Swine Feeding Operations Research Articles

Optimal design of manure management for intensive swine feeding operation: A modeling method based on analytical target cascading

One of the most significant challenges in existing livestock production is the negative impact of animal waste on the environment. Accumulative manure produced in intensive swine feeding operations (ISFO) cannot be efficiently utilized in a sustainable and economical way. A successful manure management system should maximize the overall economic benefits while satisfying the environmental requirements. To address the manure management problem in a region that lacks adequate land for manure spreading, this project presents a novel modeling approach (Analytic target cascading, ATC) to optimize the design and operation of a swine manure management system by formulating economic objectives, engineering objectives and environmental objectives into individual tasks. This modeling structure simplifies the formulation of a systematic problem, decomposes “all-in-one” model into small tasks, and integrates the professional assessment models into optimal design. We organized the local agricultural information (swine production, crop production) and treatment operational data into parameters and constraints, then optimized the design capacities of main components, operations of manure management and crop management sequentially through updating the targets and responses in each iteration. To explore the viability of the proposed models and solution methodology, a case study in Hangzhou, China (a swine farm with Anaerobic Digestion process + Ectopic Fermentation) is designed using ATC approach. Additionally, the scenario analyses are discussed to provide further insights of opportunities and risks. Our analysis will improve the ability to deal with agricultural systematic problems with social, environmental and economic agreements.

A High Docosahexaenoic Acid Diet Alters the Lung Inflammatory Response to Acute Dust Exposure.

Agricultural workers are at risk for the development of acute and chronic lung diseases due to their exposure to organic agricultural dusts. A diet intervention using the omega-3 fatty acid docosahexaenoic acid (DHA) has been shown to be an effective therapeutic approach for alleviating a dust-induced inflammatory response. We thus hypothesized a high-DHA diet would alter the dust-induced inflammatory response through the increased production of specialized pro-resolving mediators (SPMs). Mice were pre-treated with a DHA-rich diet 4 weeks before being intranasally challenged with a single dose of an extract made from dust collected from a concentrated swine feeding operation (HDE). This omega-3-fatty-acid-rich diet led to reduced arachidonic acid levels in the blood, enhanced macrophage recruitment, and increased the production of the DHA-derived SPM Resolvin D1 (RvD1) in the lung following HDE exposure. An assessment of transcript-level changes in the immune response demonstrated significant differences in immune pathway activation and alterations of numerous macrophage-associated genes among HDE-challenged mice fed a high DHA diet. Our data indicate that consuming a DHA-rich diet leads to the enhanced production of SPMs during an acute inflammatory challenge to dust, supporting a role for dietary DHA supplementation as a potential therapeutic strategy for reducing dust-induced lung inflammation.

Seasonal variations in export of antibiotic resistance genes and bacteria in runoff from an agricultural watershed in Iowa

Seasonal variations of antimicrobial resistance (AMR) indicators in runoff water can help improve our understanding of AMR sources and transport within an agricultural watershed. This study aimed to monitor multiple areas throughout the Black Hawk Lake (BHL) watershed (5324 ha) in central Iowa during 2017 and 2018 that consists of both swine and cattle feeding operations as well as known areas with manure application. The measured indicators included plate counts for fecal indicator bacteria (FIB) E. coli, Enterococcus, antibiotic resistant fecal indicator bacteria (ARBs) tylosin resistant Enterococcus, tetracycline resistant Enterococcus, and antibiotic resistance genes (ARGs): ermB, ermF (macrolide), tetA, tetM, tetO, tetW (tetracycline), sul1, sul2 (sulfonamide), aadA2 (aminoglycoside), vgaA, and vgaB (pleuromutilin). Both the plate count and the ARG analyses showed seasonal trends. Plate counts were significantly greater during the growing season, while the ARGs were greater in the pre-planting and post-harvest seasons (Wilcoxon Rank-Sum Test p < 0.05). The ermB gene concentration was significantly correlated (p < 0.05) with E. coli and Enterococcus concentrations in 2017, suggesting a potential use of this ARG as an indicator of environmental AMR and human health risk. Flow rate was not a significant contributor to annual variations in bacteria and AMR indicators. Based on observed seasonal patterns, we concluded that manure application was the likely contributor to elevated ARG indicators observed in the BHL watershed, while the driver of elevated ARB indictors in the growing season can only be speculated. Understanding AMR export patterns in agricultural watersheds provides public health officials knowledge of seasonal periods of higher AMR load to recreational waters.

