The silica and respiratory concerns are the same as the discussion about using DE. As Sweet PDZ contains DE, this is where the issue is coming from. I was using DE and it WAS super dusty - so I can see the issue there. Does anyone find that the Sweet PDZ is really dusty? The Stall Dry isn't dusty at all, which is nice. Silicosis, the respiratory disease that could arise from products containing silica could be life threatening. Has anyone known of this to occur in anyone's flock or individual chickens? It would be interesting to know what the likelihood of the disease would be..