Yeah, seems likely. Lower level but constant exposure from that, and directly into the lungs, too.
I bet this kit could vary a lot, depending on just how you played with it. Like did you have your head over the crucible inhaling fumes, or off to the side? Did you wash your hands after handling the figures and before eating food? Etc.



That seems possible.
I did some searching and there are sites that claimed the metals used in home casting kits varied, and were often an alloy of tin and lead, but could also be pure lead, pure tin, pewter alloy made without lead, or some kits would also use molten plastic.
So through history it sounds like it varied a lot as to materials.