Report to Congressional Requesters

United States Government Accountability Office

GAO 

September 2008 CONCENTRATED 

ANIMAL FEEDING 

OPERATIONS 

EPA Needs More 

Information and a 

Clearly Defined 

Strategy to Protect Air 

and Water Quality 

from Pollutants of 

Concern

GAO-08-944 
What GAO Found

United States Government Accountability Office

Why GAO Did This Study

Highlights

Accountability Integrity Reliability

September 2008

CONCENTRATED ANIMAL FEEDING 

OPERATIONS 

EPA Needs More Information and a Clearly Defined 

Strategy to Protect Air and Water Quality from

Pollutants of Concern 

Highlights of GAO-08-944, a report to 

congressional requesters 

Concentrated Animal Feeding 

Operations (CAFO) are large 

livestock and poultry operations 

that raise animals in a confined 

situation. CAFOs can improve the 

efficiency of animal production but

large amounts of manure produce 

can, if not properly managed,

degrade air and water quality. The 

Environmental Protection Agency

(EPA) is responsible for regulating

CAFOs and requires CAFOs that

discharge certain pollutants to

obtain a permit. 

This report discusses the (1) trends 

in CAFOs over the past 30 years, 

(2) amounts of waste they 

generate, (3) findings of key 

research on CAFOs’ health and

environmental impacts, (4) EPA’s 

progress in developing CAFO air

emissions protocols, and (5) effect 

of recent court decisions on EPA’s 

regulation of CAFO water

pollutants. GAO analyzed U.S.

Department of Agriculture’s 

(USDA) data from 1982 through 

2002, for large farms as a proxy for

CAFOs; reviewed studies, EPA 

documents, laws, and regulations; 

and obtained the views of federal

and state officials. 

Because no federal agency collects consistent, reliable data on CAFOs, GAO

could not determine the trends in these operations over the past 30 years. 

However, using USDA data for large farms that raise animals as a proxy for 

CAFOs, it appears that the number of these operations increased by about 230 

percent, going from about 3,600 in 1982 to almost 12,000 in 2002. Also, during 

this 20-year period the number of animals per farm had increased, although it 

varied by animal type. Moreover, GAO found that EPA does not have 

comprehensive, accurate information on the number of permitted CAFOs 

nationwide. As a result, EPA does not have the information it needs to 

effectively regulate these CAFOs. EPA is currently working with the states to 

establish a new national data system. 

The amount of manure generated by large farms that raise animals depends on

the type and number of animals raised, but large operations can produce more 

than 1.6 million tons of manure a year. Some large farms that raise animals 

can generate more raw waste than the populations of some U.S. cities produce 

annually. In addition, according to some agricultural experts, the clustering of 

large operations in certain geographic areas may result in large amounts of 

manure that cannot be effectively used as fertilizer on adjacent cropland and 

could increase the potential of pollutants reaching nearby waters and 

degrading water quality.

 

Since 2002, at least 68 government-sponsored or peer-reviewed studies have 

been completed that examined air and water quality issues associated with 

animal feeding operations and 15 have directly linked air and water pollutants 

from animal waste to specific health or environmental impacts. EPA has not 

yet assessed the extent to which these pollutants may be impairing human 

health and the environment because it lacks key data on the amount of 

pollutants that are being emitted from animal feeding operations. 

As a first step in developing air emissions protocols for animal feeding 

operations, in 2007, a 2-year nationwide air emissions monitoring study, 

largely funded by industry, was initiated. However, as currently structured, 

the study may not provide the scientific and statistically valid data it was

intended to provide and that EPA needs to develop air emissions protocols. 

Furthermore, EPA has not established a strategy or timetable for developing a 

more sophisticated process-based model that considers the interaction and 

implications of all emission sources at an animal feeding operation. 

Two recent federal court decisions have affected EPA’s ability to regulate

water pollutants discharged by CAFOs. The 2005 Waterkeeper case required 

EPA to abandon the approach that it had proposed in 2003 for regulating 

CAFO water discharges. Similarly, the 2006 Rapanos case has complicated 

EPA’s enforcement of CAFO discharges because EPA believes that it must 

now gather significantly more evidence to establish which waters are subject

to the Clean Water Act’s permitting requirements. 

What GAO Recommends

To more effectively regulate

CAFOs, GAO recommends that 

EPA complete its inventory of

permitted CAFOs, reassess the 

current nationwide air emissions 

monitoring study, and establish a 

strategy and timetable for 

developing a process-based model 

for measuring CAFO air emissions. 

EPA partially agreed with GAO’s 

recommendations. 

To view the full product, including the scope 

and methodology, click on GAO-08-944. 

For more information, contact Anu Mittal (202) 

512-3841, mittala@gao.gov. 
Page i GAO-08-944 Concentrated Animal Feeding Operations 

Letter 1

Results in Brief 4 

Background 9 

The Number of Large Farms Raising Animals Has Increased, but 

Specific Data on CAFOs Are Not Available 13 

Large Farms That Raise Animals Can Produce Thousands of Tons 

of Manure Each Year, and Regional Clustering of Farms Can 

Exacerbate Manure Management Problems 18 

Studies Have Identified Impacts of Pollutants from Animal Waste, 

but EPA Has Not Assessed the Extent of Such Impacts 23 

It Is Unclear If EPA’s Efforts to Develop Air Emissions Protocols 

for Animal Feeding Operations Will Be Effective and How EPA 

Intends to Regulate These Emissions in the Future 33 

Two Federal Court Decisions Have Affected EPA’s and Some 

States’ Ability to Regulate Water Pollutants Discharged by 

CAFOs 43 

Conclusions 48 

Recommendations for Executive Action 48 

Agency Comments and Our Evaluation 49 

Appendix I Objectives, Scope, and Methodology 52 

Appendix II EPA’s Definition of Concentrated Animal Feeding 

Operations 61 

Appendix III Nationwide Trends in the Number of All Animal Farms 

and the Number of Animals Raised on Large Farms, 

1982-2002 63 

Appendix IV Government-Sponsored or Peer-Reviewed Studies 

Completed Since 2002 on the Impacts of Pollutants 

from Animal Waste 65 

` 

Contents 
Page ii GAO-08-944 Concentrated Animal Feeding Operations 

Appendix V Comments from the Environmental Protection 

Agency 76 

Appendix VI GAO Contact and Staff Acknowledgments 79

Tables 

Table 1: Nationwide Trends in the Number of Large Farms Raising 

Animals for All Animal Types, 1982 through 2002 14 

Table 2: Median Number of Animals Raised on Large Farms, by 

Animal Type, 1982 through 2002 15 

Table 3: Nationwide Trends in the Number of Animals Raised on 

Large Farms as a Proportion of the Number of Animals 

Raised on All Farms, by Animal Type, 1982 and 2002 16 

Table 4: Estimated Typical Manure Production for Three Different 

Sizes of Large Farms That Raise Animals, 2002 18 

Table 5: Studies Completed Since 2002 Linking Water Pollutants 

from Animal Feeding Operations with Impacts on Human 

Health or the Environment 24 

Table 6: Studies Completed Since 2002 Directly Linking Air 

Pollutants from Animal Feeding Operations to Impacts on 

Human Health 25 

Table 7: Studies Completed Since 2002 Finding No Links between 

Pollutants from Animal Feeding Operations and Impacts 

on Human Health or the Environment 26 

Table 8: Studies Completed Since 2002 That Found an Indirect Link 

between Pollutants from Animal Feeding Operations and 

Human Health or Environmental Impacts 28 

Table 9: Number of Participants in the Air Compliance Agreement, 

Funding Provided by Animal Type, and Source of the 

Funding for the National Air Emissions Monitoring Study 35 

Table 10: States That Reported Having Regulations for Air 

Emissions from Animal Feeding Operations, 2008 42 

Table 11: State Officials’ Views of the Impact of the Waterkeeper

Decision on Their CAFO Programs 45 

Table 12: EPA Designation of Large, Medium, and Small CAFOs for 

Various Size Thresholds by Animal Type 61 
Page iii GAO-08-944 Concentrated Animal Feeding Operations 

Table 13: Nationwide Trends in the Number of All Farms That 

Raise Animals for All Animal Types, 1982 through 2002 63 

Table 14: Nationwide Trends in the Number of Animals Raised on 

Large Farms per Day for All Animal Types, 1982 through 

2002 63 

Figures 

Figure 1: Geographic Concentration of Hogs in Five Contiguous 

North Carolina Counties, 2002 21 

Figure 2: EPA Timeline for Development of Air Emission Protocols 

for Animal Feeding Operations 37 

Abbreviations 

CAFO Concentrated Animal Feeding Operation 

CERCLA Comprehensive Environmental Response, 

 Compensation and Liability Act of 1980 

EPA Environmental Protection Agency 

EPCRA Emergency Planning and Community 

 Right-to-Know Act of 1986 

NAS National Academy of Sciences 

NPDES National Pollutant Discharge Elimination System 

USDA U.S. Department of Agriculture 

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Page 1 GAO-08-944 Concentrated Animal Feeding Operations 

September 4, 2008

Congressional Requesters 

Over the last 40 years, diversified, independent, family-owned-andoperated farms that produce a variety of crops and a few animals are 

becoming a smaller share of the agricultural sector and are being replaced 

by fewer, much larger farms. For animal production, this change has 

meant a movement to significantly larger operations that can raise, for 

example, as many as 2 million chickens or 800,000 hogs at one facility at 

one time. 

These large-scale livestock and poultry operations are generally referred 

to as animal feeding operations. An animal feeding operation is one that 

(1) raises animals in a confined situation for a total of 45 days or more 

during a 12-month period and (2) brings feed to the animals rather than 

having the animals graze or seek feed in pastures and fields or on 

rangeland. Concentrated animal feeding operations (CAFO) are a subset of 

animal feeding operations and usually operate on a much larger scale. 

Generally, a CAFO is an animal feeding operation that raises enough 

animals to meet or exceed certain minimum thresholds, depending upon 

the type of livestock being raised. For example, as defined in Clean Water 

Act regulations, an animal feeding operation would be considered a CAFO 

if it raised 1,000 or more beef cattle, 2,500 hogs weighing more than 55 

pounds, or 125,000 broiler chickens.1

 In addition, an animal feeding 

operation of any size can be designated a CAFO if it meets certain 

conditions, such as being a significant contributor of pollutants to 

federally regulated waters.2

While CAFOs may have improved the efficiency of the animal production 

industry, they have also raised environmental and health concerns 

because of the large amounts of manure they produce. Generally, to 

minimize potential environmental problems, these operations retain the 

manure that they produce in storage facilities onsite and periodically 

dispose of it by spreading it on nearby or adjacent cropland as fertilizer. If 

the manure is properly contained and managed, it can benefit crop 

production; if improperly contained and managed, it can degrade air and 

 1

40 C.F.R. § 122.23(b). 

2

Federally regulated waterways include waters of the United States as defined in 33 C.F.R. 

§ 328.3(a)(1)-(7) and may include rivers, wetlands, impoundments, the territorial seas, and 

waters used in interstate commerce. 

United States Government Accountability Office

Washington, DC 20548 
Page 2 GAO-08-944 Concentrated Animal Feeding Operations 

water quality, thereby potentially impairing human health and damaging 

the environment. Specifically, these operations can potentially degrade air 

quality because large amounts of manure may emit unsafe quantities of 

ammonia, hydrogen sulfide, and particulate matter,3

 and they can 

potentially degrade water quality because pollutants in manure such as 

nitrogen, phosphorus, bacteria, and organic matter could enter nearby 

water bodies. 

Several federal laws provide the Environmental Protection Agency (EPA) 

with the authority to regulate water and air pollutants from CAFOs. The 

Clean Water Act specifically addresses CAFOs by requiring EPA to 

consider CAFOs like any other industry if they discharge pollutants into 

federally regulated waters. As a result, CAFOs that have such discharges 

must obtain a permit that establishes design standards and management 

practices for retaining and disposing of manure in such a way as to limit 

the amounts and types of pollutants from manure that are released into 

federally regulated waters. EPA, or the states that have been authorized by 

EPA to administer the Clean Water Act, are responsible for issuing these 

permits. In contrast, three other acts provide EPA with certain authorities 

related to air emissions from these operations, although they do not 

specifically cite CAFOs as regulated entities. Under the Clean Air Act, any 

animal feeding operation, regardless of size, that exceeds established air 

emission thresholds for certain pollutants can be regulated. For example, 

pollutants such as particulate matter that are emitted by animal feeding 

operations are regulated under the Clean Air Act and other pollutants such 

as hydrogen sulfide or ammonia may be regulated under the act in certain 

circumstances. Similarly, the Comprehensive Environmental Response, 

Compensation, and Liability Act of 1980 (CERCLA) and the Emergency 

Planning and Community Right-to-Know Act of 1986 (EPCRA) do not 

specifically mention CAFOs, but they do require owners or operators of 

these facilities to report to federal or state and local authorities when a 

“reportable quantity” of certain hazardous substances, such as hydrogen 

sulfide or ammonia,4

 is released into the environment. Together, 

CERCLA’s and EPCRA’s reporting requirements provide government 

authorities, emergency management agencies, and citizens the ability to 

 3

Particulate matter is a complex mixture of extremely small particles and liquid droplets. 

Particulate matter can be made up of a number of components, including acids (such as 

nitrates and sulfates), organic chemicals, metals, and soil or dust particles. 

4

Each of these hazardous substances has a reportable quantity of 100 pounds in a 24-hour 

period. 
Page 3 GAO-08-944 Concentrated Animal Feeding Operations 

know about the source and magnitude of hazardous releases into the 

environment. 

In light of the growing concerns regarding the potential human health and 

environmental impacts of CAFOs, you asked us to determine the (1) trends 

in CAFOs over the past 30 years; (2) amount of waste they generate; (3) 

findings of recent key academic, industry, and government research on the 

impacts of CAFOs on human health and the environment, and the extent 

to which EPA has assessed the nature and severity of such impacts; (4) 

progress that EPA and the states have made in regulating and controlling 

the emissions of, and in developing protocols to measure, air pollutants 

from CAFOs that could affect air quality; and (5) extent to which recent 

court decisions have affected EPA and the states’ ability to regulate CAFO 

discharges that impair water quality. 

In conducting our work, we reviewed laws and regulations and federal and 

state agencies’ documents; met with officials from EPA and the U.S. 

Department of Agriculture (USDA), industry, citizen and environmental 

groups, and academia. We also spoke with state officials and visited 

CAFOs in eight states. These states were Arkansas, California, Colorado, 

Iowa, Maryland, Minnesota, North Carolina, and Texas. We chose these 

states because they were geographically dispersed and contained 

numerous CAFOs representing various animal types. In addition, to 

determine trends in CAFOs over the past 30 years, from 1974 through 2002, 

we obtained the most recent data available from USDA on large farms that 

raise animals to use as a proxy for CAFO data. However, because of 

limitations in USDA’s data for 1974 through 1982, we could not determine 

from these data which farms prior to 1982 would meet EPA’s minimum 

size thresholds for CAFOs. Consequently, our analysis of trends in CAFOs 

focuses on the 20-year period between 1982 and 2002. We also obtained 

and reviewed the data that EPA compiled over the last 5 years from each 

of its regions on the number of CAFOs that were issued a permit. To 

identify the amount of waste CAFOs generate, we estimated the amounts 

of manure generated by various size farms that raise animals. To provide a 

perspective of the amount of waste that large farms that raise animals can 

generate, we selected certain cities based on their population and 

estimated the amount of sanitary waste generated by the human 

population and compared these amounts with the amount of waste 

generated by three different sizes of large farms.5

 To report on key 

research on the impacts of CAFOs on human health and the environment, 

 5

Human sanitary waste includes feces and urine but does not include wastes such as water 

from showers, washing dishes and clothes, and flushing toilets. 
Page 4 GAO-08-944 Concentrated Animal Feeding Operations 

we reviewed EPA’s 2003 Rule regulating discharges from CAFOs under the 

Clean Water Act and the National Academy of Sciences study on air 

emissions from animal feeding operations.6 We also conducted library and 

Internet searches to identify key studies completed since 2002 on air and 

water pollutants from waste generated by animal feeding operations. We 

compared the findings from these studies with EPA assessments to date 

and interviewed EPA officials regarding these assessments. To assess the 

progress that EPA and the states have made in regulating and controlling 

the air emissions of, and in developing protocols to measure, air pollutants 

from CAFOs, we reviewed relevant documents and interviewed EPA 

officials, as well as officials responsible for an ongoing national air 

emissions monitoring study. In addition, we contacted state officials in all 

50 states to determine which states had developed air emission regulations 

applicable to CAFOs. Finally, to determine the extent to which recent 

court decisions have affected EPA and the states’ ability to regulate CAFO 

discharges that impair water quality, we reviewed the results of recent 

federal and state court decisions. We also interviewed EPA and state 

officials on how the court decisions have affected their ability to regulate 

CAFOs. A more detailed description of our scope and methodology is 

presented in appendix I. 

We conducted this performance audit between July 2007 and August 2008, 

in accordance with generally accepted government auditing standards. 

These standards require that we plan and perform the audit to obtain 

sufficient, appropriate evidence to provide a reasonable basis for our 

findings and conclusions based on our audit objectives. We believe that 

the evidence obtained provides a reasonable basis for our findings and 

conclusions based on our audit objectives. 

No federal agency collects accurate and consistent data on the number, 

size, and location of CAFOs. However, according to USDA officials, the 

data USDA collects for large farms that raise animals can serve as a proxy 

in estimating trends in CAFOs nationwide from 1982 through 2002. Using 

these data, we found that the number of large farms that raise animals has 

increased 234 percent, from about 3,600 in 1982 to almost 12,000 in 2002. 

We found that the number of animals raised on these large farms had also 

increased, but the rate of increase varied greatly by animal type. For 

example, the average number of hogs raised on large farms increased by 

37 percent, from about 3,400 in 1982 to nearly 4,600 in 2002. In contrast, 

 6

National Academy of Sciences, Air Emissions from Animal Feeding Operations: Current 

Knowledge, Future Needs (Washington, D.C.: National Academies Press, 2003). 

Results in Brief 
Page 5 GAO-08-944 Concentrated Animal Feeding Operations 

during the same time period, the average number of broiler chickens 

raised on large farms only increased by about 3 percent, from 

approximately 155,000 to nearly 160,000. Furthermore, almost half of the 

livestock and poultry raised in the United States in 2002, about 43 percent, 

were raised on large farms. Over the last 5 years, EPA has been compiling 

data from its regions in an effort to develop information on the number of 

permitted CAFOs nationwide. However, we determined that these data 

are inconsistent and inaccurate and do not provide necessary information 

on the characteristics of these CAFOs. Without a systematic and 

coordinated process for collecting and maintaining accurate and complete 

information on the number, size, and location of permitted CAFOs, EPA 

does not have the information that it needs to effectively regulate these 

operations. EPA has indicated that it is working with the states to develop 

and implement a new national system to collect and maintain these data. 

The amount of manure that a large farm raising animals can generate 

depends on the types and numbers of animals being raised at a specific 

operation; such farms can produce from over 2,800 tons to more than 1.6 

million tons of manure annually. For example, a layer farm that meets 

EPA’s minimum large CAFO threshold of 82,000 laying hens could produce 

more than 2,800 tons of manure a year, while a farm with 10,000 beef cattle 

(cattle fattened with feed) could produce about 117,000 tons of manure a 

year. In fact, some large farms can produce more raw waste than the 

human population of a large U.S. city. For example, a very large hog farm, 

with as many as 800,000 hogs, generates more than 1.6 million tons of 

manure annually—more than one and a half times the sanitary waste 

produced by the about 1.5 million residents of Philadelphia, Pennsylvania 

in 1 year. Furthermore, while manure is a valuable resource often used as 

fertilizer, agricultural experts and government officials have raised 

concerns about the large amounts of manure produced by animal feeding 

operations that are increasingly clustered within specific geographic areas 

within a state. For example, five contiguous North Carolina counties had 

an estimated hog population of over 7.5 million hogs in 2002 and the hog 

operations in these counties could have produced as much as 15.5 million 

tons of manure that year. According to agricultural experts and 

government officials that we spoke to, such clustering of operations raises 

concerns that the amount of manure produced could result in the 

overapplication of manure to croplands in these areas and the release of 

excessive levels of some pollutants that could potentially damage water 

quality. 

At least 68 government-sponsored or peer-reviewed studies have been 

completed on air and water quality issues associated with animal waste 

since 2002 and 15 of these studies have directly linked pollutants from 
Page 6 GAO-08-944 Concentrated Animal Feeding Operations 

animal waste to specific health or environmental impacts. Of the 

remaining 53 studies, 7 found no impacts, 12 made indirect linkages 

between these pollutants and health and environmental impacts, and 34 of 

the studies focused on measuring the amount of water or air pollutants 

emitted by animal feeding operations. However, EPA has not yet assessed 

the extent to which air and water pollution from CAFOs may be impairing 

human health and the environment because it lacks key data on the 

amount of pollutants that CAFOs are discharging. Of the 15 studies we 

found directly linking pollutants from animal waste to human health or 

environmental impacts, 8 focused on water pollutants and 7 on air 

pollutants. Most of the water studies found that nutrients or hormones 

released from animal feeding operations were causing environmental 

harm, such as reproductive disorders in fish and degraded water quality. 

One water study found that animal feeding operations were causing 

pathogens such as E. coli to contaminate drinking water, which were then 

causing gastrointestinal illnesses in humans. Similarly, all seven air studies 

linked air emissions from animal feeding operations to adverse human 

health effects. Specifically, six found exposure to these emissions caused 

respiratory inflammation and one found an increased incidence of 

headaches, eye irritation, and nausea in people working at or living near 

these operations. According to EPA officials, although the agency has long 

recognized the potential impacts that water pollutants from CAFOs can 

have on human health and the environment, it has not yet assessed these 

impacts because it lacks information on the extent to which water 

pollutants are actually being discharged by CAFOs. According to other 

officials at EPA, the agency does not have the resources needed to 

conduct a study that would provide this information. Likewise, EPA has 

not yet assessed the air quality impacts from animal feeding operation 

emissions because, according to agency officials, it lacks key data on the 

extent to which these operations are emitting pollutants. To gather this 

information, EPA entered into a series of agreements with animal feeding 

operations to implement a national air emissions monitoring study that is 

currently ongoing and is being funded by the industry and will measure 

and quantify air emissions from animal feeding operations. 

The ongoing national air emissions monitoring study is considered a first 

step in EPA’s efforts to develop protocols for measuring and quantifying 

air contaminants from animal feeding operations; however, it is not clear if 

the study will provide EPA the data that it needs to develop these 

protocols. EPA believes that this 2-year study, initiated in 2007, will 

provide a scientific basis for estimating air emissions from animal feeding 

operations so that the agency can develop protocols that these operations 

can use to more quickly determine if they exceed regulatory thresholds. 

However, concerns have been raised that the animal feeding operations 
Page 7 GAO-08-944 Concentrated Animal Feeding Operations 

being monitored in the study do not represent a valid sample of all animal 

feeding operations and that the data collected during the early phases of 

the study may be incomplete. As a result, it is uncertain whether the study 

will ultimately provide data of sufficient quantity and quality that will 

enable the agency to develop its planned protocols. In addition, it is 

uncertain if and when EPA will develop a process-based model that 

considers the interaction and implications of all sources of emissions at an 

animal feeding operation. Furthermore, other EPA actions make it 

unclear at this time how the agency intends to regulate air emissions from 

animal feeding operations once the data collection effort is complete. For 

example, EPA has not yet decided if it will aggregate the emissions 

occurring on an animal feeding operation or if the emissions from barns 

and manure storage areas will be considered separately when determining 

if an operation has exceeded air emissions thresholds. Moreover, in 

December 2007, EPA proposed a rule to exempt releases to the air of 

hazardous substances, such as ammonia and hydrogen sulfide, from 

manure at farms, including animal feeding operations, which meet or 

exceed their reportable quantity from both CERCLA and EPCRA 

notification requirements. EPA stated that, in all instances, the source and 

nature of the release make emergency responses unnecessary, impractical, 

and unlikely for these operations, and hence it found notifications to be 

unnecessary. It is unclear to us how EPA made this determination when it 

has not yet completed its data collection effort and does not yet know the 

extent to which animal feeding operations are emitting these pollutants. In 

the absence of federal guidance on how to regulate air emissions from 

animal feeding operations, officials in six states told us that they are 

regulating some emissions covered under the Clean Air Act, CERCLA, and 

EPCRA. For example, Minnesota has established state emissions 

thresholds for hydrogen sulfide that apply to CAFOs and the state requires 

CAFO operators to develop an air emissions plan specifying how they will 

control these emissions. 

