There are two strange aspects in respect of the use of propylene glycol that concerns the domestic cat.
Firstly, this chemical is an alternative to ethylene glycol antifreeze, which is highly toxic to cats and which causes the death of thousands of cats every year. Almost 90% of animals that consume anti-freeze die. Propylene is less toxic.
So why hasn't propylene glycol replaced ethylene glycol many years ago? It must be about cost and a disregard for companion animals by the manufacturers combined with a lack of knowledge with respect to pet owners. It seems extraordinary to me that anti-freeze for cars cannot be made non-toxic to cats while keeping the price the same. There is just a lack of will to do it.
There is another very odd feature of propylene glycol. Apparently it is a common pet food ingredient! Yes, the manufacturers put it in pet food as a moistening agent. It is found in semi-moist pet food. Apparently it is approved for use in dog food ("generally recognized as safe" (GRAS) in the USA). Approval will be country specific, meaning in certain countries it will be approved while in others it might not be. Propylene glycol is said to destroy red blood cells. Apparently veterinary research indicates that it is toxic to dogs. There seems to be a conflict in respect of scientific information. How is it approved for dog food and toxic at the same time?
However, propylene glycol is not allowed to be used in cat food. I presume this means in the USA. It is deemed unsafe for a cat to ingest the chemical when an ingredient in cat food. So how is it safe for cats as an anti-freeze where it would be in larger quantities?
It looks chaotic to me. One thing is clear. Big business cares more about profit than the long term health of cats or dogs.