For several years, I was selling once-fired M118 LR brass straight from a Marine firing range. I would tumble them for about an hour in my non-ventilated basement, before packaging them up and shipping them. I did this for well over 100,000 cases in a relatively short period of time. I also cast bullets in the same unventilated basement environment. I had my lead blood level checked several times, and as I recall, it was at ~3, in which a level of 25 called for some kind of medical intervention. Keep your fingers out of your mouth and nose when tumbling or casting, and you will have nothing to worry about.
Don