Respirable Crystalline Silica Exposure in University Concrete Labs

Respirable crystalline silica (RCS) is a hazardous, breathable dust particle found in common construction materials like portland cement. Construction workers who handle portland cement-based concrete materials can suffer severe lung health illnesses due to the unmitigated presence of airborne RCS during typical handling and mixing processes. Enclosed indoor areas typically have higher levels of RCS than outdoor settings, therefore OSHA regulations tend to provide significantly more guidance for worker exposure limits in indoor work. There have been studies exploring the levels of RCS and respirable dust (RD) in indoor construction sites, but currently there exists no studies specifically focused on university-based concrete research labs where student, staff, and faculty come into infrequent but regular exposure with RCS and RD. Therefore, this paper summarizes the findings of air quality testing (AQT) in a university concrete lab. Testing was conducted over a period of approximately four hours while university students wore air quality sampling instruments to measure the extent of exposure to RCS and RD in an indoor university concrete lab environment. In that time period, students handled portland cement during typical concrete mixing activities following standard lab procedures, such as manipulating cement, mixing, compressive strength testing, and cleaning so that measuring exposure to RCS and RD was at usual levels. AQT was performed according to the National Institute of Occupational Safety and Health (NIOSH) Manual of Analytical Methods (NMAM) test method 0600 Particulates Not Otherwise Regulated for RD and also NIOSH test method 7500 for RCS. After sampling, the air quality sampling devices were delivered to an air quality testing consultancy to quantify the measured results. The results indicated that students were exposed to RCS and RD within safe limits over an 8-hour time-weighted-average (TWA). While the specific findings suggest that typical RCS and RD levels may not pose a significant risk per OSHA's thresholds at university concrete labs, it remains advisable to use personal protective equipment (PPE) and exercise other best practices to reduce excess exposure levels to university students, staff, and faculty of hazardous particles like RCS and RD.