Two recent federal court decisions have affected EPA’s and some states’ 

ability to regulate CAFOs for pollutants that may impair water quality. 

Specifically: 

• In 2005, in Waterkeeper Alliance Inc. v. EPA (Waterkeeper), the U.S. Court 

of Appeals for the Second Circuit set aside key provisions of a CAFO rule 

EPA had issued in 2003. This rule would have provided EPA with 

comprehensive information on the universe of CAFOs and their operations 

and would have subjected large numbers of previously unregulated CAFOs 

to monitoring and reporting requirements, as well as periodic inspections. 

However, the court concluded that EPA did not have the authority under 

the Clean Water Act to require CAFOs that were not discharging pollutants 
Page 8 GAO-08-944 Concentrated Animal Feeding Operations 

into federally regulated waters to apply for permits. As a result, CAFO 

operators currently determine for themselves whether they need to apply 

for a federal permit, and EPA must rely on other means of acquiring 

information about CAFOs that are illegally discharging pollutants, such as 

through citizens’ reports. EPA has developed proposed revisions to its 

2003 rule in response to the court’s ruling. The resulting rule is currently 

awaiting the Office of Management and Budget’s approval, but EPA is not 

certain when that review will be completed and the final rule issued. The 

Waterkeeper decision has had mixed impacts on states’ regulation of 

CAFOs. Some states have not been affected by the Waterkeeper decision 

because they have used their own authorities to adopt regulations more 

stringent than federal regulations. As a result, these states, such as 

Minnesota, have continued to require all CAFOs to obtain state permits. In 

contrast, officials in those states, such as Colorado, that base their 

regulations on the Clean Water Act and federal regulations told us that 

their programs will remain in limbo until EPA issues its final revised rule. 

• The Supreme Court’s 2006 decision—Rapanos v. United States

(Rapanos)—has also complicated EPA’s enforcement of CAFO 

regulations. The Court’s decision has raised questions that have not yet 

been resolved about which “waters” are considered federal waters and, 

therefore, fall under the jurisdiction of the Clean Water Act. According to 

EPA enforcement officials, the agency may be less likely to seek 

enforcement against a CAFO that it believes is discharging pollutants into 

a water body because it is now more difficult to prove that the water body 

is federally regulated. Congress is considering legislation that seeks to 

clearly define the scope of the Clean Water Act and resolve the questions 

raised by the Rapanos decision. 

To more effectively regulate CAFOs, we are recommending that the 

Administrator of EPA direct the agency to complete its efforts to develop a 

comprehensive national inventory of permitted CAFOs that incorporates 

appropriate internal controls to ensure the quality of the data collected. To 

ensure that the national air emissions monitoring study will provide the 

scientific and statistically valid data that EPA needs for developing its air 

emissions protocols, we are recommending that EPA reassess the current 

data collection efforts, including its internal controls. We are also 

recommending that EPA establish a strategy and timetable for developing 

a process-based model that will provide more sophisticated air emissions 

estimating methodologies for animal feeding operations. In commenting 

on a draft of this report, EPA partially agreed with our recommendations. 
Page 9 GAO-08-944 Concentrated Animal Feeding Operations 

The livestock and poultry industry is vital to our nation’s economy, 

supplying meat, milk, eggs, and other animal products; however, the past 

several decades have seen substantial changes in America’s animal 

production industries. As a result of domestic and export market forces, 

technological changes, and industry adaptations, food animal production 

that was integrated with crop production has given way to fewer, larger 

farms that raise animals in confined situations. These large-scale animal 

production facilities are generally referred to as animal feeding operations. 

CAFOs are a subset of animal feeding operations and generally operate on 

a larger scale. While CAFOs may have improved the efficiency of the 

animal production industry, their increased size and the large amounts of 

manure they generate have resulted in concerns about the management of 

animal waste and the potential impacts this waste can have on 

environmental quality and public health. 

Animal manure can be, and frequently is, used beneficially on farms to 

fertilize crops and to restore nutrients to soil. However, if improperly 

managed, manure and wastewater from animal feeding operations can 

adversely impact water quality through surface runoff and erosion, direct 

discharges to surface water, spills and other dry-weather discharges, and 

leaching into the soil and groundwater. Excess nutrients in water can 

result in or contribute to low levels of oxygen in the water and toxic algae 

blooms, which can be harmful to aquatic life. Improperly managed manure 

can also result in emissions to the air of particles and gases, such as 

ammonia, hydrogen sulfide, and volatile organic compounds, which may 

also result in a number of potentially harmful environmental and human 

health effects. 

Most agricultural activities are considered to be nonpoint sources of 

pollution because the pollution that occurs from these activities is in 

conjunction with soil erosion caused by water and surface runoff of 

rainfall or snowmelt from diffuse areas such as farms and rangeland. 

However, section 502(14) of the Clean Water Act specifically defines point 

sources of pollution to include CAFOs, which means that under the act, 

CAFOs that discharge into federally regulated waters are required to 

obtain a federal permit called a National Pollutant Discharge Elimination 

System (NPDES) permit. These permits generally allow a point source to 

discharge specified pollutants into federally regulated waters under 

specific limits and conditions. These permits are issued by EPA or a state 

agency authorized by EPA to implement the NPDES program for that 

state. Currently, 45 states are authorized to administer the NPDES permit 

program, and their programs must be at least as stringent as the federal 

Background 
Page 10 GAO-08-944 Concentrated Animal Feeding Operations 

program.7 In 1976, in accordance with the Clean Water Act’s designation of 

CAFOs as point sources, EPA defined which poultry and livestock 

facilities constituted a CAFO and established permitting regulations for 

CAFOs. According to EPA regulations issued in 1976, to be considered a 

CAFO a facility must first be considered an animal feeding operation. 

Animal feeding operations are agricultural operations where the following 

conditions are met: 

• animals are fed or maintained in a confined situation for a total of 45 days 

or more in any 12-month period, and 

 

• crops, vegetation, forage growth, or post harvest residues are not 

sustained during normal growing seasons over any portion of the lot. 

If an animal feeding operation met EPA’s criteria and either met or 

exceeded minimum size thresholds based on the type of animals being 

raised, EPA considered the operation to be a CAFO. For example, an 

animal feeding operation would be considered a CAFO if it raised 1,000 or 

more beef cattle, 2,500 pigs weighing more than 55 pounds, or 125,000 

chickens. In addition, EPA could designate an animal feeding operation of 

any size as a CAFO under certain circumstances. For example, if an animal 

feeding operation was a significant contributor of pollutants to federally 

regulated water, EPA could designate the operation as a CAFO. Appendix 

II lists the full text of EPA’s current CAFO definition, including the size 

thresholds established for small, medium, and large CAFOs. 

Under EPA’s 1976 CAFO regulations, certain animal feeding operations did not 

require permits. These included (1) those animal feeding operations that only 

discharged during a 25-year, 24-hour storm event—which is the amount of 

rainfall during a 24-hour period that occurs on average once every 25 years or 

more and (2) chicken operations that use dry manure-handling systems—

systems that do not use water to handle their waste. In addition, EPA generally 

did not regulate animal waste that was applied to cropland or pastureland. 

In January 2003, we reported that although EPA believed that many animal 

feeding operations degrade water quality, it had placed little emphasis on its 

permit program and that exemptions in its regulations allowed as many as 60 

 7

EPA has retained program authority for Alaska, Idaho, Massachusetts, New Hampshire, 

and New Mexico. Oklahoma has been authorized to issue permits for most sources but not 

for CAFOs. 
Page 11 GAO-08-944 Concentrated Animal Feeding Operations 

percent of the largest operations to avoid obtaining permits.8 In its response 

to our 2003 report, EPA acknowledged that the CAFO program was hampered 

by outdated regulations and incomplete attention by EPA and the states. EPA 

pointed out that it had revised its permitting regulations for CAFOs to 

eliminate the exemptions that allowed most animal feeding operations to 

avoid regulation. The revisions, issued in February 2003 and known as the 

2003 CAFO rule, resulted, in part, from the settlement of a 1989 lawsuit by the 

Natural Resources Defense Council and Public Citizen, in which these groups 

alleged that EPA had failed to comply with the Clean Water Act. EPA’s 2003 

CAFO rule included the following key provisions: 

• Duty to apply. All CAFOs were required to apply for an NPDES permit 

unless the permitting authority determined that the CAFO had no potential 

to discharge to federally regulated waters. 

• Expanded CAFO definitions to include all poultry operations and standalone operations raising immature animals. The previous rule had 

applied only to poultry operations that used a liquid manure-handling 

system. The 2003 rule expanded the CAFO definition to all types of poultry 

operations, and EPA officials estimated that this revision could result in 

almost 2,200 additional poultry operations requiring a permit. 

• More stringent design standard for new facilities in the swine, poultry, 

and veal categories. Under the previous rule, facilities were to be 

designed, constructed, and operated to contain runoff from a 25-year, 24-

hour rainfall event; this continues to be the rule for existing facilities. For 

new facilities, the 2003 rule established a no-discharge standard that can 

be met if the facilities are designed, constructed, and operated to contain 

the runoff from a 100-year, 24-hour storm event. 

• Best management practices. Operations would be required to implement 

best management practices for applying manure to cropland and for 

animal production areas. The rule required, among other things, specified 

setbacks from streams, vegetated buffers, depth markers in lagoons, and 

other impoundments for production areas to prevent or reduce pollution 

from the operation. 

• Nutrient management plans. CAFO operations would be required to 

develop a plan for managing the nutrient content of animal manure as well 

 8

GAO, Livestock Agriculture: Increased EPA Oversight Will Improve Environmental 

Program for Concentrated Animal Feeding Operations, GAO-03-285 (Washington, D.C.: 

Jan. 16, 2003). 
Page 12 GAO-08-944 Concentrated Animal Feeding Operations 

as the wastewater resulting from CAFO operations, such as water used to 

flush manure from barns. 

• Compliance schedule. The 2003 rule required newly defined CAFOs to 

apply for permits by April 2006 and existing CAFOs to develop and 

implement nutrient management plans by December 31, 2006.9

According to EPA officials, the 2003 rule was expected to ultimately lead 

to better water quality because the revised regulations would extend 

coverage to more animal feeding operations that could potentially 

discharge and contaminate water bodies and subject these operations to 

periodic inspections. 

Three laws provide EPA with certain authorities related to air emissions 

from animal feeding operations: the Clean Air Act,10 the Comprehensive 

Environmental Response, Compensation, and Liability Act of 1980 

(CERCLA), and the Emergency Planning and Community Right-to-Know 

Act of 1986 (EPCRA).11 Although these laws provide EPA with authority 

related to air emissions from various sources, they do not expressly 

identify animal feeding operations as a regulated entity. Specifically: 

• The Clean Air Act authorizes EPA to regulate stationary and mobile 

sources of air pollution and emphasizes controlling sources that emit more 

than threshold quantities of regulated pollutants. Livestock producers and 

other agricultural sources whose emissions meet or exceed specific 

statutory or regulatory thresholds are therefore subject to Clean Air Act 

requirements. Although EPA has authorized states and local governments 

to carry out certain portions of the act, EPA retains concurrent 

enforcement authority. 

• Taken together, CERCLA and EPCRA require owners or operators of a facility 

to report to federal or state authorities the release of hazardous substances 

that meet or exceed their reportable quantities so as to alert federal, state, and 

local agencies, as well as the public, to the release of these substances. 

Section 103 of CERCLA requires that the person in charge of a facility notify 

the National Response Center of any non-permitted release of “hazardous 

 9

In July 2007, EPA extended these deadlines to February 27, 2009. 

10The Clean Air Act, 42 U.S.C. §§7401-7671q. 

11CERCLA, Pub. L. No. 96-510, 94 Stat. 2767 (codified as amended at 42 U.S.C. §§9601-9675) 

and EPCRA, Pub. L. No. 99-499, Tit. III, 100 Stat. 1728 (codified as amended at 42 U.S.C. 

§§11001-11050). 
Page 13 GAO-08-944 Concentrated Animal Feeding Operations 

substances” in a reportable quantity as soon as he or she has knowledge of 

that release. Section 304 of EPCRA requires that the owner or operator of a 

facility at which a hazardous chemical is produced, used, or stored give 

immediate notice of a release of any “extremely hazardous substance” to the 

community emergency coordinator. Among the reportable substances that 

could be released by livestock facilities are hydrogen sulfide and ammonia. 

The reportable quantity for each of these hazardous substances is 100 pounds 

in a 24-hour period. Under these acts, EPA can assess civil penalties for 

failure to report releases of hazardous substances or extremely hazardous 

substances that equal or exceed their reportable quantities—up to $32,500 per 

day or $32,500 per violation for first time offenders. 

EPA is also working with USDA to address the impacts of animal feeding 

operations on air and water quality and public health. In 1998, EPA 

entered into a memorandum of understanding with USDA that calls for the 

agencies to coordinate on air quality issues relating to agriculture and 

share information. In addition, in 1999, the two agencies issued a unified 

national strategy aimed at having the owners and operators of animal 

feeding operations take actions to minimize water pollution from 

confinement facilities and land application of manure and in 2001 adopted 

an agreement to develop a process for working together constructively. To 

help minimize water pollution from animal feeding operations and meet 

EPA’s regulatory requirements, USDA, through its Natural Resources 

Conservation Service, provides financial and technical assistance to CAFO 

operators in developing and implementing nutrient management plans. 

Because no federal agency collects accurate and consistent data on the 

number, size, and location of CAFOs nationwide, it is difficult to 

determine precise trends in CAFOs over the last 30 years. According to 

USDA officials, the data USDA collects for large farms raising animals can 

be used as a proxy for estimating trends in CAFOs nationwide. Using these 

data, we determined that between 1982 and 2002, the number of large 

farms raising animals has increased sharply, from about 3,600 to almost 

12,000. Moreover, EPA has compiled some data from its regions on the 

number of CAFOs that have been issued permits; however, these data are 

inconsistent and inaccurate. As a result, EPA does not have a systematic 

way of identifying and inspecting all of the CAFOs nationwide that have 

been issued permits. 

The Number of Large 

Farms Raising 

Animals Has 

Increased, but 

Specific Data on 

CAFOs Are Not 

Available 
Page 14 GAO-08-944 Concentrated Animal Feeding Operations 

We found that the number of large farms raising animals for all animal types 

increased by 234 percent between 1982 and 2002. Table 1 shows the changes 

in the number of large farms by animal type for 1982 through 2002. 

Table 1: Nationwide Trends in the Number of Large Farms Raising Animals for All 

Animal Types, 1982 through 2002 

Type of animal farm 1982 1987 1992 1997 2002

Percentage 

change, 

1982-2002

Beef cattlea 966 1,014 1,004 958 982 2

Dairy cow 541 712 1,009 1,445 1,939 258

Hogb 916 1,257 2,061 4,170 5,571 508

Layer 720 808 788 788 706 (2)

Broiler 173 357 737 1,331 2,227 1,187 

Turkey 278 437 504 577 570 105

Total of all animal typesc 3,594 4,585 6,103 9,269 11,995 234 

Source: GAO analysis of USDA data. 

Notes: The phrase “all animal types” refers to the following animals: beef cattle, dairy cows, hogs, 

layers, broilers, and turkeys. 

The criteria for a large farm varied by animal type, consistent with EPA’s CAFO thresholds, and 

represent the average number of animals on a farm per day. 

a

Beef cattle includes only cattle on feed, not grazing on pasture, and sold weighing 500 pounds or 

more. 

b

Hogs include swine of all sizes from birth to market size. 

c

The number of large farms for all animal types is the total of large farms for each animal type and 

may include some farms multiple times if they were considered large for more than one animal type. 

As table 1 shows, large broiler and hog farms experienced the largest 

increase, with large farms raising broilers increasing by 1,187 percent and 

large farms raising hogs increasing by 508 percent. Large farms raising 

layers and large farms raising beef cattle remained relatively stable over 

these 20 years, while layer farms were the only farms that experienced an 

overall decrease in number over the period, declining by 2 percent. In 

contrast, while the number of large farms raising animals has increased, 

the number of all farm raising animals has decreased. Appendix III 

presents trends in the number of all farms raising animals, from 1982 to 

2002. 

Just as the number of large farms for almost all animal types increased 

between 1982 and 2002, so did the size of these farms as illustrated by the 

Since 1982 the Number of 

Large Farms Raising 

Animals Has Increased as 

Has the Average Number 

of Animals on Farms 
Page 15 GAO-08-944 Concentrated Animal Feeding Operations 

median number of animals raised on each farm.12 Table 2 shows the trends 

in the median number of animals raised on large farms for all animal types 

from 1982 through 2002. 

Table 2: Median Number of Animals Raised on Large Farms, by Animal Type, 1982 

through 2002 

Animal type 1982 1987 1992 1997 2002

Percentage 

change,

 1982-2002

Beef cattlea 2,820 2,950 2,919 3,308 3,424 21

Dairy cows 910 988 1,020 1,100 1,200 32

Hogsb 3,350 3,500 3,778 4,334 4,588 37

Layers 131,530 146,383 155,319 168,000 180,000 37

Broilers 154,830 168,593 159,840 161,820 159,840 3

Turkeys 80,000 79,500 81,000 79,697 80,491 1

Source: GAO’s analysis of USDA data. 

Note: We used the median number of animals raised on large farms to represent the average 

concentration of animals raised on large farms per day. 

The criteria for a large farm varied by animal type, consistent with EPA’s CAFO thresholds, and 

represent the average number of animals on a farm per day. 

The median is the point above and below which half of the cases exist. For large animal farms, half of 

the farms of a particular animal type have more animals than the median farm and half have fewer 

animals. For example, in the table above, half of large layer farms in 2002 have more than 180,000 

layers and half have less than 180,000 layers. 

a

Beef cattle includes only cattle on feed, not grazing on pasture, and sold weighing 500 pounds or 

more. 

b

Hogs include swine of all sizes from birth to market size. 

The layer and hog sectors had the largest increases in the median number 

of animals raised per farm, both growing by 37 percent between 1982 and 

2002. Specifically, for layers, large farms increased the number of birds 

they raised from 131,530 in 1982 to 180,000 in 2002 and for hogs, large 

farms increased the number of animals they raised from 3,350 in 1982 to 

4,588 in 2002. In contrast, large farms that raised either broilers or turkeys 

only increased slightly in size with an overall increase of 3 and 1 percent, 

respectively, from 1982 to 2002. 

 12The median is the point above and below which half of the cases exist. For large farms 

that raise animals, half of the farms of a particular animal type have more animals than the 

median farm and half have fewer animals. 
Page 16 GAO-08-944 Concentrated Animal Feeding Operations 

The increases in the number of large farms for almost all animal types, as well 

as the increases in the median number of animals raised on these farms, are 

also reflected in the percentage of animals raised on large farms as compared 

with animals raised on all farms. Specifically, the number of animals raised on 

large farms increased from over 257 million in 1982 to over 890 million in 

2002—an increase of 246 percent. In contrast, the number of animals raised 

on all farms increased from over 1,145 million in 1982 to 2,072 million in 

2002—an increase of 81 percent. This is particularly noteworthy because the 

number of animals raised on large farms only accounted for 22 percent of 

animals raised on all farms in 1982; yet, the number of animals raised on large 

farms accounted for 43 percent of animals raised on all farms in 2002. Table 3 

shows the trends in the number of animals raised on large farms and the 

number of animals raised on all farms from 1982 to 2002. 

Table 3: Nationwide Trends in the Number of Animals Raised on Large Farms as a Proportion of the Number of Animals 

Raised on All Farms, by Animal Type, 1982 and 2002 

Number of animals raised 

on all animal farms 

Number of animals raised 

on large farms 

The number of 

animals raised on 

large farms as a 

percentage of 

the number of 

animals raised on all 

animal farms Animal 

type 1982 2002 

Percent 

change,

1982-2002 1982 2002 

Percent 

change, 

1982-2002 1982 2002

Beef cattlea 11,064,096 11,264,122 2 6,601,928 8,677,892 31 60 77

Dairy cows 10,849,880 9,103,959 (16) 632,583 3,183,086 403 6 35

Hogsb 45,944,318 66,318,763 44 4,176,477 47,789,951 1,044 9 72

Layers 386,638,856 420,742,205 9 160,005,126 304,500,225 90 41 72

Broilers 612,092,410 1,440,501,856 135 52,140,827 457,461,691 777 9 32

Turkeys 78,550,564 124,152,525 58 33,443,754 68,417,853 105 43 55

Total of all 

animal 

typesc

 1,145,140,124 2,072,083,430 81 257,000,695 890,030,698 246 22 43

Source: GAO analysis of USDA data. 

Note: The phrase “all animal types” refers to the following animals: beef cattle, dairy cows, hogs, 

layers, broilers, and turkeys. 

A farm was included in all farms, for a particular animal type, only if it had one or more animals of that 

type. For example, if a farm had broilers only, it would not be counted in all farms for other animal 

types. If a farm raised no animals of any type, then it would also not be included in all farms. 

Reported percentages have been rounded to the nearest whole number but calculations involving 

percentages used non-rounded percentages. 

a

Beef cattle includes only cattle on feed, not grazing on pasture, and sold weighing 500 pounds or 

more. 
Page 17 GAO-08-944 Concentrated Animal Feeding Operations 

b

Hogs include swine of all sizes from birth to market size. 

c

The number of large farms for all animal types is the total number of large farms for each animal type 

and may include some farms multiple times if they were considered large for more than one animal 

type. 

As table 3 shows, most of the beef cattle, hogs, and layers raised in the 

United States in 2002 were raised on large farms. Specifically, 77 percent 

of beef cattle and 72 percent of both hogs and layers were raised on large 

farms. 

EPA does not have its own data collection process to determine the 

number, size, and location of CAFOs that have been issued permits 

nationwide. Since 2003, the agency has compiled quarterly estimates from 

its regions on the number of permits that have been issued to CAFOs. 

These data are developed by EPA’s regional offices or originates with the 

state permitting authority. However, we determined that these data are 

inconsistent and inaccurate and do not provide EPA with the reliable data 

that it needs to identify and inspect permitted CAFOs nationwide. For 

example, according to EPA some uncertainty in the data exists because 

some states may be using general permits to cover more than one 

operation. In addition, EPA has not established adequate internal controls 

to ensure that the data are correctly reported. For example, officials from 

17 states told us that data reported by EPA for their states were 

inaccurate. In one case, when we asked a state official for the number of 

CAFOs in his state, the official realized that the CAFO numbers reported 

by EPA’s regional office were incorrect because of a clerical error, which 

resulted in some CAFO statistics for the state being doubled. After the 

state official discovered this error the state’s data were corrected and 

resubmitted to EPA. Without a systematic and coordinated process for 

collecting and maintaining accurate and complete information on the 

number, size, and location of permitted CAFOs nationwide, EPA does not 

have the information it needs to effectively regulate these operations. 

In commenting on a draft of this report, EPA stated that the information 

from permit files is available to EPA upon request; however, the 

information is currently not readily compiled in a national database. EPA 

is currently working with the states to develop and implement a new 

national data system to collect and record operation-specific information. 

As part of this effort, the agency plans to develop national requirements 

for data that should be collected and entered into the database by the 

states. According to EPA, it may require the states to provide data that 

identifies operations that have been issued or applied for a CAFO permit 

EPA Does Not Have a 

Systematic Means of 

Identifying Permitted 

CAFOs Because It Lacks 

Accurate Data 
Page 18 GAO-08-944 Concentrated Animal Feeding Operations 

as well as operations that should have applied for a permit based on an 

inspection or enforcement action. 

