There is a form of silica (crystalline silica) known to cause cancer and permanent lung damage, but that form of silica is not used in the blending powder. Evidence for the potential harm of inhaling the form of silica used in the blending powder (amorphous silica) is mixed. Similarly, heating up silica to produce glass, which is another form of amorphous silica, also leads to some contamination with crystalline silica. So, although one page notes that amorphous silica may cause some eye and lung irritation, it's unclear whether the risks refer to diatomaceous earth in particular, which may be contaminated with crystalline silica, or all forms of amorphous silica, including fully synthetic amorphous silica that is not contaminated with crystalline silica. Because each bag of Starbucks' blending powder contains 350 grams of powder, each bag contains 7 grams of silica at most.