What is silica, and where is it found?
Crystalline silica is a naturally occurring substance found in materials such as rock, sand, concrete, brick, and mortar. In its respirable form, silica dust particles are tiny and can enter the deepest parts of the lungs, where they may cause severe lung diseases like silicosis. The CDC recognizes respirable crystalline silica as a carcinogen, while OSHA treats it as a hazardous material in an airborne state. Protecting workers from long-term exposure is vital to their health and well-being.
How is crystalline silica created?
Silica dust is produced during high-energy operations such as cutting, grinding, drilling, crushing, and polishing materials that contain silica. Common tasks in mining and construction can generate respirable silica, especially during:
- Cutting or breaking rocks and concrete
- Sweeping dusty areas
- Using compressed air for cleaning
- Driving heavy equipment on unpaved roads
- Demolishing structures
- Abrasive blasting with sand
How do you measure respirable silica?
Gravimetric Sampling
Gravimetric sampling is a traditional method used to measure respirable crystalline silica. A sample pump pulls air through a cyclone to collect particles. Larger particles are filtered out, and smaller ones (including respirable silica) are captured for lab analysis. While necessary for final compliance, gravimetric samples are time-consuming, expensive, and do not provide immediate feedback.
Real-Time Monitoring
Real-time monitoring instruments, such as those manufactured by TSI, offer a faster, more cost-effective way to measure silica dust levels. These instruments use light-scattering photometric technology to assess total respirable dust in the air. Proper calibration enables them to estimate the amount of crystalline silica, providing immediate exposure data and helping companies adjust engineering controls before gravimetric samples are taken.
Why not just use gravimetric sampling all the time?
While gravimetric sampling is required for compliance, it’s not ideal for frequent or quick assessments due to long turnaround times and costs. Real-time monitoring, on the other hand, allows for frequent, repetitive testing that provides instant results. This is especially useful for confirming the effectiveness of controls before performing final gravimetric sampling, helping to avoid costly rework.
Why is real-time monitoring essential?
Real-time monitoring provides immediate feedback on exposure levels, allowing companies to make quick decisions to protect workers. The key advantages include:
- Instant Alerts: Workers are notified of unsafe conditions in real-time, allowing immediate corrective action.
- Cost Savings: Repeated gravimetric testing is costly. Real-time monitoring reduces the number of tests needed by verifying the effectiveness of control measures beforehand.
- Accurate Data Logging: Real-time instruments provide a comprehensive data trail of exposure levels, ensuring that companies can document their compliance efforts.
Do TSI instruments measure total respirable silica?
Not directly. TSI instruments measure total respirable dust using photometric technology. However, by calibrating the instruments to the silica content in the dust, they can estimate the amount of crystalline silica exposure in real-time. This allows companies to measure respirable silica efficiently, giving results that are close to what would be expected from a gravimetric sample.
Where should we place real-time instruments on a mining site?
The placement of real-time monitoring instruments depends on the processes, materials, and work areas involved. It's often beneficial to consult an Industrial Hygienist (IH) to develop a written exposure control plan. This plan should identify tasks and locations for monitoring, ensuring that all areas where respirable silica could be generated are monitored effectively.
What is a competent person for handling silica exposure?
According to OSHA, a "competent person" is someone qualified to identify existing or foreseeable respirable crystalline silica hazards and has the authority to take corrective action. This individual is responsible for implementing the written exposure control plan and regularly inspecting job sites and equipment to minimize silica exposure risks.
How can I find a qualified consultant or laboratory for silica exposure monitoring?
The American Industrial Hygiene Association (AIHA) provides links to industry consultants who specialize in silica exposure control. Additionally, AIHA Laboratory Accreditation Programs, LLC (AIHA-LAP) offers a directory of accredited laboratories for silica sample analysis.
TSI provides a range of real-time monitoring instruments designed to help companies efficiently measure and manage silica exposure on job sites:
- SidePak™ AM520 Personal Aerosol Monitor: For personal exposure monitoring in the worker’s breathing zone.
- DustTrak™ II Aerosol Monitor – Desktop: Ideal for work area monitoring with the option to collect gravimetric samples.
- DustTrak™ II Aerosol Monitor – Handheld: Perfect for walk-through facility surveys and detecting point source dust.
- DustTrak™ Environmental Aerosol Monitor: Designed for extended outdoor monitoring of fugitive dust in large areas.
- PortaCount™ Respirator Fit Tester: Ensures that respirators are properly fitted to protect workers from inhaling hazardous particles.