Metallic aluminium is produced by an electrochemical reduction process in a heated bath (approx950 deg C)of molten cryolithe (Na_3AlF_6)and alumina (Al_2O_3).Fumes of complex physical and chemical composition,so called potroom fumes,are generated in this process.There is epidemiological evidence of adverse health effects,for example potroom asthma,related to inhalation of these fumes.A detailed chemical and physical characterization of the exposure atmosphere is required in order to improve the mechanistic understanding of this association.The high temperature alumina reduction process is likely to be a significant source of nanoparticles since the hot bath is exposed to environmental air when the electrolytic cells are opened for routine changing of the carbon anodes.This study was aimed at measuring number concentration,number size distribution and particle morphology of ultrafine particles directly at the source during the process of changing the anodes,and at locations representing typical mean exposure situations to aged smoke in a plant site of the primary aluminium industry.Two site with different reduction technologies were selected:1)the Prebake area where prebaked carbon anodes are used in the electrolytic reduction cells.These anodes had to be changed regularly.The cells had to be opened for this purpose;2)the Soderberg area where the mass loss of the anodes of the reduction cells is continuously replaced by adding a paste (petroleum coke and pitch)during the production process.
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