The amount of manure a large farm that raises animals can generate 

primarily depends on the types and numbers of animals raised on that 

farm, and the amount of manure produced can range from over 2,800 tons 

to more than 1.6 million tons a year. To further put this in perspective, the 

amount of manure produced by large farms that raise animals can exceed 

the amount of waste produced by some large U.S. cities. In addition, 

multiple large farms that raise animals may be located in a relatively small 

area, such as two or more adjacent counties, which raises additional 

concerns about the potential impacts of the manure produced, stored, and 

disposed of by these farms. 

Table 4 shows the estimated number of animals and the typical amounts of 

manure produced each year, by type of animal, for three different sizes of 

large farms: (1) large farms that meet EPA’s thresholds for each animal 

type, (2) large farms that raise the median number of animals according to 

our analysis of USDA farm census data, and (3) large farms that fell into 

the 75th percentile based on our analysis. As table 4 shows, a dairy farm 

that meets the minimum threshold of 700 dairy cows could produce almost 

17,800 tons of manure a year; a median-sized dairy farm with 1,200 dairy 

cows could produce about 30,500 tons of manure a year; and a larger dairy 

farm with 1,900 dairy cows could produce almost 48,300 tons of manure a 

year. 

Table 4: Estimated Typical Manure Production for Three Different Sizes of Large Farms That Raise Animals, 2002 

Animal 

type 

EPA’s minimum 

thresholds for 

large CAFOsa

Estimated tons 

of manure 

produced 

annually by large 

CAFOs meeting 

EPA’s minimum 

threshold

Median number 

of animals raised 

on large farmsb

Estimated tons 

of manure 

produced 

annually by large 

farms that raised 

median number 

of animals 

Number of 

animals raised 

on large farms in 

the 75th 

percentilec

Estimated tons 

of manure 

produced 

annually by large 

farms in the 75th 

percentile 

Beef cattled 1,000 11,690 3,424 40,025 10,000 116,895

Dairy cows 700 17,793 1,200 30,502 1,900 48,295

Hogse 2,500 5,100 4,588 9,360 7,700 15,708

Layers 82,000 2,843 180,000 6,242 400,000 13,870

Broilers 125,000 4,125 159,840 5,275 195,383 6,448

Turkeys 55,000 3,633 80,491 5,317 124,500 7,719

Source: GAO analyses based on EPA CAFO definitions, USDA data, and standards for manure production cited by the American 

Society of Agricultural and Biological Engineers, “Manure Production and Characteristics,” March 2005. 

Large Farms That 

Raise Animals Can 

Produce Thousands 

of Tons of Manure 

Each Year, and 

Regional Clustering of 

Farms Can 

Exacerbate Manure 

Management 

Problems 
Page 19 GAO-08-944 Concentrated Animal Feeding Operations 

Note: The amounts of manure reported are estimates. The actual amount of manure produced by an 

animal will vary based on, among other things, feeding programs, feeds used, climatic conditions, 

production techniques, and animal genetics. 

EPA reports its minimum thresholds for large CAFOs in terms of inventory data for all the animal 

types included in table 4. To be able to compare the annual manure estimates for EPA’s thresholds, 

the median, and 75th percentile animal counts, we used USDA data on animal sales, inventories, and 

production cycles, and adjusted these to determine typical inventory during a year. 

The criteria for a large farm varied by animal type, consistent with EPA’s CAFO thresholds, and 

represent the average number of animals on a farm per day. 

a

This category captures the minimum inventory threshold that an animal feeding operation must meet 

to be designated as a large CAFO by EPA and the Clean Water Act. 

b

This column represents the median-sized animal farm in 2002, for each animal type. The median is 

the point above and below which half of the cases exist. For large farms that raise animals, half of the 

farms of a particular animal type have more animals than the median farm and half have fewer 

animals. For example, in table 4, half of large layer farms have more than 180,000 layers and half 

have less than 180,000 layers. 

c

This column represents the farms ranked in the 75th percentile for the amount of animals raised per 

farm in 2002, for each animal type. The 75th percentile is the point where 25 percent of the cases are 

larger and 75 percent are smaller. For large farms that raise animals, the 75th percentile indicates the 

larger of the large farms. The 75th percentile gives a more complete picture of how big a large farm 

can be. For example, for beef cattle the 75th percentile farm is about 3 times larger than the mediansize farm and 25 percent of the beef cattle farms are larger than 10,000 cattle. 

d

Beef cattle includes only cattle on feed, not grazing on pasture, and sold weighing 500 pounds or 

more. The beef cattle manure estimates are for cattle fed from about 700 pounds to about 1,200 

pounds. 

e

Hogs include swine of all sizes from birth to market size. The hog manure estimates are for hogs fed 

from about 27 pounds to about 260 pounds. 

Additionally, individual large farms that raise animals can generate as 

much waste as certain U.S. cities.13 For example, a dairy farm meeting 

EPA’s large CAFO threshold of 700 dairy cows can create about 17,800 

tons of manure annually, which is more than the about 16,000 tons of 

sanitary waste per year generated by the almost 24,000 residents of Lake 

Tahoe, California. Likewise, a median-sized beef cattle operation with 

3,423 head of beef cattle can produce more than 40,000 tons of manure 

annually, which is more than the almost 38,900 tons of sanitary waste per 

year generated by the nearly 57,000 residents of Galveston, Texas. 

Similarly, some larger farms can produce more waste than some large U.S. 

cities. For example, a large farm with 800,000 hogs could produce over 1.6 

million tons of manure per year, which is one and a half times more than 

the annual sanitary waste produced by the city of Philadelphia, 

Pennsylvania—about 1 million tons—with a population of almost 1.5 

 13Human sanitary waste includes urine and feces only; it does not include any other 

household sewage wastes such as water from washing dishes or clothes or water used for 

showers or flushing. 
Page 20 GAO-08-944 Concentrated Animal Feeding Operations 

million.14 Moreover, a beef cattle farm with 140,000 head of cattle could 

produce over 1.6 million tons of manure annually, more than the almost 

1.4 million tons of sanitary waste generated by the more than 2 million 

residents of Houston, Texas.15

Although manure is considered a valuable commodity, especially in states 

with large amounts of farmland, like Iowa, where it is used as fertilizer for 

field crops, in some parts of the country, large farms that raise animals are 

clustered in a few contiguous counties. This collocation of large farms that 

raise animals has resulted in a separation of animal production from crop 

production because many of these operations purchase feed rather than 

grow it on adjacent cropland. As a result, there is much less cropland on 

which the manure can be applied as fertilizer. This clustering of large 

farms that raise animals has occurred because of structural changes in the 

farming sector. According to agricultural experts and USDA officials, the 

overall decrease in the number of farms and increase in the average 

number of animals raised on a farm may have occurred because these 

operations wanted to achieve economies of size. To achieve these 

economies, operators often need significant amounts of capital, which 

they obtain through production contracts with large processing 

companies. 

A USDA report identified this concern as early as 2000 when it found that 

between 1982 and 1997 as livestock production became more spatially 

concentrated that when manure was applied to cropland, crops were not 

fully using the nutrients in manure and this could result in ground and 

surface water pollution from the excess nutrients.16 According to the 

report, the number of counties where farms produced more manure 

nutrients, primarily nitrogen and phosphorus, than could be applied to the 

land without accumulating nutrients in the soil increased. Specifically, the 

numbers of counties with excess manure nitrogen increased by 103 

percent, from 36 counties in 1982 to 73 counties in 1997. Similarly, the 

number of counties with excess manure phosphorous increased by 57 

percent, from 102 counties in 1982 to 160 counties in 1997. As a result, the 

potential for runoff and leaching of these nutrients from the soil was high, 

and water quality could be impaired, according to USDA. Agricultural 

 14EPA officials told us that the agency has identified a hog farm of this size. 

15EPA officials told us that the agency has identified a cattle farm of this size. 

16R. L. Kellogg, C.H. Lander, D. C. Moffitt, and N. Gollehon. Manure Nutrients Relative to 

the Capacity of Cropland and Pastureland to Assimilate Nutrients: Spatial and 

Temporal Trends for the United States. (Washington, D.C.: December 2000). 
Page 21 GAO-08-944 Concentrated Animal Feeding Operations 

experts and government officials who we spoke to during our review 

echoed the findings of USDA’s report and provided several examples of 

more recent clustering trends that have resulted in degraded water quality, 

including the following: 

• As a result of adopting the poultry industry’s approach of developing close 

ties between producers and processors,17 North Carolina experienced a 

rapid growth in the number of hog CAFOs, primarily in five contiguous 

counties. Based on our analysis of 2002 USDA data, we estimated that the 

hog population of the five North Carolina counties was more than 7.5 

million hogs in 2002 and that hog operations in these counties produced as 

much as 15.5 million tons of manure that year. Figure 1 shows the 

geographic concentration of hog farms in North Carolina in 2002. 

Figure 1: Geographic Concentration of Hogs in Five Contiguous North Carolina 

Counties, 2002 

Note: Hog populations are the number of hogs on a typical day per county in 2002. The number of 

hogs was estimated by dividing hogs-to-market sales by two production cycles and adjusting for 

inventory on hand at the end of the year. 

 17GAO, Animal Agriculture: Information on Waste Management and Water Quality 

Issues, GAO/RCED-95-200BR (Washington, D.C.: June 1995). 

Total number of hogs

in five counties:

7,551,920 producing 

about 15.5 million tons

of manure per year

a

Sampson County

hog population: 2,587,421 Bladen County

hog population: 1,150,667

Duplin County

hog population: 2,575,444

Wayne County

hog population: 717,849

Greene County

hog population: 520,539

Wayne

Sampson

Raleigh

Duplin

Bladen

Greene 

Source: GAO analysis of USDA data.
Page 22 GAO-08-944 Concentrated Animal Feeding Operations 

a

This is the amount of manure that would be produced if all of these hogs were in the feeder-finish 

production phase where they start at about 27 pounds and are marketed at about 260 pounds. The 

amount of manure would be less if a large percentage of these hogs were nursery pigs (up to about 

27 pounds). Although we were unable to determine what percentage of hogs in these counties was 

not in the feeder-finish production cycle, we adjusted our estimates based on 1997 USDA data that 

showed that 25 percent of swine sold were not in the feeder-finish production cycle. 

According to North Carolina agricultural experts, excessive manure 

production has contributed to the contamination of some of the surface 

and well water in these counties and the surrounding areas. According to 

these experts, this contamination may have occurred because the hog 

farms are attempting to dispose of excess manure but have little available 

cropland that can effectively use it. According to state officials, partly out 

of concern for the potential contamination of waterways and surface 

water from manure, in 1997, North Carolina placed a moratorium on new 

swine farms and open manure lagoons, which was subsequently continued 

through 2007. While the moratorium included exceptions that could allow 

a new swine farm to begin operations in this area, according to state 

officials, the requirements for these exceptions are so stringent that they 

effectively have prevented the construction of new swine operations or 

the expansion of existing operations. 

• Similarly, a California water official told us that the geographic clustering 

of large farms that raise animals is causing concern in his state as well. 

Our analysis of USDA data shows that in 2002 two counties in the San 

Joaquin Valley in California had 535,443 dairy cows that produced about 

13.6 million tons of manure that year. According to the official, because of 

the limited flow of water through the Valley, once pollutants reach the 

water, they do not dissipate, resulting in a long-term accumulation of these 

pollutants. 

• Regional clustering is also occurring in Arkansas. Two counties in 

northwest Arkansas, located on the Arkansas-Oklahoma border, raised 

14,264,828 broiler chickens that produced over 471,000 tons of manure 

that year. According to EPA Region 6 officials, the Arkansas-Oklahoma 

border is an area of concern due to the number of poultry operations 

(primarily broilers, but also turkeys and layers) within this area. 

Furthermore, region 6 officials identified numerous water bodies in 

northwest Arkansas and northeast Oklahoma that have been impaired by 

manure from animal feeding operations and identified these locations as 

“areas of general ground water concern.” 

While USDA officials acknowledge that regional clustering of large animal 

feeding operations has occurred, they told us that they believe the nutrient 

management plans that they have helped livestock and poultry producers 

develop and implement have reduced the likelihood that pollutants from 

manure are entering ground and surface water. They also believe that as a 
Page 23 GAO-08-944 Concentrated Animal Feeding Operations 

result of new technologies such as calibrated manure spreaders, improved 

animal feeds, and systems that convert manure into electricity, large 

animal feeding operations are able to more effectively use the manure 

being generated. However, USDA could not provide information on the 

extent to which these techniques are being utilized or their effectiveness in 

reducing water pollution from animal waste. 

Since 2002, at least 68 government-sponsored or peer-reviewed studies 

have been completed on air and water pollutants from animal feeding 

operations. Of these 68 studies, 15 have directly linked pollutants from 

animal waste generated by these operations to specific health or 

environmental impacts, 7 have found no impacts, and 12 have made 

indirect linkages between these pollutants and health and environmental 

impacts. In addition, 34 of the studies have focused on measuring the 

amount of certain pollutants emitted by animal feeding operations that are 

known to cause human health or environmental impacts at certain 

concentrations. Appendix IV presents information, including the sponsor, 

the pollutants, and impacts, identified for each of the 68 studies we 

reviewed.18 Although EPA is aware of the potential impacts of air and 

water pollutants from animal feeding operations, it lacks data on the 

number of animal feeding operations and the amount of discharges 

actually occurring. Without such data, according to EPA officials, the 

agency is unable to assess the extent to which these pollutants are 

harming human health and the environment. 

Of the 15 studies completed since 2002 that we reviewed that directly link 

pollutants from animal waste to human health or environmental impacts, 8 

focused on water pollutants and 7 on air pollutants. Academic experts and 

industry and EPA officials told us that only a few studies directly link 

CAFOs with health or environmental impacts because the same pollutants 

that CAFOs discharge also often come from other sources including 

smaller livestock operations; row crops using commercial fertilizers; and 

wastes from humans, municipalities, or wildlife, making it difficult to 

distinguish the actual source of pollution. Table 5 shows the eight 

government-sponsored or peer-reviewed studies completed since 2002 that 

found direct links between water pollutants from animal waste and 

impacts on human health or the environment. 

 18Sponsors are agencies, organizations, or universities responsible for conducting the study 

and not necessarily the group funding the study. 

Studies Have 

Identified Impacts of 

Pollutants from 

Animal Waste, but 

EPA Has Not 

Assessed the Extent 

of Such Impacts 

Some Recent Studies 

Directly Link Pollutants 

from Animal Waste to 

Health and Environmental 

Impacts 
Page 24 GAO-08-944 Concentrated Animal Feeding Operations 

Table 5: Studies Completed Since 2002 Linking Water Pollutants from Animal Feeding Operations with Impacts on Human 

Health or the Environment 

Study title Sponsora

Pollutant(s) 

studied Impact identified 

Effects of the Feedlot Contaminant 17αTrenbolone on Reproductive Endocrinology 

of the Fathead Minnow 

EPA Hormones Adverse effects to reproductive 

system of aquatic life 

Endocrine-Disrupting Effects of Cattle 

Feedlot Effluent on an Aquatic Sentinel 

Species, the Fathead Minnow 

University of Florida, St. Mary’s 

College of Maryland, University 

of Nebraska, EPA, Tufts 

University 

Hormones Adverse effects to reproductive 

system of aquatic life 

Effects of the Androgenic Growth Promoter 

17ß-Trenbolone on Fecundity and 

Reproductive Endocrinology of the Fathead 

Minnow 

EPA, University of Minnesota Hormones Adverse effects to reproductive 

system of aquatic life 

In Vitro and in Vivo Effects of 17ßTrenbolone: A Feedlot Effluent 

Contaminant 

EPA Hormones Reproductive malformations in 

laboratory rats and human cells 

Characterization of Waterborne Outbreakassociated Campylobacter jejuni, 

Walkerton, Ontario 

Health Canada Bacteria Gastrointestinal illness and death 

in humans 

Impact of Animal Waste Application on 

Runoff Water Quality in Field Experimental 

Plots 

Jackson State University, 

National Institutes of HealthCenter for Environmental 

Health, Louisiana State 

University 

Nutrients, bacteria Water degradation 

Nutrient Loading Patterns on an 

Agriculturally Impacted Stream System in 

Huntingdon County Pennsylvania over 

Three Summers 

Juniata College Nutrients Water degradation; unable to 

sustain aquatic life 

Concentrated Animal Feeding Operations, 

Row Crops, and Their Relationship to 

Nitrate in Eastern Iowa Rivers 

University of Iowa Nutrients Water degradation 

Source: GAO’s analysis of identified studies. 

a

Sponsor refers to the organization under whose auspices the research was conducted or with whom 

the primary researchers were affiliated. 

As table 5 shows, EPA sponsored four of the water quality studies that 

identified reproductive alterations in aquatic species caused by hormones 

in discharges from animal feeding operations. Two of these studies found 

that hormones from these discharges caused a significant decline in the 

fertility of female fish in nearby water bodies. Similarly, three other 

studies found water bodies impaired by higher nitrogen and phosphorus 

levels from manure runoff from animal feeding operations. For example, 

the study by Juniata College found that the runoff resulted in nutrient 
Page 25 GAO-08-944 Concentrated Animal Feeding Operations 

concentrations in the water that were too high to sustain fish populations. 

Only one of the eight water pollutant studies linked pollutants from animal 

feeding operations to human health effects. This study, conducted by 

Health Canada, directly linked water discharges from a cattle farm to 

bacteria found in nearby waters. These bacteria, which included 

Campylobacter and E. coli, caused gastrointestinal illnesses in more than 

2,300 residents and 7 deaths in a nearby community. 

Table 6 shows the seven government-sponsored or peer-reviewed studies 

completed since 2002 that we reviewed that directly link air pollutants 

from animal feeding operations with human health effects. 

Table 6: Studies Completed Since 2002 Directly Linking Air Pollutants from Animal Feeding Operations to Impacts on Human 

Health 

Study title Sponsora

Pollutant(s) 

studied Impact identified 

Feedlot Dust Stimulation of Interleukin-6 and 8 

Requires Protein Kinase C-Epsilon Human 

Bronchial Epithelial Cells 

Nebraska Medical Center, 

Department of Veterans Affairs 

Medical Center, Texas A&M 

Dust Respiratory inflammation 

Farm Residence and Exposures and the Risk of 

Allergic Diseases In New Zealand Children 

University of Otago, New 

Zealand 

Dust Greater prevalence of 

allergies in children living on 

farms 

Exhaled Nitric Oxide and Bronchial 

Responsiveness in Healthy Subjects Exposed to 

Organic Dust 

National Institute of 

Environmental Medicine, 

Sweden 

Dust Respiratory inflammation 

(occupational) 

Hog Barn Dust Extract Augments Lymphocyte 

Adhesion to Human Airway Epithelial Cells 

Department of Veterans Affairs 

Medical Center, University of 

Nebraska Medical Center 

Dust Respiratory inflammation 

(occupational) 

Hog Barn Dust Extract Stimulates IL-8 And IL-6 

Release in Human Bronchial Epithelial Cells Via 

PKC Activation 

Department of Veterans Affairs 

Medical Center, University of 

Nebraska Medical Center 

Dust Respiratory inflammation 

(occupational) 

Experimental Human Exposure to Inhaled Grain 

Dust and Ammonia: Towards a Model of 

Concentrated Animal Feeding Operations 

University of Iowa Dust, ammonia Tightening of airway in 

asthmatics (occupational) 

Symptomatic Effects of Exposure to Diluted Air 

Sampled from a Swine Confinement Atmosphere 

on Healthy Human Subjects 

Duke University Hydrogen sulfide, 

ammonia, 

endotoxin, dust, 

odor 

Headaches, eye irritation, 

nausea 

Source: GAO’s analysis of identified studies. 

a

Sponsor refers to the organization under whose auspices the research was conducted or with whom 

the primary researchers were affiliated. 

As table 6 shows, six of these studies identified airway inflammation or 

wheezing in people working at or living on an animal feeding operation. 
Page 26 GAO-08-944 Concentrated Animal Feeding Operations 

For example, the studies conducted by the Department of Veterans Affairs 

show that the dust of hog confinement facilities induces airway 

inflammation in workers. The seventh study, completed by Duke 

University in a laboratory setting, exposed healthy volunteers to air 

emissions consistent with those that would occur downwind from animal 

feeding operations. These volunteers reported headaches, eye irritation, 

and nausea following this exposure. According to experts who we spoke 

with, the effects of air emissions from animal feeding operations on 

workers are well known, but the impacts of these emissions on nearby 

communities are still uncertain, and more research is needed to identify 

these impacts. Additionally, experts said it is difficult to determine which 

specific contaminant or mixture of contaminants causes particular health 

symptoms. For example, while hydrogen sulfide causes respiratory and 

other health problems, other contaminants emitted from animal feeding 

operations, such as ammonia, can also cause similar symptoms. 

We found seven government-sponsored or peer-reviewed studies that have 

been completed since 2002 that found no impact on human health or the 

environment from pollutants released by animal feeding operations. These 

seven studies are shown in table 7. 

Table 7: Studies Completed Since 2002 Finding No Links between Pollutants from Animal Feeding Operations and Impacts on 

Human Health or the Environment 

Study title Sponsora

 Pollutant(s) studied Finding(s) 

Prevalence of Escherichia coli O157:H7 

Bacterial Infections Associated with the Use of 

Animal Wastes in Louisiana for the Period 

1996-2004 

Grambling State University, 

Louisiana State University, 

Jackson State University 

Escherichia coli No clear indication that any 

cases of E. coli infection are 

related to animal waste 

Prevalence of Selected Bacterial Infections 

Associated with the Use of Animal Waste in 

Louisiana 

Jackson State University, 

Louisiana State University 

Escherichia coli No clear indication that any 

cases of E. coli infection are 

related to animal waste 

Impacts of Swine Manure Pits on 

Groundwater Quality 

Illinois State Geological 

Survey, University of 

Illinois, Illinois Department 

of Agriculture 

Chloride, ammonium, 

phosphate, potassium, 

nitrate, bacteria 

Manure seepage from swine 

facilities has had limited 

impacts on groundwater 

Some Studies Found No 

Links between Pollutants 

from Animal Feeding 

Operations and Harm to 

Human Health or the 

Environment 
Page 27 GAO-08-944 Concentrated Animal Feeding Operations 

Study title Sponsora Pollutant(s) studied Finding(s) 

Ground-Water Quality and Effects of Poultry 

Confined Animal Feeding Operations on 

Shallow Ground Water, Upper Shoal Creek 

Basin, Southwest Missouri, 2000 

U.S. Geological Survey Nutrients, bacteria The results do not indicate 

that poultry CAFOs are 

affecting the shallow ground 

water with respect to nutrients 

and fecal bacteria 

Environmental Exposure to Endotoxin and Its 

Relation to Asthma in School-Age Children 

Institute of Social and 

Preventive Medicine 

(Switzerland), Children’s 

Hospital (Austria), Philipps 

University (Germany), Ruhr 

University (Germany), 

University Children’s 

Hospital (Switzerland), 

University of Munich 

(Germany 

Dust Decreased risk of hay fever, 

asthma, and wheeze in 

children exposed to high 

levels of endotoxin in dust 

Ecological Associations between Asthma 

Prevalence and Potential Exposure to 

Farming 

University of North 

Carolina 

Farm air Farm exposures may be 

protective against childhood 

asthma. 

Atmospheric Pollutants and Trace Gases: 

Atmospheric Ammonia, Volatile Fatty Acids, 

and Other Odorants near Beef Feedlots 

Research Centre, 

Agriculture and Agri-Food 

Canada 

Ammonia, odor, organic 

compounds, dust 

Odorants from feedlots were 

effectively dispersed. Emitted 

ammonia was deposited to 

the soil downwind. 

Source: GAO’s analysis of identified studies. 

a

Sponsor refers to the organization under whose auspices the research was conducted or with whom 

the primary researchers were affiliated. 

