HOG FARMS AND YOUR HEALTH

Neighbors of Vast Hog Farms Say Foul Air Endangers Their Health


By JENNIFER 8. LEE

Published: May 11, 2003

Robert Thornell says that five years ago an invisible swirling poison invaded his family farm and the house he had built with his hands. It robbed him of his memory, his balance and his ability to work. It left him with mood swings, a stutter and fistfuls of pills. He went from doctor to doctor, unable to understand what was happening to him.

The 14th doctor finally said he knew the source of the maladies: cesspools the size of football fields belonging to the industrial hog farm a half-mile from the Thornell home.

''I never related it to the hogs at all,'' said Mr. Thornell, who is now 55.

A growing number of scientists and public health officials around the country say they have traced a variety of health problems faced by neighbors of huge industrial farms to vast amounts of concentrated animal waste, which emit toxic gases while collecting in open-air cesspools or evaporating through sprays. The gases, hydrogen sulfide and ammonia, are poisonous.

The waste is collected in pools because the concentration of hogs is so high that it must be treated before it can be used as fertilizer.

Livestock trade officials and Bush administration regulators say more study is needed before any cause and effect can be proved. But Dr. Kaye H. Kilburn, a professor at the University of Southern California who studies the effects of toxic chemicals on the brain, said evidence strongly supported a link between the farms and the illnesses.

In Iowa, one of the country's two biggest pork-producing states (North Carolina is the other), state environment officials started conducting air quality tests for hydrogen sulfide and ammonia at six neighborhood locations around hog farms last month. Brian Button, an air information specialist with the state, said preliminary data showed that 22 times in April, the gases exceeded the state's recommended air standards of 15 parts per billion of hydrogen sulfide and 150 parts per billion of ammonia, averaged over an hour. The highest level recorded for hydrogen sulfide was 70 parts per billion, a level that would have exceeded the air standards for at least six other states.

Dr. Kilburn, who runs a business diagnosing neurological disorders, said that over the last three years he had seen about 50 patients, including Mr. Thornell and his wife, Diane, who had suffered neurological damage he judged to be a result of hydrogen sulfide poisoning from industrial farms. The Thornells are considering a lawsuit based on his work.

''The coincidence of people showing a pattern of impairment and being exposed to hydrogen sulfide arising from lagoons where hog manure is stored and then sprayed on fields or sprayed into the air'' makes a connection ''practically undeniable,'' Dr. Kilburn said in an interview.

Industrial farms often house thousands, if not tens of thousands, of hogs, which generate millions of gallons of waste each year. Runoff and water pollution have been the focus of many of the government and academic studies of such farms' environmental impact.

In comparison, little has been done by federal or state environmental officials to monitor or limit air pollution from these farms. The Agriculture Department and the Environmental Protection Agency have formed a joint committee to look at farm air pollution.

Around industrial hog farms across the country, people say their sickness rolls in with the wind. It brings headaches that do not go away and trips to the emergency room for children whose lungs suddenly close up. People young and old have become familiar with inhalers, nebulizers and oxygen tanks. They complain of diarrhea, nosebleeds, earaches and lung burns.

Paul Isbell of Houston, Miss., started experiencing seizures after a hog farm moved in down the road. Jeremiah Burns of Hubbardston, Mich., now carries a six-pound oxygen tank with him. Kevin Pearson of Meservey, Iowa, carried a towel in his car because he vomited five or six times a week on his way to work. Julie Jansen's six children suffered flulike symptoms and diarrhea when farms moved into their neighborhood in Renville, Minn. One of Ms. Jansen's daughters was found by Dr. Kilburn to have neurological damage. She has problems with balance and has lost some feeling in her fingers.

Public health officials have been cautious in drawing a clear link from hydrogen sulfide to neurological damage, though they say low-level exposure has been connected to fatigue, loss of appetite, headaches, poor memory, dizziness and other health problems.

