Air Pollution Resources

Effects of Hog Production on Ambient Air Pollution in the Top Ten Hog-Producing States

Hog production has been increasingly implicated in negative air quality. What has been missing in the research is studies of effects of hog production on ambient air pollution, the type of pollution to which community residents are exposed. In order to estimate health-based externality costs of hog operations, it is necessary to estimate the effects of this industry on ambient air quality. In this paper, I use annual county- level data for 1980 to 2005 from the top ten hog-producing states in order to examine effects in the most intensive areas. The results show a 0.10 elasticity between hog production and air pollution, after controlling for a number of covariates and fixed effects. Further, this effect is increasing over time. The Environmental Protection Agency’s current endeavor to regulate large-scale hog operations under the Clean Air Act appears justified and well- timed.

Rural Air Quality and Respiratory Health

This PhD thesis in Occupational and Environmental Health has several parts. Chapter II describes the evaluation of indoor and outdoor air quality (particulate matter and endotoxin) for 197 rural households. Chapter III describes the monitoring of hydrogen sulfide in proximity to a swine confinement. Chapter IV evaluates the association between childhood asthma and relative residential proximity to swine operations. Results showed that “children with a larger relative environmental exposure to CAFOs had a significantly increased risk of physician-diagnosed asthma.”

Modeling Hydrogen Sulfide Emissions: Are Current Swine Animal Feeding Operation Regulations Effective At Protecting Against Hydrogen Sulfide Exposure In Iowa?

The intent of this study was to evaluate whether the current separation distances mandated by law are sufficient to mitigate the effects of hydrogen sulfide air pollution from CAFOs. The author estimated the hydrogen sulfide concentration near the largest swine CAFO in Iowa, and in locations that are dense in swine CAFOs using a validated plume dispersion modeling technique. He then calculated the resulting health effect values (HEV) and health effect standards (HES) and compared the results with state air quality standards.

Respiratory dysfunction in swine production facility workers: dose-response relationships of environmental exposures and pulmonary function.

This medical epidemiological and dose-response study was conducted at 108 farms with intensive swine housing systems. The purpose of the study was to specifically identify hazardous substances in the air of these buildings, as well as determine what concentrations had negative health impacts. Ammonia and dust were identified as the two air pollutants most likely to impair pulmonary function and the concentrations of the likely to be hazardous were determined. Researchers evaluated the exposure of 171 pig farmers to dust and endotoxin over a three-year period. During this period a longitudinal decline in lung function was observed.

Concentrated swine feeding operations and public health: a review of occupational and community health effects.

This paper is a review of the environmental and health effects of modern, intensive swine production. It describes the occupational health, community health and environmental hazards that have been well researched and documented. It also points out areas of inadequate knowledge that require further research.

Health effects of airborne exposures from concentrated animal feeding operations.

This article in Environmental Health Perspective discusses the range of air pollutants that are emitted from CAFOs, including ammonia, hydrogen sulfide, carbon dioxide, malodorous vapors and particles. The authors (part of the Conference on Environmental Health Impacts of Concentrated Animal Feeding Operations: Anticipating Hazards-Searching for Solutions) point out that there is a scarcity of data on the community health effects of these low level particulate and gas emissions, with most of the available information coming from studies on CAFO workers. They state that there is a great need for more research in this area, and recommend that investigations focus on the potential health impacts of microbial exposures in addition to the effects of nuisance and odors.

Health Effects From Breathing Air Near CAFOs for Feeder Cattle or Hogs

This article in Journal of Agromedicine discusses the issue of substances released into the air by CAFOs. These contaminants, including dust containing endotoxin, hydrogen sulfide, ammonia and volatile organic compounds are documented to have negative health impacts on the respiratory health of CAFO employees. People living near CAFOs have also raised concerns about possible impacts on their health. The authors call for more research to better document the impacts of exposure to airborne CAFO emissions on local residents.

Environmental Concerns about Animal Manure

This article discusses the negative environmental impacts of swine manure spread on fields, such as the leaching of soil nitrate into ground and surface water. It also addresses emissions that arise from large swine confinements, including unacceptable levels of ammonia, dust and odors. Some countries have already passed legislation that limits both the size of pig confinements and the use of manure.