As table 7 shows, the results of a U.S. Geological Survey study did not 

indicate that poultry animal feeding operations were causing an increase 

of nutrient concentrations and fecal bacteria in groundwater. Similarly, 

another study by Agriculture and Agri-Food Canada found that odorants, 

including ammonia and dust emitted by animal feeding operations, never 

exceeded the established irritation threshold. According to EPA and 

academic experts we spoke with, the concentrations of air pollutants and 

water pollutants emitted by animal feeding operations can vary, which 

may account for the differences in the findings of these studies. These 

variations may be the result of numerous factors, including the type of 

animals being raised, feed being used, and manure management system 

being employed, as well as the climate and time of day when the emissions 

occur. 
Page 28 GAO-08-944 Concentrated Animal Feeding Operations 

We also identified 12 government-sponsored or peer-reviewed studies 

completed since 2002 that indirectly link pollutants from animal feeding 

operations to human health or environmental impacts. While these studies 

found that animal feeding operations were the likely cause of human 

health or environmental impacts occurring in areas near the operations, 

they could not conclusively link waste from animal feeding operations to 

the impacts, often because other sources of pollutants could also be 

contributing. For example, 5 of these 12 studies found an increased 

incidence of asthma or respiratory problems in people living or attending 

school near animal feeding operations, compared with a control group. 

These studies hypothesized that the pollutants emitted from animal 

feeding operations were likely the cause of the increased incidence of 

asthma, but some of these studies acknowledged that pollutants from 

other sources could also be contributing to the increased incidence. Table 

8 lists the 12 studies that have been completed since 2002 that made 

indirect links between emissions from animal feeding operations and 

human health and environmental impacts. 

Table 8: Studies Completed Since 2002 That Found an Indirect Link between Pollutants from Animal Feeding Operations and 

Human Health or Environmental Impacts 

Study title Sponsora Impact(s) 

Associations between Indicators of Livestock 

Farming Intensity and Incidence of Human 

Shiga Toxin-Producing Escherichia coli 

Infection 

University of Guelph; Université de 

Montréal; Centre for Infectious 

Disease Prevention and Control – 

Health Canada 

The strongest associations with human 

Escherichia coli infection were the ratio of beef 

cattle to human population and the application 

of manure to the surface of agricultural land by 

a solid spreader and by a liquid spreader. 

The Potential Impact of Flooding on Confined 

Animal Feeding Operations in Eastern North 

Carolina 

University of North Carolina Flood events have a significant potential to 

degrade environmental health because of 

dispersion of wastes from industrial animal 

operations in areas with vulnerable 

populations. 

Odor from Industrial Hog Farming Operations 

and Mucosal Immune Function in Neighbors 

University of North Carolina, Duke 

University 

This study suggests that malodor from 

industrial swine operations can affect the 

secretory immune system, although the 

reduced levels reported are still within normal 

range. 

Environmental Stressors, Perceived Control, 

and Health: The Case of Residents Near 

Large-Scale Hog Farms in Eastern North 

Carolina 

University of North Carolina 

Wilmington 

Residents living near large-scale hog farms in 

eastern North Carolina report symptoms 

related to respiratory, sinus, and nausea 

problems. 

Some Recent Studies 

Indirectly Link Pollutants 

from Animal Feeding 

Operations with Human 

Health and Environmental 

Impacts 
Page 29 GAO-08-944 Concentrated Animal Feeding Operations 

Study title Sponsora Impact(s) 

Asthma Prevalence and Morbidity Among 

Rural Iowa Schoolchildren 

University of Iowa, EPA Among children who wheeze, farm and 

nonfarm children were equally likely to have 

been given a diagnosis of asthma and had 

comparable morbidity. Asthma in rural 

schoolchildren was comparable to 

schoolchildren in large cities. 

Occupational Asthma in Newly Employed 

Workers in Intensive Swine Confinement 

Facilities 

Institute of Agricultural Rural and 

Environmental Health, University of 

Saskatchewan, Laval University 

Newly employed workers in intensive swine 

confinement facilities reported development of 

acute onset of wheezing and cough 

suggestive of asthma. 

Asthma and Farm Exposures in a Cohort of 

Rural lowa Children 

University of Iowa, EPA, Colorado 

State University, Kaiser Permanente 

There was a high prevalence of asthma health 

outcome among farm children living on farms 

that raise swine and raise swine and add 

antibiotics. 

Asthma Symptoms among Adolescents Who 

Attend Public Schools That Are Located Near 

Confined Swine Feeding Operations 

University of North Carolina, RTI 

International 

Estimated exposure to airborne pollution from 

confined swine feeding operations is 

associated with adolescents’ wheezing 

symptoms. 

Airway Responses of Healthy Farmers and 

Nonfarmers to Exposure in a Swine 

Confinement Building 

National Institute of Environmental 

Medicine (Sweden), National 

Institute for Working Life (Sweden) 

Altered lung function and bronchial 

responsiveness was found in nonfarming 

subjects. Only minor alterations were found in 

the farmers. 

Environmental Exposure to Confined Animal 

Feeding Operations and Respiratory Health of 

Neighboring Residents 

Institute for Occupational and 

Environmental Medicine (Germany), 

National Research Centre for 

Environment and Health (Germany), 

Boston University, Municipal Health 

Service Amsterdam 

Respiratory disease was found among 

residents living near confined animal feeding 

operations. 

School Proximity to Concentrated Animal 

Feeding Operations and Prevalence of Asthma 

in Students 

University of Iowa Carver College of 

Medicine, University of Iceland 

Children in the study school, located one-half 

mile from a CAFO, had a significantly 

increased prevalence of physician-diagnosed 

asthma. 

Lung Function and Farm Size Predict Healthy 

Worker Effect in Swine Farmers 

University of Saskatchewan 

(Canada) 

Some swine workers are less affected by 

swine air and continue in the profession. Other 

workers are more affected. 

Source: GAO’s analysis of identified studies. 

a

Sponsor refers to the organization under whose auspices the research was conducted or with whom 

the primary researchers were affiliated. 
Page 30 GAO-08-944 Concentrated Animal Feeding Operations 

Thirty-four government-sponsored or peer-reviewed studies completed 

since 2002 have focused on measuring the amounts of water or air 

pollutants emitted by animal feeding operations that are known to cause 

harm to humans or the environment. Specifically: 

• Nineteen of the 34 studies focused on water pollutants. Four studies found 

increased levels of phosphorus or nitrogen in surface water and 

groundwater near animal feeding operations. According to EPA, excessive 

amounts of these nutrients can deplete oxygen in water, which could 

result in fish deaths, reduced aquatic diversity, and illness in infants. The 

other 15 studies measured water pollutants such as pathogens, hormones, 

and antibiotics. 

• Fifteen of the 34 studies focused on measuring air emissions from animal 

feeding operations. Seven of the 15 studies found high levels of ammonia 

surrounding animal feeding operations. EPA considers ammonia a 

hazardous substance that may harm human health or the environment, and 

that must be reported when emissions exceed its reportable quantity. The 

other eight studies measured the levels of other air pollutants, such as 

hydrogen sulfide, particulate matter, and carbon dioxide. 

Appendix IV provides additional details about each of the 34 studies. 

While EPA recognizes the potential impacts that water and air pollutants 

from animal feeding operations can have on human health and the 

environment, it lacks the data necessary to assess how widespread these 

impacts are and has limited plans to collect the data it needs. 

Water quality. EPA has long recognized the impacts of pollution from 

CAFOs on water quality. For example, almost a decade ago, in its 1998 

study on feedlot point sources, EPA documented environmental impacts 

that may be attributed to these operations.19 This report identified 

pollutants from animal feeding operations and listed about 300 spills and 

runoff events that were attributable to animal feeding operations from 

1985 through 1997. More recently when developing the 2003 CAFO rule, 

EPA documented the potential water quality impacts from CAFOs. It 

reported that contaminants in manure will have an impact on water quality 

if significant amounts reach surface water or groundwaters. Moreover, as 

discussed above, numerous studies completed since 2002 have provided 

 19EPA, Office of Water, Feedlots Point Source Category Study (Washington, D.C.: 1999). 

Many Recent Studies Have 

Measured the Level of 

Pollutants Emitted by 

Animal Feeding 

Operations 

EPA Has Not Yet Assessed 

the Extent of the Human 

Health and Environmental 

Impacts of Pollutants from 

Animal Feeding 

Operations 
Page 31 GAO-08-944 Concentrated Animal Feeding Operations 

additional information on the direct and indirect impacts of discharges 

from animal feeding operations on human health and the environment, and 

many more studies have been completed that have measured the amounts 

of pollutants being discharged. 

EPA officials we spoke with acknowledged that the potential human 

health and environmental impacts of some CAFO water pollutants, such as 

nitrogen, phosphorus, and pathogens, are well known. They told us that 

the agency has recently focused its research efforts on obtaining more 

information on emerging pollutants, such as hormones and antibiotics, and 

on how the concentrations of nutrients and pathogens differ among the 

various types of animal feeding operations. However, these officials also 

stated that EPA does not have data on the number and location of CAFOs 

nationwide and the amount of discharges from these operations. Without 

this information and data on how pollutant concentrations vary by type of 

operation, it is difficult to estimate the actual discharges occurring and to 

assess the extent to which CAFOs may be contributing to water pollution. 

According to agency officials, because of a lack of resources, the agency 

currently has no plans for a national study to collect information on CAFO 

water discharges. However, the agency has recently taken the following 

three steps that may help gather additional data on CAFO pollutants that 

affect water quality: 

• EPA has begun research to determine (1) how the concentration of 

pathogens and nutrients vary in manure on the basis of certain 

characteristics, such as animal type and animal feed, and (2) how manure 

management techniques can reduce the amount of pathogens and 

nutrients in runoff. 

• EPA has set a long-term research goal, as part of its Multi-Year Plan for 

Endocrine Disruptors (FY2007-2013), to characterize the magnitude and 

extent of the impact of hormones released by CAFOs and to determine the 

impact of management strategies on the fate and effects of hormones. At 

the time of our review, according to an EPA official, the agency had only 

limited preliminary findings because it has just recently begun this work. 

• EPA and the U.S. Geological Survey have discussed a joint project to 

identify (1) the location of CAFOs nationwide and (2) those watersheds 

where many CAFOs might be located. According to EPA officials, this 

project is still in the discussion phase. 

Air quality. More recently, EPA has recognized concerns about the 

possible health impacts from air emissions produced by animal feeding 

operations. Prompted in part by public concern, EPA and USDA 
Page 32 GAO-08-944 Concentrated Animal Feeding Operations 

commissioned a 2003 study by the National Academy of Sciences (NAS) to 

evaluate the scientific information needed to support the regulation of air 

emissions from animal feeding operations.20 The NAS report identified 

several air pollutants from animal feeding operations and their potential 

impacts. For example, the study identified ammonia and hydrogen sulfide 

as two air pollutants emitted from animal feeding operations that can 

impair human health. According to the study, ammonia can cause eye, 

nose, and throat irritation at certain concentrations, and hydrogen sulfide 

can cause respiratory distress. While such effects are known to occur, the 

study noted that additional research is warranted to determine if air 

emissions from animal feeding operations are occurring in high enough 

concentrations to cause these effects. The NAS report also concluded that 

in order to determine the human health and environmental effects of air 

emissions from animal feeding operations, EPA and USDA would first 

need to obtain accurate estimates of emissions and their concentrations 

from animal feeding operations with varying characteristics, such as 

animal type, animal feed, manure management techniques, and climate. 

Since the NAS report was issued, EPA has conducted one hypothetical 

assessment of the impacts of air emissions from animal feeding 

operations. In 2004, EPA updated a preliminary analysis to estimate the 

levels of emissions of ammonia and hydrogen sulfide that occur downwind 

from a manure lagoon and that could pose a risk to human health. EPA 

found that ammonia would not reach levels associated with respiratory 

irritation if emitted at the reportable quantity of 100 pounds per day.21 On 

the other hand, the agency found that hydrogen sulfide could cause 

respiratory irritation and central nervous system effects about one mile 

downwind if emitted at the reportable quantity of 100 pounds per day.22

EPA officials who conducted this analysis told us that there have been no 

documented cases of hydrogen sulfide emissions from animal feeding 

operations exceeding the reportable quantity. However, other officials 

noted that the agency does not know exactly what type of species and 

what size of operations are likely to have emissions above the reportable 

quantity, and, as noted in the NAS report, accurate measurements of the 

 20National Academies of Sciences, Air Emissions from Animal Feeding Operations: 

Current Knowledge, Future Needs (Washington, D.C.: National Academies Press, 2003). 

21Section 302.4 of title 40 of the Code of Federal Regulations notes that the reportable 

quantity for ammonia is 100 pounds per 24 hours. 

22Section 302.4 of title 40 of the Code of Federal Regulations notes that the reportable 

quantity for hydrogen sulfide is 100 pounds per 24 hours. 
Page 33 GAO-08-944 Concentrated Animal Feeding Operations 

air pollutants being emitted by animal feeding operations are currently not 

known. 

In 2007, a national air emissions monitoring study to collect data on air 

emissions from animal feeding operations was undertaken as part of a 

series of consent agreements EPA entered into with individual animal 

feeding operations. This study, funded by industry and approved by EPA, 

is intended to help the agency determine how to measure and quantify air 

emissions from animal feeding operations. The data collected will in turn 

be used to estimate air emissions from animal feeding operations with 

varying characteristics, and, according to EPA officials, it is only the first 

step in a long-term effort to accurately quantify air emissions from animal 

feeding operations. According to agency officials, until EPA can determine 

the actual level of emissions occurring, it will be unable to assess the 

extent to which these emissions are affecting human health and the 

environment. Progress in conducting the national air emissions monitoring 

study is discussed in greater detail in the following section. 

The National Air Emissions Monitoring Study—a 2-year effort to collect 

data on air emissions from animal feeding operations—is intended to 

provide a scientific basis for estimating air emissions from these 

operations. The results of this study were intended to help EPA develop 

protocols that will allow it to determine which operations do not comply 

with applicable federal laws. As currently structured, however, the study 

may not provide the quantity and quality of data needed for developing 

appropriate methods for estimating emissions. Furthermore, it is uncertain 

if and when EPA will develop a process-based model that considers the 

interaction and implications of all sources of emissions at an animal 

feeding operation. Also, other more recent decisions suggest that the 

agency has not yet determined how it intends to regulate air emissions 

from animal feeding operations. In the absence of federal guidance on how 

to regulate air emissions from animal feeding operations, a few states have 

developed their own regulations. 

It Is Unclear If EPA’s 

Efforts to Develop Air 

Emissions Protocols 

for Animal Feeding 

Operations Will Be 

Effective and How 

EPA Intends to 

Regulate These 

Emissions in the 

Future 
Page 34 GAO-08-944 Concentrated Animal Feeding Operations 

According to EPA, although it has the authority to require animal feeding 

operations to monitor their emissions and come into compliance with the 

Clean Air Act on a case-by-case basis, this approach has proven to be time 

and labor intensive. As an alternative to the case-by-case approach, in 

January 2005, EPA offered animal feeding operations an opportunity to 

sign a voluntary consent agreement and final order, known as the Air 

Compliance Agreement. To participate in the agreement, animal feeding 

operations were required to take the following actions: 

• Pay a civil penalty ranging from $200 to $1,000 per animal feeding 

operation, depending on the number of animals at the operation and the 

number of operations that each participant signed up.23

• Pay up to $2,500 per farm to help fund a nationwide emissions monitoring 

study and make their facilities available as a monitoring site for emissions 

testing. 

• Once emission protocols are published, apply for all applicable air permits 

and comply with permit conditions, if deemed necessary. 

• Once emission protocols are published, report any releases of ammonia 

and hydrogen sulfide above the threshold levels established by CERCLA 

and EPCRA.24, 25

 23The total penalty is capped at $10,000 for a participant having 10 or fewer farms to 

$100,000 for a participant having over 200 farms. 

24Since announcing the Air Compliance Agreement, EPA has proposed exempting such 

releases from the CERCLA and EPCRA reporting requirements. The exemption, proposed 

in December 2007, has not been finalized. 

25Any farm more than 10 times larger than EPA’s established size thresholds for CAFOs 

must, within 120 days of receiving an executed copy of the agreement, provide the National 

Response Center with a written statement noting the facility’s location, estimating air 

emissions of ammonia, and stating that it will notify the Center of reportable releases when 

emission rates are determined by the monitoring study. 

A National Air Emissions 

Monitoring Study Has 

Begun, but the Study May 

Not Provide the Data EPA 

Needs to Develop Air 

Emissions Protocols 
Page 35 GAO-08-944 Concentrated Animal Feeding Operations 

In return for meeting these requirements, EPA agreed not to sue 

participating animal feeding operations for certain past violations or 

violations occurring during the emissions monitoring study.26

Almost 13,900 animal feeding operations were approved for participation 

in the agreement, representing the egg, broiler chicken, dairy, and swine 

industries. Some turkey operations volunteered but were not approved 

because there were too few operations to fund a monitoring site, and the 

beef cattle industry chose not to participate. EPA collected a total of $2.8 

million in civil penalties from participating animal feeding operations and 

deposited these funds into the U.S. Treasury. An additional $14.8 million 

was collected by a nonprofit, industry-established organization to fund the 

national air emissions monitoring study. Industry groups representing the 

participating operations provided the funding for the study as was called 

for under the agreement. Table 9 shows the level of participation by type 

of operation and the amount of funding provided by different industry 

groups for the national air emissions monitoring study. 

Table 9: Number of Participants in the Air Compliance Agreement, Funding Provided by Animal Type, and Source of the 

Funding for the National Air Emissions Monitoring Study 

(Dollars in millions)

Air Compliance Agreement National Air Emissions Monitoring Study 

Animal type Number of participants 

Number of animal 

feeding operations Funding provided Funding source 

Swine 1,878 4,865 $6.0 National Pork Board 

Dairy 474 573 5.0 National Milk Producers 

Council 

Layers 218 2,693 2.8 United Egg Producers 

Broilers 41 5,752 1.0 National Chicken Council 

Total 2,611 13,883 $14.8 

Source: EPA. 

The purpose of the National Air Emissions Monitoring Study is to collect 

data that will provide a scientific basis for measuring and estimating air 

 26EPA placed certain conditions and limits on its agreement not to sue animal feeding 

operations participating in the Air Compliance Agreement. For example, EPA can continue 

to pursue cases that present an imminent and substantial endangerment to public health, 

welfare, or the environment. In addition, EPA’s agreement not to sue only covers emissions 

from agricultural livestock and livestock waste and does not extend to generators or land 

application of animal waste. 
Page 36 GAO-08-944 Concentrated Animal Feeding Operations 

emissions from animal feeding operations and will help EPA to determine 

operations’ compliance status. To provide a framework for the monitoring 

study and develop a sampling plan that was representative of animal 

feeding operations in the United States, in 2003 EPA convened a panel of 

industry experts, university and government scientists, and other 

stakeholders knowledgeable in the field. In 2004, the nonprofit 

organization founded by the various livestock sectors selected an 

independent science adviser to oversee the data collection at 20 of the 

13,883 animal feeding operations that were selected to participate in the 

study. Their selection was submitted to and approved by EPA. Data 

collection began in May 2007. Once 2 years of data has been collected, 

EPA will use these data to develop air emissions protocols. Figure 6 shows 

EPA’s expected timeline for the development of air emissions protocols. 
Page 37 GAO-08-944 Concentrated Animal Feeding Operations 

Figure 2: EPA Timeline for Development of Air Emission Protocols for Animal Feeding Operations 

However, the National Air Emissions Monitoring Study may not provide 

the data that EPA needs to develop comprehensive protocols for 

quantifying air emissions from animal feeding operations for a variety of 

reasons. First, the monitoring study does not include the 16 combinations 

of animal types and geographic regional pairings recommended by EPA’s 

expert panel. The panel recommended this approach so that the study 

sample would be representative of the vast majority of participating 

animal feeding operations, accounting for differences in climatic 

conditions, manure-handling methods, and density of operations. 

However, EPA approved only 12 of the 16 combinations recommended by 

the expert panel, excluding southeastern broiler, eastern layer, 

midwestern turkey, and southern dairy operations. Second, site selection 

for the study has been a concern since the plan to select monitoring sites 

for the monitoring study was announced in 2005. At that time, many 

agricultural experts, environmental groups, and industry and state officials 

disagreed with the site selection methodology. In commenting on EPA’s 

Federal Register notice of the Animal Feeding Operation Consent 

Protocol development

Staffing, budgeting

Producer signup

EPA reviews Consent Agreements

Site selections

EPA reviews plan

National Air Emissions Monitoring Study

Equipment Acquisition/

Purdue Training sessions

Data

collection 

(2 years)

Site setup

EPA develops Emission 

Estimated Methodologies

Jan. 2004 Jan. 2005 Jan. 2006 Jan. 2007 Jan. 2008 Jan. 2009 Jan. 2010 Jan. 2011

Source: EPA.
Page 38 GAO-08-944 Concentrated Animal Feeding Operations 

Agreement and Final Order, these experts and officials stated that the 

study did not include a sufficient number of monitoring sites to establish a 

statistically valid sample. Without such a sample, we believe that EPA will 

not be able to accurately estimate emissions for all types of operations. 

More recently, in June 2008, the state of Utah reached an agreement with 

EPA to separately study animal feeding operations in the state because of 

the state’s continuing concerns that the National Air Emissions Monitoring 

Study will not collect information on emissions from operations in Rocky 

Mountain states and therefore may not be meaningful for those operations 

that raise animals in arid areas. Finally, agricultural experts have raised 

concerns that the National Air Emissions Monitoring Study does not 

include other sources that can contribute significantly to emissions from 

animal feeding operations. For example, these experts have noted that the 

monitoring study will not capture data on ammonia emissions from 

feedlots and manure applied to fields. According to these experts, feedlots 

and manure on fields, as well as other excluded sources, account for 

approximately half of the total ammonia emissions from animal feeding 

operations. 

Furthermore, USDA’s Agricultural Air Quality Task Force has also recently 

raised concerns about the quantity and quality of the data being collected 

during the early phases of the study and how EPA will eventually use the 

information.27 In particular, the task force expressed concern that the 

technologies used to collect emissions data were not functioning reliably. 

For example, according to data provided by EPA, almost one-third of the 

preliminary data from one site were incomplete during a 2-month data 

collection period. The task force was also concerned about EPA’s plans to 

extrapolate the data across a variety of CAFO operating configurations. At 

its May 2008 task force meeting, the members requested that the Secretary 

of Agriculture ask EPA to review the first 6 months of the study’s data to 

determine if the study needs to be revised in order to yield more useful 

information. 

EPA acknowledged that emissions data should be collected for every type 

of animal feeding operation and practice, but EPA officials stated that 

such an extensive study is impractical. According to EPA officials, the 

industry identified those monitoring sites that they believed best 

represented the type of operations and manure management practices that 

 27The Agricultural Air Quality Task Force, created in accordance with the 1996 farm bill, is 

charged with advising the Secretary of Agriculture with respect to providing oversight and 

coordination related to agricultural air quality, and consists of leaders in farming, industry, 

health, and science. 
Page 39 GAO-08-944 Concentrated Animal Feeding Operations 

are in their various animal sectors. EPA reviewed and approved these site 

selections. According to EPA, it believes that the selected sites provide a 

reasonable representation of the various animal sectors. EPA has also 

indicated that it plans to use other relevant information to supplement the 

study data and has identified some potential additional data sources. For 

example, a study conducted at two broiler facilities in Kentucky has been 

accepted as meeting the emissions study’s requirements. However, 

according to agricultural experts, until EPA identifies all the supplemental 

data that it plans to use, it is not clear if these data, together with the 

emissions study data, will enable EPA to develop comprehensive air 

emissions protocols. 

Furthermore, EPA has also indicated that completing the National Air 

Emissions Monitoring Study is only the first step in a multiyear effort to 

develop a process-based model for predicting overall emissions for animal 

feeding operations. A process-based model would capture emissions data 

from all sources and use these data to assess the interaction of all sources 

and the impact that different manure management techniques have on air 

emissions for the entire operation. For example, technologies are available 

to decrease emissions from manure lagoons by, among other things, 

covering the lagoon to capture the ammonia. However, if an operation 

spreads the lagoon liquid as fertilizer for crops, ammonia emissions could 

increase on the field. According to NAS, a process-based model is needed 

to provide scientifically sound estimates of air emissions from animal 

feeding operations that can be used to develop management and 

regulatory programs. Although EPA plans to develop a process-based 

model after 2011, it has not yet established a timetable for completing this 

model and, therefore, it is uncertain when EPA will have more 

sophisticated approaches that will more accurately estimate emissions 

from animal feeding operations. 

