially even thirdhand (residual) smoke, has documented and well established negative impacts. Children, in particular, are very susceptible to harm from secondhand smoke. They can experience a host of ill effects from exposure to the pollutants found in both mainstream and sidestream smoke.

The vapor produced by e-cigarettes has consistently been shown by researchers to contain far fewer harmful chemicals than smoke from combusted tobacco. Additionally, many of the products in vapor, including nicotine, are largely absorbed by the user. As there is no sidestream effect when vaping, all the vapor that bystanders could inhale will have passed through the user. It is unlikely that harmful products will be present in secondhand vapor at any appreciable level.

For the time being, at least, the verdict on secondhand vape is clear – Don’t stress! All signs point to it being a benign, harmless side effect of vaping.

Jules M
Jules M
Jules is our vaping font of knowledge. He has been a passionate vaping supporter since 2013 and spends his time trying to educate people with ‘facts’ on the safety and benefits of vaping.

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