Odor influence on well-being and health with specific focus on animal production emissions

This paper reviews the effects of odors from livestock operations on the health and well-being of nearby residents. Research suggests that the main symptoms resulting from exposure to odors are headache, drowsiness, and irritation of the eye, nose, and throat. Mood and memory can also be impacted by odors. The authors call for additional research to better evaluate the health impacts of odors, so that air quality guidelines based on scientific data can be created.

Critical review: The health significance of environmental odor pollution

This paper discusses the health significance of noxious environmental odors, as well as the challenges inherent in the environmental regulatory response to this type of air pollution.

Associations between bioaerosols coming from livestock facilities and asthmatic symptoms in children

This epidemiological study investigated the association between living in the neighborhood of intensive livestock facilities and the development of respiratory and allergic symptoms in five and six year old children. A correlation analysis was performed between exposure to endotoxin and asthmatic symptoms based on 3867 questionnaires. Children of atopic parents showed an increase in asthmatic symptoms with higher endotoxin levels.

Experimental human exposure to inhaled grain dust and ammonia: towards a model of concentrated animal feeding operations

This study was designed to reproduce the exposure to air contaminants experienced by workers in swine confinement facilities. Pulmonary function and exhaled NOx were measured before and after exposure to ammonia and/or endotoxin-rich grain dust in six normal and eight mildly asthmatic subjects. Results showed that grain dust induced a transient decrease in ,

 Assessment of air quality at neighbor residences in the vicinity of swine production facilities

Researchers assessed air quality at 35 homes in three regions of the Upper Midwest of the U.S. Region 1 had primarily large scale CAFOs. Region 2 had primarily smaller scale operations with hoop structure facilities. Region 3 had primarily row-crop production (control area). The average hydrogen sulfide concentration was higher in the CAFO area. Carbon dioxide, ammonia and particulate matter were higher in the hoop structure area. The EPA recommended community standard for hydrogen sulfide 0.7 parts per billion was exceeded in all three areas, and may present a potential health risk.

Race, poverty, and potential exposure of middle-school students to air emissions from confined swine feeding operations

This epidemiological study investigated the association between race and socioeconomic status and exposure to livestock odor in middle school students. Schools located closer to swine CAFOs (mean = 4.9 miles) had enrollment of less than 63% white students and ³ 47% of students receiving subsidized lunches. Remaining schools were a mean of 10.8 miles from CAFOs. This analysis indicates that in-school exposure to airborne pollution from CAFOs in North Carolina varies with the economic and racial characteristics of the students.

Impact of odor from industrial hog operations on daily living activities.

Industrial animal production systems produce enormous quantities of waste that generates odors. This community-based research study utilized questionnaires to investigate the public’s perception of the impact of these industrial odors on activities of daily living. The results of this study indicate that odor from hog confinements limits leisure activities and social interactions “which could have adverse public health consequences.”

Does animal feeding operation pollution hurt public health? A national longitudinal study of health externalities identified by geographic shifts in livestock production

The Environmental Protection Agency has been gathering the data necessary to set rational policy for regulating livestock facilities under the Clean Air Act. This study measured the effect of pollution on infant health utilizing geographic shifts in the industry. The authors found that a doubling of production leads to a 7.4% increase in infant mortality. This increase in mortality is the result of higher levels of respiratory disease, which suggests air pollution as the causative factor.

Livestock Odors and Quality of Life of Neighboring Residents

Individuals living in neighborhoods in proximity to intensive livestock production facilities have concerns about the health impacts of exposures to livestock contaminants. In addition, they have frequent complaints of odor annoyance. This study surveyed residents in a rural area with a high concentration of animal farms. Results showed that 61% of responders had complaints about livestock odors, and their scores on physical and emotional well-being were inversely proportional to annoyance scores.