Differences in Microbial Communities and Pathogen Survival Between a Covered and Uncovered Anaerobic Lagoon

Anaerobic lagoons are a critical component of confined swine feeding operations. These structures can be modified, using a synthetic cover, to enhance their ability to capture the emission of ammonia and other malodorous compounds. Very little has been done to assess the potential of these covers to alter lagoon biological properties. Alterations in the physicochemical makeup can impact the biological properties, most notably, the pathogenic populations. To this aim, we performed a seasonal study of two commercial swine operations, one with a conventional open lagoon, the other which employed a permeable, synthetic cover. Results indicated that lagoon fecal coliforms, and Escherichia coli were significantly influenced by sampling location (lagoon vs house) and lagoon type (open vs. covered), while Enterococcus sp. were influenced by sampling location only. Comparisons against environmental variables revealed that fecal coliforms (r2 = 0.40), E. coli (r2 = 0.58), and Enterococcus sp. (r2 = 0.25) significantly responded to changes in pH. Deep 16S sequencing of lagoon and house bacterial and archaeal communities demonstrated grouping by both sampling location and lagoon type, with several environmental variables correlating to microbial community differences. Overall, these results demonstrate that permeable synthetic covers play a role in changing the lagoon microclimate, impacting lagoon physicochemical and biological properties.

Sources and pollution characteristics of antibiotic resistance genes and conditional pathogenic bacteria in concentrated swine feeding operation.

Air in concentrated animal feeding operations contains antibiotic resistance genes and airborne pathogens, with potential threat to human and animal health. In this study, air was sampled in the living area, outside, and inside of a fattening pig house in a pig farm for 24 and 48 hours. Feedstuffs, drinking water additives, and feces in the pig house were collected. Three kinds of antibiotic resistance genes (macrolide, β-lactam, and tetracycline) and seven pathogenic microorganisms (Campylobacter, Clostridium perfringens, Enterococcus, Escherichia coli, Yersinia enterocolitica, Staphylococcus spp., and Streptococcus suis) were detected by polymerase chain reaction (PCR). Six genes with high detection rates were selected, with their concentrations being determined by real-time quantitative PCR (qPCR). Results showed that three macrolide and two tetracycline resistance genes were detected in all air samples. Enterococcus, Escherichia coli, Yersinia enterocolitica, and Staphylococcus spp. were detected in air samples and drinking water additive. The concentrations of most target genes were above 104 copies·m-3. The gene concentrations near the pig house were much higher than those in the living area. Main sources of antibiotic resistance genes and pathogens in the air were pig manure and drinking water additive. Sampling time of 24 h in the pig farm met the requirements for PCR detection. Sampling time of 48 h had a higher sampling efficiency than that of 24 h in the living area of the pig farm, whereas sampling time of 24 h was more appropriate than that of 48 h in high bioaerosol concentration area such as the pig house.

Seasonal variation of macrolide resistance gene abundances in the South Fork Iowa River Watershed

The Midwestern United States is dominated by agricultural production with high concentrations of swine, leading to application of swine manure onto lands with artificial subsurface drainage. Previous reports have indicated elevated levels of antibiotic resistance genes (ARGs) in surface water and groundwater around confined animal feeding operations which administer antimicrobials. While previous studies have examined the occurrence of ARGs around confined swine feeding operations, little information is known how their transport from tile-drained fields receiving swine manure application impacts downstream environments. To further our knowledge in this area, water samples were collected from five locations in the agriculturally dominated South Fork Iowa River Watershed with approximately 840,000 swine present in the 76,000ha basin. Samples were collected monthly from three stream sites and two main artificial subsurface drainage outlets. Samples were analyzed for macrolide resistance genes ermB, ermF and 16S rRNAgene abundance using qPCR. Abundance of erm genes ranged from below limits of quantification to >107 copies 100mL−1 water. Eighty-nine percent of stream water samples contained one of these two ARGs. Results indicate significantly more ermB and ermF in main drainage outlets than stream samples when normalized by 16S rRNA abundance (p<0.0001). Both artificial drainage locations revealed temporal trends for ermB and ermF abundance when normalized to 16S rRNA abundance. The higher resistance gene concentrations identified in artificial drainage samples occurring mid-Spring and late-Fall are likely due to manure application.

