http://npic.orst.edu/factsheets/degen.html#exposed
Quote:After inhalation of amorphous diatomaceous earth, it is rapidly eliminated from lung tissue. However, crystalline diatomaceous earth is much smaller, and it may accumulate in lung tissue and lymph nodes. Very low levels of crystalline diatomaceous earth may be found in pesticide products.
...Amorphous diatomaceous earth has not been associated with any cancers in people.
I keep my cultures in vented covered bins and generally I put them back in the same depression they were in which seems to minimize the dust. Every once in a while I gently fluff it back up but I'm pretty careful to not kick up a dust storm (I use the amorphous stuff).