I don't know how to deal with this effectively because my own parents were so relaxed I could do absolutely anything when I was growing up. As such, I did more naughty things than my friends but learned to generally move back to the straight and narrow pretty quickly after realising most of the bad stuff was bad. I guess you would call it learning the hard way.
Now I'm a parent, when I come across something like this I have no idea how to deal with it. Part of me (relaxed parent side) thinks it's only vaping, could be way worse and I could lay down rules like never when his brother is awake, so maybe early morning or evening.
But then the other part of me thinks much better parents than me would have a detailed friendly chat about this explain health things, lay down boundaries. I just don't know what an excellent parent would do in this scenario because I don't class myself as having that knowledge guidance or awareness .
Please hit me with your "I'm a great parent and this is what I would do in your shoes' responses please 🙏