Swine Sewage Air Pollution: A Dangerous Health Risk

Swine sewage air pollution is a pressing issue that has severe environmental and health impacts. The waste produced by swine farms is similar to human waste and contains harmful bacteria, pathogens, and high amounts of ammonia. The waste is often stored in large open-air pits, known as lagoons, and then sprayed onto crops as fertiliser. This practice, known as the lagoon and sprayfield system, is still legal in some places, including North Carolina, despite efforts to ban it.

The air pollution caused by swine sewage has serious consequences for nearby communities, who suffer a range of adverse health effects, including respiratory diseases, infections, increased risk of cancer, and stress. The pollution also affects water quality, as the waste can leak into nearby water sources, contaminating them with toxic nutrients like nitrates and ammonia.

The impact of swine sewage air pollution is not evenly distributed

Swine waste and air pollution

Swine waste is a major contributor to air pollution, with gases such as ammonia, methane, and hydrogen sulfide being released into the atmosphere. These gases can have harmful effects on both the environment and human health, including eye and throat irritation, headaches, nausea, and respiratory issues.

Swine waste, particularly from concentrated animal feeding operations (CAFOs), has been identified as a significant source of air pollution. CAFOs are large-scale, high-density operations that confine animals for more than 45 days per year and generate large amounts of waste. Swine CAFOs specifically produce enormous amounts of animal waste—a mixture of feces, urine, water, and spilled feed—which must be properly treated and managed to avoid air and water pollution.

Air Pollutants from Swine Waste

Swine waste releases several gases that contribute to air pollution, including:

• Ammonia (NH3): Swine waste contains high levels of nitrogen, which can be converted into ammonia through anaerobic decomposition. Ammonia emissions can have negative impacts on environmental quality and human health, including the formation of fine particulate matter (PM2.5) that can cause respiratory problems.
• Methane (CH4): Methane is a potent greenhouse gas that contributes to climate change. It is produced during the anaerobic decomposition of organic matter in swine waste.
• Hydrogen Sulfide (H2S): Hydrogen sulfide is a toxic gas with a characteristic odor. It is produced in all anaerobic swine waste storage systems and can cause eye and throat irritation, headaches, nausea, and other health issues.
• Volatile Organic Compounds (VOCs): Swine waste emits various VOCs, including acetic acid, propionic acid, butyric acid, and indole, among others. VOCs are responsible for the unpleasant odors associated with swine waste and can have negative impacts on human health.
• Particulate Matter: Swine waste also releases particulate matter, such as dust and suspended particles, which can be inhaled and cause respiratory issues.

Environmental and Health Impacts

The release of these gases from swine waste has significant environmental and health impacts:

• Environmental Impacts: Ammonia emissions can contribute to the formation of smog and acid rain, while methane emissions contribute to climate change. Additionally, nutrient runoff from swine waste can lead to water pollution and eutrophication.
• Human Health Impacts: Exposure to high levels of these gases can cause a range of health issues. For example, ammonia can irritate the eyes, nose, and throat, while hydrogen sulfide can cause headaches, nausea, and respiratory problems. VOCs and particulate matter can also have negative effects on respiratory health.

Mitigation Strategies

To address the air pollution caused by swine waste, several mitigation strategies have been proposed and implemented:

• Lagoon and Sprayfield Systems: Conventional waste management technologies, such as lagoon and sprayfield systems, are commonly used to treat swine waste. However, these systems have been found to be inadequate in preventing air and water pollution.
• Anaerobic Digestion and Biogas Production: Anaerobic digestion is a process that converts swine waste into methane biogas, which can be captured and used for energy production. This helps reduce greenhouse gas emissions and improve air quality.
• Environmentally Superior Technologies (ESTs): In North Carolina, the "Super Soils" technology was developed and designated as an EST, meeting stringent environmental performance standards. This technology treats swine waste using solid-liquid separation, nitrogen and phosphorus removal processes, and pathogen reduction, resulting in a clean, deodorized, and disinfected effluent.
• Policy and Regulatory Changes: There have been calls for stricter pollution controls and regulations to address the impacts of swine waste on air and water quality. This includes incentivizing the adoption of new technologies, such as the Super Soils system, and implementing standards for ammonia and other air pollutants.

