Global pesticide use is currently estimated at approximately 2. 5 billion kg per year (Pimentel eta/., 1998). To be effective, pesticides need to persist for a certain period of time. However, the longer their persistence, the greater the potential for transport of a fraction of the amount applied away from the target area. Pesticides are dispersed in the environment by water currents, wind, or biota. Pesticides can directly contaminate ground and surface waters by leaching, surface run-off and drift. Pesticides can also enter the atmosphere during application by evaporation and drift of...