The liquid or “smoke juice” used in most electronic cigarettes is made up of four main ingredients: propylene glycol, vegetable glycerin, nicotine and added flavoring. These ingredients are almost always listed on the label, but what happens after the liquid is vaporized and inhaled? Although there's plenty of information about what's inside e-liquid, research is finally shedding some light on the vapor as well. Studies report what many of us have suspected all along, that it's significantly less harmful than tobacco smoke and poses virtually no health risks to users or bystanders.

Common E-Liquid Ingredients

The liquid inside an e-cigarette, often referred to as ‘e-liquid' or ‘smoke juice,' is the key to delivering nicotine to users (if they so desire). Once heated, it creates a vaporized mist that's inhaled just like real cigarette smoke. Before we get to the vapor, let's discuss the main ingredients used in virtually all e-liquid:

Propylene Glycol (PG)

Propylene Glycol is an organic compound created in laboratories and has been approved by the FDA for various purposes. It's used in theatrical smoke machines, skin and personal care products, pharmaceutical goods and as a food additive in thousands of different products that we consume everyday. In an electronic cigarette, PG is used as an e-liquid base to produce vapor and is known for creating a strong ‘throat hit.' The liquid is colorless, odorless and tasteless, and it’s been studied extensively for years. Research has confirmed its safety in various forms, including vapor.

Vegetable Glycerin (VG)

Like PG, vegetable glycerin (or vegetable glycerol) is another base ingredient used in electronic cigarettes. VG is derived from vegetable plant oils and is considered 100% natural and safe. Because of it's thicker properties it tends to produce more vapor, but less throat hit, so many e-cig companies use a combination of PG and VG to produce the most accurate and enjoyable experience.

Nicotine

Nicotine gets a bad rap, and although it can be highly addictive and produce mild side effects, nicotine DOES NOT cause cancer. There are more than 4,000 other chemicals found in cigarette smoke, many of which are cancer-causing carcinogens and the source of most smoking-related diseases. A stimulant similar to caffeine, nicotine is found naturally in tobacco leaves, as well as 66 other plants such as tomatoes, eggplants, potatoes, and more. Not all e-liquid contains nicotine, and it's level can be customized by the user based up their personal preference.

Distilled Water

In some cases, especially when VG is the primary base ingredient, distilled water is added as a diluent to reduce the viscosity of the e-liquid mixture. This helps to prevent build up and ensures smooth and trouble-free e-cig operation.

Added Flavoring

One of the attractions to e-cigs for many users is the wide array of flavors. Although the actual ingredients vary between manufacturers, flavoring is typically made-up of naturally occurring, FDA-approved, food-grade additives. Examples include:

Acetylpyrazine – A commonly used food flavoring added to coffee, popcorn, potato chips, sesame seed, almonds, wheat bread, cocoa, pork and beef.

Beta-Ionone – A food-grade fragrance found in essential oils used to provide aroma. It's currently being tested for the treatment of colon cancer.

Dimethylpyrazine – Another commonly used flavoring ingredient found in the food, drug, and perfume industries.

Ethylpyrazine – A flavoring used in food products such as pork and soups.

Linalool – A naturally-occurring chemical found in many flowers and spice plants.

Mallic Acid – An organic compound used in fruit flavored e-liquids. It provides a sour, tarty taste and is also added to some cola drinks to lower their pH levels.

Rose Oil – A natural extract from roses used for it's scent.

Trimethylpyrazine – An FDA approved flavoring commonly used in caramel, chocolate, cocoa, and coffee.

Vanillin – Used in vanilla and other desert or cereal flavored liquids, like the Fruity Pebbles vape juice. It's the primary component of vanilla bean extract. Vanillin may be extracted from vanilla pods or artificially made from lignin.

Let's Talk About the Vapor

Knowing about the different ingredients and what is (or isn't) in an electronic cigarette may give you peace of mind, but the ingredients are only a small part of the equation. Once the liquid is heated, vaporized and inhaled – it's qualities change as it enters your lungs and eventually gets released into the atmosphere. Just like every product that we eat, drink or ingest, impurities can be found in electronic cigarettes, but do these impurities have any effect on users? What about others? Do bystanders need to worry about ‘second-hand' exposure to e-cigarette vapor?

