Hydraulic fracturing has been used for hydrocarbon recovery for decades, but has become widespread in North America due to a modern process known as horizontal slick water fracking, as well as other technologies that provide more efficient access to oil and gas deposits. Pressurized fluid and sand injected via drilled wellbores into shale formations cause rock fractures that allow natural gas and petroleum to be released and collected.
Crystalline silica, A.K.A frac sand, is used as part of the mix is injected into wells for hydrocarbon recovery. Frac sand acts as a proppant, or means of holding open fracture drock to allow access to oil and natural gas for extraction. Thousands of pounds of sand are transported to well sites, then conveyed and blended with fracking fluids before high-pressure injection; all of these processes can expose well site workers to respirable silica dust.