''In community exposures, when they are exposed to a mixture of chemicals -- hydrogen sulfide included -- there have been neurological effects reported as well,'' said Selene Chou, who manages the hydrogen sulfide toxicological profile for the Agency for Toxic Substances and Disease Registry, a sister agency of the Centers for Disease Control and Prevention.

''Based on what I see, there could be neurological effects, but we don't know at what low level of chronic exposure,'' Ms. Chou said. ''That information is badly needed, because communities have experienced these effects.''

The agricultural industry, backed by some government officials, contends that these health effects are at best poorly documented. They say that scientific studies have relied too much on the testimony of the people with medical problems, and that there is no way to prove that those problems are directly attributable to the farms.

''The health concern issues raised by the residents are totally unfounded,'' said Ron Prestage, an owner of Prestage Farms, the target of two suits filed by Mississippi residents. ''There has never been a neighbor of a farm who has come forward with any documentation of a health problem of any kind.''

Ohio pork producers agree.

''I do not think there is any way that it can be proven that that hog farm, which is a half-mile away, has any effect,'' said Dick Isler, the executive vice president of the Ohio Pork Producers Council, who said he knew about Mr. Thornell's case. Mr. Isler said studies showed that ''any time you are more than a hundred feet away it is not a problem.''

Residents say they do not have difficulty proving that they are ill -- their medications and oxygen tanks demonstrate that. They acknowledge that for many symptoms, the link to the farms is circumstantial. But in the most extreme cases, they say the evidence of a link is clear.

Bush administration officials are negotiating with lobbyists for the large farms to establish voluntary monitoring of air pollution, which will give farm operators amnesty for any Clean Air Act violations while generating data that will enable regulators to track the type and source of pollutants more accurately.

''We are negotiating with industry to work on capturing better information as to what emissions factors are in play,'' said J. P. Suarez, who is in charge of enforcement for the environmental agency.

Growing layers of lawsuits, government reports and regulatory tussles on the state and federal levels are signs of increasing tensions. Some 1,800 residents of Mississippi have filed class-action lawsuits against factory farms, and the state health agency has put a moratorium on new ones. In response to citizen complaints, a few states, including Texas and Minnesota, have set pollution standards aimed at the farms. Iowa's state environmental agency recently announced that it would institute new pollution regulations affecting the farms. But the state legislature, under industry pressure, nullified those regulations last week, saying they were overreaching.

State and federal efforts to regulate the water pollution from factory farms may actually cause the farms to divert chemicals into the air, the National Academy of Sciences says. Farms have adopted the practice of spraying liquid manure into the air when cesspool levels get too high, a practice that creates mists that are easily carried by the wind.

When Mr. Thornell first became ill, he said, he thought he had suffered a nervous breakdown. Unable to go back to work as a schoolteacher, he retired on disability at 53. For two years, he had no idea what was happening. Then he learned about Dr. Kilburn's research while watching television. He sent an e-mail message to Dr. Kilburn, who told him to come to Pasadena for a diagnosis.

The Thornells, who had never been to California, drove all the way, with a stop at the Grand Canyon. The diagnosis for both Mr. Thornell and his wife was irreversible brain injuries from the hydrogen sulfide gas.

Mrs. Thornell said her husband had lost his energetic smile. Now he speaks slowly and often loses his train of thought. He does not drive far from the house by himself, because he often gets lost.

''It's like I have a 2.1 gigahertz body with a 75 megahertz mind,'' Mr. Thornell said. ''I feel like collateral damage.''

Mrs. Thornell added, ''It's the price we pay for cheap food.''

Over the last 20 years, the industrialization of agriculture, especially the emergence of large-scale livestock farms, has raised concerns about pollution in rural areas.

''It is no longer the mom-and-pop operation it used to be,'' said Viney Aneja, a professor of marine, earth and atmospheric sciences at North Carolina State University who has studied factory farms' air pollution. ''This is a factory. Treat it as one. It should be under the same constraints as a chemical operation.''

Some former government employees said industry pressure had limited their ability to study and combat the problem.

