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OSHA's Proposed Silica Health Standard: A Summary of Key Elements

Lawrence P. Halprin
Manesh K. Rath
David G. Sarvadi
Keller and Heckman LLP - Washington Office

October 11, 2013

Previously published on October 8, 2013

On September 12, 2013, the Occupational Safety and Health Administration (OSHA) issued a proposed rule to establish comprehensive, substance-specific health standards for occupational exposure to respirable crystalline silica (RCS) for General Industry, Maritime, and Construction activities. The stated objective of the proposed rule is to reduce the numbers of fatalities and illnesses caused by workplace exposure to RCS. As proposed, the final rule would go into effect 60 days after its publication in the Federal Register.  The proposal includes a comment period of 90 days ending December 11, 2013, and informal hearings are scheduled to be held in Washington beginning on March 4, 2014.  Notices of Intent to appear at the hearing are due in 60 days, on November 12, 2013. Does the large gap in time between the end of the scheduled comment period and the beginning of the hearings indicate that OSHA contemplated extending the comment period?  Such requests have already been filed.

Keller and Heckman LLP created the attached Fact Sheet to summarize the primary provisions of the proposed rule.  With the exception of required engineering controls and testing laboratory requirements, employers would be required to comply with the provisions of the final rule 180 days after the effective date. The proposed rule would require engineering controls to be implemented no later than one year after the effective date, and testing laboratory requirements to be implemented two years after the effective date.

Proposed PEL and Action Level

OSHA is proposing a new permissible exposure limit (PEL) of 50 µg/m3 and action level of 25 µg/m3 as an 8-hr TWA for all forms of RCS in all industry sectors covered by the rule, essentially a reduction of 50% of the current PELs. According OSHA’s conservative risk assessment, unprotected exposure to RCS at the proposed PEL over a 45 year working lifetime (8 hours per day, 5 days per week, and 50 weeks per year for 45 years) would result in an estimated 6 to 26 additional deaths from lung cancer, and an estimated additional 43 additional deaths from silicosis, and an estimated 32 deaths from renal disease per 1,000 exposed workers. The OSH Act has been interpreted to require OSHA to reduce the risk of death and other serious illness below the significant risk level of 1/1000 workers.  OSHA has stated that a PEL of less than 50 µg/m3 would be infeasible and labor interests are expected to challenge that determination.

The current OSHA PELs for the three forms of crystalline silica (quartz, cristobalite, and tridymite) in General Industry, construction, and shipyards (maritime) were established in the early 1970s. The PELs for respirable quartz (the most common form of crystalline silica) in General Industry, construction, and shipyards are approximately 100 micrograms per cubic meter of air (µg/m3) as an 8-hour time-weighted average (8-hr TWA).[1] The current General Industry PELs for respirable cristobalite and tridymite are approximately 50 µg/m3 (one-half of the PEL  for respirable quartz).

OSHA is also proposing many of the other traditional elements of a comprehensive health standard, including requirements for exposure assessment, preferred methods for controlling exposure, respiratory protection, medical surveillance, hazard communication, and recordkeeping. The proposal does not include a medical removal provision, but labor interests have stated they will urge OSHA to adopt one.

The proposed standard would apply to “all occupational exposures.”  Thus, it would appear that coverage under the proposed rule would be triggered whenever there is any detectable airborne RCS in a workplace, even if the exposure is due, in whole or in part, to ambient environmental conditions.  If this interpretation is correct, the presence of detectable airborne RCS would trigger the proposed training requirements, and conceivably affect large numbers of employers whose activities do not involve handling materials containing crystalline silica.  If actual or reasonably expected airborne exposures were at or above the action level, exposure monitoring requirements would also be triggered.  If actual or reasonably expected airborne exposures were at or above the PEL, but for less than 30 days per year, all requirements of the proposed rule other than medical monitoring automatically would be triggered. The medical monitoring requirements would be added to an employer’s obligations if actual or reasonably expected airborne exposures were at or above the PEL for 30 or more days per year.

What Employers Should Do

Employers need to determine if the proposed standard will affect them, and if so, they should consider two tracks of activity. One track would be participating in the OSHA rulemaking and/or supporting the efforts of participants who are committed to ensuring any OSHA rule is supported by sound science and provides the necessary protection to employees in the most cost-effective manner. This would include identifying additional tasks that should be included in Table 1. The second track would be to determine what changes in their operations and practices would  be required if OSHA adopted the proposed rule, taking into account the possibility that OSHA might consider adoption of different PELs for different activities.

