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What is the “Pig Pen Effect?”

 In its 2013, June/July issue of The Synergist, the American Industrial Hygienists Association ( identified at least eight (8) points of “silica-containing dust release or generation from equipment used on the site, the site itself, or the worker.”

The authors, Eric Esswein and Ryan Hill, identified the eighth point, “work clothing (for example, flame retardant coveralls) contaminated with crystalline silica” is considered a dust release or generation point. In addition, they pointed out that hydraulic fracturing companies should consider a variety of dust generation controls including, “methods to clean silica-containing dusts that contaminate workers’ clothing.”

When a worker is wearing contaminated clothing, respirable silica dust is traveling with the worker and stays in their breathing zone until the uniform is cleaned.  This critical eighth point was previously identified by HalenHardy and was appropriately named the “Pig Pen Effect.”

Understanding the “Pig Pen Effect” is critical to protecting workers from respriable silica dust exposure:

  • U.S. Bureau of Mines report documented a number of workers that experienced a ten-fold increase in dust exposure over previous levels from an experience that significantly soiled the worker’s clothing.
  • The report goes on, “The respirable dust concentrations on the workers’ lapel after these occurrences indicated their Time Weighted Average (TWA) concentration would exceed the Permissible Exposure Limit (PEL) in two hours or less.”
  • As these individuals performed their work duties, dust was continuously emitted from their clothing and the only way to eliminate the dust source was to clean or change their work clothing.

To learn more about the “Pig Pen Effect,” read our entry, “NIOSH Adds an Eighth Source of Respirable Silica Dust: Workers’ Clothing” on the MASHH Blog.

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