I believe a lot of places won't even carry it anymore. I couldn't find it at Wal-Mart last year. I did find it though. they sell nice sized bags of it for artificial fireplaces. I guess the sparkly attributes sell the effect of ashes. I have no idea, but you can find it there.
To me, this is like the silica in sand and how it is causes silicanosis of the lungs etc. Since the dark ages, sand has pretty much always consisted of some portion of silica. Its been in there a long, long time. I think this information is released to boost the sale of calcisand and other marketed products.
My advice...don't open the bags, and stick your head inside when your winded. Don't pursue a job at a sand or vermiculite packaging facility. Your exposure with your lizards is pretty minimal in reality.
J