Regional Updates

Water Pollution by Agricultural Chemicals
By Dr. Stephen R. Overmann
Southeast Missouri State University

No one would question the critical value of water and food to human life and human civilizations. American agriculture has been supremely successful in producing amazing quantities of food. However, the cornucopia of American agricultural production poses a serious threat to the quality of water in America. The productivity of American agriculture has been based, at least in part, upon large-scale application of agricultural chemicals to the land. These chemicals include fertilizers rich in nitrogen and phosphorus, herbicides, insecticides, and fungicides. Water pollution results from runoff of these chemicals into surface waters or from infiltration of these chemicals into groundwater.

Significant improvement in the quality of U.S. waters since enactment of the Clean Water Act has been due mainly to reductions in point-source pollution from industrial and municipal sources. Agricultural contamination of waters remains a major source of water pollution. Estimates by the US Environmental Protection Agency indicate that agriculture is the leading source of pollution of the nation's rivers, lakes, and wetlands, and among the leading sources of pollution of estuaries. The status of groundwaters is not as well known as that of surface waters. However, when groundwater pollution has been found, agriculture is most often cited as the source.

Runoff and infiltration of agricultural chemicals from farm fields into water constitute nonpoint source pollution of water.. Unlike pollution from point sources, such as a particular factory or building, nonpoint sources of water pollution come from widespread geographic areas. America's farmlands represent a vast nonpoint source for input of polluting chemicals into the nation's waters.

Essentially all areas of the United States are impacted by nonpoint-source water pollution from agricultural sources. This environmental issue is not limited to the Midwest. However, because of the large agricultural areas and high utilization of agricultural chemicals in the region, this issue is of particular concern for the Midwest. For example, the risk of nitrate contamination of groundwater is particularly prevalent in the Midwest. Similarly, Midwestern use of agricultural chemicals is particularly heavy for such compounds as atrazine, cyanazine, quizalofop, chlorpyrifos, simazine, pendimethalin and paraquat. These chemicals are just a few of the many compounds applied to American farmlands that pose potential threats to our water quality.

Bountiful food production is an obvious benefit of the use of fertilizers and agricultural chemicals, but what are the water-related risks and costs? Of primary concern must be human health consequences of water pollution from nonpoint-source agricultural inputs. Excess nitrates in drinking water may lead to methemoglobinemia, reducing blood's ability to carry oxygen. This condition is a threat to infants and is often referred to as "blue-baby disease". Excess nitrate in water may similarly affect ruminant farm animals.

The human-health consequences of drinking-water contamination by non-fertilizer agricultural chemicals are less well documented than the effects of excess nitrates. However, there is widespread concern about potential adverse human-health consequences from long-term, low-level exposure to agricultural chemicals in drinking water. There is particular concern about potential effects of these pesticides as carcinogens or as endocrine disruptors.

In addition to human health concerns, water pollution by agricultural chemicals adversely affects fish and wildlife, commercial fisheries, recreational uses of surface waters, and water treatment facilities. Excess nutrients, particularly nitrogen and phosphorus from fertilizers can promote eutrophication of surface waters. Pesticide residues in waters may affect the health and vigor of aquatic and riparian wildlife species. Also, the runoffs of excess fertilizer nutrients and toxic agricultural pesticides are thought to be the major causes of the "Dead Zone" in the Gulf of Mexico and coastal estuaries.

The real and potential financial costs, both direct and indirect, of agrochemical pollution of water are enormous. Simply testing all of the private and public sources of drinking water for agricultural chemicals would be an expense estimated at between one and two billion dollars. Estimated annual costs of damages caused by agricultural nonpoint sources of water pollution range from four to 12 billion dollars to recreational fishing and water use, water storage and treatment facilities, and commercial fishing.

Recent historical efforts to address water pollution problems in the United States have focused on control of point sources of pollution. Contemporary concern is shifting toward the more difficult task of controlling nonpoint sources, including agricultural sources, of water pollution. There are numerous initiatives underway to reduce agricultural chemical impacts on water resources.