The effect of Chamaecyparis obtus extract on the concentrations of odorous compounds and odor activity value from air in swine feeding operation

The effect of Chamaecyparis obtus extract on the concentrations of odorous compounds and odor activity value from air in swine feeding operation

Are People Living Near Modern Swine Production Facilities at Increased Risk of Influenza Virus Infection?

Swine can harbor influenza viruses that are pathogenic to humans. Previous studies support an increased risk of human influenza cases among individuals with swine contact. North Carolina has the second-largest swine industry in the United States. We investigated the spatiotemporal association between influenza-like illnesses (ILIs) and licensed swine operations from 2008 to 2012 in North Carolina. We determined the week in which ILI cases peaked and statistically estimated their week of onset. This was performed for all 100 North Carolina counties for 4 consecutive influenza seasons. We used linear models to correlate the number of permitted swine operations per county with the weeks of onset and peak ILI activity. We found that during the 2009-2010 and 2010-2011 influenza seasons, both seasons in which the pandemic 2009 H1N1 influenza A virus circulated, ILI peaked earlier in counties with a higher number of licensed swine operations. We did not observe this in 2008-2009 or 2011-2012, nor did we observe a relationship between ILI onset week and number of swine operations. Our findings suggest that concentrated swine feeding operations amplified transmission of influenza during years in which H1N1 was circulating. This has implications for vaccine strategies targeting swine workers, as well as virologic surveillance in areas with large concentrations of swine.

Changes in dissolved organic matter composition and metabolic diversity of bacterial community during the degradation of organic matter in swine effluent.

In this study, an incubation experiment was conducted with effluent collected from the concentrated swine-feeding operations (CSFOs) located in Yujiang County of Jiangxi Province, China. The purpose of this study was to elucidate the relationships between the composition of dissolved organic matter (DOM) and the community-level physiological profiles (CLPPs) of microorganisms in swine effluent. For all samples examined, the concentrations of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) were decreased by an average of 58.2 ± 30.4 and 49.2 ± 38.7%, whereas total dissolved phosphorus (TDP) exhibited an average final accumulation of 141.5 ± 43.0%. In the original samples, ammonium nitrogen accounted for 88.9 ± 4.9% of the TDN, which was reduced to a final average of 83.9 ± 9.6%. Two protein-like (tyrosine and tryptophan) and two humic-like (fulvic acids and humic acids) components were identified using a three-dimensional excitation-emission matrix. With the increase in incubation time, the relative concentrations of two protein-like components in effluent were reduced by an average of 83.2 ± 24.7%. BIOLOG(™) ECO plates were used to determine the metabolic fingerprint of the bacterial community, and a shift in the utilization patterns of substrates was observed over the study period. Additionally, the Shannon-Wiener index of CLPP was ultimately reduced by an average of 43.5 ± 8.5%, corresponding to the metabolic diversity of the bacterial community. The redundancy analysis identified significant relationships between environmental parameters and the CLPP of microorganisms. To a certain degree, the DOM compositions were linked with the substrate utilization patterns of the bacterial community during the degradation of organic matter in swine effluent.

