Air Quality

On This Page:
Mountains of Manure
Air Pollution and Feed
Major Pollutants
Effects on Workers
Effects on Communities
Environmental Effects
Remedies and Regulations

Industrial farms  , also called factory farms or CAFOs (confined animal feeding operations) pollute the air in many ways, emitting foul odors, airborne particles, greenhouse gases, and numerous toxic chemicals. In the United States and elsewhere, industrial farms are leading producers of noxious substances such as nitrous oxide   2 and ammonia.   3 United States farms alone produce more than 400 different gases,   4 in addition to dust and airborne particles known as endotoxins generated during the handling and disposal of manure,   5 the production and use of animal feeds, and the shipping and distribution of farm products. Air pollution from industrial farms can cause health problems in agricultural workers, in residents of neighboring communities, and in farm animals. Although strategies exist to reduce air pollution, many industrial farms do little or nothing in this regard.

Mountains of Manure

The USDA estimates that more than 335 million tons of manure are produced annually on U.S. farms.   6 Stored for long periods of time in giant tanks or lagoons, the animal waste decomposes and pollutes the air with hundreds of different gases.   7 These storage facilities are often located next to animal confinement facilities, with the livestock and the people who work with them continually exposed to harmful gases.   8 Additional air pollution is caused when huge amounts of stored manure are sprayed onto fields.

Hydrogen sulfide, methane, ammonia, and carbon dioxide are the major hazardous gases produced by decomposing manure.   8 The EPA estimates that methane emissions from manure increased by 26 percent in the United States between 1990 and 2004, due primarily to larger, more concentrated dairy cow and swine facilities.   2 North Carolina’s hog industry alone produces about 300 tons of ammonia each day.   4

Air Pollution and Feed

While manure is the largest contributor to air pollution from factory farms, industrial animal feed also plays a role. In 2004, the EPA estimated that 20 percent of all man-made methane production resulted from livestock digestion, primarily cows,   2 which on factory farms are kept alive with low-quality grain-based feed that their bodies were not designed to digest. This feed fattens animals cheaply but causes chronic indigestion that contributes to higher methane emissions.   2 Producing the vast crops required for this animal feed also pollutes the air with soil management techniques, especially the use of synthetic fertilizers, that were responsible for 68 percent of all nitrous oxide released into the atmosphere in 2004.   2

Major Pollutants

Effects of air pollution vary depending on the specific pollutants involved, how they are vented into the atmosphere, and local conditions, such as weather patterns. Some of the principle air pollutants created by industrial livestock facilities are listed here, along with their effects.

Effects on Workers

As many as 70 percent of workers on CAFOs experience acute bronchitis, while 25 percent contract chronic bronchitis.   14 In one study a host of other respiratory ailments were linked to working in indoor swine facilities for two hours a day over a period of six years, most likely as a result of dust inhalation.   14 Some of the gases produced on factory farms also are fatal in high concentrations.  In the United States, at least 12 cases were documented over five years of workers dying from asphyxiation in manure pits.   15

Effects on Communities

Residents of communities near hog farms often have increased respiratory problems.   16 A number of studies have demonstrated that fatigue, depression, and mood disturbances occur in higher proportions in people living near such facilities.   17 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 started operating.   18 Minnesota’s Pollution Control Agency has documented hydrogen sulfide concentrations in excess of World Health Organization maximum exposure standards on properties neighboring industrial hog facilities.   18 A 2006 study comparing two rural Iowa elementary schools, one located near a CAFO and one not, found a significant prevalence of asthma in children at the school near the factory farm.   19

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 percent of U.S. ammonia emissions came from livestock manure.   3 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.”   7 Particulate emissions from factory farms also contribute to haze.   7 Through the production of greenhouse gases—primarily methane and nitrous oxide—the agricultural industry was directly responsible for 6 percent of the U.S. contribution to global warming in 2004, according to the EPA.   2

Remedies and Regulations

A number of techniques can reduce the emissions and effects of air pollutant from industrial farms, including better storage of manure, air-breaks positioned near farms, and increased attention to the nutritional needs of specific types of livestock.   20 Allowing cows to graze on pasture is healthier, for both cows and humans, than feeding them grain, and has the potential to reduce greenhouse gas emissions.   21 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 result in the emission of large amounts of carbon dioxide and other pollutants.

There is little regulatory incentive to reduce pollution from factory farms. While most pollutants emitted by farms are regulated under the federal Clean Air Act, most federal enforcement is focused on cars and non-farm factories.   22 The federal government has largely left it to the states to police factory farms,   22 while leaving research on the effects of industrial farming to academics.   23 In 2008 the Bush Administration published a rule exempting CAFOs from federal reporting requirements for hazardous emissions.   24

There is also concern that better environmental regulation will lead corporate farmers to move overseas, rather than stop polluting the air. Already, some of the biggest U.S. owned livestock corporations, including Perdue and Smithfield, are operating in Canada, Mexico, Europe, China and Brazil to reduce costs and avoid U.S. regulations.   25

The most efficient way to reduce air pollution from farms is to reduce the size and increase the number of farms. Many small farms scattered throughout the country will create less air pollution than huge, centralized factory farms. Sustainable livestock farms are pasture-based systems that rely on the animals to harvest feed and spread manure.  This is the way livestock has been raised for thousands of years, right up until the 20th Century, and it remains the model for sustainable farming and reducing farm-related air pollution.

