Speciation of fluoride in workroom air during primary production of aluminium

Abstract

Exposure to fluorides (F⁻) and particulate matter (PM) was assessed by personal sampling with use of Respicon® sampler in Prebake and Søderberg pot rooms in seven aluminium smelters. The inhalable PM mass was dominated by the extra-thoracic aerosol sub-fraction, which contributed with around 70% for both Prebake and Søderberg pot room workers. Quantitative and qualitative differences in exposure were found between pot room workers in smelters using these two technologies. Prebake pot room workers were exposed to 1.4 to 1.7 times higher PM concentrations than Søderberg pot room workers, depending on aerosol sub-fraction. Prebake pot room workers were also exposed to 2.5 to 2.9 higher air concentrations of water-soluble F⁻ (F_WS⁻) and 2.8 to 5.3 higher air concentrations of non water-soluble F⁻ (F_AS⁻) than Søderberg pot room workers, depending on aerosol sub-fraction. However, exposure to hydrogen fluoride (HF) was 1.3 times higher among Søderberg pot room workers. The relative amount of F_WS⁻, however, was higher among Søderberg pot room workers, while the relative amount of particulate F⁻ (sum of F_WS⁻ and F_AS⁻) was higher among Prebake pot room workers (6.5 vs. 3.9%). Exposure to the same PM concentration yielded higher F_WS⁻ and F_AS⁻ air concentrations among Prebake compared to Søderberg pot room workers.