Health effects of air pollution from swine sewage

Air pollution from swine sewage can have adverse health effects on nearby residents. A 2008 study found that malodour from swine operations was commonly present in communities and was linked to objective environmental measurements and interruptions of daily life. The study found that participants reported 1,655 episodes of swine odour, with odour ratings related to temperature, PM10, and semivolatile PM10.

Swine sewage contains odour compounds that can affect human health in several ways. Firstly, at high enough concentrations, these compounds can irritate the eyes, nose and throat. Secondly, they can induce symptoms such as nausea, vomiting, headaches and stress at lower concentrations. Thirdly, symptoms may be caused by a non-odourant component of the sewage, such as endotoxin, which can cause inflammation and airflow obstruction.

A 2025 study found that air pollution from industrial swine facilities disproportionately affects marginalised communities. The study used satellite data to show that ammonia (NH3) levels were significantly higher in areas with dense populations of Black, Hispanic and Indigenous residents. Calm and hot weather conditions amplified these disparities, as low wind speeds reduced the dispersion of pollutants.

A 1997 study found that the emission rate of methane, ammonia and volatile organic compounds (VOCs) was dependent on manure loading rate and was influenced by animal numbers. The study also found that the concentration of VOCs in air samples was highest with high-load, outdoor manure management systems. These systems also had the highest odour intensity levels.

A 1995 study found that the concentration of VOCs in air samples was positively correlated with odour intensity. The study also found that wind, temperature and irradiance were major factors in the emission rate of VOCs.

A 1998 study found that the emission rate of methane was influenced by manure management loading parameters. The study found that systems with relatively low methane emission rates showed higher concentrations of organic carbon and nitrogen in the solution phase. These systems also had the highest odour intensities.

Environmental impact of pig farming

The environmental impact of pig farming is largely driven by the spread of feces and waste to surrounding areas, polluting the air and water with toxic particles.

Effects on Air Quality

Communities located near factory pig farms experience negative health and environmental effects due to several factors associated with industrial pig farming. One of the main issues that arises out of intensive animal agriculture is the waste that the huge number of animals produce. Pig waste is similar to human waste and is filled with bacteria and high amounts of ammonia. At most intensive pig farms, hog waste is kept in large open-air pits called lagoons, where waste is broken down by anaerobic bacteria and then sprayed onto crops as fertilizer. This is called the lagoon and sprayfield system and remains legal in the United States.

The waste then reaches neighboring towns, resulting in civilians not being able to even leave their houses in order to avoid pig waste-filled air. People living in nearby towns have suffered a variety of adverse health effects, including respiratory diseases, infections, increased risk of cancer, and other health risks.

Effects on Water Quality

Many intensive pig farms store swine waste in vats often referred to as lagoons. These lagoons often contain pathogens such as salmonella, pharmaceuticals like antibiotics and antimicrobials, as well as nitrogen and phosphorus. This can lead to widespread pollution within the watershed the farm is located within, if the water from these lagoons leaches out into the soil and trickles down into the water table beneath. Unlike human sewage, which is always treated with chemical and mechanical filtration, the waste from these lagoons is untreated when it is released back into the environment. Spills are the most common contributor to pollution, but regardless of spills, toxic nutrients like nitrates and ammonia can seep into the water table located just below the surface, infecting the groundwater that nearby communities drink. It has been estimated that 35,000 miles of river across over 20 states have been contaminated by manure leakage.

Social Justice Concerns

Social justice concerns regarding agricultural lands in rural areas have been rising because of the way minority communities are disproportionately affected by hazards and health risks associated with pig farming. Due to the immense amount of waste produced by pigs, foul odors and airborne molecules disturb local citizens. There is an unfair distribution of these swine farms, where around 90% are located along the "black-belt", which is known for its previous production of cotton and tobacco farming. Many of the minority farmers are being put out of business because of concentrated animal feeding operations (factory farms).

