CAFO regulations

Evidence Rating  
Expert Opinion
Evidence rating: Expert Opinion

Strategies with this rating are recommended by credible, impartial experts but have limited research documenting effects; further research, often with stronger designs, is needed to confirm effects.

Health Factors  
Decision Makers

Animal feeding operations (AFOs) keep and raise animals in a confined area for 45 days or more in any 12-month period and do not sustain vegetation in the normal growing season. Confined animal feeding operations (CAFOs) are AFOs with more than 1,000 animal units (e.g., 700 dairy cows, 2,500 swine, or 125,000 broiler chickens) or AFOs of any size that discharge manure or wastewater into a ditch, stream, or waterway1. CAFOs are regulated by the federal Clean Water Act (CWA) under the National Pollution Discharge Elimination System (NPDES) permitting program2. State and local governments can establish additional regulations to further limit CAFO location, size, and pollution discharge, and increase monitoring, enforcement, and assessment of pollution prevention practices. State and local regulations can also require certification and review of comprehensive nutrient management plans (CNMPs) or manure management plans and expand CNMP requirements3, 4. State and local regulations vary5; some local governments have limited ability to enact regulations due to state preemption legislation6, 7

Expected Beneficial Outcomes (Rated)

  • Reduced run-off

  • Improved water quality

Other Potential Beneficial Outcomes

  • Improved air quality

  • Improved health outcomes

  • Improved quality of life

  • Reduced emissions

Evidence of Effectiveness

State or local confined animal feeding operation (CAFO) regulations are a suggested strategy to reduce environmental contamination and improve water quality5, 8. Available evidence indicates changes in CAFO management practices9, 10 and CAFO siting11 in response to regulations. However, additional evidence is needed to confirm the effects of state and local regulations and management changes on environmental contamination and water quality.

CAFOs have been shown to pollute water with excess nutrient run-off and nitrate contamination12, 13, 14, 15, estrogen and steroids16, 17, and bacteria and fecal contamination14, 18, 19, 20, 21. In some circumstances, CAFO waste has been shown to increase antibiotic resistant bacteria in surface and groundwater14, 17, 20, 21, 22, 23. CAFO waste can also increase arsenic levels24, hormone concentrations, and algae blooms that can lead to fish kills5, 16, 25, 26. CAFOs emit air pollutants such as ammonia, hydrogen sulfide, particulate matter, volatile organic compounds (VOCs), and nitrous oxide27, 28, 29, 30, 31, 32, 33, 34, 35.

Studies show negative health outcomes among CAFO workers including symptoms of pulmonary disease and lung function abnormalities36, 37. Available evidence also suggests negative health effects for those living near CAFOs, such as increased risk of respiratory illnesses37, 38, and increased incidence of chest tightness, wheezing, coughing, nausea, fainting, headache, and plugged ears, compared to those further from CAFOs. CAFO neighbors also more commonly report increased anger, depression, fatigue, stress, sore throat, diarrhea, and burning eyes36, 37.

CAFOs appear to negatively affect nearby housing prices, especially for homes within a 3 mile radius39, 40. CAFO odors spur decreases in reported quality of life among neighbors36.   

Prior to adopting CAFO regulations, legal experts suggest that local municipalities examine state law closely, define “CAFO” to reflect regulatory goals, implement a permitting and siting system, consider potential effects on local agriculture, and require a bond7. Adequate funding for oversight, research, and enforcement are key to implementation26. Researchers also suggest that relying on size-based regulations alone may have limited effects on small farms and may encourage large farms to downsize to avoid regulation41.

Regulations can encourage CAFOs to adopt technology to capture methane emissions for renewable energy, which can help to mitigate climate change effects8, 42, 43, 44. Models suggest that CAFO regulations based on downstream emissions are more cost-effective for producers than quantity controls or limits for field manure applications, especially with technology to reduce emissions45.