Former Environmental Protection Agency prosecutors said they started looking at air pollution from factory farms in 1998, but political appointees issued a directive in early 2002 that effectively stymied new cases. ''You had decisions about enforcement that were being made on the political level without any input from the enforcement,'' said Michele Merkel, a prosecutor who resigned from the agency in protest.

Eric Schaeffer, the former director of civil enforcement at the environmental agency, said Agriculture Department officials tried to exert influence to protect the industrial farms. ''They essentially wanted veto power,'' he said.

Lisa Harrison, a spokeswoman for the environmental agency, said, ''Given the sensitivity of air emissions issues, headquarters is directly involved in the decision-making process.'' She said enforcement decisions were made within the agency, and enforcement was continuing.

At the Agriculture Department, officials have reclassified research topics relating to industrial farms and health, including antibiotic-resistant pathogens, as ''sensitive.'' As a result, at least one scientist, James Zahn, has left the department. ''It was a choke hold on objective research,'' said Dr. Zahn, who had studied swine and bacteria until he left last fall. ''Originally we were praised for the work we were doing. All of a sudden we were told, no more antibiotic resistance work.''

Internal department e-mail messages made available by the Natural Resources News Service show that Dr. Zahn's superiors barred him from presenting research at a conference in Iowa in 2002. A message from a supervisor advised Dr. Zahn that ''politically sensitive and controversial issues require discretion.''

Julie Quick, an Agriculture Department spokeswoman, said that Dr. Zahn was discouraged from speaking about his research because he is not an expert on how the compounds in swine manure affect human health.

Disputes within regulatory agencies seem distant concerns to the Thornells, who have been advised by Dr. Kilburn to move out of their home. Their neurological damage is irreversible, but they can prevent it from getting worse, he told them.

''If I could sell the house, I would move in a second, but I don't know where to go,'' Mr. Thornell said. ''I've lived here for 44 years. This is home to me.''







HOG FARM CONTAMINATION INFORMATION

WITH ADDITIONAL LINKS TO ARTICLES ON BOTTOM

Industrial farms pollute the air in many ways, emitting foul odors, dust and other small airborne particles, greenhouse gases, and numerous toxic chemicals. In the United States, these farms are among the leading producers of noxious substances such as nitrous oxidei and ammonia. Air pollution from industrial farms can cause health problems in agricultural workers, in neighboring communities and even for farm animals, and also results in significant environmental damage. Although there are a variety of techniques to reduce or minimize the impact of air pollution, many large farms still do little or nothing to prevent it.
Farm operations in the United States produce more than 400 different gases.iii In addition to gases, the other airborne particulates they create—such as dust and organic matter known as endotoxinsiv— can have damaging effects on air quality for both the farm and surrounding areas. These gases and particulates are generated during the handling and disposal of byproducts such as manure, the production and use of animal feeds, and also in the shipping and distribution of products.
Mountains of Manure
The USDA estimates that more than 335 million tons of manure are produced annually on farms in the United States.v This manure is generally stored for long periods of time in giant tanks or lagoons, where it decomposes and gives off hundreds of gases.vi Manure lagoons and tanks are often located directly next to animal confinement facilities, so harmful gases are continuously present in animal living quarters.vii They also pollute the outdoor air when stored gases are vented out of barns or manure slurry is sprayed onto fields as fertilizer.
Hydrogen sulfide, methane, ammonia, and carbon dioxide are the four main hazardous gases produced by decomposing manure,viii and they all cause a range of health and environmental problems. The EPA estimates that methane emissions from manure in the United States increased by 26% between 1990 and 2004, most of which it attributes to the trend towards larger and more concentrated dairy cow and swine facilities.ix The North Carolina hog industry alone produces about 300 tons of ammonia per day.x
Air Pollution and Feed
While manure is the largest contributor to farm-generated air pollution, a number of other factory farm components, such as conventional animal feed, also increase the production of some gases. The EPA estimated that in 2004, 20% of all man-made methane production came from the digestion processes of livestock—primarily cows.xi Factory farms use low-quality feed in large amounts to fatten animals cheaply, and this practice contributes to higher methane emissions.xii
Producing crops for animal feed also contributes to farm-generated air pollution. Soil management techniques (especially the use of fertilizers) are the leading contributor to nitrous oxide emissions, accounting for 68% of all nitrous oxide released into the air in 2004.xiii
Centralized Food Production and Fossil Fuel Use
The centralized nature of American food production contributes to air pollution, as food has to be stored for days and then transported over long distances before it reaches supermarket shelves. Conventionally-produced fruits and vegetables travel over a thousand miles on average between being harvested and sold.xiv Because of this, shipping agricultural products accounted for at least 1% of all freight trucking emissions in the United States in 2002, and that does not include the amount of freight (in the form of feed, building materials, etc.) shipped to farms in order to grow the food.xv
Health Effects of Farm-related Air Pollution
Health effects can vary widely by area, due to the various kinds and amounts of pollutants produced on farms and the different ways they’re vented. Below are some of the principle air pollutants released by factory livestock facilities, and the health problems that they may cause:

