The quality of the environment in Košice is affected mainly by the heavy industry of the VSŽ Košice iron works (since 2000 VSŽ Košice and US Steel Košice). The production of the said company represents a closed metallurgical cycle that includes energy distribution, raw material supply, media distribution, preparation, coke production with subsequent chemical operation, service equipment as well as traditional metallurgical aggregates such as blast furnaces, converters and rolling mills. This means, that a large number of technological assemblies and equipment participate in environmental pollution.

Out of large stationary sources of air pollution (with the thermal output > 5 MW) VSŽ produced in 1999 46.5 % of solid particulate matters, 9.4% of SO₂, 18% of NO_x and 69.5% of CO. Thus, they participated with 95.7% in the total emission of selected basic pollutants produced in Košice by stationary units. Almost all emissions of heavy metals come from air pollution sources of the VSŽ iron works. When compared with 1990, a positive trend of gradual reduction of SO₂ and NO_x emissions is recorded.

After the construction of the wastewater treatment plant of VSŽ in 1991, the water quality in Sokoliansky brook has improved considerably. Another ecological measure was the construction of phenol-ammoniac wastewater treatment plant. Its construction started in 1996 and it was put into operation in 1998. Thus, the city wastewater treatment gained some free capacity and the long pipeline, which represented a potential risk of water and soil contamination, is not in operation any more.

Wastes are disposed at the Suchá halda dry waste pile and at the metallic dust landfill. Neither of the said landfills meets the technical or ecological conditions. It is similar situation with other wastes from VSŽ iron works as they are also disposed at landfills that do not comply with ecological conditions. These are the wastes from water management installations such as the sludge-drying bed in Sokoľany, water treatment plant in Krásna nad Hornádom and Mokrá halda wet waste pile in VSŽ iron works.