Evaluating Toxicity of Different Types of Respirable Crystalline Silica Particles to Lung Cells and Tissues

Silica dust represents one of the most significant occupational hazards globally, predominantly due to its potential to cause lung diseases such as silicosis. In coal mining, workers might be exposed to various forms of respirable crystalline silica (RCS) related to their working tasks and locations. The surface chemistry of RCS is potentially critical in influencing the health outcomes of exposed workers. This project investigates how RCS surface chemistry affects lung cell responses and induces pathological changes.

The literature survey revealed that exposure to freshly generated RCS may induce higher cell death compared to aged RCS. Toxicology studies suggest that the biological response to RCS is largely determined by its surface chemistry, influenced by the generation method, hydration degree, and atmospheric aging, leading to varying chemical reactivity and toxicity. This project constructed various RCS types, including freshly generated, hydrated, and aged RCS with or without iron impurities using ball milling methods. Advanced techniques such as Electron Paramagnetic Resonance (EPR) and Reactive Oxygen Detections were used to characterise their surface chemistry. It was found that freshly generated RCS produced significant amounts of free radicals, which decreased during aging and hydration. In vitro tests showed that freshly generated RCS with iron impurities induced oxidative stress, resulting in cell death and low cell viability. These findings highlight the critical role of surface chemistry and iron impurities in determining the biological responses to RCS exposure. The oxidative stress is a key mechanism driving the toxicity of RCS.

These insights emphasise the necessity of implementing targeted health and safety measures to mitigate the exposure of mine workers to the most hazardous forms of RCS. Understanding the specific toxicological impacts of different RCS types, especially freshly generated ones with iron impurities, allows for the development of more effective strategies to protect workers' health.