Monitoring Exposure of and Protecting Employees from Silica Dust
Understanding the challenge posed by silica dust exposure on site and in confined spaces, and the comprehensive standards and measures used to combat its peril.
- By Tim Turney
- Oct 11, 2023
Approximately 2.3 million workers in the United States are exposed to Respirable Crystalline Silica (RCS) or silica dust every year, which is now known to possess a similar magnitude of risk as the more widely understood asbestos dust. Crystalline silica is found in many commonly used construction materials, including sand, gravel, clay, stones, concrete, bricks and quartz. When these materials are broken, stirred or otherwise disturbed through cutting, drilling, grinding or crushing, minuscule dust particles are created. When inhaled, these particles travel deep into the lungs and can cause incurable and sometimes deadly respiratory diseases such as silicosis, chronic obstructive pulmonary disease and kidney disease.
The Department of Labor has recently (June 2023) proposed a new ruling to limit silica dust exposure by its Mine Safety and Health Administration (MHSA) to better protect miners’ health. This comes almost exactly ten years after The Occupational Safety and Health Administration (OSHA) proposed a rule aimed at curbing workers’ exposure to crystalline silica across all industries by updating the Permissible Exposure Limit (PEL) to be in line with modern understanding of the hazard. The newest proposal by the MHSA would see the PEL of silica dust at or below 50μg/m3 (micrograms per cubic meter of air) for a full shift of exposure, equal to an eight-hour time-weighted average. For reference, the PEL of any hazardous dust in the workplace is ten milligrams per cubic meter.
As with any known workplace health risk, the most effective means of reducing worker exposure to respirable crystalline silica is a correctly implemented scheme of controls using the hierarchy of controls. This can help reduce both the likelihood of workers developing health complications such as silicosis and the potential legal ramifications for employers. Measures include a correctly executed program of air monitoring, which can include both monitoring at the site level and on an individual employee level using personal sampling pumps. Air monitoring can quantify exposure levels, or if controls are in place, check that they are effective and measure any residual risk. These pumps are essential in places where there is a significant risk of highly concentrated hazardous pollutants in the surrounding air, for example, confined spaces and sites that emit large quantities of fumes.
Control Measures
In controlling dust, the usual risk control hierarchy applies. Where the risk cannot be eliminated entirely, a safer form of the product should be used. If this is not feasible, the process should be changed to emit less dust or enclose the process so that the dust does not escape or by extracting the dust near the source using local exhaust ventilation (LEV). Employers should make the process efficient enough to have as few workers in harm’s way as possible. In the hierarchy of control, the last thing you apply is respiratory protection. Often, because of poor understanding of toxicity and dust concentration, the wrong respiratory protection is used.
This article originally appeared in the October 2023 issue of Occupational Health & Safety.