Two recent decisions by EPA suggest that the agency has not yet 

determined how it intends to regulate air emissions from animal feeding 

operations. EPA’s first decision in this context was made in December 

2007. At that time EPA proposed to exempt releases to the air of 

hazardous substances from manure at farms that meet or exceed the 

reportable quantities from both CERCLA and EPCRA notification 

requirements. According to EPA, this decision was in response to language 

that was contained in congressional committee reports related to EPA’s 

appropriations legislation for 2005 and 2006. EPA was directed to 

promptly and expeditiously provide clarification on the application of 

these laws to poultry, livestock, and dairy operations. In addition, the 

agency received a petition from the National Chicken Council, the 

Recent EPA Decisions 

Suggest That the Agency 

Has Not Yet Determined 

How It Plans to Regulate 

Air Emissions from Animal 

Feeding Operations 
Page 40 GAO-08-944 Concentrated Animal Feeding Operations 

National Turkey Federation, and the U.S. Poultry and Egg Association 

seeking an exemption from the CERLA and EPCRA reporting 

requirements for ammonia emissions from poultry operations. The petition 

argued that ammonia emissions from poultry operations pose little or no 

risk to public health, and emergency response is inappropriate. In 

proposing the rule, EPA noted that the agency would not respond to 

releases from animal wastes under CERCLA or EPCRA nor would it 

expect state and local governments to respond to such releases because 

the source and nature of these releases are such that emergency response 

is unnecessary, impractical, and unlikely. It also noted that it had received 

26 comment letters from state and local response agencies supporting the 

exemption for ammonia from poultry operations. However, during the 

public comment period ending on March 27, 2008, a national association 

representing state and local emergency responders with EPCRA 

responsibilities questioned whether EPA had the authority to exempt 

these operations until the agency had data from its monitoring study to 

demonstrate actual levels of emissions from animal feeding operations. 

This national association further commented that EPA should withdraw 

the proposal because it denied responders and the public the information 

necessary to protect themselves from dangerous releases.28 The timing of 

this proposed exemption, before the National Air Emissions Monitoring 

Study has been completed, we believe calls into question the basis for 

EPA’s decision. 

The second decision that EPA has recently made that calls into question 

how the agency intends to regulate air emissions from animal feeding 

operations involves the timing of key regulatory decisions. EPA has stated 

that it will not make key regulatory decisions on how federal air 

regulations apply to animal feeding operations until after 2011, when the 

monitoring study is completed. According to EPA, the agency will issue 

guidance defining the scope of the term “source” as it relates to animal 

agriculture and farm activities. As a result, EPA has not decided if it will 

aggregate the emissions occurring on an animal feeding operation as one 

source or if the emissions from the barns, lagoons, feed storage, and fields 

will each be considered as a separate source when determining if an 

operation has exceeded air emissions’ reportable quantities. Depending on 

the approach EPA takes, how emissions are calculated could differ 

significantly. For example, according to preliminary data EPA has received 

from an egg-laying operation in Indiana, individual chicken barns may 

 28The National Association of SARA Title III Program Officials. The Superfund 

Amendments and Reauthorization Act (SARA) amended CERCLA on October 17, 1986, 

after the first 6 years of the program. 
Page 41 GAO-08-944 Concentrated Animal Feeding Operations 

exceed the CERCLA reportable quantities for ammonia. Moreover, if 

emissions from all of the barns on the operation are aggregated, they 

might be more than 500 times the CERCLA reportable quantities. In 

addition, EPA does not intend to issue guidance to address emissions, and 

sources of emissions, that cannot reasonably pass through a stack, 

chimney, or other functionally equivalent opening, i.e., fugitive emissions, 

until after the conclusion of the monitoring study. 

EPA has already been asked to clarify what it considers a source on an 

animal feeding operation but has declined to do so. In a 2004 ruling on an 

appeal of a civil suit against a swine operation, the U.S. Court of Appeals 

for the 10th Circuit overturned a 2002 federal district court ruling that a 

farm’s individual barns, lagoons, and land application areas could be 

considered separate “sources” for purposes of CERCLA reporting 

requirements.29 The Court of Appeals ruled that the whole farm site was 

the proper entity to be assessed for purposes of CERCLA reporting. The 

Court invited EPA to file a friend-of-the-court brief in order to clarify the 

government’s position on this issue, but EPA declined to do so within the 

court-specified time frame.30 Another court reached similar conclusions in 

2003.31 Despite these court rulings, EPA has indicated that it will not 

decide on what it considers a source until the National Air Emissions 

Monitoring Study is completed. 

In the absence of federal guidance on how to regulate air emissions from 

animal feeding operations, officials in 6 states, out of the 47 states that 

responded to our survey, are regulating some emissions covered under the 

Clean Air Act, CERCLA and EPCRA. As table 10 shows, state officials in 

California, Idaho, Minnesota, Missouri, Nebraska, and North Dakota 

reported that they have developed state air regulations for certain 

pollutants that are emitted by CAFOs. 

 29Sierra Club v. Seaboard Farms Inc., 387 F.3d 1167 (10th Cir. 2004). 

30In commenting on a draft of this report, EPA noted that it had a very limited time to 

respond to the court’s request. 

31Sierra Club v. Tyson Foods, Inc., 299 F. Supp. 2d 693 (W.D. Ky. 2003). 

Lacking Federal Guidance, 

Some States Have Begun 

to Regulate Air Emissions 

from Animal Feeding 

Operations 
Page 42 GAO-08-944 Concentrated Animal Feeding Operations 

Table 10: States That Reported Having Regulations for Air Emissions from Animal 

Feeding Operations, 2008 

Hydrogen 

sulfide Ammonia

Particulate 

matter 

Volatile organic 

compounds 

California X X X X 

Idaho X 

Minnesota X 

Missouri X X 

Nebraska X 

North Dakota X 

Source: State officials, as reported to GAO. 

Specific examples of the types of regulations that the states have 

developed include the following: 

• Minnesota has established state emissions thresholds for hydrogen sulfide 

that apply to CAFOs. CAFO operators in the state must develop an air 

emissions control plan and must implement it if the Minnesota Pollution 

Control Agency detects elevated levels of hydrogen sulfide. According to 

state officials, once an operator reduces emissions, the agency re-monitors 

to ensure the emission levels remained below the state-established 

threshold.32 Minnesota may take legal action against CAFO operators 

violating this standard. For example, in June 2008, monitoring by the 

Minnesota Pollution Control Agency at a dairy operation recorded 

hydrogen sulfide levels above the state threshold and in cooperation with 

the State Attorney General, the agency, using state authorities, filed a 

lawsuit against the dairy’s operator. 

• In 2003, California passed a law that authorized the state and local air 

districts to require animal feeding operations above a certain size to apply 

for clean air permits and develop a plan to decrease air emissions. For 

example, one air district in California—the San Joaquin Valley Air 

Pollution Control District with large clusters of animal feeding 

operations—developed a rule in 2006 to implement the law that required 

large animal feeding operations to apply for a permit that includes a plan 

for mitigating their emissions. According to air district officials, the district 

 32The standard is: 50 ppb average over 1/2 hour not to be exceeded more than two times per 

year; 30 ppb average over 1/2 hour not to be exceeded more than two times in any 5 

consecutive days. 
Page 43 GAO-08-944 Concentrated Animal Feeding Operations 

has implemented specific regulations for dairy animal feeding operations 

that require these operations to obtain five separate permits for 

components of their operations, including barns and land application of 

manure. The officials told us that these regulations were put in place, in 

part because the area is designated as a severe nonattainment area under 

the Clean Air Act and they are required to regulate a broader range of 

emission sources. According to state officials we spoke with, as a result of 

these more stringent state regulations, CAFOs in California may be 

relocating to other states—such as Texas and Iowa. 

Two federal court decisions have affected EPA and some states’ abilities 

to regulate CAFOs for water pollutants. The 2005 Waterkeeper Alliance

Inc. v. EPA decision forced EPA to revise its 2003 rule for permitting 

CAFOs and abandon its approach of requiring all CAFO operators to 

obtain a permit. Although this court decision affected EPA’s ability to 

regulate CAFOs, states’ reaction to the Waterkeeper decision has varied: 

some states such as Minnesota continue to require all CAFOs to obtain 

permits while others such as Colorado have delayed developing new rules 

until EPA issues its final revised rule. In addition, the Supreme Court’s 

2006 decision—Rapanos v. United States—has made determination of 

Clean Water Act jurisdiction over certain types of waters more complex. 

According to EPA, this has required the agency to gather significantly 

more evidence to establish Clean Water Act jurisdiction in some 

enforcement cases. 

In its 2005 Waterkeeper decision, the U.S. Court of Appeals for the Second 

Circuit set aside a key provision of EPA’s 2003 CAFO rule requiring every 

CAFO to apply for a NPDES permit. Under the 2003 rule, large numbers of 

previously unregulated CAFOs were required to apply for permits and 

would have been subject to monitoring and reporting requirements 

imposed by the permit as well as periodic inspections. According to EPA, 

the 2003 rule would have expanded the number of CAFOs requiring 

permits from an estimated 12,500 to an estimated 15,300, an increase of 

about 22 percent. According to EPA officials, when fully implemented, this 

requirement for all CAFOs with a potential to discharge to apply for 

permits would have provided EPA with more comprehensive information 

on the number and location of CAFOs and how they are operated and 

managed, thus allowing EPA to more effectively locate and inspect CAFOs 

nationwide. 

However, in 2003, both environmental and agricultural groups challenged 

EPA’s 2003 rule. In the Waterkeeper case, environmental groups argued, 

Two Federal Court 

Decisions Have 

Affected EPA’s and 

Some States’ Ability 

to Regulate Water 

Pollutants Discharged 

by CAFOs 

The Waterkeeper Decision 

Has Impacted EPA’s Ability 

to Regulate CAFOs, but 

Has Not Had a Similar 

Impact on Some States 
Page 44 GAO-08-944 Concentrated Animal Feeding Operations 

among other things, that EPA’s 2003 rule did not adequately provide for (1) 

public review and comment on a CAFO’s nutrient management plan and 

(2) permitting authorities to review the CAFO’s nutrient management plan. 

The court agreed with the environmental groups and instructed EPA to 

revise the rule accordingly. The agricultural groups challenged the 2003 

rule’s CAFO permitting requirement, arguing that the agency exceeded its 

authority under the Clean Water Act by requiring CAFOs that were not 

discharging pollutants into federally regulated waters to apply for permits 

or demonstrate that they had no potential to discharge. The court also 

agreed with the agricultural groups and set aside the permitting 

requirements for CAFOs that did not actually discharge. Following the 

court’s decision, many aspects of the 2003 rule remained in effect, 

including EPA’s revised regulatory definition of CAFOs and the expansion 

of the number of CAFOs needing permits by deleting a significant 

exception. 

In effect, the Waterkeeper decision returned EPA’s permitting program to 

one in which CAFO operators are not required to apply for a NPDES 

permit unless they discharge, or propose discharging, into federally 

regulated waters. As a result, EPA must identify and prove that an 

operation has discharged or is discharging pollutants in order to require 

the operator to apply for a permit. To help identify unpermitted discharges 

from CAFOs, EPA officials stated that they have to rely on other methods 

that are not necessarily all-inclusive, such as citizens’ complaints, drive-by 

observations, aerial flyovers, and state water quality assessments that 

identify water bodies impaired by pollutants associated with CAFOs. 

According to EPA officials, these methods have helped the agency identify 

some CAFOs that may be discharging as well as targeting inspections to 

such CAFOs. 

In response to the Waterkeeper decision, EPA proposed a new rule in June 

2006 requiring that (1) only CAFO operators that discharge, or propose to 

discharge, apply for a permit; (2) permitting authorities review CAFO 

nutrient management plans and incorporate the terms of these plans into 

the permits; and (3) permitting authorities provide the public with an 

opportunity to review and comment on the nutrient management plans. 

According to EPA officials, the final rule is currently being reviewed by the 

Office of Management and Budget before it is formally published in the 

Federal Register. These officials said it is uncertain when the OMB review 

will be completed and the final rule issued. Estimates vary on how this 

rule, when implemented, will affect the number of CAFOs that will obtain 

a permit. EPA estimates that 25 percent fewer CAFOs will need to apply 

for a permit under the new rule than would have been required to apply 

for a permit under the 2003 rule. In contrast, an association representing 
Page 45 GAO-08-944 Concentrated Animal Feeding Operations 

state water program officials believes that many fewer CAFOs than EPA 

estimates will voluntarily apply for a permit under the new 2006 rule, when 

it is finalized. 

The need to develop and implement a new rule that meets the Waterkeeper

requirements has also resulted in delays in implementing the provisions of 

the 2003 rule that the Court upheld. Specifically, EPA has not yet 

implemented, among other things the expanded CAFO definitions, which 

cover operations such as dry-manure poultry operations. This is 

particularly significant since, according to a USDA official with extensive 

knowledge of the poultry industry and another agricultural expert that we 

spoke to, at least 90 percent of poultry operations use a dry-manure 

management system. An EPA Region 6 official told us that in Texas alone 

this expanded definition would result in about 1,500 additional dry-manure 

poultry operations being covered under the new CAFO definition. 

Although the Waterkeeper decision has affected EPA’s ability to regulate 

CAFOs’ water pollutant discharges, this decision has not had the same 

impact on the ability of some of the states to regulate these operations. 

According to officials in the 47 states responding to our survey, the impact 

of the Waterkeeper decision on their ability to regulate water pollution 

from CAFOs has been mixed. As table 11 shows, the impacts of the 

Waterkeeper decision ranged from having little impact on state regulation 

of CAFOs to impairing state CAFO programs. 

Table 11: State Officials’ Views of the Impact of the Waterkeeper Decision on Their 

CAFO Programs 

Impact of Waterkeeper

Number of states 

reporting impact

Waterkeeper had little or no impact 16

Reduced the number of CAFOs with permits 15

Impaired state program 10

Waiting for EPA to issue revised rule 9

Prompted state legislation to require permits for CAFOs 1

Source: GAO analysis of state official responses. 

Note: Some state officials identified more than one impact. 

Officials from several of the states that told us that the Waterkeeper

decision had little impact on their regulation of CAFOs, saying that this 

was primarily because their states had implemented CAFO regulations 

that were more stringent than those required under the Clean Water Act. 

For example, Minnesota officials stated that the Waterkeeper decision had 
Page 46 GAO-08-944 Concentrated Animal Feeding Operations 

no impact on their state’s regulations because the state used its own 

authority to adopt regulations more stringent than EPA’s regulations. 

Moreover, according to Minnesota officials, even after the Waterkeeper

decision, the state has continued to require all CAFOs to obtain permits 

from the state environmental agency. Similarly, Kansas officials stated that 

the Waterkeeper decision had only minimal effects because the state has 

regulated CAFOs since the 1960s. 

However, 34 states indicated that the Waterkeeper decision directly 

affected their state programs. Officials from 15 states told us that the 

number of CAFOs that had obtained permits since the Waterkeeper

decision had decreased although none provided us with numbers on what 

this decrease had been. Similarly, officials in 10 states told us that the 

Waterkeeper decision had impaired their state’s ability to regulate CAFOs 

because it discredited the program, created confusion or uncertainty, or 

made it difficult for them to determine which operations needed a permit. 

For example, according to the state official responsible for Indiana’s 

CAFO permitting program, although the state has had a CAFO permitting 

program since 1971, it adopted EPA’s 2003 CAFO Rule because the rule 

was more protective. However, when the Waterkeeper decision set aside 

portions of the 2003 rule, this official told us that the decision, in effect, 

discredited the state’s regulatory program. In addition, officials from nine 

states who are responsible for their state’s permitting program told us that 

their programs remain in limbo while they wait for EPA to issue its final 

revised rule. These state officials, including officials in Colorado, said that 

they will update their state rules once EPA’s final rule is issued. 

Finally, state water pollution control officials have expressed some 

concerns that EPA’s new 2006 rule will place a greater administrative 

burden on states than the 2003 rule would have. In an August 2006 letter to 

EPA, the Association of State and Interstate Water Pollution Control 

Administrators noted that the “reactive” enforcement that EPA will now 

follow will require permitting authorities to significantly increase their 

enforcement efforts to achieve the level of environmental benefit that 

would have been provided by the 2003 rule. These officials believe that 

requiring EPA and the states to identify CAFOs that actually discharge 

pollutants into federally regulated water bodies will consume more 

resources than requiring all CAFOs to apply for a permit. 
Page 47 GAO-08-944 Concentrated Animal Feeding Operations 

The Supreme Court’s 2006 Rapanos decision has also affected EPA’s 

enforcement of the Clean Water Act because the agency believes that it 

must gather significantly more evidence to establish which waters are 

subject to the act’s permitting requirements. At issue in the Rapanos

decision was whether the Clean Water Act’s wetlands permitting program 

applied to four specific wetlands that were adjacent to non-navigable 

tributaries of traditional navigable waters. The Court rejected the 

standards applied by the lower courts in determining whether wetlands at 

issue fell under the act’s jurisdiction and, therefore, could be subject to 

permitting requirements. Although a majority of the justices rejected the 

standards applied by the lower courts, a majority could not agree on how 

to determine which waters would fall under the act’s jurisdiction, and thus 

how far EPA could reach to regulate discharges of pollutants under the 

act. 

Although the Rapanos case arose in the context of a different permit 

program, the scope of EPA’s pollutant discharge permit program 

originates in the same Clean Water Act definition that was discussed in the 

decision. According to EPA enforcement officials, the agency may now be 

less likely to seek enforcement against a CAFO that it believes is 

discharging pollutants into a water body because it may be more difficult 

to prove that the water body is federally regulated. According to EPA 

officials, as a result of the Rapanos decision, the agency must now spend 

more resources developing an enforcement case because the agency must 

gather proof that the CAFO not only has illegally discharged pollutants, 

but that those discharges ultimately entered a federally regulated water 

body. These officials told us that the farther a CAFO is from a regulated 

water body, the more evidence they will need to prove that the discharges 

entered that water body. To ensure “nationwide consistency, reliability, 

and predictability in their administration of the statute,” EPA has issued 

national guidance to clarify the agency’s responsibilities in light of the 

Supreme Court’s decision. However, in a March 4, 2008, memorandum, 

EPA’s Assistant Administrator for Enforcement and Compliance 

Assurance stated that the Rapanos decision and EPA’s guidance has 

resulted in significant adverse impacts to the clean water enforcement 

program. According to the memorandum, the Rapanos decision and 

guidance negatively affected approximately 500 enforcement cases, 

including as many as 187 cases involving NPDES permits. In May 2007, 

Members of Congress, in both the House and Senate, introduced a bill 

entitled the Clean Water Restoration Act of 2007 to clearly define the 

scope of the Clean Water Act. As of August 2008, neither bill had been 

reported out of committee. 

The Rapanos Decision Has 

Affected EPA’s Overall 

Ability to Regulate 

Pollutants Entering 

Federally Regulated 

Waters 
Page 48 GAO-08-944 Concentrated Animal Feeding Operations 

For more than 30 years, EPA has regulated CAFOs under the Clean Water 

Act and during this time it has amassed a significant body of knowledge 

about the pollutants discharged by animal feeding operations and the 

potential impacts of these pollutants on human health and the 

environment. Despite its long-term regulation of CAFOs, EPA still lacks 

comprehensive and reliable data on the number, location, and size of the 

operations that have been issued permits and the amounts of discharges 

they release. As a result, EPA has neither the information it needs to 

assess the extent to which CAFOs may be contributing to water pollution, 

nor the information it needs to ensure compliance with the Clean Water 

Act. More recently, EPA has also begun to address concerns about air 

pollutants that are emitted by animal feeding operations. The Nationwide 

Air Emissions Monitoring Study, along with EPA’s plans to develop air 

emissions estimating protocols, are important steps in providing much 

needed information on the amount of air pollutants emitted from animal 

feeding operations. However, questions about the sufficiency of the sites 

selected for the air emissions study and the quantity and quality of the data 

being collected could undermine EPA’s efforts to develop air emissions 

protocols by 2011 as planned. Finally, while the study and resulting 

protocols are important first steps, a process-based model that more 

accurately predicts the total air emissions from an animal feeding 

operation is still needed. While EPA has indicated it intends to develop 

such a model, it has not yet established a strategy and timeline for this 

activity. 

In order to more effectively monitor and regulate CAFOs, we recommend 

that the Administrator of the Environmental Protection Agency should 

complete the agency’s effort to develop a national inventory of permitted 

CAFOs and incorporate appropriate internal controls to ensure the quality 

of the data. 

In order to more effectively determine the extent of air emissions from 

animal feeding operations, the Administrator of the Environmental 

Protection Agency should 

• reassess the current data collection efforts, including its internal controls, 

to ensure that the National Air Emissions Monitoring Study will provide 

the scientific and statistically valid data that EPA needs for developing its 

air emissions protocols; 

• provide stakeholders with information on the additional data that it plans 

to use to supplement the National Air Emissions Monitoring Study; and 

Conclusions 

Recommendations for 

Executive Action 
Page 49 GAO-08-944 Concentrated Animal Feeding Operations 

• establish a strategy and timetable for developing a process-based model 

that will provide more sophisticated air emissions estimating 

methodologies for animal feeding operations. 

We provided a draft of this report for review and comment to the EPA and 

the Secretary of USDA. We received written comments from EPA. USDA 

did not provide written comments, but did provide technical comments 

and clarifications, which we incorporated, as appropriate. 

EPA partially concurred with our conclusions and recommendations. In 

its written comments, EPA acknowledged that currently no national 

inventory of permitted CAFOs exists. The agency stated that it is currently 

working with its regions and the states to develop and implement a new 

national data system to collect and record facility-specific information on 

permitted CAFOs. We have revised our recommendation to reflect the 

actions that EPA has underway. In response to our recommendations that 

EPA reassess the current data collection effort, EPA stated that the agency 

has developed a quality assurance plan for the study and is continuously 

evaluating the National Air Emissions Monitoring Study. We are aware 

that EPA has developed a quality assurance plan for the data collected 

during the study. However, our recommendation also reflects other 

concerns with the study. For example, the monitoring sites selected may 

not represent a statistically valid sample or animal feeding operations that 

account for the differences in climatic conditions, manure-handling 

methods, and density of operations; and the study does not address other 

sources that can contribute significantly to emissions from animal feeding 

operations. EPA did not address these issues in its comments. Therefore, 

we continue to believe that EPA should reassess the ongoing effort to 

ensure that the study, as currently structured, will provide the data that 

EPA needs. 

In response to our recommendation that the agency identify the 

information that it plans to use to supplement the National Air Emissions 

Monitoring Study, EPA stated that it cannot yet identify the data that it will 

use to augment the data collected during the monitoring study. However, 

the agency indicated that it has begun discussions with USDA to identify 

ongoing research that is focused on agricultural air emissions and gaps 

that may still exist, but did not provide any additional information on 

when it plans to identify the supplemental data that it plans to use to 

augment the monitoring study. Until it does so, neither EPA nor 

stakeholders can be assured that these data, in combination with the 

emissions study data, will enable EPA to develop the planned protocols. 

The agency also agreed with our recommendation to establish a strategy 

Agency Comments 

and Our Evaluation 
Page 50 GAO-08-944 Concentrated Animal Feeding Operations 

and timetable for developing a process-based model and said that it has 

begun to evaluate what is needed to develop such a model. However, the 

agency did not provide any information on when it expects to complete 

plans for developing a process-based model. EPA also provided technical 

comments, which we have incorporated, as appropriate. EPA’s written 

comments are provided in appendix V. 

As agreed with your offices, unless you publicly announce the contents of 

this report earlier, we plan no further distribution until 30 days from the 

report date. At that time, we will send copies to interested congressional 

committees, the Administrator of the Environmental Protection Agency, 

the Secretary of the United States Department of Agriculture and other 

interested parties. We also will make copies available to others upon 

request. In addition, the report will be available at no charge on GAO’s 

Web site at http://www.gao.gov. 