Improvements to Pig Farming Practices

Due to the many environmental repercussions associated with common pig farming techniques, new technologies were created and tested to help prevent these problems. Manure from swine contains excess nitrogen and phosphorus which gets released into nearby water bodies, polluting streams and rivers and contributing to eutrophication. In order to combat this issue, scientists in North Carolina have tested treatment technologies that are designed to separate the manure. Once the pigs drop their manure, a screening device can be used to separate the solid particles from the liquids. A filtration process can be even more effective with removing extra nitrogen and phosphorus that is still remaining. A filter cloth can catch any remaining particles with a pore size less than an inch. Applying this method can greatly reduce organic matters that come from manure which end up in near-by waterways causing pollution and eutrophication.

Air pollution inequalities

A recent study by the University of Virginia has revealed air pollution inequalities linked to industrial swine facilities. The study, led by researchers from the University's Department of Environmental Sciences, used satellite data to demonstrate the long-term existence of air pollution inequalities connected to industrialised swine facilities in Eastern North Carolina. The inequalities were found to disproportionately affect marginalised communities, particularly Black, Hispanic, and Indigenous populations.

The Study's Findings

The study, published in the *American Chemical Society* journal, *Environmental Science & Technology*, analysed ammonia (NH3) levels in the atmosphere over a 15-year period from 2008 to 2023. NH3 is a pollutant emitted by swine operations. The key findings of the study include:

• Air pollution inequalities can be measured from space.
• NH3 levels were significantly higher in areas with larger Black, Hispanic, and Indigenous populations. During 2016-2021, compared to non-Hispanic white populations, NH3 levels were 27% higher for Black communities, 35% higher for Hispanic communities, and 49% higher for Indigenous communities.
• Calm and hot weather conditions amplify these disparities. Low wind speeds reduce the dispersion of pollutants from swine facilities, while higher temperatures increase NH3 emissions through evaporation.
• The environmental impacts of swine facilities extend beyond their immediate surroundings, affecting areas several kilometres downwind.
• Disparities in NH3 concentrations have not decreased over time, indicating a persistent, long-term issue.

Addressing Inequalities

The study highlights the role of industrial agriculture in perpetuating environmental racism, with communities of colour bearing the brunt of air pollution linked to swine operations. It calls for regulatory action to address the unfair and unaddressed air quality issues raised by residents. The findings also come amid debates about air quality regulations and the lack of federal standards for NH3, which is not covered by the Environmental Protection Agency's National Ambient Air Quality Standards.

Swine wastewater treatment

Swine wastewater is a major environmental concern, particularly in intensive pig farming. The waste is similar to human waste and contains high levels of bacteria and ammonia. In addition, it can carry pathogens, antibiotic-resistant bacteria, and heavy metals that can be toxic when ingested.

The most common method of treating swine wastewater is through a conventional anaerobic-aerobic treatment. This typically involves an up-flow anaerobic blanket sludge reactor followed by an activated sludge reactor. However, this method can be costly and requires specialized operations, which may not be feasible for small or medium-sized farms.

As such, there have been various studies and new technologies developed to explore more efficient and cost-effective treatment methods. For example, a study in Mexico assessed the performance of a novel system composed of a septic tank, an up-flow anaerobic filter packed with volcanic rocks, and an aerobic biofilter packed with waste wood chips. This system was found to efficiently remove chemical oxygen demand, total suspended solids, volatile suspended solids, and ammoniacal nitrogen. The advantage of this system is that it is cost-effective, easy to handle, and utilizes sustainable and readily available packing materials in rural zones.

Another study combined microbial fuel cells with flocculation to treat swine wastewater. This method was found to remove up to 82.5% of chemical oxygen demand (COD) and 99.1% of ammonia, with a net economic benefit of $0.026 per cubic meter.

Constructed wetlands have also been explored as a treatment option. A study in Thailand used a vertical subsurface flow constructed wetland (VSF CW) planted with Napier grass to treat swine wastewater. The grass productivities were also compared to provide information for species selection. The study found that both species of Napier grass achieved over 70% removal efficiency of biochemical oxygen demand (BOD) and total Kjeldahl nitrogen (TKN).

Overall, while the conventional anaerobic-aerobic treatment method is effective, there is a need for more affordable and accessible treatment options for small and medium-sized farms. The novel systems described above show promising results and could provide viable alternatives for swine wastewater treatment.

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