In Food

Agricultural Pollution

Posted by: on Feb 25, 2012 | 2 Comments

Just how harmful are our conventional farming methods? Conventional farming uses large inputs of pesticides to control insects, weeds, and fungi; fertilizers to ensure large crop yields; and energy to run machinery, produce pesticides and fertilizers, and transport, store, process, and pack end products. All of these contribute significantly to the agricultural pollution problem.

The Source

Agricultural pollution falls under the non-point source pollution (NPS) category. NPS pollution comes from many dispersed sources rather than a single, defined source (like a pipe) and is caused by runoff. Runoff carries pollutants to ground and surface waters where they have the potential to travel long distances and end up in unexpected places. In fact, agriculture is the number one source of surface water pollution, the second leading source of wetland impairment, and a major contributor to estuary and groundwater pollution. Agriculture introduces pesticides and excess nutrients into waterways and is the leading cause of soil erosion, which clogs surface water with silt and sediment (Zaring, 1996). In addition to these NPS pollutants, the oil and natural gasses used in agriculture for front-end inputs (energy to power equipment), pesticide and fertilizer production, and back-end inputs (transportation, storage, and preparation) contribute significantly to environmental damage.


Pesticides, including insecticides, herbicides, and fungicides, cause monumental environmental havoc, polluting ground water, throwing the ecosystem off-balance, and contaminating the human body. Pesticides cause ecosystems to lose their natural equilibrium. Removing one species can cause related species to flourish and increase exponentially. If an insect that usually preys upon a weed or another insect is killed with pesticides, the prey species may become a problem because its natural control was removed. Additionally, more pesticides may be needed to control this newly prolific pest, causing a ripple effect. Furthermore, pesticides pose an evolutionary catch 22. Pesticide use may wipe out most of a species for a season; however, those pests that survive the application will evolve a resistance to the chemical (Hopp, 2007). Insects have a short life span and adapt quickly. Again this adaptation may increase the amount of pesticides needed in the future. Pesticides also have adverse human health effects and can be fatal. Twenty-percent of the approved pesticides are listed by the EPA as carcinogenic in humans (Hopp, 2007). While the EPA banned DDT, chlordane, and dieldrin, many pesticides continue to be used at alarming rates. According to Hopp (2007), American farmers used 335 million pounds of pesticides in 1965 and by the year 2000 that number nearly tripled to 985 million pounds. Despite, eloquent arguments against pesticide use and clear evidence of the harm they cause, usage is increasing.

Nutrient Pollution: Nitrogen and Phosphorus

Nitrogen and phosphorus are essential nutrients in the development of plants and only become a problem when there are more nutrients in the soil than the crop can take up. When there are excess nutrients, rainwater and snow melts cause runoff into the groundwater and surface water: “Agricultural chemical and manure runoff pollute the country’s water by introducing carcinogens (such as nitrates) and excess nutrients (such as nitrogen and phosphorous)” (Zaring, 1996, p. 520). In large quantities, nitrogen and phosphorus speed up the natural process of eutrophication, a process that usually occurs very slowly over long periods of time. This results in dead zones where fish and other aquatic life cannot survive because of reduced concentrations of dissolved oxygen. Two well-known affected areas are the Gulf of Mexico at the mouth of the Mississippi River and the Chesapeake Bay. Human health concerns are related to the level of nitrates in drinking water. Nitrates are linked with high cancer rates and “blue baby syndrome,” which reduces the amount of oxygen in the blood of infants and can cause fatalities (Zaring, 1996). The major sources of non-point nitrogen and phosphorus pollution are manure and synthetic fertilizers (DCR). Despite the harm being done to our fresh water supply, synthetic fertilizers continue to be applied at alarming rates and in quantities that far exceed the nutrient needs of the crops. Like pesticides, “fertilizer application rates have also increased: between 1979 and 1981 they rose sixty-eight percent” (Zaring, 1996, p. 519).

Energy Use

Energy consumption is a concern in every aspect of our lives. Agriculture is no exception: “We’re consuming about 400 gallons of oil a year per citizen—about 17 percent of our nation’s energy use—for agriculture, a close second to our vehicular use” (Hopp, 2007). It is a complicated issue, considering most farm equipment runs on gas. Asking farmers to stop using modern equipment is unrealistic and would not solve the problem. Oil and natural gasses are the building blocks for pesticides and synthetic fertilizers (Hopp, 2007). And the largest share of energy use comes in delivering the food to the table: processing, warehousing, packaging, refrigerating, and transporting (Hopp, 2007, p. 5; Martinez et al., 2010).*

*For more on energy use and agriculture read this article from The Oil Drum.

It’s difficult to sum up the monumental problems caused by pesticides, fertilizers, and fossil fuels. Water contamination, soil erosion, unbalanced ecosystems, cancer, and greenhouse gas emissions are just some of the concerns. However, if these common agricultural practices are causing so much harm, why are we continuing to use them? Is it solely cost motivated and bottom-line business strategy? Is organic the alternative? And just how much better is organic farming?


Carson, Rachel (1962). Silent spring. Houghton Mifflin Company: New York, NY.

Hopp, Steven L., Kingsolver B., and Kingsolver, C. (2007). Losing the bug arms race. Animal, vegetable, miracle: A year of food life.

Hopp, Steven L., Kingsolver B., and Kingsolver, C. (2007). Oily food. Animal, vegetable, miracle: A year of food life.

Martinez, S., Hand, M., Da Pra, M., Pollack, S., Ralston, K., Smith, T., . . . Newman, C. (May 2010). Local Food Systems: Concepts, Impacts, and Issues Economic Research Report 97 (pp. 1-87): United States Department of Agriculture.

Pollan, Michael. The omnivore’s dilemma: A natural history of four meals. Penguin Books: London.

Zaring, David (1996). Agriculture, nonpoint source pollution, and regulatory control: The clean water act’s bleak present and future. Harvard environmental law review, 20, 515-545.


  1. Eat the Leaves » What is Organic, Anyway?
    February 25, 2012

    […] have adverse environmental effects. For more information, look for my upcoming posts on sources of agricultural pollution and the pros and cons of organic […]

  2. Eat the Leaves » Raise your voice: Support the Chesapeake Bay’s diet
    November 15, 2012

    […] is one of the major sources of pollutants to the Bay watershed. Nitrogen and phosphorus wreck havoc in large quantities, causing algal blooms, fish kills, and an overall imbalance in the […]


Leave a Reply