Hydrogen Sulfide
Hydrogen sulfide is a gas that limits the ability of cells to use oxygen. Exposure to hydrogen sulfide in high levels can have a variety of acute affects, including skin, eye, and respiratory irritation, neurologic and cardiac problems, seizures, comas, and death. Chronic exposure at lower levels can cause low blood pressure, headache, chronic coughs, and psychological disorders.xvi Hydrogen sulfide is generally associated with hog production facilities.
Ammonia
Ammonia can cause irritation of the eyes, skin, and respiratory tract.xvii Ammonia is released in largest quantities by chicken and hog production.
Particulate matter
Particulate matter (in the form of dust blown directly off farms or produced chemically when some gases, like ammonia, are present in high concentrations) can cause a variety of health problems, especially in people who are regularly exposed to them. These problems include bronchitis and asthma, and cardiac problems such as arrhythmias and heart attacks.xviii
Endotoxins
Endotoxins are produced when the cell walls of bacteria degenerate, and are often measured in high concentrations on large farms. These air pollutants can cause respiratory problems even in extremely low concentrations.xix
Carbon dioxide
Carbon dioxide is also produced in significant amounts in the decomposition of manure. While its health effects for humans are generally limited to shortness of breath or dizziness, it often kills confined animals by asphyxiation due to insufficient ventilation of their houses.xx
Methane
Methane is an asphyxiate at extremely high concentrations, but is not particularly toxic. It is, however, highly flammable and poses a risk of explosion if manure storage facilities are poorly ventilated.xxi Methane production is most commonly associated with cows—who produce it naturally during digestion—but it is a byproduct of most manures stored in oxygen-depleted lagoons.xxii
Effects on Workers
Since most of the air pollutants produced by farms are in much higher concentrations on the farms themselves than in neighboring areas, farm workers are at particular risk. Among workers on confined animal feeding operations, as many as 70% experience acute bronchitis and 25% chronic bronchitis.xxiii Additionally, a host of other respiratory ailments in workers have been linked to working in indoor swine production facilities for 2 hours a day over the course of six years, most likely as a result of organic dust inhalation.xxiv Some of the gases produced on farms also are fatal in high concentrations, and in the US there were 12 cases where workers were killed due to asphyxiation in manure pits between 1992 and 1997.xxv
Effects on Communities
Neighboring communities are also at risk for health problems from large farms. People living near hog farms, for example, often have increased respiratory problems.xxvi A number of studies have demonstrated that fatigue, depression, and mood disturbances occur in higher proportions in communities near such facilities.xxvii A study of one town in Utah found a four-fold increase in diarrhea-related hospitalizations and a three-fold increase in respiratory-related hospitalizations over a five-year period during which an industrial hog farm was constructed and became operational.xxviii The Minnesota Pollution Control Agency has documented that hydrogen sulfide concentrations in excess of World Health Organization maximum exposure standards can be found on neighboring properties of hog facilities in that state.xxix
Environmental Effects
Air pollution from farms directly affects the environment , chiefly through the production of gaseous nitrogen and some of the greenhouse gases responsible for global warming. About 80% of U.S. ammonia emissions came from livestock manure.xxx As a report from the National Academy of Sciences explains, atmospheric ammonia and nitric oxide—both produced on farms—contribute to what is known as the “nitrogen cascade,” in which each ammonia molecule “can, in sequence, impact atmospheric visibility, soil acidity, forest productivity, terrestrial ecosystem biodiversity, stream acidity, and coastal productivity.”xxxi Particulate matter emissions contribute to haze.xxxii Through the production of greenhouse gases—primarily methane and nitrous oxide—the agricultural industry was directly responsible for 6 percent of the United States’ impact on global warming in 2004, according to the EPA.xxxiii
Remedies and Regulations
There are already a number of proven techniques that can reduce the impact and total emissions of air pollutants from farms, including better storage of manure, air-breaks positioned near farms, and increased attention to the nutritional needs of specific livestock.xxxiv Additionally, some measures as simple as allowing cows to graze on pasture (which has also been shown to be healthier than grain-feeding for both cows and humans) have the potential to reduce greenhouse gas emissions.xxxv Raising animals on pasture also reduces the need for cultivation and transportation of feed, as well as storage and spreading of manure, all of which require the use of fossil fuels and emit significant amounts of carbon dioxide and other pollutants.
However, since most methods that reduce air pollution from farms would increase maintenance costs without increasing production, factory farms don’t see it as in their interest to implement them. In addition to the financial disincentive against regulating emissions from farms, there is little regulatory incentive to promote their regulation. While most farm emissions are legally regulated under the Clean Air Act, most enforcement attention has been focused on factories and cars—both of which are far easier to measure in terms of their contribution to air pollution.xxxvi The federal government has also done relatively little to handle the problem, leaving enforcement of farm-related air pollution to individual state governments, xxxvii and generally leaving research on the topic to academics.xxxviii