CAFOs are typically located in rural areas. In several areas of the country, such as North Carolina and Mississippi, CAFOs are also clustered in low income, minority communities, raising environmental justice concerns46, 47

Impact on Disparities

Likely to decrease disparities

Implementation Examples

Some state’s regulations are broad in scope with detailed definitions and designated enforcement support, while others simply comply with federal requirements. Examples of states with strong CAFO regulations include: Alabama, Arkansas, Colorado, Georgia, Illinois, Indiana, Iowa, Kansas, Minnesota, Nebraska, Ohio, Oklahoma, Pennsylvania, South Carolina, Texas, Vermont, Virginia, and Wisconsin. States with weaker CAFO regulations include: Alaska, Arizona, Connecticut, Massachusetts, Mississippi, Montana, Nevada, New Hampshire, New Mexico, New York, Washington, and West Virginia5.

Thirteen states have preemption legislation that prevents local communities from adopting regulations or zoning restrictions for CAFOs that are more restrictive than state laws6. In states with preemption legislation, communities and municipalities can shift from deterrence-based efforts to partnerships with industry and voluntary programs that educate producers about practices to minimize pollution discharge and enhance pollution controls48. In all states, local boards of health can increase water and air quality testing in the areas surrounding CAFOs; and in some areas, local boards of health can also pass ordinances or regulations directed at CAFOs8.

The US Department of Agriculture’s Natural Resource Conservation Service supports voluntary adoption of comprehensive nutrient management plans to reduce nutrient run-off, which have stronger protections for natural resources than other nutrient management plans1.

Implementation Resources

NALC-State statutes - National Agricultural Law Center (NALC). States’ Right-To-Farm statutes.

US EPA-NPDES AFOs - US Environmental Protection Agency (US EPA). National pollutant discharge elimination system (NPDES): Animal feeding operations (AFOs).

MEA-Legal action guide 2013 - Midwest Environmental Advocates (MEA). Protecting your community from existing and proposed concentrated animal feeding operations (CAFOs): A guide to legal actions. 2013:4-8.

UCS-Gurian-Sherman 2008 - Gurian-Sherman D. CAFOs uncovered: The untold costs of confined animal feeding operations. Cambridge, MA: Union of Concerned Scientists (UCS); 2008.


* Journal subscription may be required for access.

1 USDA-NRCS AFOs - US Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS). Animal feeding operations (AFOs).

2 US EPA-NPDES AFOs - US Environmental Protection Agency (US EPA). National pollutant discharge elimination system (NPDES): Animal feeding operations (AFOs).

3 Centner 2007 - Centner TJ. Clarifying NPDES requirements for concentrated animal feeding operations. National Agricultural Law Center. 2007.

4 UCS-Gurian-Sherman 2008 - Gurian-Sherman D. CAFOs uncovered: The untold costs of confined animal feeding operations. Cambridge, MA: Union of Concerned Scientists (UCS); 2008.

5 Koski 2007* - Koski C. Examining state environmental regulatory policy design. Journal of Environmental Planning and Management. 2007;50(4):483-502.

6 Grassroots Change - Grassroots Change: Connecting for better health. Preemption Watch.

7 ABA-Kapplan 2012 - Kapplan AR. CAFOs: Five essential tools for local regulation. American Bar Association’s (ABA) State & Local Law News. 2012;35(4).

8 NALBOH-Hribar 2010 - Hribar C. Understanding concentrated animal feeding operations and their impact on communities. Bowling Green, OH: National Association of Local Boards of Health (NALBOH); 2010.

9 Savage 2013* - Savage JA, Ribaudo MO. Impact of environmental policies on the adoption of manure management practices in the Chesapeake Bay watershed. Journal of Environmental Management. 2013;129:143-148.

10 ERS-Sneeringer 2013 - Sneeringer S, Key N. Effects of CAFO regulations on livestock producers’ behaviors. 2013 AAEA & CAES Joint Annual Meeting. Washington, DC: Agricultural and Applied Economics Association (AAEA); 2013.

11 Brands 2014* - Brands E. Siting restrictions and proximity of Concentrated Animal Feeding Operations to surface water. Environmental Science & Policy. 2014;38:245-253.

12 Lockhart 2013* - Lockhart KM, King AM, Harter T. Identifying sources of groundwater nitrate contamination in a large alluvial groundwater basin with highly diversified intensive agricultural production. Journal of Contaminant Hydrology. 2013;151(3):140-154.