Environmental exposure to confined animal feeding operations and respiratory health of neighboring residents

This study was conducted in 2002-2004 among adults living in four rural German towns with a high density of confined animal feeding operations. A questionnaire was filled out by 6937 residents. Researchers collected on odor annoyance and on the number of confinements hear the home. Physiological measurements of allergic sensitization and lung function also were measured in a random sample. Self-reported odor annoyance was correlated with self-reported asthma symptoms and nasal allergies. Self-reported wheeze and decreased forced expiratory volume in 1 second was associated with the number of animal houses. The correlation between self-reported exposure and the results of clinical measurements was poor.

A control study of the physical and mental health of residents living near a large-scale swine operation

This study collected physical and mental health data on individuals living within a two mile radius of a large swine confinement facility. This information was compared with data from individuals living in a similar rural environment with minimal livestock production. Results showed that neighbors of the animal large-scale swine operation reported significantly higher rates of symptoms that have also been documented to occur in swine confinement workers. These symptoms are characteristic of inflammatory or toxic effects on the respiratory tract.

Symptomatic Effects of Exposure to Diluted Air Sampled from a Swine Confinement Atmosphere on Healthy Human Subjects

This study was designed to expose healthy human subjects to diluted aerial emissions from a swine facility in a laboratory setting for one hour. In a separate control session the same subjects were exposed to clean air. There were no differences found in objective measures of physical symptoms (such as heart rate, blood pressure or respiratory rate) or mood between the two sessions. However, when exposed to swine air subjects were 7.8 times more likely to report nausea, 6.1 times more likely to report eye irritation, and 4.1 times more likely to report headaches.

School Proximity to Concentrated Animal Feeding Operations and Prevalence of Asthma in Students

This study compared the incidence of an asthma diagnosis in children in two rural Iowa schools one adjacent to a CAFO (study school) and one that was distant from any large scale animal facility (control school). Results showed a significantly higher rate of physician-diagnosed asthma at the study school. Potentially confounding factors did not account for the increased incidence of asthma.

Intensive livestock operations, health, and quality of life among eastern North Carolina residents

This study was conducted due to reports of decreased health and quality of life by individuals living near industrial swine operations. Residents of three rural communities were surveyed one in the vicinity of two intensive cattle operations, one in the vicinity of a 6,000-head hog operation, and one agricultural area without livestock operations using liquid waste management systems. Results showed that there was an increased incidence of certain respiratory and gastrointestinal problems in the community near the hog confinement. The quality of life of these residents was also compromised.

Asthma Symptoms Among Adolescents who Attend Public Schools that are Located Near Confined Swine Feeding Operations

This epidemiological study assessed the relationship between asthma symptoms among adolescents in North Carolina schools and their exposure to airborne pollution from confined swine feeding operations. Exposure to airborne effluent was calculated using publicly available data, and 58,169 students aged 12-14 years answered questions about household environment, socioeconomic status, respiratory symptoms, medications and allergies. Results showed that students with allergies experienced more wheezing symptoms in schools within a three mile radius of a swine operation, and at schools with noticeable indoor livestock odor at least twice per month.

Odor from Industrial Hog Farming Operations and Mucosal Immune Function in Neighbors

Researchers evaluated the effect of malodor from industrial hog farming operations of fifteen adults living within 1.5 miles of a facility. Subjects rated odor intensity on a 9-point scale and provided saliva samples for testing of secretory immunoglobulin A (sIgA). Results showed that oderate or high odor resulted in reduced levels of sIgA, suggesting an immunosuppressive effect of malodor on mucosal immunity.

Examination of Atmospheric Ammonia Levels Near Hog CAFOs, Homes, and Schools in Eastern North Carolina

This study investigated average weekly atmospheric ammonia (NH3) concentrations in North Carolina communities in close proximity to hog CAFO’s. Distance to a hog CAFO was found to be the key variable in determining weekly atmospheric NH3 concentration. Other important predictors were live weight per operation, temperature, wind speed, and wind direction.

A Review of Literature Concerning Odors, Ammonia, and Dust fromBroiler Production Facilities: 4. Remedial Management Practices

This article aims to collect and review the literature on remedial technologies for reducing off-site transport of dust, ammonia and odorous compounds generated by broiler production facilities. The authors also identify technologies and management practices that warrant further research or investigation.