Effect of horseradish, mushroom waste and almond hull on the concentrations of odorous compounds in swine manure for spreading on grassland in spring

The objective of the current study was to investigate the effect of odor reducing agents on the levels of pH, total carbon, total nitrogen, and odorous compounds [phenols, indoles, short chain fatty acid (SCFA), branched-chain fatty acid (BCFA), and ammonium nitrogen] of swine manure during the spring season (temperature around 20°C). Odor reducing agents included horseradish powder, mushroom waste powder, and almond hull powder. A manure sample (15 L) was taken from the pit under the pens of a swine feeding operation and incubated with 0.03% horseradish powder, 1% mushroom waste powder, and 1% almond hull powder, respectively, in acryl chambers for 14 days. Addition of almond hull powder showed the lowest pH (p < 0.05) and the highest level of total carbon (p < 0.05) among treatments of odor reducing agents. Although addition of odor reducing agents increased the level of phenols (p < 0.05), addition of almond hull powder decreased the level of indoles (p < 0.05). Levels of SCFA and BCFA were higher in almond hull powder than those in control (p < 0.05). Taken together, the results from our current study showed that odor reducing agents can be used for reducing the odor of swine manure by providing fermentable carbohydrates. At 20°C, however, the function of odor reducing agents might be decreased due to lower microbial activity.

Air Pollution, Lung Function, and Physical Symptoms in Communities Near Concentrated Swine Feeding Operations

Concentrated animal feeding operations emit air pollutants that may affect health. We examined associations of reported hog odor and of monitored air pollutants with physical symptoms and lung function in people living within 1.5 miles of hog operations. Between September 2003 and September 2005, we measured hydrogen sulfide (H2S), endotoxin, and particulate matter (PM10, PM2.5, and PM2.5-10) for approximately 2-week periods in each of 16 eastern North Carolina communities. During the same time periods, 101 adults sat outside their homes twice a day for 10 minutes, reported hog odor and physical symptoms, and measured their lung function. Conditional fixed-effects logistic and linear regression models were used to derive estimates of associations. The log odds (±1 standard error) of acute eye irritation following 10 minutes outdoors increased by 0.53 (±0.06) for every unit increase in odor, by 0.15 (±0.06) per 1 ppb of H2S, and by 0.36 (±0.11) per 10 μg/m of PM10. Odor and H2S were also associated with irritation and respiratory symptoms in the previous 12 hours. The log odds of difficulty breathing increased by 0.50 (±0.15) per unit of odor. A 10 μg/m increase in mean 12-hour PM2.5 was associated with increased log odds of wheezing (0.84 ± 0.29) and declines in forced expiratory volume in 1 second (-0.04 ± 0.02 L). A 10 EU/mg increase in endotoxin was associated with increased log odds of sore throat (0.10 ± 0.05), chest tightness (0.09 ± 0.04), and nausea (0.10 ± 0.05). Pollutants measured near hog operations are related to acute physical symptoms in a longitudinal study using analyses that preclude confounding by time-invariant characteristics of individuals.

Occurrence and Persistence of Erythromycin Resistance Genes (erm) and Tetracycline Resistance Genes (tet) in Waste Treatment Systems on Swine Farms

Animal manure from modern animal agriculture constitutes the single largest source of antibiotic resistance (AR) owing to the use of large quantities of antibiotics. After animal manure enters the environment, the AR disseminates into the environment and can pose a potentially serious threat to the health and well-being of both humans and animals. In this study, we evaluated the efficiency of three different on-farm waste treatment systems in reducing AR. Three classes of erythromycin resistance genes (erm) genes (B, F, and X) conferring resistances to macrolide-lincosamides-streptogramin B (MLS(B)) and one class of tetracycline resistance genes (tet) gene (G) conferring resistance to tetracyclines were used as models. Real-time polymerase chain reaction assays were used to determine the reservoir sizes of these AR genes present in the entire microbiome. These classes of AR genes varied considerably in abundance, with erm(B) being more predominant than erm(F), erm(X), and tet(G). These AR genes also varied in persistence in different waste treatment systems. Aerobic biofiltration reduced erm(X) more effectively than other AR genes, while mesophilic anaerobic digestion and lagoon storage did not appreciably reduce any of these AR genes. Unlike chemical pollutants, some AR genes could increase after reduction in a preceding stage of the treatment processes. Season might also affect the persistence of AR. These results indicate that AR arising from swine-feeding operations can survive typical swine waste treatment processes and thus treatments that are more effective in destructing AR on farms are required.

