What are the harmful side effects if you don't have a preexisting health condition?
We do however have studies showing that vaping can be implicated in lung cancer [2].
[1] https://www.moffitt.org/cancers/lung-cancer/faqs/lung-cancer... [2] https://www.news-medical.net/news/20240520/Study-reveals-inc...
Tar as I understand it does break down very slowly over time but many smoke at a greater rate than it can be broken down and smoke itself is a worse irritant than oil vapor.