Groundwater and surface water are the two main sources of water for consumption and agricultural use in the United States. Surface water is comprised of rivers, streams, and lakes, and includes run-off from storm events and rainwater.

Herbicides and other pesticides contaminate run-off that finds its way to streams and rivers. Insecticides and rodenticides are the most toxic pesticides to humans.

In a study conducted by the U.S. Geological Survey, pesticides were found to pollute every stream and 90% of the wells tested.

Pollution comes from one of two sources: point and non-point sources. Non-point sources include residences and farms, while point-sources include municipalities and industries.
 
In a study conducted in 1991 called the National Water Quality Assessment Program, 20 locations were tested for pollutants in the water. The following information was collected:

• Mixtures of nutrients and pesticides are found in most or all water areas studied

• Nitrogen and phosphorus are the main nutrients found

• Pesticides were found in nearly all streams in both water and fish samples

• Pesticides were found in more than half the shallow wells sampled in agricultural and urban areas 

The highest frequencies of pesticide ingredients found were all organophosphates: DDT, dieldrin, and chlordane. All of these have been banned, but have continued to be persistent in fish and sediment.

Unfortunately, many urban dwellers consider the storm drain as a waste disposal site, or they simply do not realize that chemicals used in their yard ends up going to non-treated areas that supply wildlife with habitat and drinking water.

In addition to fertilizers and pesticides, urban stormwater carries pet and yard waste, motor oil, anti-freeze, household hazardous wastes, paint, and street litter.

Appropriate landscaping practices in response to the presence of pesticides in water are to reduce the use of toxic chemicals in the landscape, eliminate the most persistent chemicals altogether, and use a variety of techniques to prevent or avoid pest problems.

Some of the approaches to avoiding pest problems include: use plants that are pest and disease resistant; use plants that have evolved in the climate and soil in a given geographical location (native plants); use less-toxic pest control measures, such as horticultural soaps and oils; use cultural and plant management practices to grow healthy plants and maintain sanitary conditions (i.e. remove diseased plant material, disinfect pruning shears when moving between different plants, and so on). These items are standard practices in an integrated pest management (IPM)  program.



SOURCES AND FURTHER READING:

Gilliom, 2007. The quality of our nation's waters: pesticides in the nation's streams and groundwater. 1992-2001. USGS.

Latimer et al. 1996. Reducing the pollution potential of pesticides and fertilizers in the environmental horticulture industry II: lawn care and landscape management. HortTech 6(3):222-232.

Sprague, L. A. and L. H. Nowell. 2008. Comparison of pesticide concentrations in streams at low flow in six metropolitan areas of the United States. Environ. Toxicol. Chem. 27, 288-298.

 

USGS. 1999. Pesticides detected in urban streams during rainstorms and relations to retail sales of pesticides in King County, Washington. USGS Fact Sheet 097-99. 4pp.

 

USGS. 2008. Pesticide national synthesis project. http://water.usgs.gov/nawqa/pnsp/ Viewed 8/1/08

 

White, R. S. 1971. Pesticides in the environment. M. Dekker. NY