The inhalation of respirable crystalline silica can increase the risk of a unique form of pneumoconiosis, referred to as silicosis, and possibly lung cancer. For this reason, respirable crystalline silica has been recognized as an occupational hazard since early in the 20th century, and occupational exposure is regulated by the Occupational Health and Safety Administration (OSHA). Our health scientists apply expertise in toxicology, epidemiology, industrial hygiene, and human health risk assessments to assist clients in characterizing occupational and consumer-product exposures and potential health risks related to respirable crystalline silica.

Project Example: Characterization of Airborne Concentrations of Respirable Crystalline Silica during the Manipulation and Use of Silica-containing Products

Project Overview: Cardno ChemRisk developed a strategy for assessing the concentration and particle size distribution of respirable crystalline silica during the handling, manipulation (i.e., cutting, grinding, and drilling) and use of silica-containing products. Products evaluated included tiles and pavers, countertops, concrete additives, mortar and grout, in addition to concrete blocks.

Our Approach: We designed an exposure assessment strategy that presents a reproducible approach aimed at characterizing the particle size distribution and concentration of respirable crystalline silica. This approach is based on the current state of knowledge in the field of industrial hygiene and relies on a combination of gravimetric and real-time monitoring methods to characterize respirable crystalline silica.

Our Value: The results of these efforts aided in characterizing the risks associated with respirable crystalline silica potentially inhaled by workers and consumers using silica-containing products. Further, this approach can be applied to a wide range of silica-containing products or modified to characterize other particulates, such as titanium dioxide, carbon black, or other metals.

Project Example: Characterizing the Properties of Respirable Silica Particles and Silicosis Risk

Project Overview: Cardno ChemRisk identified and analyzed the role of different properties of respirable crystalline silica in the development of silicosis.

Our Approach: We conducted a systematic review of available literature to identify and integrate relevant scientific information on the properties of silica particles that can affect lung toxicity. Additionally, a data gap analysis was conducted to assess the degree of evidence for toxicological impacts of each property

Our Value: These efforts identified multiple properties, including concentration, size, shape, surface properties (e.g., piezoelectric surfaces), form (i.e., crystalline vs. amorphous), and surface area, that may affect potential lung toxicity of respirable silica particles. Overall, the findings of this analysis revealed that many of these properties may contribute to the onset of silicosis and that the reduction of the overall exposure (i.e., the cumulative dose) remains the most feasible method to reduce the risk of adverse effects.