"Lead is supposed to be hazardous to your health and I'm not just talking about .45 caliber 230 grain slugs flying your way. When lead is heated, you end up breathing in some of the vapors. Over time it accumulates in your system and you get heavy metal poisoning (and I'm not talking about too much good ole rock and roll either)."
The amount of lead vapor created is very low unless you use an open flame played on the lead to melt it.
The vapor pressure of lead at typical casting temperatures is low enough to not create a signifiacnt problem if you use an electric pot. Tin will come out of the alloy around 725F-750F, so the casting temperature is usually lower than that.
Even OSHA agrees that normal soldering temperatures (around 700F) do not require any special protection from lead vapor. The flux smoke is actually more of a long term problem.