Risk Assessment of Nanoparticle Exposure in a Calcium Carbonate Manufacturing Workshop with Six Control Banding Tools

With wide production and use, nanometer calcium carbonate (nano-CaCO₃) has attracted much more concerns due to its potential inhalation toxicity in the occupational setting. It is of great significance to protect exposure workers by scientifically measuring the concentration of aerosol nano-CaCO₃ particles, evaluating the risk levels at the production sites and accordingly providing suggestions of improvement. In this study, the aerosol particle concentrations of six operating procedures in a nano-CaCO₃ production workshop were determined, including digesting, carbonization, modification, pressure filtration, drying and packaging. The relevant occupational exposure risk was assessed by six control banding (CB) tools, CB Nanotool, Stoffenmanager Nano, Nanosafer, the Guidance on Working Safely with Nanomaterials and Nanoproducts (GWSNN), French Agency for Food, Environmental and Occupational Health and Safety method (ANSES) and Precautionary Matrix for Synthetic Nanomaterials (Precautionary Matrix). It was found that there are quite high concentrations of airborne nanoparticles released from the nano-CaCO₃ production procedures in this workshop. Most aerosol particles were agglomerated with the sizes of primary particles about 100 nm. The number concentration of aerosol particles at packaging site is 407000 particles/cm³ in size range of 0.02-1.0 μm, which is 10 times higher than the aerosol particle concentration at the digestion site. Furthermore, there is a significant correlation between the metrics of number and surface area concentrations detected in this workshop. The risk assessment results indicate that this workshop has medium or high exposure risks of the occupational nanoparticle exposure. Detailed engineering control or personal occupational protection should be implemented to protect the occupational health in this workshop. Similar and comparable judgment results were obtained, although the input parameters for six risk assessment CB tools are different. It was found that Stoffenmanager nano and Nanosafer are more suitable for the risk assessment of this workshop comparing to the other four tools. It is recommended a wide applications of risk assessment tools to various nanotechnology related occupational settings for controlling the occupational health risks.