Like the Romans used to drink from lead cups. Something like that.
(it appears that the moderator is removing any replies with which he disagrees. It might be a piefed issue. But all the removed replies are top level and upopular. Stranger coincidences have happened I suppose.)
Things that could be harmful but we don’t know for sure yet?
Possibly porn. Currently we really lack research on porn’s effect on people. Whoever tells you confidently it’s normal or degenerate is a liar. No one knows. We are just running a society-wide experiment in real time.
Have you actually looked if there’s scholarship on it? Because I’d be amazed if there isn’t, and I’m gonna be pissed if I use my library and find a shitload of it.