Pesticides are used in agriculture, in homes and businesses, on lawns and gardens, along roads, in recreational areas, and on pets and livestock. There are hundreds of different pesticide chemicals in use in the United States. In 2007, about 390 million kilograms (430,000 tons) of pesticides, including herbicides, insecticides, and fungicides, were used in the United States. Pesticides released into the environment for agricultural and nonagricultural purposes can contaminate surface water and groundwater, which are critical sources of drinking water. The USGS, through its National Water Quality Program, researches numerous aspects of pesticides and water quality, and has developed maps, graphics, and tools to aid in understanding where pesticides occur, at what concentrations, and potential consequences (Introduction).