NIOSH Sounds Alarm on Fracking Silica Exposures

Full-shift breathing zone sampling at 11 hydraulic fracturing sites in five states found 79 percent exceeded the NIOSH REL and ACGIH TLV, with 31 percent 10 times or more above the NIOSH REL.

Crystalline silica exposure among workers should be evaluated at all U.S. hydraulic fracturing sites and effective controls should be implemented if necessary, four NIOSH employees recommend in a new report posted on the agency's Science Blog. Their report sets off alarm bells because the measured levels of respirable silica are so high and fracking is so prevalent across large areas of the country.

The report's authors are Eric Esswein, MSPH, senior industrial hygienist in the NIOSH Western States Office; Max Kiefer, MS, director of that office; John Snawder, Ph.D., a research toxicologist in the NIOSH Division of Applied Research Technology; and Michael Breitenstein, BS, a research biologist in the same division.

They wrote that NIOSH recently collected 116 air samples at 11 hydraulic fracturing sites in Arkansas, Colorado, North Dakota, Pennsylvania, and Texas. "At each of the 11 sites, full-shift personal-breathing-zone (PBZ) exposures to respirable crystalline silica consistently exceeded relevant occupational health criteria [e.g., the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL), NIOSH Recommended Exposure Limit (REL), and the American Conference of Governmental Industrial Hygienists' (ACGIH) Threshold Limit Value (TLV®)]," they reported. "At these sites, 54 (47%) of the 116 samples collected exceeded the calculated OSHA PELs; 92 of 116 (79%) exceeded the NIOSH REL and ACGIH TLV. The magnitude of the exposures is particularly important; 36 of the 116 (31%) samples exceeded the NIOSH REL by a factor of 10 or more. The significance of these findings is that even if workers are properly using half-mask air-purifying respirators, they would not be sufficiently protected because half-mask air-purifying respirators have a maximum use concentration of 10 times the occupational health exposure limit."

The report says NIOSH notified company representatives of its findings and provided reports with recommendations to control exposures. "We recommend that all hydraulic fracturing sites evaluate their operations to determine the potential for worker exposure to crystalline silica and implement controls as necessary to protect workers," the authors wrote, adding that NIOSH found seven primary points where dust is released or generated from fracking equipment or operations:

  • Dust emitted from "thief" hatches (open ports on the top of the sand movers used to allow access into the bin)
  • Dust ejected and pulsed through side fill ports on the sand movers during refilling operations
  • Dust generated by on-site vehicle traffic and by winds
  • 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 dragon’s tail (end of the sand transfer belt) on sand movers

The report says NIOSH is designing conceptual engineering controls to minimize silica exposures and hopes to have a working prototype next month. Industry partners interested in assisting in testing it are asked to make contact via the blog comment box or by e-mailing nioshblog@cdc.gov. "NIOSH is also looking for additional partners in drilling and well servicing to work with us to evaluate worker exposures to other chemical hazards and develop controls as needed. Other potential workplace exposures can include hydrocarbons, lead, naturally occurring radioactive material and diesel particulate matter which have not been fully characterized," it says, asking interested parties to refer to the document "NIOSH Field Effort to Assess Chemical Exposure Risks to Gas and Oil Workers" document for details.

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