We'd have to wait for a study to tell us what the safe levels for e-liquid and VG / PG is.
This is only speculation: I don't think setting it up to 500°F is too dangerous. The boiling point of 80%VG and 20% water is 250°F (121°C). For 90%VG 10% water it's
281°F (138°C). A mixture with 10% PG (e.g. flavor) could have a higher boiling point but somewhere around that. I do actually get the faintest wisps of vapor at 250°F, but we are already way above the boiling point simply to increase the amount of vapor production.
I'm not sure at what temperatures acrolein (the simplest
aldehyde, whatever that means) will get created, but googling quickly I found
this: "Over 530 F is the temp I've read on here that the ecig must reach in order for it to produce Acrolein.".
But depending on your wicking, any temp above 400°F will increase the "brownification" of your wick. So if you stay below 500°F you MIGHT be fine and just have to rewick more often.