Recovery of Salmonella from Bermudagrass Exposed to Simulated Wastewater

Most confined swine (Sus scrofa) feeding operations in the southeastern United States hold manure in lagoons and apply effluent on bermudagrass [Cynodon dactylon (L.) Pers.] as fertilizer. Salmonella enterica subsp. enterica (ex Kauffman and Edwards) Le Minor and Popoff, has been reported in Mississippi lagoons, but levels and potential for contamination of bermudagrass were unknown. A laboratory method was developed to examine Salmonella contamination of bermudagrass and levels of Salmonella were determined in lagoons. The U.S. Environmental Protection Agency (EPA) worst case water was used to simulate effluent in exposing bermudagrass to Salmonella. Exposed leaves were washed and bacteria enumerated. Contamination of leaves exposed to 10(6) cfu mL(-1) varied from 0 to 10(4) cfu per leaf within and among eight bermudagrass cultivars and five Salmonella isolates. No differences (P < 0.05) occurred between cultivars (n = 20) or isolates (n = 10). Data fitted (R2 = 0.93) to a contamination equation (y = 5 x 10(-6)X6.623) described the relationship between levels (Log10 cfu mL(-1)) of exposure (x) and contamination (y). In fall 2007 Salmonella levels from six lagoons ranged from 1.9 to 2.8 log10 MPN 100 mL(-1) and were below the threshold for contamination predicted by the equation. These preliminary results must be tested with effluents in the field, but considered alongside work of others, which report lagoon Salmonella levels to be highest in fall, suggest that Salmonella levels in effluents from these lagoons may be too low to produce measurable contamination on bermudagrass.

Field Sampling Method for Quantifying Odorants in Humid Environments

Most air quality studies in agricultural environments use thermal desorption analysis for quantifying semivolatile organic compounds (SVOCs) associated with odor. The objective of this study was to develop a robust sampling technique for measuring SVOCs in humid environments. Test atmospheres were generated at ambient temperatures (23 +/- 1.5 degrees C) and 25, 50, and 80% relative humidity (RH). Sorbent material used included Tenax, graphitized carbon, and carbon molecular sieve (CMS). Sorbent tubes were challenged with 2, 4, 8, 12, and 24 L of air at various RHs. Sorbent tubes with CMS material performed poorly at both 50 and 80% RH dueto excessive sorption of water. Heating of CMS tubes during sampling or dry-purging of CMS tubes post sampling effectively reduced water sorption with heating of tubes being preferred due to the higher recovery and reproducibility. Tenaxtubes had breakthrough of the more volatile compounds and tended to form artifacts with increasing volumes of air sampled. Graphitized carbon sorbent tubes containing Carbopack X and Carbopack C performed best with quantitative recovery of all compounds at all RHs and sampling volumes tested. The graphitized carbon tubes were taken to the field for further testing. Field samples taken from inside swine feeding operations showed that butanoic acid, 4-methylphenol, 4-ethylphenol, indole, and 3-methylindole were the compounds detected most often above their odor threshold values. Field samples taken from a poultry facility demonstrated that butanoic acid, 3-methylbutanoic acid, and 4-methylphenol were the compounds above their odor threshold values detected most often, relative humidity, CAFO, VOC, SVOC, thermal desorption, swine, poultry, air quality, odor.

Antibiotic-Resistant Enterococci and Fecal Indicators in Surface Water and Groundwater Impacted by a Concentrated Swine Feeding Operation