“Influence of farming exposure on the development of asthma and asthma-like symptoms”

This paper reviews studies on the impacts of farming exposure in the development of asthma and allergies in children. Research with European children indicates that farming exposure has a protective effect in this regard. However, children in the U.S. who are exposed to CAFOs, especially swinae CAFOs, have increased rates of asthma.

“Rural Air Quality and Respiratory Health”

This PhD thesis for a degree in Occupational and Environmental Health has several parts. Chapter II describes the evaluation of indoor and outdoor quality (particulate matter and endotoxin) for 197 rural households. Chapter III describes the monitoring of hydrogen sulfide in proximity to a swine confinement. Chapter IV evaluates the association between childhood asthma and relative residential proximity to swine operations. Results showed that “children with a larger relative environmental exposure to CAFOs had a significantly increased risk of physician-diagnosed asthma.”

Relative exposure to swine animal feeding operations and childhood asthma prevalence in an agricultural cohort

This epidemiological study evaluated the relationship between relative environmental exposure to Animal Feeding Operations (AFOs) and prescribed medication for wheezing and/or a diagnosis of asthma in 565 children in rural Iowa. Researchers found significantly increased odds of both outcomes in children with a greater relative exposure to AFO’s.

Agricultural Lung Diseases

This article discusses the occupational hazards of agriculture, focusing on “the emerging respiratory health issues in a changing agricultural economic and technologic environment.”

Alterations in bronchoalveolar lavage fluid but not in lung function and bronchial responsiveness in swine confinement workers.

A variety of tests for lung function, immune system function and bronchial reactivity were performed on 20 randomly selected non-smoking swine confinement workers. These results were compared with the same battery of tests performed on 20 non-smoking urban dwellers. Results showed that swine farmers had signs of immune system activation and inflammatory airway reaction without alteration in bronchial activity or lung function.

Endotoxin exposure as a major determinant of lung function decline in pig farmers

Researchers evaluated the exposure of 171 pig farmers to dust and endotoxin over a three year period. During this period a longitudinal decline in lung function was observed.

“Community health and socioeconomic issues surrounding concentrated animal feeding operations”

This paper by the Workgroup on Community and Socioeconomic Issues discusses the principles that define healthy rural communities. It also evaluates the impact of CAFOs on rural community health. Finally it makes recommendations for policy changes, including limiting animal density per watershed and mandating environmental impact statements

Health effects of airborne exposures from concentrated animal feeding operations.

This article in Environmental Health Perspective discusses the range of air pollutants that are emitted from CAFOs, including ammonia, hydrogen sulfide, carbon dioxide, malodorous vapors and particles. The authors (part of the Conference on Environmental Health Impacts of Concentrated Animal Feeding Operations: Anticipating Hazards-Searching for Solutions) point out that there is a scarcity of data on the community health effects of these low level particulate and gas emissions, with most of the available information coming from studies on CAFO workers. They state that there is a great need for more research in this area, and recommend that investigations focus on the potential health impacts of microbial exposures in addition to the effects of nuisance and odors.

Health Effects From Breathing Air Near CAFOs for Feeder Cattle or Hogs

This article in Journal of Agromedicine discusses the issue of substances released into the air by CAFOs. These contaminants, including dust containing endotoxin, hydrogen sulfide, ammonia and volatile organic compounds are documented to have negative health impacts on the respiratory health of CAFO employees. People living near CAFOs have also raised concerns about possible impacts on their health. The authors call for more research to better document the impacts of exposure to airborne CAFO emissions on local residents.

Odour influence on well-being and health with specific focus on animal production emissions

Odour and odorants may affect the quality of life of exposed individuals. A review of the literature on olfaction and reactions to odours was carried out with the aim of reaching an understanding of their influence on well-being and health, and to suggest possible improvements in odour environment. This review has focussed specifically on the impact of animal production emissions.

