Bentonite is a ground naturally occurring clay. It is inorganic, non-toxic, non-irritating. It is not considered hazardous on skin contact (it is employed in cosmetics and skin products as a suspender). Eye contact hazards are similar to those of any other clay, flush to remove the particles.
As a natural clay product it contains many trace elements and minerals. It also contains free quartz. Thus the primary hazard to consider is inhalation. While the aluminum silicate bentonite particles are much smaller than those of ball clay or kaolin, it is difficult to say whether this is also true of the quartz particles that may be associated with them (it is the quartz particles that present the inhalation hazard).
Bentonite is normally employed in very small amounts in glaze and clay body mixes (typically less than 3%) and only a small part of this is free quartz. However the free quartz is potentially finer it therefore more likely to become airborne.