NSP Correspondent - Mirosław Dworniczak | 21 March 2016

Something really awful is happening now. In October 2015 German Federal Office for Chemicals, a part of Federal Institute for Occupational Safety and Health submitted a proposal to the European Chemicals Agency for a new toxicological classification of propylene glycol. 

The PDF of the formal document can be found here: http://echa.europa.eu/documents/10162/13626/clh_propane-1%2C2-diol_en.pdf

Their idea is to classify propylene glycol as STOT SE 3. What does that abbreviation mean? ‘Single target organ toxicity – single exposure – class 3’. In plain words: they state that this compound is toxic for a specific organ (in this case – the respiratory tract) in our body even after a single contact.

Sounds weird, right? Exactly – this definitely is weird. What's more – the implications of such a classification might be devastating for us vapers.

Although I am not a specialist in the field of classification of chemicals, I am still a chemist able to analyze the submitted report.

What is propylene glycol (PG)?

Propylene glycol (propane-1,2-diol; CAS: 57-55-6) belongs to the class of alcohols, namely diols (this means that two -OH groups are present in the molecule). It is a popular chemical used mainly in the chemical industry, but also as a de-icing fluid, a solvent in pharmaceutical preparations, humectant, and preservative in food and cosmetics. It is also one of the main ingredients of e-liquids for electronic cigarettes (usually denoted as PG).

Federal Drug Administration (USA) classified propylene glycol as GRAS (Generally Recognized As Safe). Medical research on this compound is profound – dating back to 1942 and the classical paper by Robertson ( http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2135271/) in which his group studied antimicrobial properties of PG. Even tiny amounts of this compound dispersed in the air killed several types of the bacteria. Further research ( http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2135271/) showed no adverse effects after prolonged (12-18 months) exposure to PG of rats, monkeys, and humans.

Robertson's conclusion was simple: PG aerosol is harmless and thus can be used as an antimicrobial agent. And there were many more papers published since.

My comment concerning the German report

Let me quote the crucial part of the report, namely this:

2. Background to the CLH proposal
2.2. Short summary of the scientific justification for the CLH proposal.
A number of internet forums indicate that the inhalation of propane-1,2-diol aerosol/vapour may have adverse effect to the respiratory tract if inhaled.

What? Internet forums are quoted as a scientific source? Now this is just ridiculous. Did anyone check the quality of the fluid used in those fog machines? The proposal refers to 99.9% degree of purity of propylene glycol. I am sure this does not apply to fog fluids, as they usually contain other chemicals (triethylene glycol, 1,3-butylene glycol etc.). What's more – no-one checks, in fact, the purity of propylene glycol used in those mixtures. Even a small amount of additives may cause irritation of mucous membranes or coughing. There is no direct evidence of propylene glycol acting as an irritating agent. Let me also quote the English translation of this forum link provided by the Germans: http://www.gutefrage.net/frage/nebel-von-nebelmaschine---gesundsheitsschaedlich

The lethal dose (LD50) for propylene glycol I remember somewhere around 1.5 grams (!!).

In fact the lethal dose data that are provided in the application, are found here: http://www.inchem.org/documents/pims/chemical/pim443.htm are in fact:

7.2.2 Relevant animal data
LD50 oral, rat = 20g/kg
iv, rat = 68g/kg
oral, dog = 22g/kg (Sax, 1989).

It is just an absurd to include in an official report a forum entry from an anonymous internet man/woman having absolutely no knowledge of the subject – as can be clearly seen from the toxicity data presented above.

Propylene glycol in medicine

Propylene glycol (C3H8O2) is a commonly used drug solubilizer in topical, oral, and injectable medications. It is used as stabilizer for vitamins, and as a water-miscible cosolvent.

Propylene glycol is used as a solvent for cyclosporine in a pharmaceutical preparation used for the treatment of patients after lung transplant (see: References). I wonder why this information (obviously scientific!) is not included in the proposal.

By the way - nicotine mouth spray (Nicorette QuickMist) also contains propylene glycol as a solvent for nicotine.

What is important

Fortunately, submission of the proposal is just the beginning. Right now it is time for consultation. The deadline is April, 21st. I do really hope that we, vapers, have to act. This applies to toxicologists, doctors, chemists, but also to organizations. Everyone should do something.

Otherwise this weird proposal will turn into an official document. Then it will be too late.

So, you should just go here:


and then follow the link ‘Give comments’. Simple as that!


  1. Preclinical safety evaluation of inhaled cyclosporine in propylene glycol
  2. Lung deposition and pharmacokinetics of cyclosporine after aerosolization in lung transplant patients.
  3. Safety and toxicology of cyclosporine in propylene glycol after 9-month aerosol exposure to beagle dogs 
  4. Lung Deposition and Pharmacokinetics of Nebulized Cyclosporine in Lung Transplant Patients - 2014