Atrazine is the most widely used herbicide for corn and sorghum and the most commonly encountered in surface water and groundwater. In addition to water quality problems, atrazine poses hazards through atmospheric transport, food residues, and exposure of applicators and wildlife. It atrazine use is restricted, substitute herbicides will come into wider use, increasing the likelihood for occurrence of their own sets of potentially undesirable side effects and imposing cost or efficacy penalties.