Question: How do I know if workers are exposed to respirable silica?

Answer: Employers must determine which jobs expose workers to silica by collecting respirable dust samples and comparing the results to current exposure limits. Employers should consult with a trained occupational safety and health professional, such as a certified industrial hygienist, or contact OSHA's free on-site consultation service. OSHA Directive CPL 03-00-007 National Emphasis Program – Crystalline Silica, has detailed information on silica hazards, guidelines for air sampling, guidance on calculating PELs for dust containing silica, and other compliance information. If air samples show levels above OSHA's calculated PEL, employers are required to take actions to reduce worker exposures. However, both OSHA and NIOSH recommend that employers take action to keep worker exposures below the NIOSH REL. In their study, NIOSH identified seven primary sources of silica dust exposure during hydraulic fracturing operations: Dust ejected from thief hatches (access ports) on top of the sand movers during refilling operations while the machines are running (hot loading). Dust ejected and pulsed through open side fill ports on the sand movers during refilling operations Dust generated by on-site vehicle traffic. Dust released from the transfer belt under the sand movers. Dust created as sand drops into, or is agitated in, the blender hopper and on transfer belts Dust released from operations of transfer belts between the sand mover and the blender Dust released from the top of the end of the sand transfer belt (dragon's tail) on sand movers.