Investigation of the presence of amino and nitro polycyclic aromatic hydrocarbons in a Söderberg primary aluminum smelter.

An excessive risk of bladder cancer among Söderberg primary aluminum smelter potroom workers has been reported by several authors, and to date, a causal agent has not been identified. Certain nitro and amino polycyclic aromatic hydrocarbons (PAHs) are either known or suspected human bladder carcinogens, and their presence in this work environment would be cause for concern. In fact, one of these, 2-aminonaphthalene, has been found in both the air and the coal tar pitch used to fabricate process electrodes following an investigation in a Söderberg plant. During the present study, monitoring was conducted in a primary Söderberg aluminum smelter over a 3-week period using novel methods having very good specificity, reproducibility, and sensitivity. Results indicated that 1-aminonaphthalene and 2-aminonaphthalene and 1-nitronaphthalene and 2-nitronaphthalene were present at low parts-per-million levels in the coal tar pitch used to prepare the process electrodes. 1-aminonaphthalene and 2-aminonaphthalene were measured 40 cm above the electrolytic cells on days 1 and 2 of the investigation when the cells' ventilation systems had been shut down for repairs and maintenance. 2-aminonaphthalene was measured at concentrations ranging from 0.080 to 0.350 microg/m3. 1-nitronaphthalene and 2-nitronaphthalene, predominant in coal tar pitch, were not detected in any of the 43 air samples collected. A plausible explanation is their reduction to their respective amine during the electrolytic process. The routine screening of coal tar pitch used to prepare the process's electrode for both amino and nitro PAHs should be adopted by the aluminum industry as an effective means of controlling the presence of these carcinogenic pollutants in their workplace.