Waste management is the collection, transport, processing or disposal of waste materials, usually ones produced by human activity, in an effort to reduce their effect on human health or local amenity. A subfocus in recent decades has been to reduce waste materials' effect on the environment and to recover resources from them. Waste management can involve solid, liquid or gaseous wastes, with different methods and fields of expertise for each. Waste management practices differ for developed and developing nations, for urban and rural areas, and for residential industrial, and commercial producers. Waste management for non-hazardous residential and institutional waste in metropolitan areas is usually the responsibility of Government authorities, while management for non-hazardous commercial and industrial waste is usually the responsibility of the generator.