BackgroundThe nontherapeutic use of antibiotics in swine feed can select for antibiotic resistance in swine enteric bacteria. Leaking swine waste storage pits and the land-application of swine manure can result in the dispersion of resistant bacteria to water sources. However, there are few data comparing levels of resistant bacteria in swine manure–impacted water sources versus unaffected sources.ObjectivesThe goal of this study was to analyze surface water and groundwater situated up and down gradient from a swine facility for antibiotic-resistant enterococci and other fecal indicators.MethodsSurface water and groundwater samples (n = 28) were collected up and down gradient from a swine facility from 2002 to 2004. Fecal indicators were isolated by membrane filtration, and enterococci (n = 200) were tested for susceptibility to erythromycin, tetracycline, clindamycin, virginiamycin, and vancomycin.ResultsMedian concentrations of enterococci, fecal coliforms, and Escherichia coli were 4- to 33-fold higher in down-gradient versus up-gradient surface water and groundwater. We observed higher minimal inhibitory concentrations for four antibiotics in enterococci isolated from down-gradient versus up-gradient surface water and groundwater. Elevated percentages of erythromycin- (p = 0.02) and tetracycline-resistant (p = 0.06) enterococci were detected in down-gradient surface waters, and higher percentages of tetracycline- (p = 0.07) and clindamycin-resistant (p < 0.001) enterococci were detected in down-gradient groundwater.ConclusionsWe detected elevated levels of fecal indicators and antibiotic-resistant enterococci in water sources situated down gradient from a swine facility compared with up-gradient sources. These findings provide additional evidence that water contaminated with swine manure could contribute to the spread of antibiotic resistance.

Airborne Antibiotic Concentrations in a Swine Feeding Operation

During the past 50 years, it has become common practice in the U.S. to add antibiotics to livestock feed to reduce disease and promote growth. Use of antibiotics in this manner has become the source of increasing controversy because overuse of antibiotics is suspected of leading to resistance in bacteria that cause human diseases. The purpose of this study was to measure airborne antibiotic concentrations in a swine production facility that routinely included antibiotics in feed. Samples were collected in a hog facility that included rooms devoted to farrowing, nursery, and growing operations. Analytical methods were developed to measure concentrations of the antibiotics tylosin and lincomycin in air samples. Tylosin was mixed in the feed in some of the rooms in the facility. While lincomycin was not added during this study, it had been used in this facility in the past and therefore was included in the analytical testing. Inhalable (n = 34), respirable (n = 37), and high-volume (n = 16) dust samples were collected on PVC filters over a two-month period. Tylosin concentrations were above the limit of quantification (LOQ) in 93% of the samples, while lincomycin concentrations were above the LOQ in only 9% of the samples (LOQ = 0.04 ng/sample). The average tylosin concentrations were 3, 18, and 49 ng/m3 in the respirable, inhalable, and high-volume samples, respectively. No occupational or environmental worker exposure criteria currently exist for antibiotics in air. The results of this study may be used to estimate potential swine production worker exposures and to further study the association between these exposures and health effects.

Asthma Symptoms Among Adolescents Who Attend Public Schools That Are Located Near Confined Swine Feeding Operations

Little is known about the health effects of living in close proximity to industrial swine operations. We assessed the relationship between estimated exposure to airborne effluent from confined swine feeding operations and asthma symptoms among adolescents who were aged 12 to 14 years. During the 1999-2000 school year, 58169 adolescents in North Carolina answered questions about their respiratory symptoms, allergies, medications, socioeconomic status, and household environments. To estimate the extent to which these students may have been exposed during the school day to air pollution from confined swine feeding operations, we used publicly available data about schools (n = 265) and swine operations (n = 2343) to generate estimates of exposure for each public school. Prevalence ratios and 95% confidence intervals for wheezing within the past year were estimated using random-intercepts binary regression models, adjusting for potential confounders, including age, race, socioeconomic status, smoking, school exposures, and household exposures. The prevalence of wheezing during the past year was slightly higher at schools that were estimated to be exposed to airborne effluent from confined swine feeding operations. For students who reported allergies, the prevalence of wheezing within the past year was 5% higher at schools that were located within 3 miles of an operation relative to those beyond 3 miles and 24% higher at schools in which livestock odor was noticeable indoors twice per month or more relative to those with no odor. Estimated exposure to airborne pollution from confined swine feeding operations is associated with adolescents' wheezing symptoms.

