The United States imposes virtually no green taxes. Most programs to reduce pollution rely on mandatory standards such as the Clean Air Act's New Source Performance Standards (NSPS) for stationary polluters and the Corporate Average Fuel Economy (CAFE) standards for automobiles. Among the few green taxes imposed in the United States at the federal level are the "gas guzzler" tax on new cars that exceed fuel efficiency standards, a tax on ozone-depleting substances, and miscellaneous taxes on fertilizers and pesticides used in agriculture.