Silica is a ubiquitous mineral-- most sand is silica-- found in abundance almost everywhere. It has long been known to cause respiratory problems when people are exposed to large quantities, and industrial sources of silica pollution are particularly problematic.
Most industrial silica is in the form of the crystal quartz. Freshly crushed quartz particles are sharper and more dangerous than aged quartz [6,36,37]. The most dangerous particles are those smaller than 5μm in diameter, and while quartz is tough and hard to break into sizes smaller than 10μm, industrial processes can produce an abundance of sub 5μm particles [25,26].
For these reasons, we're interested in monitoring particles of silica.