Livestock odors: implications for human health and well-being

This paper reviews the effects of odors from livestock operations on the health and well-being of nearby residents. Research suggests that the main symptoms resulting from exposure to odors are headache, drowsiness, and irritation of the eye, nose, and throat. Mood and memory can also be impacted by odors. The authors call for additional research to better evaluate the health impacts of odors, so that air quality guidelines based on scientific data can be created.

Critical review: The health significance of environmental odor pollution

This paper discusses the health significance of noxious environmental odors, as well as the challenges inherent in the environmental regulatory response to this type of air pollution.

Integrating Epidemiology, Education, and Organizing for Environmental Justice: Community Health Effects of Industrial Hog Operations

This epidemiological study was conducted in eastern North Carolina where high-density industrial swine production takes place in communities of low-income people and people of color. The study design references the precepts of the environmental justice movement. The authors investigated the impacts of industrial agricultural pollution on the health and quality of life of neighboring communities while providing opportunities for community education and organizing.

Associations between bioaerosols coming from livestock facilities and asthmatic symptoms in children.

This epidemiological study investigated the association between living in the neighborhood of intensive livestock facilities and the development of respiratory and allergic symptoms in five and six year old children. A correlation analysis was performed between exposure to endotoxin and asthmatic symptoms based on 3867 questionnaires. Children of atopic parents showed an increase in asthmatic symptoms with higher endotoxin levels.

Experimental human exposure to inhaled grain dust and ammonia: towards a model of concentrated animal feeding operations

This study was designed to reproduce the exposure to air contaminants experienced by workers in swine confinement facilities. Pulmonary function and exhaled NOx were measured before and after exposure to ammonia and/or endotoxin-rich grain dust in six normal and eight mildly asthmatic subjects. Results showed that grain dust induced a transient decrease in Forced Expiratory Volume (FEV1) in the asthmatic group.

Assessment of air quality at neighbor residences in the vicinity of swine production facilities

Researchers assessed air quality at 35 homes in three regions of the Upper Midwest of the U.S. Region 1 had primarily large scale CAFOs. Region 2 had primarily smaller scale operations with hoop structure facilities. Region 3 had primarily row-crop production (control area). The average hydrogen sulfide concentration was higher in the CAFO area. Carbon dioxide, ammonia and particulate matter were higher in the hoop structure area. The EPA recommended community standard for hydrogen sulfide ¾ 0.7 parts per billion was exceeded in all three areas, and may present a potential health risk.

Prevalence of hay fever and allergic sensitization in farmer’s children and their peers living in the same rural community

This epidemiological study investigated rates of allergic diseases in children growing up on a farm versus children children of non-farming families in the same village. Results showed statistically significant lower rates of sneezing and atopic sensitization in children of farming parents. There was no difference in the rates of wheezing or itchy skin rash.

Livestock Odours and Quality of Life of Neighboring Residents

Individuals living in neighborhoods in proximity to intensive livestock production facilities have concerns about the health impacts of exposures to livestock contaminants. In addition, they have frequent complaints of odor annoyance. This study surveyed residents in a rural area with a high concentration of animal farms. Results showed that 61% of responders had complaints about livestock odors, and their scores on physical and emotional well-being were inversely proportional to annoyance scores.

Environmental exposure to confined animal feeding operations and respiratory health of neighboring residents

This study was conducted in 2002-2004 among adults living in four rural German towns with a high density of confined animal feeding operations. A questionnaire was filled out by 6937 residents data was collected on odor annoyance and on the number of confinements hear the home. Physiological measurements of allergic sensitization and lung function also were measured in random sample. Self-reported odor annoyance was correlated with self-reported asthma symptoms and nasal allergies. Self-reported wheeze and decreased forced expiratory volume in 1 second was associated with the number of animal houses. The correlation between self-reported exposure and the results of clinical measurements was poor.

Environmental Stressors, Perceived Control, and Health: The Case of Residents Near Large-Scale Hog Farms in Eastern North Carolina

This study compared differences between 48 individuals living near industrial hog farms and a control group with no exposure to hog farms. Nearby residence was associated with an increase in 12 out of 22 physical complaints, primarily related to respiratory, sinus and nausea symptoms. Increasing physical health symptoms also appears to increase psychological distress.

