[literallycancer]

>There are already so many reasons to get in contact with synthetic chemicals.

Such a pointless distinction. There are many chemicals that occur naturally and will kill you.

[sametmax]

Anything can kill you. You can kill somebody with a piece of wood, a nuclear device, gaz, light, shock waves, a baby, a golden coin...

And any matter is a chemical. Using "synthetic" as a qualifier allow me to distinguish "fructose" from "paracetamol". You will less likely see important traces of cobra venom in the water.

It's not perfect, but I fail to find a better term.