Lars Jordbekken

Ultrafine particles at workplaces of a primary aluminium smelter

The number concentration and size distribution of ultrafine particles in a Søderberg and a prebake potroom of an aluminium primary smelter have been measured using a scanning mobility particle spectrometer. The particle morphology was studied by transmission electron microscopy (TEM). The study shows the existence of elevated number concentrations of ultrafine particles in both potrooms. The main source of these particles is likely to be the process of anode changing. The ultrafine particles were measured directly at the source but could also be identified as episodes of high number concentrations in the general background air. Unlike the larger particles belonging to the 50-100 nm mode, the nanoparticle mode could not be detected in the TEM indicating that they may not be stable under the applied sampling conditions and/or the high vacuum in the instrument.

Intersampler Field Comparison of Respicon®, IOM, and Closed-Face 25-mm Personal Aerosol Samplers During Primary Production of Aluminium

Intersampler field comparison of Respicon(®), 25-mm closed-face total dust cassette (CFC), and IOM inhalable aerosol sampler was conducted in pot rooms at seven aluminium smelters. The aerosol mass and water-soluble fluoride were selected as airborne contaminants for the comparisons. The aerosol masses of 889 sample pairs of IOM and Respicon(®) inhalable aerosol sub-fraction, 165 of IOM and 25-mm CFC, and 194 of CFC and Respicon(®) thoracic aerosol sub-fraction were compared. The number of sample pairs for the comparison of water-soluble fluoride was 906, 170, and 195, respectively. The geometric mean aerosol mass collected with the inhalable Respicon(®) was 2.91 mg m(-3) compared with 3.38 mg m(-3) with the IOM. The overall ratio between IOM and Respicon(®) inhalable sub-fraction was 1.16 [95% confidence interval (CI) = 1.11-1.21] for aerosol mass and 1.13 (95% CI = 1.08-1.18) for water-soluble fluoride. The results indicate that Respicon(®) undersampled the aerosol mass and water-soluble fluoride in the inhalable sub-fraction compared with the IOM. The results indicated undersampling of the Respicon(®) at mass concentrations higher than 1.35 mg m(-3) and oversampling at lower mass concentrations. The overall ratio between aerosol mass collected with IOM and CFC was 4.19 (95% CI = 3.79-4.64) and 1.61 (95% CI = 1.51-1.72) for water-soluble fluoride. Thus, for this industry, a correction factor of 4.2 is suggested for the conversion of CFC to inhalable aerosol masses and a conversion factor of 1.6 for water-soluble fluoride if wall deposits in the CFC are included. CFC and thoracic Respicon(®) collected similar aerosol masses (ratio = 1.04; 95% CI = 0.97-1.12), whereas the ratio was 1.19 (95% CI = 1.11-1.28) for water-soluble fluoride. The variability of the exposure is substantial; thus, large data sets are required in sampler performance field comparisons.