There is also concern that better environmental regulation will not stop much of the air pollution from farms. Instead, tighter regulations could cause many of the largest corporate farmers to move to overseas locations. Already, some of the biggest American agricultural companies (including Perdue and Smithfield) are now producing and processing foods in Canada, Mexico, Europe, China and Brazil to reduce costs and avoid being hindered by existing environmental regulations.xil Because of this, the best way to get industrial farms to change their ways is not through tightening regulations, but with consumers’ food dollars.
What You Can Do

The problems associated with most farm emissions are primarily local and regional, and the most efficient way to reduce air pollution from farms is to reduce the size and increase the number of farms. In other words, many small farms scattered throughout the country will have less of an impact on air quality than conventional factory farms do. Sustainable livestock farms depend less on cheap feed and fuel-guzzling machinery, because natural pasture systems rely on the animal’s own energy to harvest feed and spread manure. Because of this, sustainable farming offers a viable opportunity to reduce farm-related air pollution.
As consumers, we can use our economic power to support farms that supply sustainably-produced meat, eggs and dairy products. By giving our dollars to farmers who work to minimize their impact on the environment and protect human health, we can vote with our wallets and help change the face of American agriculture, so we can all breathe easier.

Visit the Eat Well Guide for a complete listing of small, sustainable farms in your local area.
Did You Know?

The odor from swine manure contains 331 separate chemical compounds.xl
Tyson Foods recently agreed to pay an undisclosed sum in air-quality damages to three neighboring residents near one of their Kentucky operations.xl Four couples in Iowa also reached settlement in 2003 with a large neighboring hog operation for excessive odors, flies, and toxic gas emissions.xli
A study in Sampson County, North Carolina indicated that ammonia concentrations in rain-water doubled between 1985 and 1996—a period during which hog operations in the state expanded rapidly.xlii
For More Information

'Human Health Effects of Agriculture: Physical Diseases and Illnesses'
This 2001 report from The National Agriculture Safety Database at the Centers for Disease Control reviews a number of the potential health effects from agriculture, including those from air pollution.
'Improving Air and Water Quality Can Be Two Sides of the Same Coin,'
This 2005 article from the USDA-published periodical Amber Waves describes many of the environmental impacts of farming, and demonstrates just how delicate the process of controlling pollutants can be.
Sources

