Control of Worker Exposure to Silica in Oil and Gas Extraction

Exposure risks to workers at oil and gas extraction sites include respirable crystalline silica (RCS). Repeated exposure to RCS can cause serious or even fatal diseases, including silicosis and lung cancer. National Institute for Occupational Safety and Health (NIOSH) researchers have identified concentrations of RCS at hydraulic fracturing sites that can be over 10 times higher than occupational exposure limits. To reduce exposures, the researchers have developed a mini-baghouse assembly prototype, to be mounted on the thief hatches on top of sand movers, one of the largest sources of dust generation. This presentation details the results of a trial of the NIOSH mini-baghouse prototype.

 A bulk sample of the dust collected by the baghouse assembly showed the likely presence of freshly fractured quartz, a particularly hazardous form of RCS. Air samples collected at locations on and around the sand mover were analyzed for respirable dust and RCS.  Results indicate that use of the mini-baghouse effectively reduced both respirable dust and RCS downwind of the thief hatches. Reduction of airborne respirable dust concentrations ranged from 85% to 98%, and reductions in airborne RCS concentrations ranged from 79% to 99%. While the results of this evaluation showed the mini-baghouse prototype effective in reducing respirable dust and silica concentrations, several design enhancements have been made to further improve control effectiveness. As a result, a new prototype design has been developed, which will be evaluated in the near future.