Review (1/5): Contains  crystalline silica: a warning not to breathe it.
I did some research on silica dust: Cancer Studies in Humans
Exposure of workers to respirable crystalline silica is associated with
elevated rates of lung cancer. The link between human lung cancer
and exposure to respirable crystalline silica was strongest in studies of quarry and granite workers and workers involved in ceramic,
pottery, refractory brick, and diatomaceous earth industries. Human
cancer risks are associated with exposure to respirable quartz and
cristobalite but not to amorphous silica.