If you or your staff have any questions regarding this report, please 

contact me at (202) 512-3841 or mittala@gao.gov. Contact points for our 

Office of Congressional Relations and Public Affairs may be found on the 

last page of this report. Key contributors to this report are listed in 

appendix VI. 

Anu Mittal 

Director, Natural Resources 

and Environment 
Page 51 GAO-08-944 Concentrated Animal Feeding Operations 

List of Requesters 

The Honorable John D. Dingell 

Chairman 

Committee on Energy and Commerce 

House of Representatives 

The Honorable James L. Oberstar 

Chairman 

Committee on Transportation and Infrastructure 

House of Representatives 

The Honorable Gene Green 

Chairman 

Subcommittee on Environment and Hazardous Materials 

Committee on Energy and Commerce 

House of Representatives 

The Honorable Eddie Bernice Johnson 

Chairwoman 

Subcommittee on Water Resources and Environment 

Committee on Transportation and Infrastructure 

House of Representatives 

The Honorable Hilda L. Solis 

House of Representatives 
Appendix I: Objectives, Scope, and 

Methodology 

Page 52 GAO-08-944 Concentrated Animal Feeding Operations 

For this report we were asked to determine the (1) trends in concentrated 

animal feeding operations (CAFOs) over the past 30 years; (2) amount of 

waste they generate; (3) findings of recent key academic, industry, and 

government research of the potential impacts of CAFOs on human health 

and the environment, and the extent to which the Environmental 

Protection Agency (EPA) has assessed the nature and severity of these 

identified impacts; (4) progress that EPA and states have made in 

regulating and controlling the air emissions of, and in developing protocols 

to measure, air pollutants from CAFOs that could affect air quality; and (5) 

extent to which recent court decisions have affected EPA and the states’ 

ability to regulate CAFO discharges that impair water quality. 

In conducting our work, we reviewed laws and regulations and federal and 

state agencies’ documents. We met with officials from EPA, the U.S. 

Department of Agriculture (USDA), the National Pork Producers Council, 

the National Pork Board, the National Cattlemen’s Beef Association, the 

Environmental Integrity Project (a nonpartisan, nonprofit environmental 

advocacy group), the Sierra Club, California Association of Irritated 

Residents, Waterkeeper Alliance, Iowa Citizens for Community 

Improvement, Environmental Defense, National Association of Clean Air 

Agencies, Association of State and Interstate Water Pollution Control 

Administrators, as well as state officials. The National Chicken Council did 

not respond to our requests for information. Additionally, we visited 

CAFOs in eight states: Arkansas, California, Colorado, Iowa, Maryland, 

Minnesota, North Carolina, and Texas. We chose these states because they 

were geographically dispersed and contained numerous CAFOs 

representing multiple types of animals. 

For our analysis of trends in CAFOs over the past 30 years, we used 

USDA’s Census of Agriculture data. We assessed the reliability of these 

data by reviewing USDA’s documentation on the development, 

administration, and data quality program for the Census of Agriculture. We 

also electronically tested the data used in this study to determine if there 

were any missing data or anomalies in the dataset. Furthermore, we 

compared the results of our nationwide results for each year by animal 

sector to USDA’s published reports. On the basis of these assessments, we 

determined the data to be sufficiently reliable for the purposes for which it 

was used in this report. In addition, respecting USDA’s requirement to 

protect the privacy of individual farmers responding to the Census of 

Agriculture surveys, we conducted these analyses at USDA and worked 

Appendix I: Objectives, Scope, and 

Methodology 
Appendix I: Objectives, Scope, and 

Methodology 

Page 53 GAO-08-944 Concentrated Animal Feeding Operations 

with USDA to review our results and verify that no single operation could 

be identified from our analysis.1

From USDA’s Census of Agriculture data, we analyzed the most recent 

data available for large farms raising animals from 1974 through 2002.2

 We 

used these data on large farms as a proxy for CAFOs because no federal 

agency collects consistent data on these types of operations. USDA has 

periodically collected data on farms nationwide using the Census of 

Agriculture survey. Prior to 1982, these surveys were conducted every four 

years; whereas since 1982, the agency has administered the survey every 

five years (the most recent survey results, conducted in 2007, will not be 

available until February 2009). In analyzing Census data prior to 1982, we 

found that the categories reported by USDA were not consistent with 

EPA’s minimum size threshold for large CAFOs: 2,500 hogs, 700 dairy or 

milk cows, 55,000 turkeys, 1,000 beef cattle, 82,000 layers, and 125,000 

broilers.3

 For instance, the largest farm categories USDA reported for 

broilers prior to 1982 was farms with sales of 100,000 and more. Since 

sales data must be converted to an inventory number, we had to make 

adjustments for production cycles to determine the number of animals on 

a farm per day.4

 Broiler farms complete six production cycles per year 

therefore, when we divided the USDA provided number of 100,000 in 

broiler sales by 6 to account for the total number of possible production 

cycles, the USDA reported broiler sales represent a farm with an inventory 

of about 17,000 broilers. Farms of this size are much smaller than the 

 1

In order to adjust the data for survey undercoverage and nonresponse, we used the official 

USDA statistical weights. However, we were unable to calculate the confidence intervals 

around the reported estimates because the Census of Agriculture’s documentation does not 

provide the necessary information to determine the statistical error associated with 

subpopulation estimates. 

2

We included a farm, for the purposes of calculating the number of farms overall and for 

each animal type, only when it reported, on the Census of Agriculture survey, either sales 

or inventory numbers for a particular animal type. 

3

By minimum size threshold, we mean the minimum number of animals required for 

classification as a large CAFO without consideration of other factors, such as whether the 

animal feeding operation is a significant contributor of pollutants to federally regulated 

waters, or whether pollutants are discharged into federally regulated waters from the 

operation through a manmade ditch. 

4

A production cycle is the length of time an animal is fed before being sold plus time 

between “crops.” For example, the feeding period for a broiler is about 48 days. Including 

time for cleaning barns between cycles, restocking, etc., a broiler farm has about 6 

production cycles per year. We used the number of cycles per animal type provided in 

“Manure Nutrients Relative to the Capacity of Cropland and Pastureland to Assimilate 

Nutrients,” USDA, December 2000. 
Appendix I: Objectives, Scope, and 

Methodology 

Page 54 GAO-08-944 Concentrated Animal Feeding Operations 

125,000 broiler CAFO threshold defined by EPA. Similarly, categories for 

farms raising other types of animals, in the pre-1982 USDA data, were also 

different than the EPA CAFO definitions for these types of operations. As 

a result, we used the time frame of 1982 through 2002 because USDA could 

provide us with detailed electronic data that allowed us to apply EPA’s 

CAFO thresholds to determine the trends in the overall number of large 

farms that raised animals and could be potentially considered a CAFO. For 

broilers and layers/pullets,5

 we used EPA’s CAFO minimum size threshold 

for dry-litter manure handling systems because these systems represent 

the majority of poultry operations. These thresholds are larger than for 

those poultry operations that have liquid manure handling systems. 

Because USDA does not report the average number of animals on a farm, 

we used USDA Census of Agriculture inventory, sales, and inventory plus 

sales data for this purpose. The choice of using inventory only, sales only, 

or inventory and sales data for a particular animal type depended on the 

wording of Census survey questions during the years we analyzed. When 

only sales data or inventory plus sales data were used, we adjusted these 

data using the appropriate USDA formulas to determine the average 

number of animals on a farm.6

 When both inventory and sales were used 

for an animal type, we applied an approved USDA approach to determine 

the average number of animals on a farm. As a result, we made the 

following adjustments for each animal type: 

• For beef cattle, USDA only collected sales data for 1982 through 1997. As a 

result, for beef cattle, we used sales of cattle on feed (2002 survey) or sales 

of fattened cattle (1982 through 1997 surveys) adjusted for the number of 

production cycles. This increased the likelihood that we were including 

cattle raised on CAFOs instead of operations that allow the cattle to graze 

on pastureland. 

• For dairy cows, we used the inventory of animals as of December 31 for 

each Census year since these animals are maintained to produce milk and 

not specifically for slaughter. For dairy cows, we included the categories: 

lactating and nonlactating cows. 

 5

A pullet is a replacement hen for laying eggs that is less than 1 year of age. 

6

“Manure Nutrients Relative to the Capacity of Cropland and Pastureland to Assimilate 

Nutrients,” USDA, December 2000. 
Appendix I: Objectives, Scope, and 

Methodology 

Page 55 GAO-08-944 Concentrated Animal Feeding Operations 

• For hogs, the Census of Agriculture reported both inventory and sales data 

for hogs and pigs.7

 These data were not reported by either the weight or 

age, so we used the total for all hogs and pigs of all ages. We used both the 

inventory and sales data for hogs and adjusted for the number of 

production or finish cycles. Hogs may be sold more than once because of 

the practice of selling feeder pigs at about 10-12 weeks of age to producers 

to be grown to typical slaughter size. For example, in 1997, about 25 

percent of all hog and pig sales reported on the Census of Agriculture were 

feeder pigs.8

 We adjusted the hog data to factor out these multiple sales. 

• For layers, we used survey responses of inventory as of December 31 for 

layers 20 weeks old and older plus pullets for laying flock replacement. 

• For broilers, we used inventory and sales data from the categories: 

broilers, fryers, capons, roaster and other chickens raised for meat. 

• For turkeys, both inventory and sales data were used and included both 

hens and tom turkeys. 

We also reviewed EPA’s data on the number of CAFOs that had been 

issued permits—these data are either collected by EPA’s regional offices 

or from the states—for the period 2003 to 2008. We assessed the accuracy 

and reliability of these data by interviewing officials in 47 states and we 

asked them to verify the information that EPA had for the numbers of 

CAFOs permitted in their state.9

 Based on the information we obtained 

from the state officials, we determined that EPA’s data for permitted 

CAFOs was not reliable and could not be used to identify trends in 

permitted CAFOs over the 5-year period. 

To identify the amount of manure, including urine, a large CAFO is 

estimated to generate for each animal type, we used EPA’s thresholds for 

the minimum number of animals that constitute a CAFO. To illustrate the 

size of a “typical” large farm for each animal type, we used the median for 

 7

The term “hogs” includes all production stages unless otherwise stated. 

8

1997 was the last Census of Agriculture survey that asked for sales of feeder pigs. The 2002 

survey asked for hogs “sold or moved from this operation, including feeder pigs.” In many 

hog contract operations, the farmer does not own the pigs being fed. GAO did not 

determine what effect changing the survey wording had on the change in total hogs sold 

between 1997 and 2002 nor whether the sales of feeder pigs as a percentage of total swine 

sales changed from 1997 to 2002. 

9

The three states that did not provide information on their state CAFO programs were 

Connecticut, Nevada, and Vermont. 
Appendix I: Objectives, Scope, and 

Methodology 

Page 56 GAO-08-944 Concentrated Animal Feeding Operations 

a large-sized farm. We used the median instead of the mean because we 

believe it provides a more representative measure for a typical large farm. 

We also present information on farms at the 75th percentile of all large 

farms for a particular animal type to represent larger farms.10

To estimate the amount of manure produced by each type of animal, we 

used engineering standards for manure production cited by the American 

Society of Agricultural and Biological Engineers (ASABE).11 These 

standards report the total amount of manure over the production cycle for 

hogs, beef cattle, turkeys, and broilers. In order to estimate the average 

pounds of manure per day, we divided the total manure produced over the 

production cycle by the number of days in the production cycle. Further, 

we converted the pounds of manure into tons of manure per farm per year. 

We adjusted the manure calculations for the following animal types: 

• For layers, the standards provided the average daily pounds of manure 

produced by layers. We multiplied the average pounds of manure per day 

times the average number of animals times 365 days to get manure 

produced per year. 

• For broilers, we determined the average daily pound of manure from the 

information provided in the standards. We multiplied the average pound of 

manure per day times the average number of animals times 365 days to get 

manure per year. 

• For dairy cows, the standards provided the average daily pounds of 

manure produced by dairy cows. We multiplied the average pounds of 

manure per day times the average number of animals times 365 days to get 

manure per year. However, we adjusted the data to take into account the 

typical percentage of cows that are either lactating or dry (nonlactating) 

and applied the different amounts of manure produced by each type of 

dairy cow. 

• For turkeys, we adjusted the turkey statistics based on the ratio of hens to 

tom turkeys raised on farms and applied different amounts of manure due 

to the different sizes of the animals. 

 10We do not report the largest farm for each particular animal type to avoid disclosing 

information that would allow the identification of the person who supplied the particular 

information to USDA. Federal law prohibits such disclosure. 

11“Manure Production and Characteristics” (St. Joseph, Mich.: March 2005). Manure is “asexcreted” and excludes bedding, waste feed, dilution water, biochemical degradation of 

solids, or dissipation of gases. 
Appendix I: Objectives, Scope, and 

Methodology 

Page 57 GAO-08-944 Concentrated Animal Feeding Operations 

• For hogs, the manure standards report manure produced by hogs covering 

a specific stage of production: feeder-pig-to-finish pigs—beginning with a 

pig weighing on average about 27 pounds and resulting in a hog weighing 

154 pounds. Estimates for other hog operation types such as nursery, 

farrow to feeder, and farrow to finish would therefore differ. Census of 

Agriculture data for 2002 indicate that about a third of all hogs sold were 

from the grow-to-finish (called finish only on the survey) operation type. 

The ASABE manure standards for this type of operation use 154 pounds as 

the finish weight. However, USDA reports that typical hog finish 

(slaughter) weights at the time of the 2002 Census were about 260 pounds. 

For hogs only, we adjusted the ASABE manure estimates by 1.7 to account 

for the larger finish weights reported by USDA. We believe this is a 

conservative adjustment because manure produced by hogs weighing 154 

to 260 pounds will be the maximum amount per day that ASABE used to 

calculate the average pounds produced for the hogs growing from about 

27 pounds to 154 pounds. 

• For beef cattle, we used the manure standard for “beef-finishing cattle.” 

This standard is for cattle fattened from about 740 pounds to about 1,200 

pounds at marketing. Beef cattle (listed as cattle on feed) data from the 

Census are for cattle sold for slaughter and thus similar in weight to those 

for the standard. The reported manure results for beef cattle are for 

operations of this type only. 

In addition, the number of days on feed for hogs, turkeys, and broilers 

used for the ASABE manure standards does not take into account time 

between herds or flocks entering and leaving an operation; therefore, we 

adjusted the manure generated to account for the time between cycles. 

We recognize that all amounts of manure reported are estimates because 

amounts of manure per animal type vary by feeding programs, feeds used, 

climatic conditions, production techniques, and animal genetics, among 

other things. As feeds, animal genetics, and production techniques change 

in the future, these estimates might change—and may have changed since 

2002—but USDA did not provide specific information on what changes 

have occurred and how those changes may have impacted the manure 

production on farms. We did not estimate the ability of the farm or 

surrounding farms to assimilate the manure if applied to pastures and crop 

land nor did we take into account various technologies to process and/or 

convert manure. Reported estimates of manure are for amounts produced. 

We did not determine whether these amounts were discharged into the air 

or streams and wetlands. Manure harvested from CAFOs for application to 

land might be less than that excreted by animals because of shrinkage due 

to evaporation. 
Appendix I: Objectives, Scope, and 

Methodology 

Page 58 GAO-08-944 Concentrated Animal Feeding Operations 

To provide a perspective of the amount of wastes generated by these large 

farms, we compared them with the amount of human sanitary waste 

generated in various cities. We selected certain cities on the basis of their 

population, as reported by the U.S. Census Bureau’s Population Estimates 

for 2002, and calculated the amount of sanitary waste generated by the 

human population of those cities by applying estimates for human sanitary 

waste production. Human sanitary waste includes feces and urine but does 

not include wastes such as water from showers, washing dishes and 

clothes, and flushing toilets. We found two sources of information for 

average daily human sanitary waste.12 Because these sources provided 

different estimates (2.68 and 4.76 pounds per person per day), we averaged 

the two amounts to use in our calculations of human sanitary waste 

produced for cities (3.72 pounds per person per day). All amounts of 

human sanitary waste reported are estimates because amounts will vary 

based on differences in age, dietary habits, activity levels, and climatic 

conditions, among other things. Human sanitary waste is a small portion of 

human discharge into sewage systems. Our reported estimates of human 

sanitary waste for a city are illustrative only and are not intended to be 

estimates of actual human sanitary waste entering a particular city’s waste 

treatment system. These estimates are for a population the size of selected 

cities assuming that the residents do not commute outside the city 

boundaries and that nonresidents do not enter the city for work or other 

reasons. 

To identify the findings of recent key academic, industry, and government 

research on the potential impacts of CAFOs on human health and the 

environment, and the extent to which EPA has assessed the nature and 

severity of such impacts, we reviewed EPA’s 2003 CAFO rule (for water 

impact studies) and the findings and supporting documents of the National 

Academy of Sciences study on air emissions from animal feeding 

operations (for air impact studies).13 In addition, we 

• conducted library, online journal and Internet searches to identify recent 

studies; 

 12Metcalf and Eddy, Inc., “Wastewater Engineering: Treatment, Disposal, and Reuse,” 3rd

Edition, (New York, N.Y..: 1991) and Parker, D. and Gallagher, S. K., “Distribution of 

Human Waste Samples in Relation to Sizing Waste Processing in Space,” in “Second 

Conference on Lunar Bases and Space Activities of the 21st Century,” Volume 2 (NASA 

Conferences Publication 3166: 1992). 

13National Academy of Sciences, Air Emissions from Animal Feeding Operations: 

Current Knowledge, Future Needs (Washington, D.C.: National Academies Press, 2003). 
Appendix I: Objectives, Scope, and 

Methodology 

Page 59 GAO-08-944 Concentrated Animal Feeding Operations 

• consulted with EPA, USDA, state agencies, industry groups, environmental 

groups, and academia to help identify additional studies; and 

• identified studies through citations in previously identified studies. 

We only included in our review studies that (1) were peer-reviewed or 

produced by a federal agency, (2) were new and original research 

completed since 2002, (3) had a clearly defined methodology, and (4) 

identified pollutants found in animal waste and/or their impacts. Through 

this effort, we found over 200 studies and identified 68 studies that 

examined air and water quality issues associated with animal waste and 

met our criteria. We also classified these studies according to whether 

they 

• found a direct link between pollutants from animal waste and impacts on 

human health or the environment; 

• did not find any impacts on human health or the environment from 

pollutants from animal waste; 

• found an indirect link between animal waste and human health or 

environmental impacts; or 

• measured pollutants from animal waste otherwise known to cause human 

health or environmental impacts. 

The classification for each study involved two reviewers. If the reviewers 

disagreed on the classification, they turned to a third reviewer for 

resolution. Finally, we compared the findings from these studies with EPA 

assessments to date and interviewed EPA officials regarding these 

assessments. 

To determine the progress that EPA and states have made in regulating 

and controlling the air emissions of, and in developing protocols to 

measure, air pollutants from CAFOs, we reviewed relevant documents, 

interviewed officials responsible for the ongoing air monitoring study and 

visited several National Air Emissions Monitoring Study sites in North 

Carolina. Additionally, we interviewed industry and environmental groups, 

the umbrella association for state and local clean air agencies, and citizen 

groups about how EPA air emissions protocols affect them. Finally, we 

contacted state CAFO officials in all 50 states to determine which states 

had developed air emission regulations applicable to CAFOs. Officials in 
Appendix I: Objectives, Scope, and 

Methodology 

Page 60 GAO-08-944 Concentrated Animal Feeding Operations 

47 states responded. 14 These 47 states account for an estimated 99 percent 

of large animal feeding operations that could be defined as CAFOs under 

EPA’s 2003 rule. 

Finally, to determine the extent to which recent court decisions have 

affected EPA and the states’ ability to regulate CAFO discharges that 

impair water quality, we examined recent federal decisions, including the 

Waterkeeper Alliance Inc. v. EPA (Waterkeeper), and the Supreme Court’s 

2006 decision in Rapanos v. United States. We interviewed EPA officials 

about how these court decisions have affected their regulations. To better 

understand the bases for the lawsuits and what has occurred since the 

court decisions, we contacted plaintiffs and defendants involved in 

Waterkeeper and other court cases, including industry and environmental 

groups. To identify the impact of these cases on states regulations, we 

contacted state CAFO officials in all 50 states to determine how the 

Waterkeeper decision affected their regulations. We asked the states if the 

Waterkeeper decision had affected their state’s CAFO program. Using the 

responses we received from 47 states, we conducted content analyses and 

classified them into six categories, including if the decision (1) had little 

impact on the state program, (2) caused the state to wait for EPA guidance 

(3) impaired the state program, (4) proactively changed legislation, (5) 

reduced the number of CAFOs with permits, or (6) other. Some officials 

identified more than one impact. The responses in the “other” category 

included such responses as “not applicable,” “because the state does not 

have delegated authority,” and “we have spent a large amount of time 

studying the ruling and commenting on EPA proposed rules that were 

developed to satisfy the ruling.” 

We conducted this performance audit between July 2007 and August 2008, 

in accordance with generally accepted government auditing standards. 

Those standards require that we plan and perform the audit to obtain 

sufficient, appropriate evidence to provide a reasonable basis for our 

findings and conclusions based on our audit objectives. We believe that 

the evidence obtained provides a reasonable basis for our findings and 

conclusions based on our audit objectives. 

 14The three states that did not provide information on their CAFO programs were 

Connecticut, Nevada, and Vermont. 
Appendix II: EPA’s Definition of 

Concentrated Animal Feeding Operations 

Page 61 GAO-08-944 Concentrated Animal Feeding Operations 

EPA’s National Pollutant Discharge Elimination System (NPDES) permit 

program regulates the discharge of pollutants from point sources to waters 

of the United States. The Clean Water Act defines point sources to include 

CAFOs. To be considered a CAFO, a facility must first be defined as an 

animal feeding operation, which is a lot or facility (other than an aquatic 

animal production facility) where the following conditions are met: 

• Animals have been, are, or will be stabled or confined and fed or 

maintained for a total of 45 days or more in any 12-month period. 

• Crops, vegetation, forage growth, or post-harvest residues are not 

sustained in the normal growing season over any portion of the lot or 

facility. 

Generally CAFOs must meet the above definition of an animal feeding 

operation and stable or confine a certain minimum number of animals at 

the operation. EPA classifies CAFOs as large, medium, or small, based on 

size. Table 12 shows the number of animals at a farm that meet EPA’s 

definition of a large, medium, and small CAFO. 

Table 12: EPA Designation of Large, Medium, and Small CAFOs for Various Size Thresholds by Animal Type 

Size thresholds (number of animals) 

Animal type Large CAFOs Medium CAFOsa

 Small CAFOsb 

Cattle or cow/calf pairs 1,000 or more 300 - 999 less than 300 

Mature dairy cows 700 or more 200 - 699 less than 200 

Veal calves 1,000 or more 300 - 999 less than 300 

Swine (weighing over 55 pounds) 2,500 or more 750 - 2,499 less than 750 

Swine (weighing less than 55 pounds) 10,000 or more 3,000 - 9,999 less than 3,000 

Horses 500 or more 150 - 499 less than 150 

Sheep or lambs 10,000 or more 3,000 - 9,999 less than 3,000 

Turkeys 55,000 or more 16,500 - 54,999 less than 16,500 

Laying hens or broilers (liquid manure handling systems) 30,000 or more 9,000 - 29,999 less than 9,000 

Chickens other than laying hens (other than a liquid manure 

handling system) 

125,000 or more 37,500 - 124,999 less than 37,500 

Laying hens (other than a liquid manure handling system) 82,000 or more 25,000 - 81,999 less than 25,000 

Ducks (other than a liquid manure handling system) 30,000 or more 10,000 - 29,999 less than 10,000 

Ducks (liquid manure handling systems) 5,000 or more 1,500 - 4,999 less than 1,500 

Source: EPA. 

a

Must also meet one of two “method of discharge” criteria to be defined as a CAFO or may be 

designated. 

Appendix II: EPA’s Definition of 

Concentrated Animal Feeding Operations 
Appendix II: EPA’s Definition of 

Concentrated Animal Feeding Operations 

Page 62 GAO-08-944 Concentrated Animal Feeding Operations 

b

May be designated as a CAFO on a case-by-case basis. 

