Researchers expect that nanocatalysts and magnetic nanoparticles will make heavily polluted water for drinking, sanitation and irrigation. Catalytic particles can chemically degrade pollutants instead of simply moving them somewhere else, including pollutants for which existing technologies are inefficient or cost prohibitive. Magnetic nanoparticles, when coated with different compounds that have a selective affinity for diverse contaminating substances, could be used to remove pollutants, including arsenic, from water. Companies have started commercializing these technologies.