Although Propylene Glycol is generally recognized as safe for humans and most domestic animals, it is cats that actually have a unique sensitivity to the chemical.
This may cause concern for some vapers, since most e-liquids are mainly made up of Propylene Glycol. Upon learning of this, it is natural to wonder if it would be better to switch to glycerin-based vegetable oils (VG), or simply not vapear close to your cat, but after knowing more about the subject, you can see that the Exposure to Propylene Glycol in the second-hand vape is unlikely to cause a problem.
Why Propylene Glycol is bad for Cats? It is well established that Propylene Glycol is not good for cats, and this is due to its effect on red blood cells: increases the amount of "Heinz bodies" between they. These are basically pieces of hemoglobin that have been "denatured", meaning they have lost their ordinary structure and therefore are not so good for carrying oxygen. This occurs due to the action of "free radicals" (reactive chemicals, which contain oxygen), and the process is not limited to cats. In general terms, the animal spleen repairs the damage or gets rid of the blood cells, but if a large amount of blood cells are sacrificed due to Heinz bodies, this exposure may Lead to anemia (which may be, basically, defined as a low count of glycocytes). Propylene Glycol is not directly responsible for this oxidative damage in cats, but it is assumed that the intermediary molecules when they break down In the body they are.
In cats, there is also a specific weakness of Heinz bodies because they are formed more easily than other animals and their spleen is also quite ineffective in eliminating them. Even in healthy cats, about 1 to 2 percent of red blood cells will have Heinz bodies, but their increased risk means that they should be minimized as much as possible.