Approximately one billion pounds of pesticides are used in a typical year in the U.S. alone. Pesticides and herbicides contaminate rivers and streams, and seep into groundwater through runoff. A U.S. Geological Survey conducted in the 1990s detected pesticide compounds in virtually every stream in agricultural, urban and mixed-use areas, as well as in over 50 percent of sampled wells assessing ground water in agricultural and urban areas. Atrazine, one of the most widely used pesticides, is a suspected endocrine disruptor and is associated with cardiovascular problems. Long-term exposure to glyphosate, a widely used herbicide, may lead to kidney problems and reproductive difficulties.