Symptomatic Effects of Exposure to Diluted Air Sampled from a Swine Confinement Atmosphere on Healthy Human Subjects

This study was designed to expose healthy human subjects to diluted aerial emissions from a swine facility in a laboratory setting for one hour. In a separate control session the same subjects were exposed to clean air. There were no differences found in objective measures of physical symptoms (such as heart rate, blood pressure or respiratory rate) or mood between the two sessions. However, when exposed to swine air subjects were 7.8 times more likely to report nausea, 6.1 times more likely to report eye irritation, and 4.1 times more likely to report headaches.

School Proximity to Concentrated Animal Feeding Operations and Prevalence of Asthma in Students

This study compared the incidence of an asthma diagnosis in children in two rural Iowa schools one adjacent to a CAFO (study school) and one that was distant from any large scale animal facility (control school). Results showed a significantly higher rate of physician-diagnosed asthma at the study school. Potentially confounding factors did not account for the increased incidence of asthma.

Asthma Symptoms Among Adolescents who Attend Public Schools that are Located Near Confined Swine Feeding Operations

This epidemiological study assessed the relationship between asthma symptoms among adolescents in North Carolina schools and their exposure to airborne pollution from confined swine feeding operations. Exposure to airborne effluent was calculated using publicly available data, and 58169 students aged 12-14 years answered questions about household environment, socioeconomic status, respiratory symptoms, medications and allergies. Results showed that students with allergies experience more wheezing symptoms in schools within a three mile radius of a swine operation, and at schools with noticeable indoor livestock odor at least twice per month.

Odor from Industrial Hog Farming Operations and Mucosal Immune Function in Neighbors

Researchers evaluated the effect of malodor from industrial hog farming operations of fifteen adults living within 1.5 miles of a facility. Subjects rated odor intensity on a 9-point scale and provided saliva samples for testing of secretory immunoglobulin A (sIgA). Results showed that oderate or high odor resulted in reduced levels of sIgA, suggesting an immunosuppressive effect of malodor on mucosal immunity.

Malodor as a Trigger of Stress and Negative Mood in Neighbors of Industrial Hog Operations

Malodor is an important facet of environmental injustice, because industrial facilities that create malodor are disproportionately located near communities of low income people and people of color. Malodor has negative impacts on physical and mental health and social wellbeing. In this epidemiological study, participants who lived within 1.5 miles of at least one industrial hog facility rated malodor intensity, mood, and stress during a two week period, while researchers monitored air pollution levels. Results showed that particulate matter, hydrogen sulfide and malodor were related to negative mood and stress in these low income communities.

Impact of odor from industrial hog operations on daily living activities.

Industrial animal production systems produce enormous quantities of waste that generates odors. This community-based research study utilized questionnaires to investigate the public’s perception of the impact of these industrial odors on activities of daily living. The results of this study indicate that odor from hog confinements limits leisure activities and social interactions “which could have adverse public health consequences.”

EPA Needs More Information and a Clearly Defined Strategy to Protect Air and Water Quality from Pollutants of Concern

In this 85 page report the Government Accountability Office analyzed data collected by the USDA from 1982-2002. Because no federal agency collects consisten, reliable data on Concentrated Animal Feeding Operations, this reports used large farms as a proxy for CAFOs. The report addresses five main topics: 1) CAFO trends over the past 30 years, 2) the amount of waste generated by CAFOs, 3) key research on the environmental and health impacts of CAFOs, 4) the progress of the EPA in developing air emissions protocols for CAFOs, and 5) the impact of recent court decisions on regulation of CAFO water pollution by the EPA.

Air Quality Facts

With the rise of large industrial CAFOs as the preeminent form of livestock production and their associated higher production of gases, vapors, and fumes, these exposures now have the potential to affect larger numbers of individuals, including members of the neighboring community not involved in agriculture or related industrial livestock production.


Air Pollution Resources used with permission from Iowa Alliance for Responsible Agriculture.