Source: https://www.hse.gov.uk/lung-disease/electronics-soldering.ht...
Children are up to five times more likely to get lead in their bodies, so under no circumstances should children get leaded tin in their hands.
It is possible to get lead poisoning through the skin even as an adult if lead is handled daily. Fortunately, nowadays lead-free tin is used, but I know that some hobbyists still have a lot of lead in their stores.
If you're worried about lead just use RoHS solder?
The dose makes the poison.
Of course, nothing is completely without risk, and an argument can be made that avoiding any avoidable risk is good, even if that risk is tiny. But the risk that comes from the fumes of soldering, unless you're doing it a whole lot, are much, much smaller than lots of risks you take every day without worry.
Everyone has a different risk tolerance. For instance, I intentionally use leaded solder because it works so much better than the lead-free varieties. But I'm cautious to avoid handling the stuff if I have any open wounds on my hands, and to avoid touching my face until I've washed my hands. That's an acceptable risk for me.
Respiratory risks of solder aware minimal, particularly ironically the leaded variety. If you’re worried solder with the window open or get an extractor. I haven’t needed either in the last 40 odd years.
The lead itself is harmless unless you ingest lots of it. Wash your hands. That is all you need to do. Take it to the WEEE bin or waste disposal if you discard it.
I learned to solder when I was 8. My kids when they were 10. It’s fine. I built my first amateur radio transceiver when I was 12!
Soldering kit is cheap. Even decent metcal stuff can be had for virtually nothing if you shop around.