Atrazine is a herbicide widely used on major food crops as well as non-crop areas across the U.S. In the environment, atrazine is mobile and found in surface water and is present in ground water in high use areas. In addition, it is persistent in surface and ground waters, with half-lives that may exceed one year in static bodies of water. In addition to exposure model predictions, extensive monitoring data show the widespread presence of atrazine and its degradates in both surface and ground water. Atrazine has been widely detected in air and rainfall samples in high use areas and also in areas far removed from regions of high use. This widespread environmental exposure has serious implications when compared to ecotoxicological endpoints of concern.