The Occupational Safety and Health Administration (OSHA) has issued a final rule to help protect workers from exposure to respirable crystalline silica. The new rule revises the permissible exposure limit (PEL) for crystalline silica to a level approximately one-half to one-fourth of the previous limits. EMSL Analytical, Inc. provides testing services for crystalline silica including alpha quartz, cristobalite and tridymite as well as amorphous silica. Let our team of laboratory experts help you with your next silica project.
The final rule took effect on June 23, 2016. Depending on the industry, organizations have one to five years to comply with most requirements based on the schedule below.
• Hydraulic Fracturing – June 23, 2018, two years after the effective date for all provisions except engineering controls, which have a compliance date of June 23, 2021.
• General Industry & Maritime – June 23, 2018, two years after the effective date.
• Construction – September 23, 2017. OSHA delayed enforcement in order to conduct additional outreach and provide educational materials and guidance for employer.
Final Rule Key Provisions
• Reduces the permissible exposure limit (PEL) for respirable crystalline silica to 50 micrograms per cubic meter of air (50 μg/m³) as an 8-hour time-weighted average.
• Implements an Action Level of airborne respirable crystalline silica of 25 micrograms per cubic meter of air (25 μg/m³) as an 8-hour time-weighted average.
• Requires employers to control silica dust through engineering controls (e.g., water spray, or local exhaust ventilation to keep the dust from getting in the air, general ventilation to reduce concentration). The construction industry standard contains a table of specified exposure control methods for specific construction equipment / tasks involving materials containing crystalline silica.
• Requires employers to provide respiratory protection as part of a respiratory protection program when the exposure is going to be over 50 micrograms, and to keep employees from areas where the exposure might be higher than the PEL.
• Requires employers to make medical surveillance available at no cost for each employee who will be occupationally exposed to respirable crystalline silica at or above the action level for 30 or more days per year.
• Requires employers to resample employees exposed over the Action Level every six months.
• Requires employers to resample employees exposed over the PEL every three months.
EMSL Silica Testing Services & Locations
• Airborne Cement Dust in Air Samples
• Amorphous Silica in Air Samples
• Amorphous Silica in Bulk Samples
• Crystalline Silica, single species*, in Air Samples
• Crystalline Silica, single species*, in Bulk Samples
• Crystalline Silica, all species*, in Air Samples
• Crystalline Silica, all species*, in Bulk Samples
• Crystalline Silica, all species (Phosphoric Acid Digestion),
in Bulk Samples
* Single species include Alpha Quartz, Cristobalite or Tridymite
* All species include Alpha Quartz, Cristobalite and Tridymite
Silica Sampling Guide
• Air Samples
According to the new rule, air samples for respirable silica may be collected on a PVC filter using a size-selective sampler meeting the ISO/CEN criteria for the respirable fraction, including cyclones (aluminum, Dorr-Oliver, GS-1, Higgins Dewell) and the Parallel-Particle Impactor (PPI).
A preweighed 37mm 5µm PVC cassette (if respirable dust fraction data are desired) or a standard 37mm 5µm PVC cassette is used with any cyclone for collection.
The Parallel-Particle Impactor (PPI) also uses 37mm 5um PVC filters, weighed for gravimetric measurement of respirable dust, or unweighed for respirable silica only.
The flowrate will vary depending on the sampler used (GS-1, Dorr-Oliver: 1.7 L/min; Higgins-Dewell: 2.2 L/min; aluminum cyclone: 2.5 L/min, PPI: 2, 4, or 8 L/min.)
Minimum collected air volume required to “see” the permissible exposure limit (PEL) of 50 ug/m³ is 500L. The minimum collected air volume to reach the Action Level (25 ug/m³) is 1000L. Care must be used when sampling near the maximum volume to prevent overloading. Analysis of the samples is by NIOSH 7500 method, analysis of crystalline silica by X-Ray Diffraction (XRD).
• Bulk Samples
A minimum of 50-100mg in weight (a spoonful is recommended) is needed and can be collected in a small container or sealable bag. A bulk sample can also be used to categorize site materials for potential silica hazards.
• Dust Samples
For any air samples collected, the method calls for a settled dust sample to be taken in order to categorize the silica types present. The dust should be 50-100mg in weight and collected in a small container, a silica sampling cassette or a sealable bag.
• Wipe & Microvac Samples
Wipe samples can be collected on ghost wipes or an equivalent media, and placed into a sampling tube or sealable bag. Surface dust can also be microvacuumed into a silica, TEM or PCM cassette for sample collection. These samples can help identify surfaces contaminated with silica dust. Typically a surface area of 1 square foot is sampled to obtain a representative dust sample.