U.S. Environmental Protection Agency, “ Agriculture ,” in Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2004 (Washington, DC: U.S. Environmental Protection Agency, 2006): 1.
Doorn, Michael R.J., et al. Review of Emissions Factors and Methodologies to Estimate Ammonia Emissions from Animal Waste Handling , Research Triangle Park (NC): Environmental Protection Agency, 2002: ii.
Schlesinger, William H. and Viney P. Aneja. “ N.C.'s country air isn't what it should be ,” News & Observer (Raleigh, NC), 3 July 2006, Opinion Section.
Hoff, Stephen J., et al. 'Emissions and Community Exposures from CAFOs,' in Iowa Concentrated Animal Feeding Operations Air Quality Study: Final Report . Environmental Health Sciences Research Center, University of Iowa, 2003:53.
USDA Agricultural Research Service. FY-2005 Annual Report Manure and Byproduct Utilization , 31 May 2006 (accessed August 10, 2006).
Hagenstein, Perry R., et al. Air Emissions from Animal Feeding Operations: Current Knowledge, Future Needs , Washington (DC): National Academies Press, 2003: 56.
Farm Safety Association. Manure Gas Dangers . Guelph, Ontario (Canada): Farm Safety Association, Inc., 2002: 1.
Farm Safety Association. Manure Gas Dangers . Guelph, Ontario (Canada): Farm Safety Association, Inc., 2002: 1.
U.S. Environmental Protection Agency, “ Agriculture,” in Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2004 (Washington, DC: U.S. Environmental Protection Agency, 2006): 7.
Schlesinger, William H. and Viney P. Aneja. “ N.C.'s country air isn't what it should be ,” News & Observer (Raleigh, NC), 3 July 2006, Opinion Section.
U.S. Environmental Protection Agency, “ Agriculture ,” in Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2004 (Washington, DC: U.S. Environmental Protection Agency, 2006): 1.
U.S. Environmental Protection Agency, “ Agriculture ,” in Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2004 (Washington, DC: U.S. Environmental Protection Agency, 2006): 2.
U.S. Environmental Protection Agency, “ Agriculture ,” in Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2004 (Washington, DC: U.S. Environmental Protection Agency, 2006): 1.
Pirog, Rich. “Checking the Food Odometer: Comparing Food Miles for Local Versus Conventional Produce Sales in Iowa Institutions.” Leopold Center for Sustainable Agriculture, July 2003.
Bureau of Transportation Statistics, the U.S. Department of Transportation. Freight in America: A New National Picture. Washington (DC): Bureau of Transportation Statistics, 2006: 5, 11.
Agency for Toxic Substances and Disease Registry. Medical Management Guidelines (MMGs) for Hydrogen Sulfide (H2S) . (accessed August 9, 2006).
Agency for Toxic Substances and Disease Registry. ToxFAQs™: Ammonia , September 2004 (accessed August 12, 2006).
U.S. EPA. Particulate Matter , 2 March 2006 (accessed 10 August 2006).
Brigham, KL and DK Meyrick, “ Endotoxin and Lung Injury. ” Medline, May 1986.
Farm Safety Association. Manure Gas Dangers . Guelph, Ontario (Canada): Farm Safety Association, Inc., 2002: 1-2.
Farm Safety Association. Manure Gas Dangers . Guelph, Ontario (Canada): Farm Safety Association, Inc., 2002: 1.
U.S. Environmental Protection Agency, “ Agriculture ,” in Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2004 (Washington, DC: U.S. Environmental Protection Agency, 2006): 2,7.
Kirkhorn, Stephen, and Mark B. Schenker. Human Health Effects of Agriculture: Physical Diseases and Illnesses 2001 (accessed 10 August 2006).
Kirkhorn, Stephen, and Mark B. Schenker. Human Health Effects of Agriculture: Physical Diseases and Illnesses 2001 (accessed 10 August 2006).
