Pesticides in Surface Waters

U.S Geological Survey Fact Sheet FS-039-97

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Pesticides in the Hydrologic System

More than 1.1 billion pounds of pesticides are used each year in the United States. National agricultural use of herbicides, insecticides, and fungicides has grown from 190 million pounds of active ingredient in 1964 to an estimated 811 million pounds in 1993. Although the use of pesticides has resulted in increased crop production and other benefits, concerns about the potential adverse effects of pesticides on environmental and human health have grown steadily. The greatest potential for adverse effects of pesticides, in many respects, is through contamination of the hydrologic system. Water is one of the primary pathways by which pesticides are transported from their application areas to other parts of the environment (Figure 1). Once pesticides reach streams, they can be widely dispersed into other streams, rivers, lakes, reservoirs, and oceans.

Figure 1. Pesticide movement in the hydrologic cycle (from Majewski and Capel, 1995).

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