Analysis of the practical effectiveness of respiratory protection programs in preventing over-exposure to respirable crystalline silica in tunnel construction.

[INTRODUCTION] Tunnel construction activities are associated with exposure to respirable crystalline silica (RCS), placing workers at risk of silicosis and lung cancer. Respiratory protective equipment (RPE) is frequently relied upon to supplement other control measures to reduce exposure. However, the practical effectiveness of RPE in preventing over-exposure can be compromised by a range of factors, reducing its expected level of protection.

[OBJECTIVE] To identify and explore the factors that influence the practical effectiveness of RPE programs in tunnel construction environments.

[METHODS] A retrospective analysis of exposure assessments between 2018 and 2024, prepared by occupational hygienists across multiple Australian tunnel construction projects, was performed. The focus was on instances where RPE was used but where RCS exposures were still judged by the occupational hygienist to have exceeded the occupational exposure limit (OEL) in place at the time. Contributing factors were identified and categorised.

[RESULTS] Occupational hygienists identified six factors that impacted the practical effectiveness of RPE when RCS was measured above the OEL. The most common factor was that the RPE provided to the worker had an insufficient minimum protection factor to reduce exposure to levels below the OEL. Other factors included the absence of fit testing, the presence of facial hair, and intermittent or non-use of the RPE. In an average of 17% of cases where RCS exposure exceeded the OEL, occupational hygienists judged the RPE to be ineffective in adequately reducing exposure levels.

[CONCLUSION] The findings highlight organisational and individual factors that lead to a gap between theoretical performance and practical effectiveness of RPE programs. The reasons underlying these deficiencies, including why RPE was not worn, not correctly used, or why lower-grade protection was issued, remain unclear. Providing workers with higher levels of protection, such as powered air purifying respirators (PAPRs), would likely mitigate many of these challenges, which supports the growing shift toward PAPR adoption in the tunnelling sector.