Ambient Air Quality Regulations that Impact Swine Operations

Agricultural air quality is a hot topic, especially for animal feeding operations. Increasing interest in regulation of farms is the result of many changes, including the trend toward larger farms having greater concentrations of animals, and increased knowledge and awareness of air emissions from livestock sources. There are federal ambient air quality regulations that apply to swine operations, with geographical and herd size considerations.  


This factsheet provides background and reporting requirements by pork producers for federal air quality rules, specifically: 

  • Clean Air Act (CAA) 
  • Greenhouse Gas Reporting Rule (GHGRR) 
  • Emergency Planning and Community Right-to-Know Act (EPCRA) and Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) 

Air Quality Basics 

In a regulatory context, ‘ambient air’ is the outdoor air that surrounds our homes, farms and businesses. For operations having non-family employees, there are worker safety regulations that might apply to indoor air quality, but the focus here is outdoor air quality.  Also, while indoor and outdoor air qualities are connected, readers should understand that indoor air quality measures by themselves are not good predictors of air emission rates or ambient air quality. 

Maintaining good ambient air quality should be a concern for pork producers and others involved in agriculture because it is an inherent part of environmental stewardship. Specific reasons of importance to many pork producers include: 

  • Manure nutrients that are lost to the air (i.e. ammoniacal nitrogen) lower the nutrient value of manure as a fertilizer. 
  • Air emissions can carry some swine disease organisms from one facility to another. 
  • Odor and other air quality degradation (even the potential for it) can create tension among neighbors. 
  • Degraded air quality leads to new and stricter regulations. 

Swine operations or facilities generally produce airborne particulate matter (eg. dust, or other solid or liquid material suspended in the air) and several gases (i.e. ammonia, hydrogen sulfide, carbon dioxide, methane, and nitrous oxide) that are addressed in current federal ambient air quality rules and regulations. Odor is not regulated by the federal government. Odor regulations may, however, exist at the state or county level. 

When it comes to air quality regulation, it is important to understand the difference between concentration and emission and the relationship between the two. Concentration is the quantity of something (odor, dust, gas, etc.) in a given amount of air; commonly stated as parts per million (ppm) or per billion (ppb), or as fractions of a gram per cubic meter of air (e.g. μg/m3). Concentration measurements are used to assess the quality of the air, and are often used to evaluate the effectiveness of control measures and regulations. If ambient air concentrations exceed established air quality standards (described in the Clean Air Act section), an area may be placed in ‘nonattainment status’ and stricter requirements may be enforced within that area. The Environmental Protection Agency (EPA) maintains a list of non-attainment areas in their ‘Green Book’ (EPA, 2019c).  

Emissions are generally expressed as rates, where the emission rate is the amount of something (odor, dust, gas, etc.) that moves from a defined source (building, storage area, surface, etc.) or set of sources into the ambient air during a measured period of time. For example, the amount of gas leaving a barn and moving into the surrounding air over a period of time establishes an emission rate (i.e. lb/day, g/hr). When air moves across the surface of an open manure storage facility or treatment lagoon, it picks up gases, resulting in another source of emissions. 

To calculate an emission rate, pollutant concentrations at the source and of the ambient air must be known. If you think of a smokestack, in order to know how much of something (e.g. hydrogen sulfide) is coming from this source, we need to know first how much air is moving through the stack, and then, how much of the something (e.g. hydrogen sulfide) is in that air. In other words, we need to know the airflow rate and the net pollutant concentration. The same principles apply for emissions from animal facilities. An important thing to keep in mind is that airflow rate and pollutant concentration are often inversely related. For example, in warmer weather, pollutant production within a barn may increase, but the ventilation also increases and so the pollutant concentration in the animal area is generally reduced. In reality, emission rates are often lowest when indoor pollutant concentrations are highest (in cold weather) and vice versa. 

Most air quality regulations are designed to regulate emissions from the source, with the intent being to favorably influence ambient air quality – as assessed by off-site pollutant concentrations. 

Federal Ambient Air Quality Regulations 

Clean Air Act (CAA) 

The Clean Air Act establishes public health-based standards called NAAQS (National Ambient Air Quality Standards). NAAQS have been established for six ‘criteria pollutants’: particulate matter (PM), ozone, carbon monoxide, sulfur oxides, nitrogen oxides, and lead. Of these, only particulate matter (PM) is typically generated by livestock production.  

Particulate matter includes dust and other small particles and liquid droplets present in air. The main public health concern with PM involves ‘fine particulates’ (PM2.5), which, because of their very small size, have been shown to get deep into human lungs and contribute to respiratory illness. EPA currently regulates both fine and ‘coarse inhalable particles’ (PM10) via NAAQS, although the more recent updates to NAAQS suggest increasing focus on fine particulates. Ammonia has been shown to react with other air pollutants in the atmosphere to form PM2.5, leading to concerns about future regulation of ammonia emissions under the Clean Air Act.  

