A More Effective Silica Exposure Monitoring Approach
By: Logan Myers, Contributor
If you work in an industry like construction, mining, oil and gas, or concrete, you have probably asked yourself the question: “How can I be sure that I am protecting my coworkers and myself in an environment that poses a variety of different health risks?” One health risk of growing concern in these industries is the inhalation of respirable crystalline silica dust. Respirable silica is a microscopic particle commonly found in materials like sand, concrete or stone.
Sources & Health Risks of Respirable Silica
Silica is found in both natural and man-made substances. It is created by any high-energy operation, such as cutting, sanding, sawing, grinding, polishing, drilling and crushing stone, rock, concrete, brick, block and mortar. Other activities, such as sand blasting; sweeping dirty areas; using compressed air to clean; driving or operating heavy equipment on dirt roads; the demolition of structures; or transferring dry materials containing silica also create respirable silica.
Over time, the inhalation of these harmful particles is considered a carcinogen by the CDC and can cause lung diseases like silicosis or lung cancer. Because of the small size of respirable particles, once silica gets into the deep part of the lungs, it cannot be removed or expelled. Although a serious and harmful disease, it is preventable through the implementation of proper health and safety precautions, such as work practices, engineering controls or the use of PPE.
OSHA’s Respirable Crystalline Silica Standard
Under OSHA’s Respirable Crystalline Silica Standard (RCS Standard), found in 29 C.F.R. §1910.53 (General Industry) and 29 C.F.R. §1926.1153 (Construction), employers must conduct monitoring to assess each employee’s eight-hour, time-weighted average (TWA) exposure to silica dust. The standard reference method for doing so is performed by taking a gravimetric sample from the worker’s breathing zone, which is collected on a filter cassette with sample media, then sent to a lab for analysis. The analysis determines how much of the dust collected throughout the shift is respirable, crystalline silica.
This process, however well-known in industries that are subject to the RCS Standard, lacks data granularity and efficiency that can be achieved through additional methods. Lab results can take weeks to months to come back, and only one data point is shown across an entire eight-hour work shift. By having to wait weeks for lab results to come back, you can never be truly sure whether or not your silica dust controls are effective until weeks later. This means workers are potentially being exposed to respirable crystalline silica continually during that waiting period.
The Power of Real-Time Monitoring
The power of retrieving data in real-time is immense. Real-time data means second-by-second, immediate and actionable data. Real-time aerosol data can be retrieved through the use of a light-scattering photometer. Through a proper calibration factor creation process, light-scattering photometers can be calibrated to estimate respirable crystalline silica exposure. The calibration includes two aspects: the photometric correction factor, which adjusts the measurement to your specific aerosol; and the response factor, which adjusts the measurement for the substance of your concerns. These correction factors are based on gravimetric silica data at a given worksite, so you can be sure that your data is specific to the work area or work process with which you are concerned.
After gathering real-time aerosol data with a silica correction factor and silica response factor, you are then able to analyze logged data that is time-stamped. By knowing when points of peak exposure occurred, you are better able to identify problematic sources of silica dust exposure. The process of identifying when and where a worker was at certain points of exposure can be referred to as “following the worker’s exposure trail.” The exposure trail is invisible through the use of gravimetric sampling methods. The timeline, below, shows a set of steps that can be taken to improve a silica monitoring program. Real-time data augments the use of gravimetric sampling; it does not replace it.
Advantages of Using Both Gravimetric Sampling and Real-Time Monitoring
A safer and more effective program for monitoring employee exposure to respirable, crystalline silica involves the combination of two methods: gravimetric reference assessments and real-time monitoring using a light-scattering photometer. Gravimetric assessments are necessary to show compliance to the OSHA RCS Standard, but this method lacks certain characteristics that are important for further safety. By including a light-scattering photometer in this process, employers can see aerosol data in real-time; better identify problematic areas of exposure; and be more confident in the engineering controls they put in place to reduce exposure.
About the Author
Logan Myers is an Associate Business Analyst at TSI, Inc. He spent much of 2020 and 2021 studying methods of reducing silica exposure in an effort to put forward solutions that help people combat overexposure of respirable crystalline silica.
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