Did You Know?

What You Can Do

Citizen advocacy and consumer demand will be critical to reducing the pollution and other problems caused by industrial farming.  As consumers, we can use our economic power by purchasing sustainably-produced meat, eggs, dairy products and produce, thereby supporting farmers who work to minimize harm to the environment and human health.

Visit the Eat Well Guide to find out where to buy sustainably produced food close to home.

Related Information:


  • Natural Resources Defense Council. (2007). America’s animal factories: How states fail to prevent pollution from livestock waste. Retrieved August 28, 2012.
  • Babcock, B., Herriges, J., & Secchi, S. (2003). Living with hogs in Iowa: The impact of livestock facilities on rural residential property values. Center for Agricultural and Rural Development, Iowa State University. Retrieved August 28, 2012.
  • Cook, C. D. (2005, February 15). New rules to stem pollution on factory farms draw fire. Christian Science Monitor. Retrieved August 28, 2012.
  • U.S. Department of Agriculture, Animal and Plant Health Information Service, Center for Emerging Issues. (2000, July). Changing times in animal agriculture: Overseas investments by U.S. meat corporations, what's the future for U.S. exports? Changing times. Retrieved August 28, 2012.
  • Food & Water Watch. (2008). Bush administration exempts factory farms from regulation.
  • Thorne, P. S. (2003). Chapter 3: Air quality issues. In Iowa Concentrated Animal Feeding Operations Air Quality Study: Final Report.  Environmental Health Sciences Research Center, University of Iowa. Retrieved August 28, 2012.
  • Ribaudo, M., & Weinberg, M. (2005). Improving air and water quality can be two sides of the same coin. Amber Waves, 3(4), 39-45. Retrieved August 28, 2012.
  • Clancy, K. (2006). Greener pastures: How grass-fed beef and milk contribute to healthy eating. Union of Concerned Scientists. Retrieved August 27, 2012.
  • Iowa Department of Natural Resources, Animal Feeding Operations Technical Workgroup. (2004). Animal feeding operations technical workgroup report on air emissions characterization, dispersion modeling, and best management practices. Retrieved August 28, 2012.
  • Sigurdarson, S. T., & Kline, J. N. (2006). School proximity to concentrated animal feeding operations and prevalence of asthma in students. Chest, 129(6), 1486-1491. Retrieved August 28, 2012.
  • Thu, K. M. (2004). Neighbor health and large-scale swine production. Northern Illinois University. Retrieved August 28, 2012.
  • Melvin, S. (1995). Executive summary: Understanding the impacts of large-scale swine production, proceedings from an interdisciplinary scientific workshop. Retrieved August 28, 2012.
  • McBride, A. D. (1998). Medical evaluation and risk assessment: The association of health effects with exposure to odors from hog farm operations. North Carolina Department of Health and Human Services.
  • U.S. Department of Health and Human Services. (2002). National Institute for Occupational Safety and Health (NIOSH) recommendations to the U.S. department of labor for changes to hazardous orders. Retrieved August 27, 2012.
  • Kirkhorn, S., & Schenker, M. B. (2001). Human health effects of agriculture: Physical diseases and illnesses. Retrieved August 30, 2012.
  • Food and Agriculture Organization of the United Nations. (2006). Livestock's long shadow: Environmental issues and options. Retrieved August 28, 2012.
  • Brigham, K.L., & Meyrick, D.K. (1986). Endotoxin and Lung Injury. The American Review of Respiratory Disease, 133(5), 913-927. Retrieved August 28, 2012.
  • Particulate matter. (2012, June 28). U.S. Environmental Protection Agency. Retrieved August 28, 2012.
  • Agency for Toxic Substances and Disease Registry. (2011). Toxic substances portal: Ammonia (CAS 7664-41-7). Retrieved August 28, 2012.
  • Agency for Toxic Substances and Disease Registry. (2006). Medical management guidelines for hydrogen sulfide (H2S) (CAS 7783-0604; UN 1053). Retrieved August 28, 2012.
  • Farm Safety Association. (2002). Manure gas dangers. Retrieved August 27, 2012.
  • National Research Council of the National Academies, Division on Earth and Life Studies. (2003). Air emissions from animal feeding operations: Current knowledge, future needs. Retrieved August 28, 2012.
  • U.S. Department of Agriculture, Agricultural Research Service. (2005). National program 206: Manure and byproduct utilization (FY-2005 Annual Report). Retrieved August 28, 2012.
  • Hoff, S.J., Hornbuckle, K.C., Thorne, P.S., Bundy, D.S., O'Shaughnessy, P.T. (2002, Feb). Chapter 4: 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. Retrieved August 27, 2012.
  • Aneja, V.P., & Schlesinger, W.H. (2006, July 3). N.C.'s country air isn't what it should be. News & Observer.
  • U.S. Environmental Protection Agency, Air Pollution Prevention and Control Division. (2002). Review of emissions factors and methodologies to estimate ammonia emissions from animal waste handling (EPA-600/R-02-017). Retrieved August 27, 2012.
  • U.S. Environmental Protection Agency. (2006). Inventory of U.S. greenhouse gas emissions and sinks: 1990-2004. Retrieved August 28, 2012.
  • Factory Farm (Industrial Farm / Industrial Agriculture)