States are responsible for establishing procedures to attain and maintain the NAAQS via ‘state implementation plans’ (SIP). The SIP procedures that must be taken and the requirements placed upon PM sources depend upon whether an area is designated by EPA to be in attainment or nonattainment of the NAAQS. An interactive map showing the status of SIP requirements for designated areas within each state is available online (EPA, 2019c). EPA may enforce the NAAQS by requiring: 

  • Air permits for major sources of criteria pollutants and other hazardous air pollutants 
  • Implementation of control technologies 

 EPA is also required to establish standards for ‘hazardous air pollutants’ (HAP). These substances are known or suspected causes of human health ailments, including cancer. EPA has identified categories of industries that have the potential to produce these substances. Livestock and poultry operations are not currently included in this list of categories. None of the main gases generated within swine facilities (ammonia, carbon dioxide, hydrogen sulfide, methane) are currently considered hazardous air pollutants in the context of having to meet HAP standards. (While the current list of about 190 HAP does include hydrogen sulfide, a note identifies this as being erroneously listed for this purpose.)  

What farms may be affected? The vast majority of swine operations are not currently affected by Clean Air Act regulations. Particulate matter (PM10) is the most prevalent of the currently regulated pollutants emitted by animal feeding operations. On the one hand, raising pigs does generate dust, and confinement buildings may have elevated concentrations of coarse and fine particulates (PM10 and PM2.5), especially when operating at minimum ventilation rates, that do warrant consideration of indoor air quality. Particulate emissions from swine facilities are relatively low, though, compared to many industrial operations and to other farming activities. Recent emission monitoring studies suggest that swine operations generally do not exceed particulate matter emission thresholds that apply within attainment areas. Designations (as of November 2019) for PM10 and PM2.5 show major pig-producing areas in the U.S. to be in attainment of the NAAQS (EPA, 2019c). The major source threshold in attainment areas is 100 tons of PM10 per year, and direct emissions from swine facilities are projected to be below 100 tons per year. The odd scenario that may receive regulatory attention might be a large concentrated animal feeding operation (>= 2,500 pigs greater than 55 lbs, or 10,000 pigs less than 55 lbs) that is located within a nonattainment area. 

Farm operations that look to install large stationary engines – like those used to generate electricity from digester biogas –may need to assess the expected nitrogen oxide (NOx) exhaust emissions, especially if the site is located in a non-attainment area, since NOx is a regulated criteria pollutant. 

Pork producers should be attentive to regulatory discussions about ammonia emissions and ‘reactive nitrogen’, since ammonia emissions from pig production and manure handling facilities can be substantial. Ammonia and farm-derived volatile organic compound (VOC) emissions are under increasing scrutiny for consideration in the Clean Air Act, due to their effects as secondary compounds. Since ensiled feeds – the main farm source of VOC – are not significant components of pig rations, VOC regulations are less of a concern for pork producers 

How to comply? If in the uncommon situation where you may need to comply, work with a qualified consultant and your state agency in charge of the State Implementation Plan. 

 What is the bottom line? Clean Air Act regulations are unlikely to impact swine operations that are in NAAQS attainment areas, but larger operations should stay informed on the direction of EPA policy in interpreting and enforcing the Clean Air Act. 

Greenhouse Gas (GHG) Reporting Rule 

The GHG Reporting Rule was implemented by the EPA to provide a better understanding of where greenhouse gases are coming from so that, in the future, policies and programs can be implemented to effectively reduce emissions (EPA, 2009b and c). Greenhouse gases include carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride. Any facility that emits more than 25,000 metric tons of ‘carbon dioxide equivalent’ is required to submit annual reports documenting measured or estimated emissions. ‘Carbon dioxide equivalent’ is a method of reporting the impact of multiple greenhouse gases with varying degrees of global warming potential as though the total warming potential came from carbon dioxide. 

The GHG Reporting Rule only addresses one component of livestock GHG emissions – manure management. In the agricultural sector, cattle and other ruminants naturally produce methane and carbon dioxide as part of their digestive and respiratory processes. Non-ruminants, like swine, also produce carbon dioxide, but methane production is considerably lower. The GHG Reporting Rule does not require reporting of methane and carbon dioxide that are directly emitted by animals. However, the methane and nitrous oxide that are produced in manure management and related biological processes are included in the GHG Reporting Rule (Subpart JJ; EPA, 2009a). The following types of manure management systems on swine operations are included in this category: 

  • Uncovered anaerobic lagoons 
  • Liquid/slurry systems (with and without crust covers) 
  • Storage pits 
  • Digesters, including covered anaerobic lagoons 
  • Solid manure storage 
  • Deep bedding systems 
  • Manure composting, aerobic treatment 

What farms may be affected? Only very large facilities are required to report GHG emissions. EPA (2009c) estimated that only 107 livestock facilities nationwide would produce the 25,000 metric tons of carbon dioxide equivalent from manure management sources, and the projected threshold sizes are shown in Table 1 for single-species operations. If the average annual population is (and remains), less than that presented in Table 1 for a given animal facility – for swine, the threshold is 34,100 pigs – there is no need to report GHG emissions.  