The first step in determining an employer’s obligations under the proposed rule would be to determine which standard applies to each activity -- General Industry/Maritime or Construction. This is important because some construction tasks offer an alternative compliance option that does not require exposure assessment and follow-up monitoring or application of the hierarchy of control measures.  Consistent with the approach of the asbestos standards, it appears that OSHA plans to treat many equipment installation tasks and building maintenance tasks that involve the cutting, drilling, sanding grinding or patching materials containing crystalline silica as construction activities.

The second step would be to conduct exposure monitoring, or use qualifying representative data from previous industry or employer monitoring, to determine what provisions of the proposed rule would apply to the activity. 

In general, monitoring to determine employee exposure must represent the employee’s actual or equivalent time-weighted average exposure to airborne respirable crystalline silica over an 8-hour workday. If the employee worked a 12 hour shift, an adjustment will have to be made to account for the longer exposure period, reducing the TWA allowed.

Except for the construction tasks covered by the alterative compliance methods, the proposed rule would require employers to implement engineering and work practice controls as the primary means to reduce exposure to the PEL or to the lowest feasible level above the PEL. This approach is based on OSHA’s position that engineering and work practice controls offer more reliable and consistent protection to a greater number of workers, and are therefore preferable to respiratory protection.  The engineering controls identified are grouped into four main categories: (1) substitution (a highly controversial area), (2) isolation, (3) ventilation, and (4) dust suppression. Depending on the sources of crystalline silica dust and the operations conducted, a combination of control methods may reduce silica exposure levels more effectively than a single method.

In situations where feasible engineering and work practice controls are not sufficient to reduce exposures to or below the PEL, employers are required to supplement these controls with respiratory protection following OSHA’s respiratory protection standard for general industry (29 CFR 1910.134). The respiratory protection standard requires written procedures for the proper selection, use, cleaning, storage, and maintenance of respirators. The proposed standards for RCS require the use of respirators in four situations: (1) periods necessary to install or implement feasible engineering and work practice controls; (2) work operations such as maintenance and repair activities where meeting the PEL with engineering and work practice controls is not feasible; (3) work operations in which an employer has implemented all feasible engineering and work practice controls and these controls do not reduce exposures to the PEL; and (4) during periods when the employee is in a regulated area, or, for construction, during periods when the employee is in an area where respirator use is required under an access control plan or if the employer opts to follow  the alternative compliance option in Table 1 of the proposed rule. The operations listed in Table 1 are summarized below.

  • Using Stationary Masonry Saws
  • Using Hand-Operated Grinders
  • Tuckpointing
  • Using Jackhammers and Other Impact Drillers
  • Using Rotary Hammers or Drills (except overhead)
  • Operating Vehicle-Mounted Drilling Rigs for Rock
  • Operating Vehicle-Mounted Drilling Rigs for Concrete
  • Milling
  • Using Handheld Masonry Saws
  • Using Portable Walk-Behind or Drivable Masonry Saws
  • Rock Crushing
  • Drywall Finishing (with silica-containing material)
  • Use of Heavy Equipment During Earthmoving

If an employee is exposed to levels at or above the proposed PEL for 30 or more days per year,  the proposed  rule would require medical surveillance every three years, to be conducted by a physician or other licensed health care professional (PLHCP), unless the PLHCP recommends that they be made available more frequently. The required periodic examinations would include medical and work history evaluations, physical examinations emphasizing the respiratory system, chest X-rays and pulmonary function tests, and other tests deemed to be appropriate by the PLHCP. The goal of periodic medical surveillance for workers is to detect adverse health effects at an early and potentially reversible stage.

[1]There appears to be some confusion as the application of those formulas and whether they represent particle counts or percentages. There are two formulae in the OSHA general industry standards, one for respirable and one for “total” dust.  The total dust standard is now considered obsolete.  The formula for the total dust standard is equivalent to a limit of approximately 300 µg/m3.  There is no universal, reliable conversion factor to convert between respirable and total dust measurements.


The views expressed in this document are solely the views of the author and not Martindale-Hubbell. This document is intended for informational purposes only and is not legal advice or a substitute for consultation with a licensed legal professional in a particular case or circumstance.

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