If you work in the hydraulic fracturing industry – better known as “fracking”, a process used to free natural gas and oil from shale rock  – you may be exposed to high levels of crystalline silica, putting you at risk of silicosis, lung cancer and other debilitating diseases. The warning came in a 22 May 2012 letter sent by US unions to top federal safety agencies.

AFL-CIO blog and letter. NIOSH science blog. Bloomberg. Risks 558.