Pg Vs. Vg Vs. Peg

[Christopher]

There are three possible base carrier liquids in use for e-liquid (the refill liquid used in electronic cigarettes): PG, VG, and PEG. PG is the most common, usually with a proportion of VG as that produces more vapor. PEG is more common in pre-filled cartomizers.

1. PG or propylene glycol or propane-1,2, diol

PG is the most common refill liquid base material, normally used with 10% to 30% VG.

It is virtually inert in the body and can even be injected into the bloodstream without effect (and it is: it is the carrier liquid for drugs like diazepam that don’t mix with water).

It is a powerful bactericide and virucide, and has been used in hospital air spray projects.

There is a vast body of research on it going back 70 years that proves it is safe in any reasonable quantity.

PG is usually the main constituent in disco fog machines. Due to strict employee health regulations that cannot be subverted, it is approved as safe for extended exposure for employees in discos, bars and theatres.

Because it is made from non-organic sources (via chemical processes) allergies are not reported.

It presents flavors well and has the best TH of the three choices.

2. VG or vegetable glycerine or glycerol or propane-1,2,3, triol

VG is an alternative carrier liquid, though more commonly used as an additive to PG liquids.

It is more viscous (thick) than PG. If used as the sole base material, it will need diluting with 10% – 20% DW (distilled water). Other additions seen include alcohol and EM (ethyl maltol).

There is little research on inhalation. It is thought to be less inert than PG, and to be treated by the body as a complex carbohydrate – that is, metabolized by being broken down into carbohydrates and/or excreted.

VG can be synthesized and made in a similar way to PG and PEG, from other chemicals, or it can be made from vegetable sources – mainly coconut oil and palm oil. For this reason there are a very small number of people who may have an allergy to a specific brand, of the same type of allergy as that to peanuts.

Because it does not have the same bactericidal action as PG, preservatives such as sulphites may be added to it to prevent deterioration; therefore, there are questions such as: are the additives the cause of ‘allergies’, or indeed whether VG with additives should be used for inhalation.

It produces more vapor than PG.

It produces less TH and does not present flavors as well.

3. PEG or polyethylene glycol

PEG is the least common carrier liquid.

It can be made in many different formulations, the one used for e-liquid is called PEG400.

This formulation appears to be chosen as it has the right viscosity, as it can be thinner, thicker, or even in the form of a wax.

As far as we know there is little research but it cannot be toxic as it is used in foods and medicines.

It is said to present flavors better than any other base liquid.

Because it handles flavors so well it is used by several of the major cartomizer-only (2-piece ecig) firms that mainly sell to first-time buyers, as it works well in cartos.

We think it comprises 1% or less of bottled eliquid volume but it is far higher in the pre-filled carto market – perhaps as much as 33%.

PEG is the most likely of all the three base materials to be contaminated with DEG as the manufacturing process can be carried out using the same equipment, so there is a risk of cross-contamination.

Uses

All these base liquids are used in medicinal preparations of one sort or another, and are considered non-toxic. They are all used in foods, skin creams and some (if not all) in medical inhalers, so any MSDS warnings can be completely ignored. PG for example is used as the mist carrier in nebulizers for lung transplant patients, so it can be assumed that it is as inert as it is possible for a material to be that is not water.

They can be used (especially PG) to make antifreeze or to make it less toxic – for example, to make it less dangerous to livestock or pets, and for winterizing boat and RV lavatory systems that may have human contact by touch or inhalation. PG is used for this purpose because it has a very low freezing point, is non-toxic, and is relatively cheap.

There is an important question about safety concerning VG, that does not affect the other two liquids: if taken to over its boiling point it can degrade into acrolein, which is poisonous. However all tests so far indicate that for some reason this does not happen in an e-cigarette although theoretically it might. Acrolein was not detected in tests carried out by Intellicig even when the temperature was raised higher than normal. This may be because the addition of other ingredients such as water changes the boiling point enough that acrolein is not created, and/or due to the fact that if the temperature within an atomizer can rise sufficiently high to produce acrolein, then there is no liquid left to convert. Acrolein apparently has a strong, characteristic odor so it would be noticed in any case.

We know less about PEG although it seems, so far, to be inert in the body.

DEG

Diethylene glycol is a poison that kills by damaging the liver and kidneys among other effects. It is very similar to PG and PEG in appearance, taste and characteristics, and it is produced in the same way from similar raw materials and as a by-product of similar manufacturing processes, although PEG seems especially implicated. It is therefore likely to be found in any materials of this type due to poor manufacturing controls or cross-contamination – for example, using drums for PEG400 that previously contained DEG. For this reason it is the main contaminant that should be tested for.

Because PEG is more likely than the others to be contaminated with DEG, and because pre-filled cartomizers are the main area of use for PEG, it follows that such cartos need testing more than other materials.

The FDA was formed in 1938 as a direct result of a wide-scale poisoning incident in 1937 in which more than a hundred people died after DEG was used in a medicine.

Source: Electronic Cigarette Forum – Rolygate