We present for the first time the use of osmium isotopic composition as a tracer of atmospheric emissions from an aluminum smelter, where alumina (extracted from bauxite) is reduced through electrolysis into metallic aluminum using carbonaceous anodes. These anodes are consumed in the process; they are made of petroleum coke and pitch and have high Re/Os elementary ratio. Due to the relatively large geological age of their source material, their osmium shows a high content of radiogenic ¹⁸⁷Os produced from in situ ¹⁸⁷Re radioactive decay. The radiogenic isotopic composition (¹⁸⁷Os/¹⁸⁸Os∼2.5) of atmospheric particulate emissions from this smelter is different from that of other typical anthropogenic osmium sources (that come from ultramafic geological contexts with unradiogenic Os isotopes, e.g., ¹⁸⁷Os/¹⁸⁸Os<0.2) and also different from average eroding continental crust ¹⁸⁷Os/¹⁸⁸Os ratios (ca. 1.2). This study demonstrates the capacity of osmium measurements to monitor particulate matter emissions from the Al-producing industry.