George, that is a very good and important point to bring up.
In my research, I read sites and saw on videos that a face mask/respirator is the first step in the process of mixing your own mix. For some people, the potting mix itself can be an irritant to the eyes and lungs. Back before 1990, some vermiculite contained asbestos - a site explaining this
https://laidbackgardener.blog/tag/is-vermiculite-toxic/