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Pork Production: Environmental Impacts
Table of Contents
Background and Overview
Best Management Practices
Environmental Impacts
Building an EMS
Alternative Technologies
Complete List of Links

Essential Links:

Ag 101 - Potential Environmental Impacts
While agriculture was reported to be the most common pollutant of rivers and streams, it is importan...

Profile of the Agricultural Chemical, Pesticide, and Fertilizer Industry
This report is one in a series of volumes published by the United States Environmental Protection Ag...

Profile of the Agricultural Crop Production Industry
This report is one in a series of volumes published by the U.S. Environmental Protection Agency (EPA...

Profile of the Agricultural Livestock Production Industry
This report is one in a series of volumes published by the U.S. Environmental Protection Agency (EPA...

U.S. EPA's National Water Quality Inventory: 1998 Report to Congress (http://www.epa.gov/305b/98report) indicated that agricultural operations, including animal feeding operations are a significant source of water pollution in the United States. States estimated that agriculture contributed in part to the impairment of at least 170,750 river miles, 2,417,801 lake acres and 1,827 estuary square miles. Agriculture was reported to be the most common pollutant of rivers and streams. As animal operations become more concentrated, there are serious concerns for the potential of increased environmental impacts to surface water, groundwater, air and soil.

Agricultural Pollutants
Animal Wastes
Air Pollutants
Whole Farm Nutrient Balance

Agricultural Pollutants

EPA has identified the top two agricultural pollutants to the nation's waterways as sediment and nutrients. In addition, EPA notes other major contributors to water pollutants from agriculture include animal wastes, salts and pesticides.

Sediment, the most significant water pollutant, enters the waterways through runoff and erosion. Nitrogen and phosphorous are probably the two most significant nutrients attributed to agricultural pollution. Phosphorous applied to fields enters water bodies through erosion and runoff. Ammonium, a form of applied nitrogen, becomes absorbed into the soil and is primarily lost when sediment erodes. Even when nitrogen is not in a readily available form when leaving the field, it can be converted to an available form either during transport or delivery to waterways. Nitrate is the form of nitrogen that can contaminate groundwater drinking supplies.

Animal Wastes

Animal waste includes the fecal and urinary wastes from hogs as well as the feed, bedding, litter and soil that has been intermixed with the bodily waste and process water. Manure and wastewaters from the hog operation have the potential to contribute pollutants, such as nutrients like nitrogen and phosphorous, organic matter, sediments, pathogens, heavy metals, hormones, antibiotics and ammonia, to soil and water sources. Groundwater contamination can be a problem if runoff results from the misapplication or over application of manure to land or if storage structures are not built to appropriate specifications meant to minimize or eliminate seepage. Animal feed can sometimes contain heavy metals like arsenic, copper and zinc. If manure is land applied improperly or over applied, it can lead to a harmful accumulation of these metals in the soil.

Pathogens contained in the manure are also of great concern because of their ability to cause diseases in humans if they come in contact with the pathogens in manure. These pathogens can be a food safety concern if the manure is directly applied to crops at inappropriate times or if the manure directly contaminates a product. In addition, pathogens have been responsible for some shellfish bed closures. Runoff from fields where manure has been applied and not properly incorporated may contain extremely high numbers of bacteria with some being harmful to humans. Some pathogens from the manure have been linked to drinking water supply impairments.


Although salt is a natural weathering product of soil and geologic material, it often becomes a serious issue on land irrigated with animal waste (manure can contain salt), both for continued agricultural production and for water quality considerations.


Pesticides and their degradation products may enter groundwater and surface water in solution, in emulsion or bound to soils. Pesticides can cause impairments to surface water uses and groundwater. At a hog operation, pesticides may be applied directly to the pigs or to structures such as barns and housing units, to control pests.

The table below lists the leading pollutants impairing surface water quality in the United States. Agricultural production is a potential source of most of these. For additional information on proper application and management of pesticides go to Best Management Practices, Pesticide Application.

Five Leading Pollutants Causing Water Quality Impairment in the United States

(Percent of incidence of each pollutant is shown in parentheses. For example, siltation is listed as a cause of impairment in 38 percent of impaired river miles.)






Siltation (38%)

Nutrients (44%)

Pathogens (47%)


Pathogens (36%)

Metals (27%)

Oxygen-Depleting Substances (42%)


Nutrients (29%)

Siltation (15%)

Metals (23%)


Oxygen-Depleting Substances (23%)

Oxygen-Depleting Substances (14%)

Nutrients (23%)


Metals (21%)

Suspended Solids (10%)

Thermal Modifications (18%)

Source: http://www.epa.gov/agriculture/ag101/impacts.html

Air Pollutants

In general, air quality problems associated with hog operations and other AFOs are caused by gases emitted from the decomposition of animal wastes and by the dust generated by the animal activity and farming practices. Odors can be a nuisance to neighbors and there is an increasing concern about the potential health effects from odorous compounds emissions. These air pollutants can cause respiratory illness, lung inflammation and increase vulnerability to respiratory diseases, such as asthma. Emissions of reactive organics and ammonia from AFOs can play a role in the formation of ozone (smog) and particulate air pollutants. Soil disturbance by animals or farm equipment can also release airborne particulate matter.

In addition to negative health impacts, ozone can reduce agricultural yields and make plants more vulnerable to disease. Odorous and potentially toxic gases, such as sulfur dioxide produced by the decomposition of animal wastes, may also cause nausea, headaches and throat and eye irritation after prolonged exposure. Methane emissions from waste decomposition at AFOs also contribute to global warming.

In January 2005, EPA announced the Animal Feeding Operations Air Quality Compliance Agreement. The primary goals of this initiative are to:

  • Reduce air pollution
  • Ensure compliance with applicable Clean Air Act, Comprehensive Environmental Response, Compensation and Liability Act and Environmental Planning and Community Right-to-Know Act provisions
  • Monitor and evaluate AFO emissions, and
  • Promote a national consensus on methodologies for estimating air pollutant emissions from AFOs.

Since its introduction, more than 2000 individuals have signed the agreement. For further information on EPA's Air Quality Compliance Agreement go to:


Other air quality resources include:

http://www.epa.gov/region09/cross_pr/animalwaste/problem.html for detailed discussion on air quality and other environmental impacts from AFOs.

http://www.epa.gov/oar/urbanair/6poll.html for information on ozone and particulates.

Whole Farm Nutrient Balance

A "Whole Farm Nutrient Balance" evaluation is a tool that can be used to evaluate the potential for generation of excess nutrients from a farm and can form the basis for developing plans to deal with nutrient buildups. Nutrients are transported along multiple pathways through feeds, fertilizers, animal manures and other off-farm inputs. These inputs are used as part of the animal production operations and plants and animals recycle some of the inputs. Nutrients leave the farm in harvested crops and animal products. These are nutrient outputs. Ideally, nutrient inputs and outputs should be roughly the same. When the inputs to the farm greatly exceed outputs from the farm, the risk of nutrient losses to groundwater and surface water increases. When the swine production inputs are compared to the outputs, a mass balance is created. This nutrient mass balance is an important part of understanding the farming operation as illustrated in the Nutrient Balance above.


Evaluating a farm's nutrient balance from a whole farm perspective provides a more complete picture of the driving forces behind nutrient-related environmental issues.


The Topic Hub™ is a product of the Pollution Prevention Resource Exchange (P2Rx)

The Pork Production Topic Hub™ was developed by:

Pollution Prevention Resource Exchange
Pollution Prevention Resource Exchange
Contact email: abray@newmoa.org

Hub Last Updated: 3/18/2009