[Sport45]

Lead vapor is a gas and therefore must behave as a gas. That means it expands to occupy all the space in a container (room). That's why you can smell ammonia or mercaptan even if you are on the opposite side of the room from the spill. Of course, you never get perfect mixing and heavier gasses tend to congregate in low areas but there are no absolutes. If lead vapor is in an open space you can be exposed just like you can with mercury.

Now don't get me wrong, there's not much lead in the room. Lead, even at melting temperatures has a very, very low vapor pressure. This means it has little volatility. The downside of low vapor pressure is that Dalton's law says you can have a lot of it in the air since its low partial pressure doesn't have much impact on the atmospheric pressure.

I don't think casting is dangerous if minimal precautions are taken. I wouldn't downplay the risks either.

My Uncle lived to a ripe old age even though he smoked most of his life. He may have had a strong opinion that because he was healthy, smoking was not harmful. My mother-in-law, who died a couple years ago from emphysema would probably disagree...