Thus, nitrogen dioxide and nitrous oxide emissions from the steel industry, which uses nitric acid in a pickling process, can be strongly reduced. At the end of the last century, acid rain was a huge environmental problem in many developed countries. One of the main reasons was the emission of sulfur dioxide (SO₂) in exhaust gases. Mercaptans, hydrogen sulfide (H₂S) and sulfur dioxide (SO₂) removal from effluents or off-gases is achieved by utilization of a wet scrubber with hydrogen peroxide. It is also used to reduce toxicity and odors at paper mills, rendering plants, metal smelters, pharmaceutical, pesticide, chemical manufacturing or petrochemical facilities.