A 2012 study published in the scientific journal Indoor Air compared the vapor of electronic cigarettes to that of conventional tobacco smoke. To determine the impact in an indoor environment, the researchers analyzed the volatile organic compounds (VOCs) released after test subjects either smoked or vaped in an 8 cubic meter steel chamber. They also examined a direct exhale into a 10 liter glass chamber to get a better picture of the contents in the vapor.

In both cases, researchers found significantly less chemicals in e-cigarette vapor than tobacco smoke. Of the twenty VOCs found in tobacco, only six were present in the electronic cigarette vapor and at much lower levels – far below occupational safety limits. The e-cigs had 2.5 to 40 times less butanone, acetic acid, acetone, isoprene, formaldehyde and acetaldehyde. Of the chemicals that were considered toxic, the levels found in e-cigs were in at least a 90 percent safety margin.

No Detectable Second-Hand Exposure

Electronic cigarettes release extremely low levels of toxins into the air, well below occupational safety limits, and further studies have shown second-hand exposure to nicotine in e-cig vapor is virtually nonexistent. Not only are e-cigs safer for users than traditional cigarettes, but there is virtually no risk for second-hand exposure. According to a 2012 study by CleanStream Air:

…we can conclude by saying that it would be more unhealthy to breath air in a big city than staying in the same room with someone who is vaping.

Besides the lack of chemicals found in electronic cigarette vapor, it's important to note that vapor disperses much more quickly than tobacco smoke, and unlike cigarettes which emit smoke even when they're not being used, electronic cigarettes only produce vapor when a user activates the device.

Misleading Study on E-Cigs

One of the earliest studies evaluating electronic cigarettes was conducted by the FDA in 2009. This controversial study led to a sudden ban of e-cigarette imports but was quickly overturned just four months later by a U.S. federal court. Although the study was considered inconclusive, it's widely referenced in the media.

In the study, the FDA evaluated 18 cartridges from two popular e-cigarette brands – Njoy and Smoking Everywhere. The study gave us our first glimpse of what's inside an electronic cigarette, but it only evaluated samples from two – out of hundreds of different brands. In particular, the agency looked for tobacco-specific nitrosamines (TSNAs) – cancer-causing carcinogens found in virtually all tobacco-based products. It found TSNAs in 5 out of the 18 samples tested, along with traces of diethylene glycol – a highly toxic substance – in one of the cartridges.

One (of many) important facts left out of the FDA report was the amount of TSNAs discovered in the samples. An analysis conducted a week later by Dr. Michael Siegel, Professor in the Department of Community Health Sciences, Boston University School of Public Health, discovered that the average e-cigarette cartridge (1ml of liquid) contained under 8.2 nanograms of TSNAs. In comparison, there are 11,190 nanograms of nitrosamines in a gram of Marlboro tobacco – almost 1,400 times the amount in an electronic cigarette. To provide some reference, In 1981, the National Academy of Sciences estimated that the average person was exposed to 1 microgram of nitrosamines per day, or one millionth (0.000001) of a gram. A nanogram is one BILLIONTH (0.000000001) of a gram!

And regarding the diethylene glycol mentioned during the study, it was found at extremely low levels (under 1%) in just one of the 18 samples. It's never been discovered in any other electronic study since then, and at these amounts it would take 750,000 e-cigs to receive a lethal dose.

The media often refers to this FDA study and it's “toxic”, “cancer-causing” findings without any mention of the lack of data or the fact that it was ultimately shown to be inconclusive. And the toxic chemicals found in the report were proven to be insignificant, at levels that are completely harmless to humans.

* See a complete list of electronic cigarette studies →

A Much Safer Alternative

No one in the electronic cigarette industry is claiming that e-cigs are 100% safe and there's undoubtedly some risk whenever you inhale something other than pure, unpolluted air. But the risks are significantly less than those from smoking tobacco, and the dangers of second-hand vapor are virtually nonexistent.

For those who are trying to quit or are looking for a safer alternative to smoking, electronic cigarettes can help you avoid hundreds of harmful chemicals and enjoy a variety of other benefits. Critics claim that there hasn't been enough long-term testing, but common sense tells most users that electronic cigarettes are a much better choice and are worth the significantly reduced risk.