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Introduction How Rivers Run Stories Value Of A River What We Can Do
Quality of a River - Water Quality
Contaminants: Toxins (pg 4 of 8)


Pesticides include many kinds of chemical poisons and biological agents used to control insects and weeds. Pesticides have been a fundamental cog in the so-called Green Revolution that has increased crop yields since the 1950s. Though the number of pesticides is vast, a few commonly used pesticides account for the overwhelming majority of pesticides in the environment.

Pesticides enter streams through polluted runoff, primarily from lawns and farm fields. They may also enter groundwater. In fact, the U.S. Environmental Protection Agency's National Pesticide Survey in 1992 found detectable levels of pesticides in more than 10 percent of community wells and 4 percent of rural wells.

Pesticides have undergone steady development. Long-lived chlorinated organic compounds such as DDT have given way to new pesticides that are generally less persistent in the environment. The ecological effects of pesticides depend on many factors-toxicity, persistence, their byproducts of degradation, and their chemical behavior.



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