1. Improved understanding of and data on agricultural impacts on water resources.
A major goal of the National Water-Quality Assessment Program is to provide greater understanding of pollution of the nation's water resources, particularly nonpoint-source contamination of ground water. These data are critical to decision-makers in identifying the agricultural chemicals and geographic/geologic areas of greatest concern and risk. This information will assist in development of the most beneficial and cost-effective approaches to preventing water pollution while maintaining agricultural productivity.

2. Improved utilization and management of fertilizers and nutrient-rich wastes.
Much of agricultural chemical pollution of water resources is due to nutrient enrichment. There are numerous ways in which this problem is being approached. One of these is through more precise nutrient application to agricultural soils. Chemical analyses to determine nutrient needs of soils are routine and relatively inexpensive. Coupling these analyses with more precise fertilizer applications will reduce both agricultural costs and runoff of excess nutrients that result in water pollution. The use of "green manure" cover crops, rather than artificial fertilizers, also reduces nutrient runoff. Domestic farm animal wastes are also a source of excess nutrients in waters and improvements in management of animal wastes from large "factory" animal livestock operations are being implemented.

3. Improved management of riparian and wetland areas in agricultural regions.
Riparian zones are areas of natural vegetation adjacent to waterways and are home to many wildlife species. These riparian zones can act as natural filters or buffers between agricultural fields and waterways, reducing the movement of agricultural chemicals into waters. In many cases, natural riparian zones have been destroyed and agricultural fields directly abut waterways. Restoration of riparian zones will reduce runoff of agricultural chemicals into water and enhance wildlife habitats. Similarly, wetland areas can act as buffers or sinks to reduce agricultural pollution runoff into surface waters. Like riparian zones, natural wetlands have often been destroyed and their restoration in agricultural areas will help to mitigate agricultural pollution.

4. Increased utilization of integrated pest management.
Integrated pest management minimizes the use of pesticides in agricultural production. If widely implemented, these practices would substantially reduce water pollution by toxic agricultural pesticides.

5. Increased utilization of organic farming techniques:
Organic farming practices could substantially reduce agricultural impacts on water quality. These practices produce food and fiber without utilization of anthropogenic chemical pesticides and fertilizers. Instead, organic farmers rely upon natural methods of pest control and maintenance of soil fertility. There is strong consumer interest in organic foods and organic agriculture. These market forces are promoting growth of the organic agriculture industry. Organic farming is among the most rapidly growing areas of American agriculture. Congress enacted the Federal Organic Foods Production Act of 1990. The intent and spirit of this law was to provide consumer confidence and protection regarding foodstuffs labeled as "organic." However, the definition of "organic food" remained problematic and controversial along with the definition of organic farming, since arrival of foodstuffs at the family table will typically be preceded by multiple steps of transport, processing, and storage/preservation of the agricultural product. After many years of controversy and public debate, Congress enacted in 2000 new national standards for organic foods.

6. Governmental programs
The federal Environmental Quality Incentives Program (EQIP) provides technical assistance, education, cost-sharing, and incentive payments to agriculturists who adopt environmentally beneficial farming practices.

Connection to Environmental Science

The textbook provides an extensive background on water resources, agriculture, pesticides, and pollution.


Agricultural Chemicals and Water Pollution
This fact sheet was prepared by the Cooperative Extension Service of the University of Florida.

Annotated Bibliography of Nonpoint Source Literature
This extensive bibliography has a well organized topic index and is also keyword-searchable.

Control of Water Pollution from Agriculture
The full text of this extensive report by the Food and Agriculture Organization of the United Nations is available on-line.

Evaluation of the Experimental Rural Clean Water Program
This page summarizes an experimental federal program to assist in the reduction of nonpoint-source pollution in rural watersheds across the country.