Hogging the Air: CAFO Emissions Reach into Schools

Confined animal feeding operations (CAFOs) can pollute the surrounding air with malodorous compounds, bacteria, fungi, and endotoxin. CAFO-related health impacts have been investigated primarily in adults, but children may be at greater risk because of their size and developmental stage. Since children spend considerable time at school, researchers at the University of North Carolina at Chapel Hill conducted an investigation of schools’ proximity to swine CAFOs to determine the extent to which students may be exposed to airborne CAFO emissions [EHP 114:591–596; Mirabelli et al.]. They determined that some students may encounter CAFO-associated exposures at school and also found that students of color and of low socioeconomic status were the most likely to be affected. Compared to people living farther away, residents living near CAFOs report a higher prevalence of headaches and respiratory symptoms such as coughing. One study found that CAFO neighbors experience lower secretion and concentration of an immune system protein during odor episodes; another reported livestock odor as having a negative impact on adult levels of tension, depression, and anger. For children, the closer they live to a CAFO, the greater their risk of asthma symptoms. CAFOs are disproportionately sited in communities of color and areas of poverty. These populations may be more susceptible to the ill effects of airborne exposures owing to existing health challenges such as higher-than-average disease rates and inadequate health care access. The study findings are based in part on the geographic locations of swine CAFOs and 339 public schools in North Carolina, a state with significant hog, cattle, and poultry industries. Additionally, personnel from 267 schools completed a 21-item survey that included questions about the frequency and intensity of livestock odors in the schools’ indoor and outdoor environments. Publicly available records detailed schools’ racial and ethnic composition and the proportion of students participating in the National School Lunch Program, which provides free or reduced-price meals to students from low-income families. Participation in the program served as an indicator of students’ socioeconomic status. Of the 226 schools included in the final analysis, distances between a school and the closest swine CAFO ranged from 0.2 to 42.0 miles. Of these, 29% were within 3 miles of one or more swine CAFOs, 21% reported livestock odors outdoors, and 8% reported noticeable livestock odors indoors. The overall average rating of odor intensity was 2.2 on a scale of 1 to 5; the average rating inside buildings was 2.8. Schools with noticeable odors were more likely attended by students of lower socioeconomic status, regardless of race. Schools with more white students or students of higher socioeconomic status tended to be farther from a swine CAFO. Although the researchers did not characterize the composition of swine CAFO–associated air pollution or identify specific health-related effects, they conclude that livestock-related odors in and around schools may indicate the presence of hazardous airborne contaminants from nearby CAFOs. Their results confirm and expand previous research describing racial and economic disparities in exposure to CAFO emissions.

Asthma Symptoms Among Adolescents Who Attend Public Schools That Are Located Near Confined Swine Feeding Operations

Asthma Symptoms Among Adolescents Who Attend Public Schools That Are Located Near Confined Swine Feeding Operations

Race, Poverty, and Potential Exposure of Middle-School Students to Air Emissions from Confined Swine Feeding Operations

Previous studies suggest that airborne effluent from swine confined animal feeding operations (CAFOs) may affect the health and quality of life of adults and the prevalence of asthma symptoms among children. To investigate the extent to which public school students may be exposed to airborne effluent from swine CAFOs and to evaluate the association between schools’ demographic characteristics and swine CAFO exposures, we assessed the proximity of 226 schools to the nearest swine CAFO and conducted a survey of school employees to identify schools with noticeable livestock odor. We used publicly available information describing the enrollment of each school to assess the association between race and socioeconomic status (SES) and swine CAFO exposure. Odor from livestock was noticeable outside (n = 47, 21%) and inside (n = 19, 8%) school buildings. Schools with < 63% enrollment of white students and ≥47% of students receiving subsidized lunches at school were located closer to swine CAFOs (mean = 4.9 miles) than were the remaining schools (mean = 10.8 miles) and were more likely to be located within 3 miles of an operation than were schools with high-white/high-SES enrollment (prevalence ratio = 2.63; 95% confidence interval, 1.59–4.33). The prevalence of reported livestock odor varied with SES (low SES, 25%; high SES, 17%). These analyses indicate that the potential for in-school exposure to pollution arising from swine CAFOs in North Carolina and the environmental health risks associated with such exposures vary according to the racial and economic characteristics of enrolled students.