Critical evaluation of analytical methods for detection of respirable crystalline silica in dust-a review

Abstract

Respirable crystalline silica (RCS) exposure is closely associated with the development of silicosis, underscoring the critical need for the accurate identification of RCS in workplace dust. Occupational health standards currently define the RCS exposure limit for an 8-hour shift and its measurement methods. However, there remains a gap in analyzing low-concentration samples and the detection of acute, high-intensity RCS exposure during specific short-term tasks or shifts. Addressing this gap is essential for facilitating rapid on-site decision-making and effectively mitigating hazards. This review evaluates current analytical methods for RCS detection and explores potential improvements to address these challenges. Established detection techniques, including the pyrophosphoric acid method, colorimetry, infrared spectrometry (IR), and X-ray diffraction (XRD), have been widely used; however, they exhibit certain limitations, such as low efficiency, limited sensitivity, and a prolonged analysis period. In recent years, both innovative technologies and refinements of traditional methods have emerged to address these shortcomings. The application of more potent laser sources, as seen in quantum cascade laser-based infrared spectroscopy (QCL-IR), has paved the way for the creation of sensitive filter-based laboratory protocols and portable sensors capable of near-real-time measurements of crystalline silica aerosol. Raman spectroscopy provides high sensitivity for detecting low-concentration RCS exposures. Beyond these advancements, additional techniques such as laser-induced breakdown spectroscopy (LIBS), scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), and photoacoustic spectroscopy (PAS) offer fresh perspectives on RCS measurements. The focus of RCS detection in workplace dust is shifting towards on-site, rapid assessment methods. This involves the use of portable, high-sensitivity equipment to provide real-time evaluation of workers' RCS exposure, which is crucial for promptly identifying hazardous levels, thereby improving worker safety and health. These advancements have the potential to impact occupational health practices by enabling immediate decision-making and effective risk mitigation.