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Worker Exposure to Silica during Hydraulic Fracturing

The American National Institute for Occupational Safety and Health (NIOSH) identified exposure to airborne silica as a health hazard to workers conducting some hydraulic fracturing operations during recent field studies.

NIOSH's recent field studies show that workers may be exposed to dust with high levels of respirable crystalline silica (called "silica" in this Hazard Alert) during hydraulic fracturing.

This Hazard Alert discusses the health hazards associated with hydraulic fracturing and focuses on worker exposures to silica in the air. It covers the health effects of breathing silica, recommends ways to protect workers, and describes how OSHA and NIOSH can help. Workers and employers need to be aware of the hazard that silica dust poses. Employers must ensure that workers are properly protected from exposure to silica. This Hazard Alert also provides a brief summary of other health and safety hazards to workers conducting hydraulic fracturing activities.

Why is silica a concern for workers during hydraulic fracturing?

Recent NIOSH field studies identified overexposure to airborne silica as a health hazard to workers. Large quantities of silica sand are used during hydraulic fracturing. Sand is delivered via truck and then loaded into sand movers, where it is subsequently transferred via conveyer belt and blended with other hydraulic fracturing fluids prior to high pressure injection into the drilling hole. Transporting, moving, and refilling silica sand into and through sand movers, along transfer belts, and into blender hoppers can release dusts containing silica into the air. Workers can be exposed if they breathe the dust into their lungs.

NIOSH identified seven primary sources of silica dust exposure during hydraulic fracturing operations:

  1. Dust ejected from thief hatches (access ports) on top of the sand movers during refilling operations while the machines are running (hot loading).
  2. Dust ejected and pulsed through open side fill ports on the sand movers during refilling operations
  3. Dust generated by on-site vehicle traffic.
  4. Dust released from the transfer belt under the sand movers.
  5. Dust created as sand drops into, or is agitated in, the blender hopper and on transfer belts.
  6. Dust released from operations of transfer belts between the sand mover and the blender; and
  7. Dust released from the top of the end of the sand transfer belt (dragon's tail) on sand movers.

NIOSH Findings on Worker Exposures to Silica

In cooperation with oil and gas industry partners, NIOSH collected 116 full shift air samples at 11 hydraulic fracturing sites in five states (Arkansas, Colorado, North Dakota, Pennsylvania, and Texas) to determine the levels of worker exposure to silica at various jobs at the worksites. Many air samples showed silica levels for workers in and around the dust generation points above defined occupational exposure limits.1

Of the 116 samples collected:

  1.     47% showed silica exposures greater than the calculated OSHA PEL.
  2.     79% showed silica exposures greater than the NIOSH REL of 0.05 milligrams per cubic meter (mg/m3).
  3.     9% of all samples showed silica exposures 10 or more times the PEL, with one sample more than 25 times the PEL.
  4.     31% of all samples showed silica exposures 10 or more times the REL, with one sample more than 100 times the REL.


Download the Safety Guide - Working with silica below in the attachment section and Download the Best Practices For Dust Control Manual on This link

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