In addition to size, EPA uses the following criteria to determine if a CAFO 

operator needs to apply for a NPDES permit. 

• A large CAFO confines at least the number of animals described in table 

12. 

• A medium CAFO falls within the size range in table 12 and either: 

• discharged pollutants into federally regulated waters through a 

manmade ditch, flushing system, or similar manmade device; 

• discharged pollutants directly into federally regulated waters that 

originate outside of and pass over, across, or through the facility or 

otherwise come into contact with animals confined in the operation; or 

• is designated as a CAFO by the permitting authority as a significant 

contributor of pollutants. 

• A small CAFO confines the number of animals described in table 12 and 

has been designated as a CAFO by the permitting authority as a significant 

contributor of pollutants. 
Appendix III: Nationwide Trends in the 

Number of All Animal Farms and the Number 

of Animals Raised on Large Farms, 1982-2002 

Page 63 GAO-08-944 Concentrated Animal Feeding Operations 

This appendix provides our analysis of USDA’s data for trends on the 

number of all animal farms and the number of animals raised on large 

farms per day for all animal types for the period from 1982 through 2002. 

Table 13: Nationwide Trends in the Number of All Farms That Raise Animals for All Animal Types, 1982 through 2002 

Type of animal farm 1982 1987 1992 1997 2002 

Percentage change, 

1982-2002

Beef cattlea 215,465 173,961 133,795 99,654 98,061 (54)

Dairy cow 277,762 202,068 155,339 116,874 91,989 (67)

Hogb 347,699 256,595 202,811 114,289 89,542 (74)

Layer 218,114 146,056 89,507 74,073 104,974 (52)

Broiler 52,890 41,097 31,427 30,979 41,572 (21)

Turkey 24,701 19,195 13,767 12,129 16,999 (31)

Total of all animal farmsc 1,136,631 838,972 626,646 447,998 443,137 (61)

Source: GAO analysis of USDA data. 

Notes: The phrase “all animal types” refers to the following animals: beef cattle, dairy cows, hogs, 

layers, broilers, and turkeys. 

The criteria for a large farm varied by animal type, consistent with EPA’s CAFO thresholds, and 

represent the average number of animals on a farm per day. 

a

Beef cattle includes only cattle on feed, not grazing on pasture, and sold weighing 500 pounds or 

more. 

b

Hogs include swine of all sizes from birth to market size. 

c

The number of large farms for all animal types is the total of large farms for each animal type and 

may include some farms multiple times if they were considered large for more than one animal type. 

Table 14: Nationwide Trends in the Number of Animals Raised on Large Farms per Day for All Animal Types, 1982 through 

2002 

Type of animal farm 1982 1987 1992 1997 2002 

Percentage change, 

1982-2002

Beef cattlea 6,601,928 7,368,109 7,533,708 8,598,508 8,677,892 31

Dairy cow 632,583 860,878 1,300,616 2,049,814 3,183,086 403

Hogb 4,176,477 6,275,200 12,133,231 32,412,839 47,789,951 1,044

Layer 160,005,126 212,871,326 229,959,901 263,660,262 304,500,225 90 

Broiler 52,140,827 102,198,894 170,873,560 298,222,567 457,461,691 777 

Turkey 33,443,754 52,905,796 62,042,552 73,029,156 68,417,853 105

Total of all animal typesc 257,000,695 382,480,203 483,843,568 677,973,146 890,030,698 246 

Source: GAO analysis of USDA data. 

Appendix III: Nationwide Trends in the 

Number of All Animal Farms and the Number 

of Animals Raised on Large Farms, 1982-2002
Appendix III: Nationwide Trends in the 

Number of All Animal Farms and the Number 

of Animals Raised on Large Farms, 1982-2002 

Page 64 GAO-08-944 Concentrated Animal Feeding Operations 

Notes: The phrase “all animal types” refers to the following animals: beef cattle, dairy cows, hogs, 

layers, broilers, and turkeys. 

The criteria for a large farm varied by animal type, consistent with EPA’s CAFO thresholds, and 

represent the number of animals on a farm per production day. 

a

Beef cattle include only cattle on feed, not grazing on pasture, and sold weighing 500 pounds or 

more. 

b

Hogs include swine of all sizes from birth to market size. 

c

The number of large farms for all animal types is the total of large farms for each animal type and 

may include some farms multiple times if they were considered large for more than one animal type. 
Appendix IV: Government-Sponsored or PeerReviewed Studies Completed Since 2002 on 

the Impacts of Pollutants from Animal Waste 

Page 65 GAO-08-944 Concentrated Animal Feeding Operations 

Study Sponsora Medium Pollutant(s) Impact 

Studies showing a direct impact 

Ankley, Gerald T., Kathleen M. Jensen, 

Elizabeth A. Makynen, Michael D. Kahl, 

Joseph J. Korte, Michael W. Hornung, Tala R. 

Henry, Jeffrey S. Denny, Richard L. Leino, 

Vickie S. Wilson, et al. “Effects of the 

Androgenic Growth Promoter 17β-trenbolone 

on Fecundity and Reproductive Endocrinology 

of the Fathead Minnow.” Environmental 

Toxicology and Chemistry. Vol. 22, no. 6 

(2003):1,350–1,360. 

EPA, University of 

Minnesota 

Water Hormones Fertility of fish was 

significantly reduced by 

hormones and female fish 

developed male sex 

characteristics. 

Clark, Clifford G., Lawrence Price, Rafiq 

Ahmed, David L. Woodward, Pasquale L. 

Melito, Frank G. Rodgers, Frances Jamieson, 

Bruce Ciebin, Aimin Li, and Andrea Ellis. 

“Characterization of Waterborne Outbreak–

Associated Campylobacter jejuni, Walkerton, 

Ontario.” Emerging Infectious Diseases. Vol. 9, 

no. 10 (2003):1,232-1,241. 

Health Canada, Ontario 

Ministry of Health 

Water Bacteria Cattle manure from a nearby 

farm entered the 

groundwater system and 

caused gastrointestinal 

illness and death in 

residents. 

Diesel, Elizabeth A., Melissa L. Wilson, Ryan 

Mathur, Evan Teeters, David Lehmann, and 

Caitlan Ziatos. “Nutrient Loading Patterns on 

an Agriculturally Impacted Stream System in 

Huntingdon County Pennsylvania Over Three 

Summers.” Northeastern Geology & 

Environmental Sciences. Vol. 29, no. 1 

(2007):25-33. 

Juniata College Water Nutrients Excess nutrients from CAFO 

manure contributed 

significantly to impaired 

water quality and resulted in 

the inability to sustain fish 

populations. 

Hill, Dagne D., William E. Owens, and Paul B. 

Tchounwou. “Impact of Animal Application on 

Runoff Water Quality in Field Experimental 

Plots.” International Journal of Environmental 

Research and Public Health. Vol. 2, no. 2 

(2005):314–321. 

Jackson State University, 

NIH-Center for 

Environmental Health, 

Louisiana State 

University 

Water Nutrients, 

bacteria 

Nutrients from manure 

spread on fields contributed 

to water pollution. 

Jensen, Kathleen M., Elizabeth A. Makynen, 

Michael D. Kahl, and Gerald T. Ankley. 

“Effects of the Feedlot Contaminant 17αTrenbolone on Reproductive Endocrinology of 

the Fathead Minnow.” Environmental Science 

& Technology. Vol. 40, no. 9 (2006): 3,112-

3,117. 

EPA Water Hormones Fertility of fish was 

significantly reduced by 

hormones and female fish 

developed male sex 

characteristics. 

Appendix IV: Government-Sponsored or PeerReviewed Studies Completed Since 2002 on 

the Impacts of Pollutants from Animal Waste 
Appendix IV: Government-Sponsored or PeerReviewed Studies Completed Since 2002 on 

the Impacts of Pollutants from Animal Waste 

Page 66 GAO-08-944 Concentrated Animal Feeding Operations 

Study Sponsora Medium Pollutant(s) Impact 

Orlando, Edward F., Alan S. Kolok, Gerry A. 

Binzcik, Jennifer L. Gates, Megan K. Horton, 

Christy S. Lambright, L. Earl Gray, Jr., Ana M. 

Soto, and Louis J. Guillette, Jr. “EndocrineDisrupting Effects of Cattle Feedlot Effluent on 

an Aquatic Sentinel Species, the Fathead 

Minnow.” Environmental Health Perspectives. 

Vol. 112, no. 3 (2004):353–358. 

University of Florida; St. 

Mary’s College of 

Maryland, University of 

Nebraska, EPA, Tufts 

University. 

Water Hormones Male fish were 

demasculinized and there 

was defeminization of 

female fish. 

Weldon, Mark B. and Keri C. Hornbuckle. 

“Concentrated Animal Feeding Operations, 

Row Crops, and Their Relationship to Nitrate 

in Eastern Iowa Rivers.” Environmental 

Science & Technology. Vol. 40, no. 10 (2006): 

3,168-3,173. 

University of Iowa Water Nitrogen High concentrations of 

nutrients in waters are a 

result of CAFO manure and 

degrade water quality. 

Mathisen, T., S. G. Von Essen, T. A. Wyatt, 

and D. J. Romberger. “Hog Barn Dust Extract 

Augments Lymphocyte Adhesion to Human 

Airway Epithelial Cells.” Journal of Applied 

Physiology. Vol. 96, no. 5 (2004):1,738–1,744. 

Department of Veterans 

Affairs Medical Center, 

University of Nebraska 

Medical Center 

Air Dust Dust from hog confinement 

facilities induces airway 

inflammation. 

Romberger, D. J., V. Bodlak, S. G. Von Essen, 

T. Mathisen, and T. A. Wyatt. “Hog Barn Dust 

Extract Stimulates IL-8 And IL-6 Release in 

Human Bronchial Epithelial Cells Via PKC 

Activation.” Journal of Applied Physiology. Vol. 

93, no. 1 (2002):289–296. 

Department of Veterans 

Affairs Medical Center, 

University of Nebraska 

Medical Center 

Air Dust Dust from hog confinement 

facilities induces airway 

inflammation. 

Schiffman, Susan S., Clare Studwell, 

Lawrence R. Landerman, Katherine Berman, 

and John S. Sundy. “Symptomatic Effects of 

Exposure to Diluted Air Sampled from a Swine 

Confinement Atmosphere on Healthy Human 

Subjects.” Environmental Health Perspectives. 

Vol. 113, no. 5 (2005):567-576. 

Duke University Air Hydrogen 

sulfide, 

ammonia, 

total 

suspended 

particulates, 

endotoxin, 

odor, dust 

Short-term exposure to 

emissions expected 

downwind from a swine 

confinement facility can 

induce headaches, eye 

irritation, and nausea. 

Sigurdarson, Sigurdur T., Patrick T. 

O’Shaughnessy, Janet A. Watt, and Joel N. 

Kline. “Experimental Human Exposure Inhaled 

Grain Dust and Ammonia: Towards a Model of 

Concentrated Animal Feeding Operations.” 

American Journal of Industrial Medicine.Vol. 

46, issue 5 (2004):345:348. 

University of Iowa Air Dust, 

ammonia 

Exposure to endotoxin-rich 

dust from CAFOs causes 

airflow obstruction in 

subjects with mild asthma. 

Sundblad, B-M., B-M. Larsson, L. Palmberg, 

and K. Larsson. “Exhaled Nitric Oxide and 

Bronchial Responsiveness in Healthy Subjects 

Exposed to Organic Dust.” European 

Respiratory Journal. Vol. 20, no. 2 (2002): 

426–431. 

National Institute of 

Environmental Medicine, 

Sweden 

Air Dust Airway inflammation is 

induced by exposure to a 

farming environment. 
Appendix IV: Government-Sponsored or PeerReviewed Studies Completed Since 2002 on 

the Impacts of Pollutants from Animal Waste 

Page 67 GAO-08-944 Concentrated Animal Feeding Operations 

Study Sponsora Medium Pollutant(s) Impact 

Wickens, K., et. Al. “Farm Residence and 

Exposures and the Risk of Allergic Diseases in 

New Zealand Children.” Allergy. Vol. 57, no. 12 

(2002): 1,171-1,179. 

University of Otago (New 

Zealand) 

Utrecht University (The 

Netherlands) 

Air Dust There was a greater 

prevalence of allergic 

disease for children on 

farms. 

Wilson, Vickie S., Christy Lambright, Joe 

Ostby, and L.E. Gray, Jr. “In Vitro and in Vivo 

Effects of 17β-Trenbolone: A Feedlot Effluent 

Contaminant.” Toxicological Sciences. Vol. 70, 

no. 2 (2002): 202-211. 

EPA Water Hormones Hormones found in feedlot 

effluent caused reproductive 

malformations in laboratory 

rats and human cells. 

Wyatt, Todd A., Rebecca E. Slager, Jane 

DeVasure, Brent W. Auvermann, Michael L. 

Mulhern, Susanna Von Essen, Tracy 

Mathisen, Anthony A. Floreani, and Debra J. 

Romberger. “Feedlot Dust Stimulation of 

Interleukin-6 And 8 Requires Protein Kinase CEpsilon Human Bronchial Epithelial Cells.” 

American Journal of Physiology-Lung Cellular 

and Molecular Physiology. Vol. 293, no. 5 

(2007):1,163-1,170. 

Nebraska Medical 

Center, Department of 

Veterans Affairs Medical 

Center, Texas A&M 

Air Dust Dust extract from cattle 

feedlots stimulates airway 

inflammation at 

concentrations found 

downwind from the 

operation. 

Studies indicating no impact 

Hill, Dagne D., William E. Owens, and Paul B. 

Tchounwou. “Prevalence of Escherichia coli 

O157:H7 Bacterial Infections Associated With 

the Use of Animal Wastes in Louisiana for the 

Period 1996-2004.” International Journal of 

Environmental Research and Public Health. 

Vol. 3, no. 1 (2006): 107-113. 

Grambling State 

University, Louisiana 

State University, Jackson 

State University 

Water Escherichia 

coli (not 

measured) 

Although some of the 

parishes surveyed had large 

amounts of animal waste 

generated each year, 

statistics did not show a 

correlations with Escherichia 

coli 0157:H7 bacterial 

infections. 

Hill, Dagne D., William E. Owens, and Paul B. 

Tchounwou. “Prevalence of Selected Bacterial 

Infections Associated with the Use of Animal 

Waste in Louisiana.” International Journal of 

Environmental Research and Public Health. 

Vol. 2, no. 1 (2005): 84–93. 

Jackson State University, 

Louisiana State 

University, 

Water Escherichia 

coli (not 

measured) 

Although the four parishes 

surveyed had large amounts 

of animal waste generated, 

statistics does not show a 

correlation between this and 

bacterial infections. 

Krapac, I.G., W.S. Dey, W.R. Roy, C.A. Smyth, 

E. Storment, S.L. Sargent, and J.D. Steele. 

“Impacts of Swine Manure Pits on 

Groundwater Quality.” Environmental Pollution. 

Vol. 120, issue 2 (2002): 475-492. 

Illinois State Geological 

Survey, University of 

Illinois, Illinois 

Department of 

Agriculture 

Water Chloride, 

ammonium, 

phosphate, 

potassium, 

nitrate, 

bacteria 

Groundwater near swine 

CAFOs has not been 

significantly impacted. 

Mugel, Douglas N. “Ground-Water Quality and 

Effects of Poultry Confined Animal Feeding 

Operations on Shallow Ground Water, Upper 

Shoal Creek Basin, Southwest Missouri, 

2000.” U.S. Geological Survey WaterResources Investigations Report 02-4125 

(2002). 

United States Geological 

Survey 

Water Nutrients, 

bacteria 

The results do not indicate 

that poultry CAFOs are 

affecting the shallow ground 

water with respect to 

nutrients and fecal bacteria. 
Appendix IV: Government-Sponsored or PeerReviewed Studies Completed Since 2002 on 

the Impacts of Pollutants from Animal Waste 

Page 68 GAO-08-944 Concentrated Animal Feeding Operations 

Study Sponsora Medium Pollutant(s) Impact 

Braun-Fahrlander, Charlotte, Josef Riedler, 

Udo Herz, Waltraud Eder, Marco Waster, 

Leticia Grize, Soyoun Maisch, David Carr, 

Florian Gerlach, Albrecht Bufe. “Environmental 

Exposure to Endotoxin and its Relation to 

Asthma in School-Age Children.” The New 

England Journal of Medicine. Vol. 347, no. 12 

(2002): 869-877. 

Institute of Social and 

Preventive Medicine 

(Switzerland), Children’s 

Hospital (Austria), 

Philipps University 

(Germany), Ruhr 

University (Germany), 

University Children’s 

Hospital (Switzerland), 

University of Munich 

(Germany) 

Air Dust Decreased risk of hay fever, 

asthma, and wheeze in 

children exposed to high 

levels of endotoxin in dust. 

Elliott, L., K. Yeatts, and D. Loomis. 

“Ecological Associations Between Asthma 

Prevalence And Potential Exposure to 

Farming.” European Respiratory Journal. Vol. 

24, no. 6 (2004): 938–941. 

University of North 

Carolina, Chapel Hill 

Air N/A Findings are consistent with 

the hypothesis that certain 

farm exposures are 

protective against childhood 

asthma. 

McGinn, S. M., H. H. Janzen, and T. Coates. 

“Atmospheric Pollutants and Trace Gases: 

Atmospheric Ammonia, Volatile Fatty Acids, 

and Other Odorants near Beef Feedlots.” 

Journal of Environmental Quality. Vol. 32, no. 

4 (2003):1,173–1,182. 

Research Centre, 

Agriculture and AgriFood Canada 

Air Ammonia, 

odor, organic 

compounds, 

total 

suspended 

particulates, 

dust 

Odorants from feedlots were 

effectively dispersed. 

Emitted ammonia was 

deposited to the soil 

downwind. 

Studies showing an indirect link between pollutants and impacts 

Valcour, James E., Pascal Michel, Scott A. 

McEwen, and Jeffrey B. Wilson. “Associations 

between Indicators of Livestock Farming 

Intensity and Incidence of Human Shiga ToxinProducing Escherichia coli Infection.” 

Emerging Infectious Diseases. Vol. 8, no. 3 

(2002): 252-257. 

University of Guelph; 

Université de Montréal; 

Centre for Infectious 

Disease Prevention and 

Control-Health Canada 

Water Escherichia 

coli (not 

measured) 

The strongest associations 

with human Escherichia coli

infection were the ratio of 

beef cattle to human 

population and the 

application of manure to the 

surface of agricultural land 

by a solid spreader and by a 

liquid spreader. 

Wing, Steve, Stephanie Freedman, and 

Lawrence Band. “The Potential Impact of 

Flooding on Confined Animal Feeding 

Operations in Eastern North Carolina.” 

Environmental Health Perspectives. Vol. 110, 

no. 4 (2002): 387–391. 

University of North 

Carolina 

Water N/A Flood events have a 

significant potential to 

degrade environmental 

health because of dispersion 

of wastes from industrial 

animal operations in areas 

with vulnerable populations. 

Avery, Rachel C., Steve Wing, Stephen W. 

Marshall, and Susan S. Schiffman. “Odor from 

Industrial Hog Farming Operations and 

Mucosal Immune Function in Neighbors.” 

Archives of Environmental Health. Vol. 59, no. 

2 (2004): 101-108. 

University of North 

Carolina, Duke University

Air N/A This study suggests that 

malodor from industrial 

swine operations can affect 

the secretory immune 

system, although the 

reduced levels reported are 

still within normal range. 
Appendix IV: Government-Sponsored or PeerReviewed Studies Completed Since 2002 on 

the Impacts of Pollutants from Animal Waste 

Page 69 GAO-08-944 Concentrated Animal Feeding Operations 

Study Sponsora Medium Pollutant(s) Impact 

Bullers, Susan. “Environmental Stressors, 

Perceived Control, and Health: The Case of 

Residents Near Large-Scale Hog Farms in 

Eastern North Carolina.” Human Ecology. Vol. 

33, no. 1 (2005): 1-16. 

University of North 

Carolina Wilmington 

Air/Water N/A Residents living near largescale hog farms in eastern 

North Carolina report 

symptoms related to 

respiratory and sinus 

problems and nausea. 

Chénard, Liliane, Ambikaipakan Senthilselvan, 

Vaneeta K. Grover, Shelley P. Kirychuk, 

Joshua A. Lawson, Thomas S. Hurst, and 

James A. Dosman. “Lung Function and Farm 

Size Predict Healthy Worker Effect in Swine 

Farmers.” Chest. Vol. 131, no. 1 (2007): 245-

254. 

Institute of Agriculture 

Rural and Environmental 

Health, University of 

Saskatchewan (Canada), 

University of Alberta 

(Canada), Canadian 

Institute of Health 

Research 

Air N/A Some swine workers are 

less affected by swine air 

and continue in the 

profession. Other workers 

are more affected. 

Chrischilles, Elizabeth, Richard Ahrens, 

Angela Kuehl, Kevin Kelly, Peter Thorne, Leon 

Burmeister, and James Merchant. “Asthma 

Prevalence and Morbidity Among Rural Iowa 

Schoolchildren.” Journal of Allergy and 

Clinical Immunology. Vol. 113, no. 1 (2004): 

66-71. 

University of Iowa, EPA Air N/A Among children who 

wheeze, farm and nonfarm 

children were equally likely 

to have been given a 

diagnosis of asthma and had 

comparable morbidity. 

Dosman, J.A., J.A. Lawson, S.P. Kirychuk, Y. 

Cormier, J. Biem, and N. Koehncke. 

“Occupational Asthma in Newly Employed 

Workers in Intensive Swine Confinement 

Facilities.” European Respiratory Journal. Vol. 

24, no. 6 (2004): 698–702. 

Institute of Agricultural 

Rural and Environmental 

Health, University of 

Saskatchewan (Canada), 

Laval University 

(Canada) 

Air N/A Newly employed workers in 

intensive swine confinement 

facilities reported 

development of acute onset 

of wheezing and cough 

suggestive of asthma. 

Merchant, James A., Allison L. Naleway, Erik 

R. Svendsen, Kevin M. Kelly, Leon F. 

Burmeister, Ann M. Stromquist, Craig D. 

Taylor, Peter S. Thorne, Stephen J. Reynolds, 

Wayne T. Sanderson, and Elizabeth A. 

Chrischilles. “Asthma and Farm Exposures in a 

Cohort of Rural lowa Children.” Environmental 

Health Perspectives. Vol. 113, No. 3 (2005): 

350-356. 

University of Iowa, EPA, 

Colorado State 

University, Kaiser 

Permanente 

Air N/A There was a high prevalence 

of asthma health outcome 

among farm children living 

on farms that raise swine 

and raise swine and add 

antibiotics. 

Mirabelli, Maria C., Steve Wing, Stephen W. 

Marshall, and Timothy C. Wilcosky. “Asthma 

Symptoms Among Adolescents Who Attend 

Public Schools That Are Located Near 

Confined Swine Feeding Operations.” 

Pediatrics. Vol. 118, no. 1 (2006): 66-75. 

University of North 

Carolina, RTI 

International 

Air N/A Estimated exposure to 

airborne pollution from 

confined swine feeding 

operations is associated with 

adolescents’ wheezing 

symptoms. 

Palmberg, Lena, Britt-Marie Larsson, Per 

Malmberg, and Kjell Larsson. “Airway 

Responses of Healthy Farmers and 

Nonfarmers to Exposure in a Swine 

Confinement Building.” Scandinavian Journal 

of Work, Environment, and Health. Vol. 28, no. 

4 (2002): 256-263. 

National Institute of 

Environmental Medicine 

(Sweden), National 

Institute for Working Life 

(Sweden) 

Air N/A Altered lung function and 

bronchial responsiveness 

was found in nonfarming 

subjects. Only minor 

alterations were found in the 

farmers. 
Appendix IV: Government-Sponsored or PeerReviewed Studies Completed Since 2002 on 

the Impacts of Pollutants from Animal Waste 

Page 70 GAO-08-944 Concentrated Animal Feeding Operations 

Study Sponsora Medium Pollutant(s) Impact 

Radon, Katja, Anja Schulze, Vera Ehrenstein, 

Rob T. van Strien, Georg Praml, and Dennis 

Nowak. “Environmental Exposure to Confined 

Animal Feeding Operations and Respiratory 

Health of Neighboring Residents.” 

