I have a vortex mixer and I love it. I usually throw my paints on there for like 30 seconds or less.

If you are extremely worried about it you could use one of those fingernail polis mixers. The kind where you strap the paint to the mixer and press a button to turn off and on. Example mixer

As far as the medical risks involved, I don't know that you'll get a good answer from this community. I personally have never had any problems or heard of them.