The Konin steel smelter is currently the only producer of aluminium for the electrolytic industry. This plant has aroused much controversy due to its adverse impact on the environment. The technology applied has resulted in excessive emissions leading to significant environmental contamination. The modernization activities undertaken by the plant have gradually decreased the amounts of emitted pollutants, but not to a sufficient extent to reduce the plant’s adverse impact. The article deals with the environmental effect of these measures.