In the United States city planning language, a brownfield site (or simply a brownfield) is land previously used for industrial purposes or certain business uses. The land may be contaminated by low amounts of hazardous waste or pollution. It has the potential to be reused once it is cleaned up. Land that is more severely contaminated and has high levels of hazardous waste or pollution, such as a Superfund site, does not fall under the brownfield classification. "Mothballed brownfields" are properties which the owners are not willing to transfer or put to productive reuse.