Public hearings were conducted the week of March 18 on a proposed rule by the Occupational Safety and Health Administration (OSHA), first published in September 2013, that creates new standards for workplace silica exposure.

OSHA regulates exposure through permissible exposure limits (PELs), which are the maximum amount of airborne dust an employee may be exposed to during a full work shift. Currently, OSHA has two standards in place for regulating silica exposure, calculated using PEL equations. Based on those formulas, the PEL for general industry is approximately 100 micrograms per cubic meter (μg/m3) averaged over an eight-hour day. For construction work and shipyards, the PEL is roughly 250 micrograms.

The new rule would dispense with the PEL equations and set a single PEL applicable to all industry—including construction and maritime—of 50 micrograms of respirable crystalline silica per cubic meter of air (μg/m3), averaged over an eight-hour day. The new rule would cover all three forms of crystalline silica: quartz, cristobalite, and tridymite.

The proposed rule also sets an “action level” of 25 micrograms per cubic meter of air. In workplaces where the action level is exceeded, employers would be required to monitor airborne exposure levels. OSHA has specifically requested comment on whether the action level is appropriate for inclusion in the final rule.

In addition to the new PEL, the proposed rule includes provisions for measuring how much silica workers are exposed to, limiting employees’ access to areas where silica exposures are high, using effective methods for reducing exposures, providing medical exams to workers with high silica exposures, and training for workers about silica-related hazards and how to limit exposure.

OSHA has stated that the new rule was needed because the current rule was put in place in 1971, is based on complicated formulas, and does not give adequate protection to workers. Industry response is expected to question whether complying with the new rule will prove too costly, and whether there is truly a need for lower PELs or merely a need to enforce the current PELs more vigorously.

Additional information on the new silica exposure rules can be found here.