13 Mallin 2015* - Mallin MA, McIver MR, Robuck AR, Dickens AK. Industrial swine and poultry production causes chronic nutrient and fecal microbial stream pollution. Water, Air, & Soil Pollution. 2015;226(12):407.

14 West 2011* - West BM, Liggit P, Clemans DL, Francoeur SN. Antibiotic resistance, gene transfer, and water quality patterns observed in waterways near CAFO farms and wastewater treatment facilities. Water, Air, and Soil Pollution. 2011;217(1):473-489.

15 Whalen 2007* - Whalen SC, DeBerardinis JT. Nitrogen mass balance in fields irrigated with liquid swine waste. Nutrient Cycling in Agroecosystems. 2007;78(1):37-50.

16 Adeel 2017 - Adeel M, Song X, Wang Y, Francis D, Yang Y. Environmental impact of estrogens on human, animal and plant life: A critical review. Environment International. 2017;99:107-119.

17 Bartelt-Hunt 2011* - Bartelt-Hunt S, Snow DD, Damon-Powell T, Miesbach D. Occurrence of steroid hormones and antibiotics in shallow groundwater impacted by livestock waste control facilities. Journal of Contaminant Hydrology. 2011;123(3-4):94-103.

18 Gentry-Shields 2015* - Gentry-Shields J, Myers K, Pisanic N, Heaney C, Stewart J. Hepatitis E virus and coliphages in waters proximal to swine concentrated animal feeding operations. Science of The Total Environment. 2015.

19 Heaney 2015* - Heaney CD, Myers K, Wing S, et al. Source tracking swine fecal waste in surface water proximal to swine concentrated animal feeding operations. Science of The Total Environment. 2015;511:676-683.

20 Casanova 2016 - Casanova LM, Sobsey MD. Antibiotic-resistant enteric bacteria in environmental waters. Water. 2016;8(12):561.

21 Li 2015 - Li X, Atwill ER, Antaki E, et al. Fecal indicator and pathogenic bacteria and their antibiotic resistance in alluvial groundwater of an irrigated agricultural region with dairies. Journal of Environment Quality. 2015;44(5):1435-1447.

22 Brooks 2014* - Brooks JP, Adeli A, McLaughlin MR. Microbial ecology, bacterial pathogens, and antibiotic resistant genes in swine manure wastewater as influenced by three swine management systems. Water Research. 2014;57:96-103.

23 Barrett 2005 - Barrett JR. Airborne bacteria in CAFOs: Transfer of resistance from animals to humans. Environmental Health Perspectives. 2005;113(2):A116-A117.

24 Makris 2008* - Makris KC, Quazi S, Punamiya P, Sarkar D, Datta R. Fate of arsenic in swine waste from concentrated animal feeding operations. Journal of Environmental Quality. 2008;37(4):1626-1633.

25 Leet 2012* - Leet JK, Lee LS, Gall HE, et al. Assessing impacts of land-applied manure from concentrated animal feeding operations on fish populations and communities. Environmental Science & Technology. 2012;46(24):13440-13447.

26 CRS-Copeland 2010 - Copeland C. Animal waste and water quality: EPA regulation of concentrated animal feeding operations (CAFOs). Washington, DC: Congressional Research Service (CRS); 2010.

27 Heinzen 2015 - Heinzen T. Recent developments in the quantification and regulation of air emissions from animal feeding operations. Current Environmental Health Reports. 2015;2(1):25-32.

28 Rumsey 2014* - Rumsey IC, Aneja VP, Lonneman WA. Characterizing reduced sulfur compounds emissions from a swine concentrated animal feeding operation. Atmospheric Environment. 2014;94:458-466.

29 Rumsey 2014a* - Rumsey IC, Aneja VP. Measurement and modeling of hydrogen sulfide lagoon emissions from a swine concentrated animal feeding operation. Environmental Science & Technology. 2014;48(3):1609-1617.

