Steel begins life as iron ore, and it is usually obtained through open-cast mining. This method of extracting resources can cause many environmental issues. When rocks are broken open, biodiversity is threatened, erosion and sinkholes occur, and harmful and radioactive substances are released into the environment.
Later in the steel production process, sulphur oxides, nitrogen oxides, and carbon monoxide are all released into the atmosphere as a result of smelting. The iron and steel industry is the largest global source of CO2 emissions and the second-largest industrial consumer of energy. A 2012 report shows that that this energy use and its resulting emission of greenhouse gasses could vastly be reduced if the industry instead relied on renewable electricity sources. This is unlikely to happen in the near future, however, because of the high cost of implementing the new technology.
There are also environmental concerns about corten steel once it has been incorporated into buildings. A study published in Environmental Pollution found that water runoff from weathering steel may cause problems in the local aquatic environment. The study found that the additional amounts of nickel, iron, and manganese in the area local to a weathering steel building were “not negligible.” The conclusion was that further study is needed to fully assess the risk of this material to the environment.