Millions of U.S. workers are exposed to respirable crystalline silica, also known as silica dust, in a variety of industries, including construction, mining, oil and gas extraction, stone countertop fabrication, foundries and other manufacturing settings. Silica dust is made up of small particles that become airborne during various work activities including cutting, drilling, chipping, sanding, or grinding materials that contain crystalline silica. These materials can include sand, concrete, brick, block, stone, and mortar.