Pesticide use and management by farmers, applicators, private and public businesses and institutions, manufacturers and distributors, and the general public provide many possible sources and opportunities for pesticide contamination. The ideal outcome of pesticide use occurs when a pesticide accomplishes the purposes for which it was applied and then rapidly breaks down into harmless components such as carbon dioxide and water. This happens in most cases, but the process and time vary among pesticide chemicals, and the application is affected by the physical, chemical, and biological characteristics of the pesticide and the associated environment. The fate of a pesticide may be affected by such factors as volatility and/or drift, method of application, type of formulation, soil and plant characteristics, solubility of the pesticide, adsorption on soil or plant surfaces, the persistence of the pesticide, and climatic conditions. Research suggests that the movement of pesticides in the environment is complex, with transfers occurring continually among the different environmental compartments. However, this does not mean that all pesticides are mobile or threaten groundwater.
The fate processes can be beneficial. They can move a pesticide to the target area or destroy its potentially harmful residues. Sometimes, however, they can be detrimental, leading to reduced control of a target pest, injury of non-target plants and animals, and environmental damage. Fate processes can be separated into three major types: adsorption, which binds pesticides; transfer processes, which move pesticides; and degradation processes, which break pesticides down. Soil type, climatic factors, and handling practices can promote or prevent each process. An understanding of the fate processes can help ensure that pesticide applications are not only effective, but also environmentally safe.