Rob Swire is back from the doctor, and his first tweet surprised all of us.

Followers were left wondering what he meant, or how vaping could possibly lead to hearing loss, for at least a few minutes. Apparently, the chemical propylene glycol, which is used as a solvent in some juices, is ototoxic – meaning toxic to the cochlea or auditory nerve. This has been a known effect since at least 1980 when applied directly to the ear (e.g., via ear drops), but its use in inhalants hasn’t been documented as of yet.

As a rule of thumb, it might be more wise to switch to a more vegetable glycerin based juice than PG in the future. Hearing loss is no trivial matter and can often end up as a permanent affliction.

However, keep in mind that research has not been done on the effects of smoking/inhaling propylene glycol. Until research is conducted, it cannot be conclusively stated that the PG was 100% at fault. Many people are already attributing his sudden loss of hearing to standing by studio monitors on tour, or possibly an allergic reaction. Both causes are unlikely, as studio monitors are a mainstay of all upper-tier producers, and would likely affect more than just a couple in every hundred if that were the case; similarly, PG is used in a vast array of products, including cosmetics and food, and has never been found to cause hearing loss except in the case of direct application.

If you already have tinnitus, be more cautious, as other users have already documented some trouble.

Obviously, anecdotal evidence will arise. Keep in mind that until these effects are studied in a controlled environment, there can be no way to analyze the true effects of PG vs VG or vaping in general.

Rob Swire would like the research to go forward, though.

Again, the most important point to take away from this is that research on propylene glycol in inhalants has not been conducted. Keep using PG if you’d like, no one is going to stop you. But if you have a career in music, you might want to be a bit cautious anyway.

On another note, looks like we’ll be seeing some more Knife Party material soon. Sure took them long enough.