Table 1. EPCRA thresholds for large CAFO status for swine and other operations (based upon animals that primarily stay in an enclosed structure like a barn or feedlot) [3]

Type of Operation Animal Numbers Equal to or More Than
Swine (more than 55 lbs) 2,500
Swine (less than 55 lbs) 10,000
Dairy Cows 700
Veal Calves 1,000
Other Cattle 1,000
Horses 500
Sheep or Lambs 10,000
Turkeys 55,000
Laying Hens or Broilers (Liquid Manure System) 30,000
Chickens, other than Laying Hens (Non-Liquid Manure System) 125,000
Laying Hens (Non-Liquid Manure System) 82,000
Ducks (Liquid Manure System) 5,000
Ducks (Non-Liquid Manure System) 30,000

Note: For a mixed operation with more than one animal type, if any one animal group type exceeds the threshold, then reporting is required for the entire operation.

How to comply? Soon after the GHG Reporting Rule was published, Congressional Appropriations Committee action prohibited EPA from expending funds to implement Section JJ of the reporting rule (EPA, 2009c).  When this factsheet was published, this restriction remained in effect. Affected livestock producers are left in the precarious position of officially being required to report GHG emissions without being able to obtain additional guidance from EPA or certainty that EPA will actually ever require the reports. While no enforcement of the reporting rule for livestock operations is currently allowed, there are producers who are reporting emissions to minimize their noncompliance risk. All affected producers are advised to maintain sufficient animal inventory and operational records to facilitate future compliance, should the restriction on implementation of the rule for manure management be lifted. 

For facilities having animal numbers above the thresholds in Table 1, reporting is only required if annual emissions of greenhouse gases (primarily methane) resulting from manure storage and handling are equivalent to at least 25,000 metric tons of carbon dioxide. EPA provides specific guidance in the rule for estimating reportable GHG emissions, assessing the need to report, and annual reporting requirements. The estimates are made using a series of calculations and look-up values that are based upon the animal type and region (EPA, 2009b). Use of a qualified consultant is advised.  

What is the bottom line? Reporting is only required of very large farms that have estimated methane emissions from manure management that exceed the threshold 25,000 metric tons of carbon dioxide equivalent. Implementation of the rule for livestock operations is in limbo due to congressional budgetary restrictions placed upon EPA. 

Emergency Planning and Community Right-to-Know Act (EPCRA) and Comprehensive Environmental Response, Compensation and Liability Act (CERCLA)  

EPCRA is designed to help federal, state and local governments, Indian tribes and industry in emergency planning, emergency release notification, hazardous chemical storage reporting, and toxic chemical release inventory (EPA, 2000). Essentially, it creates a public list of where hazards are located in a community so that emergency personnel and others are aware and can act accordingly. A related regulation, the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) is implemented by EPA to facilitate remediating hazards via ‘Superfund’ projects. 

For many years, it was commonly assumed that EPCRA and CERCLA did not pertain to the normal emissions associated with agricultural practices, but pressures grew that questioned this assumption. In 2005, a voluntary air compliance agreement with EPA led to initiating the National Air Emissions Monitoring Study (NAEMS) – an extensive field study conducted to help inform when regulatory thresholds are reached.  The NAEMS and follow-up studies generated much of the current knowledge about air emissions from confined livestock and poultry operations. 

In 2009, EPA implemented a ruling (EPA, 2009a) that exempted all animal feeding operations from reporting ‘releases’ of normal agricultural emissions under CERCLA. The same rule also exempted ‘small and medium animal feeding operations’ from reporting these emissions under EPCRA. The main impact of this ruling was that it became clear that larger swine confinement facilities that met EPA’s ‘large CAFO’ status (>= 2,500 pigs greater than 55 lbs, or 10,000 pigs less than 55 lbs; EPA, 2009) needed to report emissions of individual hazardous pollutants exceeding specified limits – the typical threshold is 100 lb. per day. The list of hazardous pollutants to report includes ammonia and hydrogen sulfide, which are both common manure-based gases. Ammonia releases are typically greater than hydrogen sulfide, with ammonia being the dominant form of nitrogen loss on farms.  Ammonia emission assessments (Liu and Powers, 2013; EPA, 2019b) demonstrated that emission of 100 lb. of ammonia a day was likely to occur for at least some large CAFO swine facilities. So, while not all large-CAFO swine facilities may actually emit more than 100 lb. a day of ammonia, they were all affected in terms of doing some sort of evaluation and risk assessment to either report or justify not needing to report under EPCRA. 

