Hello Molten Metal, I'm shooting from the hip a bit, but I do believe there are some grades of bronze, or brass, that do have a bit of zinc in them. If that were the case, I would agree with your question of toxicity, more a long term issue, but nontheless an issue. I have never noticed any ill effects in welding the parts that I have had exposure to, but, they have been in a repair type scenario and not a long-term exposure situation. Anyone else care to comment on this issue? Regards, aevald