The fumes come from the flux, and they're not that great for you in quantity. Soldering temperatures will not vaporize lead or the metals in unleaded solder.

The fumes come from the flux, and they're not that great for you in quantity. Soldering temperatures will not vaporize lead or the metals in unleaded solder. There is also some conjecture that the fluxes used in unleaded solder produce more aggressive fumes.