National Extension Water Quality Database
This very useful web page hosted by Purdue University is a cooperative effort of all US land grant institutions. The site features clickable maps of the United States that provide state-by-state hyperlinks to water-related experts, documents, universities, and government agencies.

US EPA Nonpoint Source Management Programs
This page from the US Environmental Protection Agency's Office of Water has useful documents on management of nonpoint-source water pollution from agriculture.

Voluntary Incentives for Reducing Agricultural Nonpoint Source Water Pollution
This lengthy report from the Department of Agriculture is available as a PDF file.

Water Quality Information Center
This is an outstanding site provided by National Agricultural Library of the US Department of Agriculture. There are many pages of hyperlinks to web sites related to water and agriculture. The page also provides on-line access to many databases related to water and agriculture.

Water Resources of the United States
This web page from the US Geological Survey is the single most comprehensive site on the Internet to begin exploration of water resources of the United States.


Bosch, D., and Pease, J. 2000. "Economic risk and water quality protection in agriculture." Review of Agricultural Economics 22:438-463.
Carrel, C. 1999. The clean water clause. Sierra 84: 58-59.

Cohen, G. 1999. Clean water: A hard act to follow. Earth Island Journal 14: 1-9.

Crutchfield, S. 1991. Agriculture and water quality conflicts. Food Review 14: 12-15.

Ervin, D. 1998. Shaping a smarter environmental policy for farming. Issues in Science & Technology 14: 73-79.

Fitch, L. and Adams, B. 1998. Can cows and fish co-exist? Canadian Journal of Plant Science 78: 191-198.

Harrison, J., Wetherbee, P., Quenzer, A. and Beduhn, B. 1999. Developing tools to tackle non-point source pollution. Pollution Engineering 31: 54-57.

Johnson, S. and Adams, R. 1991. The on-farm costs of reducing groundwater pollution. American Journal of Agricultural Economics 73: 1063-1073.

Johnson, S. and Adams, R. 1991. The on-farm costs of reducing groundwater pollution. American Journal of Agricultural Economics 73: 1063-1073.

Kluge, J. 1998. "Farming by the foot: How site-specific agriculture can reduce nonpoint source water pollution." Columbia Journal of Environmental Law 23:89-135.

Knopman, D., and Smith, R. 1993. "20 years of the Clean Water Act." Environment 35: 16-28.

Krautz, J. 1994. Poisoning the fount of life -- fresh water pollution and its consequences. Contemporary Review 265: 144-147.

Kuch, P. and Ogg, C. 1996. The 1995 farm bill and natural resource conservation: Major new opportunities. American Journal of Agricultural Economics 78: 1207-1214.

Liban, C. 1998. Non-point source pollution. National Forum 78: 7-9.

Lockeretz, W. 1994. Soil and water quality: An agenda for agriculture. Environment 36: 28-31.

Loeb, P. 1998. How clean is your river? Investigative Reporters & Editors 21: 14-15.

Loeb, P. 1998. Very troubled waters. U.S. News & World Reports 125: 39-43.

Lok, C. 2001. "Farming accused of eco-damage." Nature 409:969-970.

Nolan, B., Ruddy, B., Hitt, K. and Helsel, D. 1998. A national look at nitrate contamination of ground water. Water Conditioning and Purification 39: 76-79.

Novotny, V. 1999. "Diffuse pollution from agriculture - a worldwide outlook." Water Science and Technology 39:1-11.
Smith, D. 1996. Unseen causes of unclean waters. World & I 11: 206-211.

Smith, M. and Ribaudo, M. 1998. The new Safe Drinking Water Act. Choices: The Magazine of Food, Farm & Resource Issues 13: 26-30.

Tucker, M. and Napier, T. 1998. Perceptions of risk associated with use of farm chemicals: Implications for conservation initiatives. Environmental Management 22: 575-587.

© Prentice-Hall, Inc.
A Pearson Education Company
Upper Saddle River, New Jersey 07458

Legal Statement