Epidemiology. Vol. 18, no. 3 (2007): 300-308. 

Institute for Occupational 

and Environmental 

Medicine (Germany), 

National Research 

Centre for Environment 

and Health (Germany), 

Boston University, 

Municipal Health Service 

Amersterdam 

Air N/A Respiratory disease was 

found among resident living 

near confined animal feeding 

operations. 

Sigurdarson, Sigurdur T. and Joel N. Kline. 

“School Proximity to Concentrated Animal 

Feeding Operations and Prevalence of Asthma 

in Students.” Chest. Vol. 129, no. 6 

(2006):1,486–1,491. 

University of Iowa Carver 

College of Medicine, 

University of Iceland 

Air N/A Children in the study school, 

located one-half mile from a 

CAFO, had a significantly 

increased prevalence of 

physician-diagnosed 

asthma. 

Studies measuring pollutants 

Anderson, M.E. and M.D. Sobsey. “Detection 

And Occurrence of Antimicrobially Resistant E. 

Coli In Groundwater on or Near Swine Farms 

In Eastern North Carolina.” Water Science & 

Technology. Vol. 54, no. 3 (2006): 211-218. 

University of North 

Carolina 

Water Antibiotics Antibiotic-resistant E. coli 

strains are present in 

groundwaters of swine 

farms. 

Batt, Angela L., Daniel D. Snow, and Diana S. 

Aga. “Occurrence of Sulfonamide 

Antimicrobials in Private Water Wells in 

Washington Country, Idaho, USA.” 

Chemosphere. Vol. 64, issue 11 (2006): 1,963-

1,971. 

State University of New 

York at Buffalo, 

University of Nebraska 

Water Antimicrobials, 

nitrate, 

ammonium 

All six sampled wells were 

contaminated by veterinary 

antimicrobials and had 

elevated concentrations of 

nitrate and ammonium. 

Three wells had nitrate 

levels exceeding EPA 

thresholds. 

Campagnolo, Enzo R., Kammy R. Johnson, 

Adam Karpati, Carol S. Rubin, Dana W. 

Kolpin, Michael T. Meyer, J. Emilio Esteban, 

Russell W. Currier, Kathleen Smith, Kendall M. 

Thu, and Michael McGeehin. “Antimicrobial 

Residues in Animal Waste and Water 

Resources Proximal to Large-Scale Swine and 

Poultry Feeding Operations.” The Science of 

the Total Environment. Vol. 299, no. 1 (2002): 

89-95. 

CDC, U.S. Geological 

Survey, Iowa Department 

of Public Health, Ohio 

Department of Health, 

University of Iowa 

Water Antimicrobials Multiple classes of 

antimicrobial compounds 

were detected in surface and 

groundwater samples 

collected proximal to the 

swine and poultry farms. 

Durhan, Elizabeth J., Christy S. Lambright, 

Elizabeth A. Makynen, James Lazorchak, 

Phillip C. Hartig, Vickie S. Wilson, L. Earl Gray, 

and Gerald T. Ankley. “Identification of 

Metabolites of Trenbolone Acetate in 

Androgenic Runoff from a Beef Feedlot.” 

Environmental Health Perspectives. Vol. 114, 

supp. 1 (2006):65–68. 

EPA Water Hormones Whole-water samples from 

the discharge contained 

detectible concentrations of 

hormones. 
Appendix IV: Government-Sponsored or PeerReviewed Studies Completed Since 2002 on 

the Impacts of Pollutants from Animal Waste 

Page 71 GAO-08-944 Concentrated Animal Feeding Operations 

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Gessel, Peter D., Neil C. Hansen, Sagar M. 

Goyal, Lee J. Johnston, and Judy Webb. 

“Persistence Of Zoonotic Pathogens in Surface 

Soil Treated With Different Rates of Liquid Pig 

Manure.” Applied Soil Ecology. Vol. 25, issue 

23 (2004): 237-243. 

University of Minnesota Water Pathogens Manure application rate was 

correlated positively with the 

persistence of fecal 

indicators but did not relate 

to survival of indicators with 

short survival times. 

Haggard, Brian E. , Paul B. DeLaune, Douglas 

R. Smith, and Philip A. Moore, Jr. “Nutrient and 

B17-Estradiol Loss in Runoff Water From 

Poultry Litters.” Journal of the American Water 

Resources Association. Vol. 41, no. 2 

(2005):245-256. 

USDA, University of 

Arkansas 

Water Nutrients, 

hormones 

In general, poultry litter 

applications increased 

nutrient and hormone 

concentrations in runoff 

water. 

Hutchins, Stephen R., Mark V. White, Felisa 

M. Hudson, and Dennis D. Fine. “Analysis of 

Lagoon Samples from Different Concentrated 

Animal Feeding Operations for Estrogens and 

Estrogen Conjugates.” Environmental Science 

& Technology. Vol. 41, no. 3 (2007): 738-744. 

EPA, Shaw 

Environmental and 

Infrastructure 

Water Hormones Estrogen conjugates 

contribute significantly to the 

overall estrogen load, even 

in different types of CAFO 

lagoons. 

Koike, S., I.G. Krapac, H.D. Oliver, A.C. 

Yannarell, J.C. Chee-Sanford, R.I. Aminov, 

and R.I. Makie. “Monitoring and Source 

Tracking of Tetracycline Resistance Genes in 

Lagoons and Groundwater Adjacent to Swine 

Production Facilities over a 3-Year Period.” 

Applied and Environmental Microbiology. Vol. 

73, no. 15 (2007): 4,813-4,823. 

University of Illinois, 

USDA, Illinois State 

Geological Survey, 

Rowett Research 

Institute (UK) 

Water Antibiotics Antibiotic resistance genes 

in groundwater are affected 

by swine manure and also 

part of the indigenous gene 

pool. 

Miller, David H. and Gerald T. Ankley. 

“Modeling Impacts On Populations: Fathead 

Minnow (Pimephales Promelas) Exposure to 

the Endocrine Disruptor 17ß-Trenbolone as a 

Case Study.” Ecotoxicology and Environmental 

Safety. Vol. 59, issue 1 (2004): 1-9. 

EPA Water Hormones Model shows that if fathead 

minnow is exposed to 

continuous concentrations of 

hormone, there will be a risk 

of extinction. 

Nelson, Nathan O., John E. Parsons, and 

Robert L. Mikkelsen. “Field-Scale Evaluation of 

Phosphorus Leaching in Acid Sandy Soils 

Receiving Swine Waste.” Journal of 

Environmental Quality. Vol. 34, no. 6 (2005): 

2,024-2,035. 

USDA, North Carolina 

State University 

Water Phosphorus The results show that 

substantial quantities of 

phosphorus can be leached 

through soils with low 

phosphorus sorption 

capacities. 

Peak, Nicholas, Knapp, Charles W, Richard K. 

Yang, Margery M. Hanfelt, Marilyn S. Smith, 

Diana S. Aga, and David W. Graham. 

“Abundance of Six Tetracycline Resistance 

Genes in Wastewater Lagoons at Cattle 

Feedlots With Different Antibiotic Use 

Strategies.” Environmental Microbiology. Vol. 

9, no. 1 (2007): 143-151. 

University of Kansas, 

Kansas State University, 

State University of New 

York at Buffalo 

Water Antibiotic 

resistant 

genes 

CAFOs using larger 

amounts of antibiotics had 

significantly higher detected 

resistance gene levels. 
Appendix IV: Government-Sponsored or PeerReviewed Studies Completed Since 2002 on 

the Impacts of Pollutants from Animal Waste 

Page 72 GAO-08-944 Concentrated Animal Feeding Operations 

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Sapkota, Amy R., Frank C. Curriero, Kristen E. 

Gibson, and Kellogg J. Schwab. “AntibioticResistant Enterococci and Fecal Indicators in 

Surface Water and Groundwater Impacted by 

a Concentrated Swine Feeding Operation.” 

Environmental Health Perspectives. Vol. 115, 

no. 7 (2007):1,040–1,045. 

Johns Hopkins 

Bloomberg School of 

Public Health; University 

of Maryland 

Water Antibiotic 

resistant 

bacteria, fecal 

indicators 

Detected elevated levels of 

fecal indicators and 

antibiotic-resistant bacteria 

in water sources down 

gradient from a swine 

facility. 

Soto, Ana M., Janine M. Calabro, Nancy V. 

Prechtl, Alice Y. Yau, Edward F. Orlando, 

Andreas Daxenberger, Alan S. Kolok, Louis J. 

Guillette, Jr., Bruno le Bizec, Iris G. Lange, and 

Carlos Sonnenschein. “Androgenic and 

Estrogenic Activity in Water Bodies Receiving 

Cattle Feedlot Effluent in Eastern Nebraska, 

USA.” Environmental Health Perspectives. Vol. 

112, no. 3 (2004):346–352. 

Tufts University; 

Southwest Research 

Institute; St. Mary’s 

College of Maryland; 

Universität MünchenWeihenstephan, 

Germany; University of 

Nebraska; University of 

Florida; Ecole Nationale 

Vétérinaire de Nantes, 

France 

Water Hormones Feedlot effluents contain 

sufficient levels of 

hormonally active agents to 

warrant further investigation 

of possible effects on 

aquatic ecosystem health. 

Thorsten, Christiana, Rudolf J. Schneider, 

Harald A. Farber, Dirk Skutlarek, Michael T. 

Meyer, and Heiner E. Goldbach. 

“Determination of Antibiotic Residues in 

Manure, Soil, and Surface Waters.” Acta 

hydrochimica et hydrobiologica. Vol. 31, no. 1 

(2003):36–44. 

University of Bonn, 

Germany; U.S. 

Geological Survey 

Water Antibiotics In each of the surface waters 

tested antibiotics could be 

detected. 

Thurston-Enriquez, Jeanette A., John E. Gilley, 

and Bahman Eghball. “Microbial Quality of 

Runoff Following Land Application of Cattle 

Manure And Swine Slurry.” Journal of Water 

and Health. vol. 3, no. 2 (2005): 157-171. 

University of Nebraska Water Microbials Large microbial loads could 

be released via heavy 

precipitation events and 

could have a significant 

impact on water bodies. 

Toetz, Dale. “Nitrate in Ground and Surface 

Waters in the Vicinity of a Concentrated 

Animal Feeding Operation.” Archives of 

Hydrobiology. Vol. 166, no. 1 (2006): 67-77. 

Oklahoma State 

University 

Water Nitrogen Drinking water was 

contaminated with CAFOs 

as the suspected source. 

U.S. Department of Interior. U.S. Geological 

Survey. In cooperation with U.S. 

Environmental Protection Agency, National 

Exposure Research Laboratory. Geochemistry 

and Characteristics of Nitrogen Transport at a 

Confined Animal Feeding Operations in a 

Coastal Plain Agricultural Watershed, and 

Implications for Nutrient Loading in the Neuse 

River Basin, North Carolina, 1999-2002. 

Scientific Investigations Report 2004-5283, 

Reston, Va.: (2004). 

U.S. Geological Survey, 

EPA 

Water Nitrogen Large amounts of nitrogen 

moving in the estuary as a 

result of extreme events may 

potentially cause algal 

growths. 
Appendix IV: Government-Sponsored or PeerReviewed Studies Completed Since 2002 on 

the Impacts of Pollutants from Animal Waste 

Page 73 GAO-08-944 Concentrated Animal Feeding Operations 

Study Sponsora Medium Pollutant(s) Impact 

United State Geological Survey in cooperation 

with Virginia Department of Health. WaterQuality Data from Ground- and Surface-Water 

Sites near Concentrated Animal Feeding 

Operations (CAFOs) and non-CAFOs in the 

Shenandoah Valley and Eastern Shore of 

Virginia, January-February, 2004. Reston, Va 

(2005). 

United State Geological 

Survey in cooperation 

with Virginia Department 

of Health 

Water Bacteria, 

antibiotics, 

trace metals, 

biological 

oxygen 

demand, 

nitrogen 

N/A 

United States Geological Survey. Fractionation 

and Characterization of Organic Matter in 

Wastewater from a Swine Waste-Retention 

Basin. Scientific Investigations Report 2004-

5217 (2004). 

United States Geological 

Survey 

Water Organic 

matter 

The bulk of the organic 

matter consists of microbial 

cellular constituents and 

their degradation products. 

Chapin, Amy, Ana Rule, Kristen Gibson, 

Timothy Buckley, and Kellogg Schwab. 

“Airborne Multidrug-Resistant Bacteria Isolated 

from a Concentrated Swine Feeding 

Operation.” Environmental Health 

Perspectives. Vol. 113, no. 2 (2005):137-142. 

Johns Hopkins University Air Antibiotic 

resistant 

bacterial 

pathogens 

Multidrug-resistant bacterial 

pathogens were detected in 

the air of a swine CAFO. 

Donham, Kelley. J., Joung Ae Lee, Kendall 

Thu, and Stephen J. Reynolds. “Assessment 

of Air Quality at Neighbor Residences in the 

Vicinity Of Swine Production Facilities.” 

Journal of Agromedicine. Vol. 11, no. 3-4 

(2006): 15-24. 

University of Iowa, 

Northern Illinois 

University, and Colorado 

State University 

Air Hydrogen 

sulfide, 

ammonia, 

carbon 

dioxide, 

particulate 

matter 

Average concentration of 

hydrogen sulfide exceeded 

EPA recommended 

community standards in all 

three areas assessed. 

Gibbs, Shawn G., Christopher F. Green, 

Patrick M. Tarwater, Linda C. Mota, Kristina D. 

Mena, and Pasquale V. Scarpino. “Isolation of 

Antibiotic-Resistant Bacteria from the Air 

Plume Downwind of a Swine Confined or 

Concentrated Animal Feeding Operation.” 

Environmental Health Perspectives. Vol. 114, 

no. 7 (2006):1,032–1,037. 

University of Texas, 

University of Cincinnati 

Air Antibioticresistant 

bacteria 

Bacterial concentrations with 

multiple antibiotic 

resistances or multidrug 

resistance were recovered 

inside and outside to 150 m 

downwind of a facility, even 

after antibiotic use was 

discontinued. 

Harper, Lowry A., Ron R. Sharpe, Tim B. 

Parkin, Alex De Visscher, Oswald van 

Cleemput, and F. Michael Byers. “Nitrogen 

Cycling through Swine Production Systems: 

Ammonia, Dinitrogen, and Nitrous Oxide 

Emissions.” Journal of Environmental Quality. 

Vol. 33, no. 4 (2004): 1,189-1,201. 

USDA, Ghent University 

(Belgium) 

Air Nitrogen In contrast with previous and 

current estimates of 

ammonia emissions from 

CAFOs, this study found 

smaller ammonia emissions 

from animal housing, 

lagoons, and fields. 

Hamscher, Gerd, Heike Theresia Pawelzick, 

Silke Sczesny, Heinz Nau, and Jörg Hartung. 

“Antibiotics in Dust Originating from a PigFattening Farm: A New Source of Health 

Hazard for Farmers?” Environmental Health 

Perspectives. Vol. 111, no. 13 (2003):1,590–

1,594. 

School of Veterinary 

Medicine Hannover, 

Germany 

Air Antibiotics Five different antibiotics 

were detected in dust 

samples swine feeding 

operation. 
Appendix IV: Government-Sponsored or PeerReviewed Studies Completed Since 2002 on 

the Impacts of Pollutants from Animal Waste 

Page 74 GAO-08-944 Concentrated Animal Feeding Operations 

Study Sponsora Medium Pollutant(s) Impact 

Hoff, Steven J., Dwaine S. Bundy, Minda A. 

Nelson, Brian C. Zelle, Larry D. Jacobson, 

Albert J. Heber, Jinqin Ni, Yuanhui Zhang, 

Jacek A. Koziel, and David B. Beasley. 

“Emissions of Ammonia, Hydrogen Sulfide, 

and Odor before, during, and after Slurry 

Removal from a Deep-Pit Swine Finisher.” 

Journal of the Air & Waste Management 

Association. Vol. 56, no. 5 (2006): 581-590. 

Iowa State University, 

University of Minnesota, 

Purdue University, 

University of Illinois, 

North Carolina State 

University 

Air Ammonia, 

hydrogen 

sulfide, odor 

Emissions of ammonia, 

hydrogen sulfide, and odor 

had large increases during 

slurry removal. A slurry 

removal even will result in 

acute exposure for animals 

and workers. 

O’Connor, Rod, Mark O’Connor, Kurt Irgolic, 

Justin Sabrsula, Hakan Gurleyuk, Robert 

Brunette, Crystal Howard, Jennifer Garcia, 

John Brien, June Brien, and Jessica Brien. 

“Transformations, Air Transport, and Human 

Impact of Arsenic from Poultry Litter.” 

Environmental Forensics. Vol. 6, no. 1 (2005): 

83-89. 

Chenard Consulting 

Services, Karl-Franzeas 

University (Austria), 

University of North 

Carolina, Frontier 

Geosciences, Aqua-Tech 

Laboratories 

Air Arsenic Levels of arsenic found in 

homes. This could represent 

a significant health risk. 

Radon, Katja, Brigitta Danuser, Martin Iversen, 

Eduard Monso, Christoph Weber, Jorg 

Hartung, Kelley J. Donham, Urban Palmgren, 

and Dennis Nowak. “Air Contaminants in 

Different European Farming Environments.” 

Annals of Agriculture and Environmental 

Medicine. Vol. 9, no. 1 (2002): 41-48. 

Ludwig-MaximiliansUniversity (Germany), 

Swiss Federal Institute of 

Technology, Aarhus 

University Hospital 

(Denmark), Hospital 

Germans Trial I Pujol 

(Spain), School of 

Veterinary Medicine 

(Germany), University of 

Iowa, Pegasus Labor 

GmbH (Germany) 

Air Dust, 

endotoxin, 

fungi 

The exposure level found in 

this study might put the 

farmers at risk from 

respiratory diseases. 

Razote, E.B., R.G. Maghirang, B.Z. Predicala, 

J.P. Murphy, B.W. Auvermann, J.P. Harner III, 

and W.L. Hargrove. “Laboratory Evaluation of 

the Dust-Emission Potential of Cattle Feedlot 

Surfaces.” Transactions of the ASABE. Vol. 

49, no. 4 (2006): 1,117-1,124. 

Kansas State University, 

Prairie Swine Center, Inc. 

(Canada), Texas A&M 

University 

Air Particulate 

Matter 

N/A 

Robarge, Wayne P., John T. Walker, Ronald 

B. McCulloch, and George Murray. 

“Atmospheric Concentrations of Ammonia and 

Ammonium at an Agricultural Site in the 

Southeast United States.” Atmospheric 

Environment. Vol. 36, no. 10 (2002): 1,661-

1,674. 

North Carolina State 

University, EPA, URS 

Corporation, North 

Carolina Department of 

Environmental and 

Natural Resources 

Air Ammonia Elevated ambient ammonia 

concentrations near an 

agricultural site. 

United State Environmental Protection Agency. 

National Emission Inventory – Ammonia 

Emissions from Animal Husbandry Operations, 

Draft Report. Washington, D.C. (2004). 

EPA Air Ammonia N/A 
Appendix IV: Government-Sponsored or PeerReviewed Studies Completed Since 2002 on 

the Impacts of Pollutants from Animal Waste 

Page 75 GAO-08-944 Concentrated Animal Feeding Operations 

Study Sponsora Medium Pollutant(s) Impact 

Walker, J.T., W.P. Robarge, Y. Wu, and T.P. 

Meyers. “Measurement of Bi-Directional 

Ammonia Fluxes Over Soybean Using 

Themodified Bowen-Ratio Technique.” 

Agricultural and Forest Meteorology. Vol. 138, 

no. 1-4 (2006): 54-68. 

EPA, North Carolina 

State University, NASA, 

NOAA 

Air Ammonia In general, the net 

deposition flux was lower 

than expected. 

Walker, John T., Wayne P. Robarge, Arun 

Shendrikar, and Hoke Kimball. “Inorganic 

Pm2.5 at a U.S. Agricultural Site.” 

Environmental Pollution. Vol. 139, no. 2 

(2006): 258-271. 

EPA, North Carolina 

State University, North 

Carolina Department of 

Environment and Natural 

Resources 

Air Particulate 

matter 

Model results show that 

reductions in atmospheric 

ammonia will have minimal 

effect on organic PM2.5 

during summer and a 

moderate effect during 

winter. 

Walker, J.T., Dave R. Whitall, Wayne P. 

Robarge, and Hans W. Pearl. “Ambient 

Ammonia and Ammonium Aerosol Across a 

Region of Variable Ammonia Emission 

Density.” Atmospheric Environment. Vol. 38, 

no. 9 (2004): 1,235-1,246. 

EPA, NOAA, North 

Carolina State University, 

University of North 

Carolina 

Air Ammonia, 

ammonium 

Agricultural ammonia 

emissions influence local 

ambient concentrations of 

ammonia and PM2.5. 

Wilson, Sacoby M. and Marc L. Serre. 

“Examination of Atmospheric Ammonia Levels 

Near Hog Cafos, Homes, and Schools In 

Eastern North Carolina.” Atmospheric 

Environment. Vol. 41, issue 23 (2007): 4,977–

4,987. 

University of Michigan, 

Ann Arbor; University of 

North Carolina at Chapel 

Hill 

Air Ammonia Distance to one or more 

CAFOs is the key variable in 

controlling atmospheric 

ammonia at the community 

level in Eastern N.C. 

Muller-Suur, C., P.H. Larsson, K. Larsson, J. 

Grunewald. “Lymphocyte Activation After 

Exposure to Swine Dust: A Role Of Humoral 

Mediators and Phagocytic Cells.” European 

Respiratory Journal. Vol. 19, issue 1 (2002): 

104-107. 

 Air Dust About immune system 

response. 

Charavaryamath, Chandrashekhar, 

Kyathanahalli S Janardhan, Hugh G 

Townsend, Philip Willson, and Baljit Singh. 

“Multiple Exposures to Swine Barn Air Induce 

Lung Inflammation and Airway HyperResponsiveness.” Respiratory Research. Vol. 

6, no. 1 (2005):50-66. 

University of 

Saskatchewan, Canada 

Air Endotoxin Does not address human 

impacts. 

Eduard, Wijnand, Ernst Omenaas, Per Sigvald 

Bakke, Jeroen Douwes, and Dick Heederik. 

“Atopic and Non-atopic Asthma in a Farming 

and a General Population.” American Journal 

of Industrial Medicine. Vol. 46, issue 4 (2004): 

396-399. 

National Institute of 

Ocupational Health 

(Norway), University of 

Bergen (Norway), 

University of Wellington 

(New Zealand) 

Air N/A Protective effect of the farm 

environment on asthma. 

Source: GAO’s analysis of identified studies. 

a

Sponsor refers to the organization under whose auspices the research was conducted or with whom 

the primary researchers were affiliated. 
Appendix V: Comments from the 

Environmental Protection Agency 

Page 76 GAO-08-944 Concentrated Animal Feeding Operations 

Appendix V: Comments from the 

Environmental Protection Agency 
Appendix V: Comments from the 

Environmental Protection Agency 

Page 77 GAO-08-944 Concentrated Animal Feeding Operations 
Appendix V: Comments from the 

Environmental Protection Agency 

Page 78 GAO-08-944 Concentrated Animal Feeding Operations 
Appendix VI: GAO Contact and Staff 

Acknowledgments 

Page 79 GAO-08-944 Concentrated Animal Feeding Operations 

Anu Mittal (202) 512-3841 or mittala@gao.gov

In addition to the individual named above, Sherry L. McDonald, Assistant 

Director; Kevin Bray; Yecenia C. Camarillo; Wendy Dye; Paul Hobart; 

Cathy Hurley; Holly L. Sasso; James W. Turkett; and Greg Wilmoth made 

key contributions to this report. Also contributing to this report were 

Elizabeth Beardsley, Ben N. Shouse, and Carol Herrnstadt Shulman. 

Appendix VI: GAO Contact and Staff 

Acknowledgments 

GAO Contact 

Staff 

Acknowledgments 

(360682) 
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