Ultrafine Particle (UFP) Exposures in an Aluminium Smelter: Soderberg vs. Prebake Potrooms

The objectives of this work were to evaluate ultrafine particle (UFP) exposures during aluminium smelting in Soderberg and prebake potrooms. Particle concentrations were monitored using the P-Trak 8525 and aerosol particle size distributions were monitored with the electrical low pressure impactor (ELPI). UFP samples were analyzed for chemical composition by transmission electron microscopy (TEM). Workers who accomplished tasks in the Soderberg cell environment were more exposed to UFP than those who worked in the prebake; however, the specific task of anode shift in the prebake process was an important source of UFPs. More than 92 % and 98 % of particles had aerodynamic diameters less than 98 nm in the Soderberg and prebake processes, respectively. TEM/EDS analysis suggests that workers are exposed to short fibrous aluminium particles with a nanometric aerodynamic diameter. Overall, this study suggests that occupational hygiene practices aimed at evaluating UFP exposures should include monitoring of the particle number concentration, monitoring of the particle size distribution, and characterization of the nanoscale fraction of the aerosol.