Even the "neutral" components of vape liquid can be bad when coated onto the insides of your lungs:

> Vaping-related lipoid pneumonia is the result of inhaling oily substances found in e-liquid

from https://www.hopkinsmedicine.org/health/wellness-and-prevention/what-does-vaping-do-to-your-lungs

See same article for various other bad effects of vaping.