In 2017, an appeals court decision ruled against the exemptions that EPA had put in place in 2009, opening the door to EPCRA and CERCLA affecting many more livestock and poultry farms.  The ruling created quite a stir nationally due to the large numbers of farmers and ranchers who were going to be impacted, which spurred legislative action.  The following year, Congress passed the “Fair Agricultural Reporting Method (FARM) Act” that exempted farmers from reporting routine farm emissions to EPA under CERCLA.  EPA later officially extended this exemption to apply to EPCRA as well (EPA, 2019a). 

What farms may be affected? With passage of the FARM Act, swine farms do not need to report normal farm air emissions under CERCLA or EPCRA.  Previously, large-CAFO size operations were affected, as potentially emitting enough ammonia to exceed the 100 lb. per day reporting threshold. 

How to comply? Reporting of farm emissions is no longer required under CERCLA or EPCRA. 

What is the bottom line? Reporting of farm emissions under CERCLA/EPCRA went from a non-issue to a significant concern for swine farms, but due to livestock industry engagement with elected officials in Congress, reporting of farm emissions is no longer required. 

State and Local Ambient Air Quality Regulations 

More pork producers are likely to be affected by state regulations and local requirements than by federal air quality regulations. Producers who are planning to expand their operations, and those with facilities of any scale that have significant potential for neighbor conflicts, are most likely to be affected. Regulatory policies vary from state to state and local rules can vary widely within states that facilitate ‘local control’. Producers need to refer to governing requirements that apply for their specific locations and should get assistance as needed from a qualified consultant. 


Federal air quality regulations exist to protect the general public and the environment from detrimental impacts of air pollutants. These regulations were often developed with industrial operations in mind, but can apply to agricultural operations. Currently, the Clean Air Act and Greenhouse Gas Reporting Rule are the federal air quality rules that apply to pig farms. However, based on average pig farm size and emission potential, there are few instances of farms that trigger reporting requirements. Also, there are funding limitations in place that restrict how the Greenhouse Gas Reporting Rule is enforced for emissions from manure management. The responsibility and decision to comply rest with individual producers. As these are federal regulations, with both known and unknown consequences for compliance, operators may want to discuss with legal counsel. Producers are more likely to be affected by state regulations and local requirements.  

For Further Information

Research is ongoing to evaluate the effects of different livestock production practices and mitigation technologies on air emission rates, as well as to assess potential regulatory ramifications. In the meantime, local Extension personnel can address your questions and can offer guidance in making calculations or estimations for your operation.
Further information can also be found at:

  • Environmental Regulation and Agriculture farmpolicy.com/wp-content/uploads/2011/02/RSEnvandAg11Feb.pdf
  • Manure Management Systems. Final Rule: Mandatory Reporting of Greenhouse Gases epa.gov/ghgreporting/documents/pdf/infosheets/manuremanagement.pdf
  • CERCLA/EPCRA Administrative Reporting Exemption for Air Releases of Hazardous Substances from Animal Waste at Farms epa.gov/oem/docs/chem/CAFO_rule_fact_sheet.pdf
  • Livestock and Poultry Environmental Learning Center – Regulations Related to Livestock and Poultry Production extension.org/pages/8953/regulations-related-to-livestock-and-poultry-production
  • Environmental Protection Agency – The Green Book Nonattainment Areas for Criteria Pollutants epa.gov/airquality/greenbook/index.html
  • Environmental Protection Agency – Status of SIP Requirements for Designated Areas epa.gov/air/urbanair/sipstatus/reports/map_s.html


[1] CRS. Environmental regulation and agriculture. 2011. Congressional Research Service Report R41622.

[2] EPA. The Emergency Planning and Community Right-to-Know Act. 2000. United States Environmental Protection Agency, Office of Solid Waste and Emergency Response. Factsheet EPA-550-F-00-004.

[3] EPA. CERCLA/EPCRA Administrative Reporting Exemption for Air Releases of Hazardous Substances from Animal Waste at Farms. Federal Register. 2009; 73(244):76948–76960.

[4] Liu Z, Powers W. Emissions of NH3, H2S, VOC, PM10 and PM2.5 from swine production facilities in North America: a meta-analysis. 2013. ASABE, St. Joseph, MI. Paper No. 131594405.

[5] EPA. Manure Management Systems. Final Rule: Mandatory Reporting of Greenhouse Gases. 2009. United States Environmental Protection Agency.

[6] EPA. Mandatory Reporting of Greenhouse Gases. Federal Register. 2009; 74(209):56337 and 56481. Factsheet EPA-430-F-09-026R.

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