OSHA’s Proposed Crystalline Silica Rule

Posted on: December 12, 2013

By Elizabeth M. Cahill

The proposed ruling on crystalline silica from the Occupational Safety and Health Administration (OSHA) was published in the Federal Register on September 12, 2013.  The ruling would amend the permissible exposure limits (PELs) for the substance in its respirable form to a time-weighted average of 50 μg/m3 (over 8 hours).  The ruling would harmonize the level of protection across industry sectors, which currently have different limits, and is estimated to effect up to two million workers.

Inhalation of crystalline silica particles increases the risk of silicosis, lung cancer and other respiratory diseases.  Since the current PELs were developed, more than 40 years ago, respirable crystalline silica has been identified as a human carcinogen by the U.S. National Toxicology Program (NTP), the International Agency for Research on Cancer (IARC), and the National Institute for Occupational Safety and Health (NIOSH).  Based on their literature review, OSHA determined:

“The available evidence indicates that employees exposed to respirable crystalline silica well below the current PELs are at increased risk of lung cancer mortality and silicosis mortality and morbidity.” – Notice of Proposed Rulemaking

In line with OSHA’s preference for engineering controls and work practice controls over respiratory protection, control measures are proposed to help employers achieve levels below the limit.  This includes a table giving control methods for specific construction operations, which also lists respirator types, when applicable.

The comment period will end on December 11, 2013 and informal public hearings will begin March 4, 2014 in Washington, D.C.


OSHA webpage on crystalline silica rulemaking:

Proposed Rule (78 FR 56274 – 56504):


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