30 Pavilonis 2013* - Pavilonis BT, O’Shaughnessy PT, Altmaier R, Metwali N, Thorne PS. Passive monitors to measure hydrogen sulfide near concentrated animal feeding operations. Environmental Science: Processes & Impacts. 2013;15(6):1271-1278.

31 Rumsey 2012* - Rumsey IC, Aneja VP, Lonneman WA. Characterizing non-methane volatile organic compounds emissions from a swine concentrated animal feeding operation. Atmospheric Environment. 2012;47:348-357.

32 Blunden 2005* - Blunden J, Aneja VP, Lonneman WA. Characterization of non-methane volatile organic compounds at swine facilities in eastern North Carolina. Atmospheric Environment. 2005;39(36):6707-6718.

33 Hoff 2002 - Hoff SJ, Hornbuckle KC, Thorne PS, Bundy DS, O’Shaughnessy PT. Emissions and community exposures from CAFOs. Iowa Concentrated Animal Feeding Operations Air Quality Study. 2002:45-85.

34 Wilson 2007* - Wilson SM, Serre ML. Examination of atmospheric ammonia levels near hog CAFOs, homes, and schools in Eastern North Carolina. Atmospheric Environment. 2007;41:4977-4987.

35 Ogneva-Himmelberger 2015 - Ogneva-Himmelberger Y, Huang L, Xin H. CALPUFF and CAFOs: Air pollution modeling and environmental justice analysis in the North Carolina hog industry. ISPRS International Journal of Geo-Information. 2015;4(1):150-171.

36 Von Essen 2005* - Von Essen SG, Auvermann BW. Health effects from breathing air near CAFOs for feeder cattle or hogs. Journal of Agromedicine. 2005;10(4):55-64.

37 Greger 2010* - Greger M, Koneswaran G. The public health impacts of concentrated animal feeding operations on local communities. Family & Community Health. 2010;33(1):11-20.

38 Sigurdarson 2006* - Sigurdarson ST, Kline JN. School proximity to concentrated animal feeding operations and prevalence of asthma in students. Chest. 2006;129(6):1486-1491.

39 Isakson 2008* - Isakson HR, Ecker MD. An analysis of the impact of swine CAFOs on the value of nearby houses. Agricultural Economics. 2008;39(3):365-372.

40 Kilpatrick 2015 - Kilpatrick JA. Animal operations and residential property values. The Appraisal Journal. 2015;83(1):41-50.

41 Azzam 2015* - Azzam A, Nene G, Schoengold K. Hog industry structure and the stringency of environmental regulation. Canadian Journal of Agricultural Economics/Revue canadienne d’agroeconomie. 2015;63(3):333-358.

42 Verheul 2011 - Verheul J. Methane as a greenhouse gas: Why the EPA should regulate emissions from animal feeding operations and concentrated animal feeding operations under the Clean Air Act. Natural Resources Journal. 2011;51(1):163-187.

43 Murray 2015 - Murray BC, Vegh T. Incentivizing the reduction of pollution at dairies: How to address additionality when multiple environmental credit payments are combined. Duke University Nicholas Institute for Environmental Policy. 2015: Working Paper 15-01.

44 Adair 2016* - Adair CW, Xu J, Elliott JS, et al. Design and assessment of an innovative swine waste to renewable energy system. Transactions of the ASABE. 2016;59(5):1009-1018.

45 Wang 2015* - Wang J, Baerenklau KA. How inefficient are nutrient application limits? A dynamic analysis of groundwater nitrate pollution from concentrated animal feeding operations. Applied Economic Perspectives and Policy. 2015;37(1):130-150.

46 Nicole 2013 - Nicole W. CAFOs and environmental justice: The case of North Carolina. Environmental Health Perspectives. 2013;121(6):a182-a189.

47 Carrel 2016 - Carrel M, Young SG, Tate E. Pigs in space: Determining the environmental justice landscape of swine concentrated animal feeding operations (CAFOs) in Iowa. International Journal of Environmental Research and Public Health. 2016;13(9):849.

48 Centner 2011* - Centner TJ. Addressing water contamination from concentrated animal feeding operations. Land Use Policy. 2011;28(4):706-711.

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