Air pollution from aluminum smelting plants I. The emission of polycyclic aromatic hydrocarbons and of mutagens from an aluminum smelting plant using the söderberg process

Abstract

The emissions of organic compounds from an aluminum smelting plant have been studied. Samples were collected at the anode paste plant, the horizontal stud Söderberg plant (HSS) with a yearly production of 13,000 tons aluminum and the vertical stud Söderberg plant (VSS) with a yearly production of 70,000 tons. The samples were analyzed for polycyclic aromatic hydrocarbons (PAH) and tested for mutagenicity with the Salmonella/microsome assay. The smelting plant was found to be a large emitter of PAH and mutagens. The anual emission of PAH was estimated to 112 tons PAH, including 2.1 tons benzo(a)pyrene (BaP). The largest contributor was the HSS‐plant which emitted 4.4 kg PAH per ton Al produced, whereas the corresponding number for the VSS‐plant was 0.7 kg PAH/ton Al. The emission from the HSS‐plant also contained more BaP. Emissions from the anode paste plant were the most concentrated with respect to PAH, but its contribution to the overall emission was low. The most volatile PAH‐compounds were dominating in this emission. All samples were clearly mutagenic in the presence of S9. The highest activity was observed with strain TA 100. As for the PAH, the HSS‐plant was the largest emitter of mutagens. The anode plaste plant gave a relatively larger contribution to the total mutagenicity than was the case for PAH. The PAH present in the samples could account for a large part of the mutagenicity observed, especially in the emission from the HSS‐plant where BaP alone could account for about 45 per cent of the mutagenic activity, measured in the presence of metabolic enzymes (S9). Activity in the absence of S9 could only be detected in samples of ventilation air. However, as all samples did also contain compounds that were toxic to the test bacteria, especially in the absence of S9, it is possible that other samples may contain direct mutagens which we were unable to detect.