U.S. Department of Health and Human Services. National Institute for Occupational Safety and Health (NIOSH) Recommendations to the U.S. Department of Labor for Changes to Hazardous Orders . 2002: 88.
McBride, A. Dennis., M.D. M.P.H., North Carolina Department of Health and Human Services. Medical Evaluation and Risk Assessment: The Association of Health Effects with Exposure to Odors from Hog Farm Operations , December 1998; last updated November 2003 (accessed 11 August 2006).
Melvin, Stuart. Executive Summary: Understanding the Impacts of Large-Scale Swine Production, Proceedings from an Interdisciplinary Scientific Workshop , 1995 (accessed 10 August 2006): 13.
Thu, Kendall M. Neighbor Health and Large-scale Swine Production September 2004 (accessed August 17, 2006).
Ibid.
Doorn, Michael R.J., et al. Review of Emissions Factors and Methodologies to Estimate Ammonia Emissions from Animal Waste Handling , Research Triangle Park (NC): Environmental Protection Agency, 2002: ii.
Hagenstein, Perry R., et al. Air Emissions from Animal Feeding Operations: Current Knowledge, Future Needs , Washington (DC): National Academies Press, 2003: 52.
Hagenstein, Perry R., et al. Air Emissions from Animal Feeding Operations: Current Knowledge, Future Needs , Washington (DC): National Academies Press, 2003: 71.
U.S. Environmental Protection Agency, “ Agriculture ,” in Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2004 (Washington, DC: U.S. Environmental Protection Agency, 2006): 1.
Iowa Department of Natural Resources Animal Feeding Operations Technical Workgroup. Animal Feeding Operations Technical Workgroup Report on Air Emissions Characterization, Dispersion Modeling, and Best Management Practices . December 2004 (accessed August 11, 2006): 7.
Clancy, Kate. Greener Pastures: How Grass-fed Beef and Milk Contribute to Healthy Eating. Cambridge (MA): Union of Concerned Scientists, 2006: 12.
Ribaudo, Mark, and Marca Weinberg. 'Improving Air and Water Quality Can Be Two Sides of the Same Coin,' Amber Waves 3:4 (2005), pp. 39-45: 40-42.
Ibid.
Thorne, Peter S., Ph.D., “ Air Quality Issues ,” in Iowa Concentrated Animal Feeding Operation Air Quality Study . Environmental Health Sciences Research Center, University of Iowa, 2003.
Center for Emerging Issues, Animal and Plant Health Information Service, USDA. Changing Times in Animal Agriculture: Overseas Investments by U.S. Meat Corporations, What's the Future for U.S. Exports? , July 2000 (accessed 11 August 2006).
Hagenstein, Perry R., et al. Air Emissions from Animal Feeding Operations: Current Knowledge, Future Needs , Washington (DC): National Academies Press, 2003: 56.
Cook, Christopher D. 'New Rules to Stem Pollution on Factory Farms Draw Fire,' Christian Science Monitor, 15 February 2005, USA—Domestic Politics.
Herriges, Joseph A., et al. “ Living with Hogs in Iowa: The Impact of Livestock Facilities on Rural Residential Property Values ,” Center for Agricultural and Rural Development, Iowa State University. Ames, Iowa: 2003: 1-2.
Natural Resources Defense Council, “ America’s Animal Factories.” NRDC, (accessed January 5, 2007.
ADDITIONAL HOG FARM INFORMATION LINKS

http://www.freerepublic.com/forum/a3aa0a67c7ca4.htm

http://www.farmsanctuary.org/media/media_e-mag.htm

http://www.factoryfarm.org/topics/health/hydrogensulfide/

http://www.pennfuture.org/files/event_camp/hogfarmtoxicchart.pdf

http://www.fass.org/FASStrack/news_item.asp?news_id=1238

http://www.rollingstone.com/politics/story/12840743/porks_dirty_secret_the_nations_top_hog_producer_is_also_one_of_americas_worst_polluters

http://www.sierraclub.org/cleanwater/that_stinks/