The science of vaping

Vaping has become a controversial topic.

On the one hand, vaping or electronic cigarettes offer a tool for smokers to quit, helping to relieve the huge health burden associated with smoking. On the other hand, there has been increasing uptake by never-smoking children and adolescents with the number of young New Zealanders aged 15 to 17 who vaped daily quadrupling from 2018-2021.

Despite the popularity and social normalisation of e-cigarettes, science still hasn’t reached a consensus on the health implications of long-term vaping.

Dr Kelly Burrowes is leading a research programme on vaping at the Auckland Bioengineering Institute. She has created a social media platform to share her knowledge in this area, and based on this, we have collated some questions and answers below.

Vapes are a type of electronic nicotine delivery system that deliver an aerosolised liquid, called an ‘e-liquid’, to the user. Vapes are battery-operated devices which power an atomiser (heating coil and wick material) to create the aerosol or vapour.

The main ingredients in an e-liquid are propylene glycol (PG) and vegetable glycerine (VG). These are solvents that are used to dissolve and carry the other ingredients. The other ingredients being flavourings and nicotine.

All these ingredients are what’s known as “generally recognised as safe” for use in food. They haven’t been tested for safety on inhalation.

When the e-liquid is heated, some different chemicals can be formed. Some studies, including ours, have found things like formaldehyde and heavy metals which come from the heating coil.

Early prototypes of devices resembling an e-cigarette emerged as early as the 1920s. One of the first ones (~1930) was designed to hold medicinal compounds for inhalation. This never made it to market. The invention of the current EC is attributed to Chinese pharmacist Hon Lik who registered a patent for the modern vape in 2003. Vapes entered the European and the US markets in 2006 and 2007. It wasn’t until 2018 that vapes, containing nicotine were freely able to be sold in New Zealand.

There is some confusion on how the amount of nicotine in e-liquids is quantified. The problem comes from the difference between freebase nicotine and nicotine salts. Freebase nicotine is the purest form of nicotine. Nicotine salts are salts formed by combining nicotine with an acid to create a nicotine salt compound. Different acids can be used to do this but one of the most common is benzoic acid. 

The maximum amount of nicotine allowed in disposable vapes in New Zealand is 20 mg/ml. This is the freebase amount of nicotine and has been shown to be equivalent (in blood) to smoking a conventional cigarette. To work out what this would equate to for a nicotine salt, we need to know how heavy the chemical molecules are. This is called the molecular mass.

Without going into detail here, a nicotine salt product that has a concentration of 35 mg/ml will contain 20 mg/ml of actual nicotine. A nicotine salt that is 50 mg/ml in concentration is equivalent to 28.5 mg/ml of freebase nicotine.

A 2023 study looking at the association between use of vaping products and insufficient sleep among adolescents (collecting data from ~28,000 adolescents) in the US found the following:

• Current vapers showed 40% increased odds of insufficient sleep, compared to adolescents who have never vaped.
• Former vapers showed 28% increased odds of insufficient sleep, compared to adolescents who have never vaped.
• Physical activity had a protective effect on insufficient sleep.

Previous studies have shown that nicotine is a risk factor for disrupted sleep. Symptoms of depression, suicidal ideation, excessive screen-time, and alcohol use were also associated with a higher likelihood of insufficient sleep.

The maximum amount of nicotine allowed in disposable vapes in NZ is 20 mg/ml. This is the freebase amount of nicotine and has been shown to be equivalent (in blood) to smoking a conventional cigarette. To work out what this would equate to for a nicotine salt, we need to know how heavy the chemical molecules are. This is called the molecular mass. Without going into detail here, a nicotine salt product that has a concentration of 35 mg/ml will contain 20 mg/ml of actual nicotine. A nicotine salt that is 50 mg/ml in concentration is equivalent to 28.5 mg/ml of freebase nicotine.

There is a lot of research focussing on this around the world and the answers aren’t yet clear. What does look likely is that vaping causes changes to blood flow and blood vessels and in the long-term can lead to stiffer blood vessels and higher changes of cardiovascular disease. Several studies have also shown that vaping causes inflammation. This is the body’s normal response to something foreign entering the body. Long term/chronic inflammation is associated with damage to the tissue in many parts of the body.