When a pesticide is put down, it doesn't always stay put. Pesticides follow any number of pathways.
Pesticides can enter plants, insects, and other living organisms.
They can volatilize, which means they change into a gas. They can be broken down by sunlight, microorganisms, or chemical reactions with water, and they can chemically attach to soil and organic particles. They can also remain in a dissolved form, then leach with water through the soil, sometimes winding up in groundwater. Among the most important factors that affect the risk of pesticide leaching is pesticide degradation. This is the breakdown of a pesticide into compounds that are usually less toxic.