Livestock Air Pollution: Understanding The Impact

Livestock farming is a major contributor to air pollution, with industrial ammonia production emitting more CO2 than any other chemical-making reaction. The air near large-scale industrialized pig, chicken, and dairy cow farms not only smells bad but can also be hazardous to human health. Livestock farms emit around 400 different harmful gases, including ammonia, nitrous oxide, and methane, which adversely affect air quality, destroy the ozone layer, and contribute to climate change. In addition, the unsanitary conditions, poor animal feed, and overuse of antibiotics in livestock farming have led to the airborne spread of diseases such as Swine Flu and Avian Flu. The large amounts of waste produced by livestock, estimated at 500 million tons of excrement annually in the US, are often left to fester in open-air lagoons, and when full, factory farms spray liquid manure into the air, creating airborne mists of pollutants.

Animal waste and manure

CAFOs produce large amounts of particulates, which are dispersed rapidly in dry regions where manure turns into dust. The EPA estimates that nearly three-quarters of the US's ammonia pollution comes from livestock facilities, and studies have found high levels of antibiotics and antibiotic-resistant genes in air samples downwind of feedlots. Animal waste is often stored in open ponds, known as lagoons, or pits and is then applied untreated as fertilizer to farm fields. This untreated manure is spread on cropland and can contaminate the environment over large regions.

To address the issue of dangerous bacteria, researchers have discovered compounds that can be added directly to manure to reduce harmful bacteria such as E. coli. One solution is the use of anaerobic manure digesters, which process waste using microbes, heat, water, and agitation. This process produces methane gas, which can be used for energy, as well as liquid and solid manure that can be used as fertilizer and for composting. These resulting manure products are supposed to be cleaned of pollutants, making them safer for agricultural use.

The air inside livestock farms contains high levels of dust and gases, which can impact the respiratory health of farmers and neighbouring residents. Studies have found associations between livestock air pollution emissions and lung function deficits in non-farming residents, with increases in NH3 levels associated with decreases in lung function.

Ammonia emissions

Livestock production, particularly in industrialised settings, contributes significantly to ammonia emissions. Dairy and beef cattle production accounts for about 54% of total ammonia emissions, poultry production contributes 33%, and swine production is responsible for 12%. The air inside livestock farms has high levels of ammonia, which can negatively affect the respiratory health of both animals and workers.

To mitigate ammonia emissions, several strategies can be employed:

• Proper manure management: This includes frequent removal of manure from livestock buildings, preventing manure from drying, and avoiding long-term manure storage in fully enclosed barns.
• Ventilation techniques: Maximising ventilation during manure agitation and pumping, as well as in cases of high ammonia concentration, can help dissipate the gas.
• Floor design: Using inclined or convex, smoothly finished surfaces in animal housing facilities can reduce emissions from the solid part of the floor.
• Feed and building hygiene management: Proper management of feed and maintaining building hygiene can help reduce ammonia emissions.
• Treatment of stored manure: Physical, chemical, and biological treatments, such as aeration, adjusting manure pH, and biofiltration, can be applied to stored manure to reduce ammonia emissions.

Nitrous oxide emissions

Animal agriculture produces 65% of the world's nitrous oxide emissions, which have a global warming impact 296 times greater than carbon dioxide. Nitrous oxide (N2O) is one of the target gases in livestock agriculture, according to the Intergovernmental Panel on Climate Change (IPCC) guidelines.

N2O emissions are produced during the decomposition of nitrogen sources in anoxic conditions. They are also emitted during manure treatment, which is affected by the location of the facilities in the climate region and the duration of the treatment. The average N2O emissions from manure treatment in 16 local administrative districts in Korea were estimated to increase by 10%–153% compared to past average emissions.

Livestock excreta on pastures is another important source of N2O emissions, particularly during the wet season when urine application stimulates soil N2O emissions. However, studies measuring these emissions in tropical regions, especially in Africa, remain limited.

The impact of N2O emissions from livestock on human health is also a concern. Studies have found an association between ambient NH3 levels and lung function deficits in non-farming residents living near livestock farms. The air inside livestock farms also contains high levels of gases, including ammonia, which can affect the respiratory health of farmers and neighbouring residents.

Airway obstruction in neighbouring residents

Air pollution from livestock farms has been associated with airway obstruction in neighbouring residents. A large-scale population-based study found that emissions from livestock farms were associated with reduced lung function in inhabitants of a rural area with a high density of livestock farms. The air inside livestock farms contains high levels of dust and gases, which can affect respiratory health. Several air pollutants are emitted into the atmosphere, including gases such as ammonia and particulate matter contaminated with microorganisms.

Livestock production is the major contributor to ambient ammonia (NH3) levels, which have been linked to obstructive lung function changes in people living near livestock farms. A 25-μg/m3 increase in NH3 was associated with a 2.22% lower FEV1, FEV1/FVC of −1.12%, and MMEF of −5.67%indicators of airway obstruction. The study also found a negative association between farm density and lung function, with lung function decreasing after weeks with higher ammonia levels.

The impact of livestock farm emissions on respiratory health has been observed in both farmers and neighbouring residents. Studies have found a correlation between residential proximity to livestock farms and respiratory issues such as asthma, allergic rhinitis, and chronic obstructive pulmonary disease (COPD). Additionally, livestock farming contributes significantly to fine particulate matter (PM) air pollution, which can have adverse effects on public health.

The mechanisms behind the relationship between air pollution from livestock farms and respiratory health in patients with COPD are not yet fully understood. However, it is hypothesized that air pollutants may influence respiratory health by modulating the airway microbiome. Studies have investigated the associations between air pollution exposure and the oropharyngeal microbiota (OPM) composition of COPD patients.

The impact of livestock farming on air pollution and the consequent health risks to neighbouring residents is a growing concern. With the livestock industry often exempt from reporting hazardous air emissions, there is a lack of information on the specific pollutants present in the air surrounding these farms. This lack of data makes it challenging to fully understand the extent of the health risks faced by residents living in close proximity to these farms.

Swine and avian flu

Animal agriculture is a significant contributor to air pollution, generating nearly 15% of total global greenhouse gas emissions. The air inside livestock farms contains high levels of dust and gases, which can affect the respiratory health of farmers and neighbouring residents. The gases emitted include ammonia, methane, and nitrous oxide, with livestock producing 65% of the world's nitrous oxide emissions.

Avian influenza, or bird flu, is often spread through contact with infected wild birds. Poultry farms are at risk of infection through wind-borne particle matter contaminated with excreta from infected wild birds. The risk of infection is higher during autumn and winter, and outbreaks have been detected in commercial poultry in the Netherlands. In the case of an outbreak, indoor housing of poultry is mandated to prevent direct contact with infected wild birds. However, despite these measures, many poultry farms still become infected.

Swine flu, or H5N1, has been detected in pigs in the United States, raising concerns about interspecies transmission and the emergence of new strains. Genomic sequencing has indicated that infected swine may have contracted the virus through contact with migratory birds.

To mitigate the spread of these diseases and reduce the impact on public health, measures such as enhanced surveillance, culling of infected flocks, and vaccination of poultry have been implemented. Reducing meat and dairy consumption can also help lower the demand for industrial livestock farming and slow the industry's contribution to air pollution.

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