I forget the name of it, but the stuff we used in the seventies gave off toluene di-isocyanates (TDIs) when heated, which could cause lung sensitisation and breathing problems. I hope the new solder-through insulations don't do things like that.
Mind you, the resin flux (colophony) wasn't very lung-friendly either. I look back in amazement at the perpetual fog in the wiring shop and think of the effect it must have had on the wiremen and women who were in it all day, every day.
George