RESUMEN

BACKGROUND: Despite growing literature on animal feeding operations (AFOs) including concentrated animal feeding operations (CAFOs), research on disproportionate exposure and associated health burden is relatively limited and shows inconclusive findings. OBJECTIVE: We systematically reviewed previous literature on AFOs/CAFOs, focusing on exposure assessment, associated health outcomes, and variables related to environmental justice (EJ) and potentially vulnerable populations. METHODS: We conducted a systematic search of databases (MEDLINE/PubMed and Web of Science) and performed citation screening. Screening of titles, abstracts, and full-text articles and data extraction were performed independently by pairs of reviewers. We summarized information for each study (i.e., study location, study period, study population, study type, study design, statistical methods, and adjusted variables (if health association was examined), and main findings), AFO/CAFO characteristics and exposure assessment (i.e., animal type, data source, measure of exposure, and exposure assessment), health outcomes or symptoms (if health association was examined), and information related to EJ and potentially vulnerable populations (in relation to exposure and/or health associations, vulnerable populations considered, related variables, and main findings in relation to EJ and vulnerable populations). RESULTS: After initial screening of 10,963 papers, we identified 76 eligible studies. This review found that a relatively small number of studies (20 studies) investigated EJ and vulnerability issues related to AFOs/CAFOs exposure and/or associated health outcomes (e.g., respiratory diseases/symptoms, infections). We found differences in findings across studies, populations, the metrics used for AFO/CAFO exposure assessment, and variables related to EJ and vulnerability. The most commonly used metric for AFO/CAFO exposure assessment was presence of or proximity to facilities or animals. The most investigated variables related to disparities were race/ethnicity and socioeconomic status. CONCLUSION: Findings from this review provide suggestive evidence that disparities exist with some subpopulations having higher exposure and/or health response in relation to AFO/CAFO exposure, although results varied across studies.

Asunto(s)

Crianza de Animales Domésticos , Exposición a Riesgos Ambientales , Justicia Ambiental , Animales , Humanos

RESUMEN

BACKGROUND: The growth of concentrated animal feeding operations (CAFOs) has caused significant environmental detriments and raised concerns regarding environmental justice with CAFOs exposure. OBJECTIVE: This study examined environmental disparities in exposure to CAFOs with several environmental justice related variables and considered exposure intensity. METHODS: We obtained data on permitted CAFOs (July 2021) from the Wisconsin Department of Natural Resources. We used Census tract level variables from the 2010 Census to evaluate environmental disparities by environmental justice related variables (i.e., percentages of Non-Hispanic White, Non-Hispanic Black, or Hispanic; percentage living below the poverty level; median annual household income; income inequality (Gini index); percentage with education less than high school diploma; racial isolation (RI) for Non-Hispanic Black; and educational isolation (EI) for population without a college degree). We assessed exposure to CAFOs as the sum of animal units (AUs) within each Census tract and investigated exposure disparities by comparing distributions of environmental justice related variables based on CAFO status (i.e., never, expired, or current) and Census tract-level CAFOs exposure intensity categories (i.e., from low exposure (quartile 1) to high exposure (quartile 4)). RESULTS: CAFOs in Wisconsin were generally located in areas with lower percentages of racial minority persons and high SES communities; however, within the areas with current CAFO exposure, areas with high CAFOs exposure intensity had higher percentages of non-Hispanic Black and Hispanic, and lower percentages of non-Hispanic White populations compared to areas with low CAFOs exposure. IMPACT STATEMENT: This study compared distributions of CAFO exposure and multiple environmental justice related variables and considered exposure intensity based on animal units for CAFOs exposure metric. Although CAFOs in Wisconsin were generally located in areas with lower percentages of racial/ethnic minority subpopulations and high SES communities, we found complex disparities with higher exposure for disadvantaged communities within areas with CAFOs. This work adds to the existing evidence that some populations such as racial/ethnic minority populations may face disproportionate burdens from CAFOs.

RESUMEN

With 9 million hogs, North Carolina (NC) is the second leading hog producer in the United States. Most hogs are housed at concentrated animal feeding operations (CAFOs), where millions of tons of hog waste can pollute air and water with fecal pathogens that can cause diarrhea, vomiting, and/or nausea (known as acute gastrointestinal illness (AGI)). We used NC's ZIP code-level emergency department (ED) data to calculate rates of AGI ED visits (2016-2019) and swine permit data to estimate hog exposure. Case exposure was estimated as the inverse distances from each hog CAFO to census block centroids, weighting with Gaussian decay and by manure amount per CAFO, then aggregated to ZIP code using population weights. We compared ZIP codes in the upper quartile of hog exposure ("high hog exposed") to those without hog exposure. Using inverse probability of treatment weighting, we created a control with similar demographics to the high hog exposed population and calculated rate ratios using quasi-Poisson models. We examined effect measure modification of rurality and race using adjusted models. In high hog exposed areas compared to areas without hog exposure, we observed a 11% increase (95% CI: 1.06, 1.17) in AGI rate and 21% increase specifically in rural areas (95% CI: 0.98, 1.43). When restricted to rural areas, we found an increased AGI rate among American Indian (RR = 4.29, 95% CI: 3.69, 4.88) and Black (RR = 1.45, 95% CI: 0.98, 1.91) residents. The association was stronger during the week after heavy rain (RR = 1.41, 95% CI: 1.19, 1.62) and in areas with both poultry and swine CAFOs (RR = 1.52, 95% CI: 1.48, 1.57). Residing near CAFOs may increase rates of AGI ED visits. Hog CAFOs are disproportionally built near rural Black and American Indian communities in NC and are associated with increased AGI most strongly in these populations.

Asunto(s)

Alimentación Animal , Industrias , Animales , Vivienda , North Carolina/epidemiología , Aves de Corral , Porcinos

RESUMEN

Concentrated animal feeding operations (CAFOs) have emerged as an environmental justice issue due to disproportionate siting in low-income and minority communities. However, CAFOs' impact on health is not fully understood. We examined risk of cause-specific mortality associated with CAFOs in North Carolina (NC) for 2000-2017 and health disparities. We obtained data on individual-level cause-specific mortality and on permitted animal facilities. We estimated associations between exposure to CAFOs and cause-specific mortality using logistic regression, controlling for demographics (e.g., age) and area-level covariates. To estimate exposure to CAFOs, we considered (1) a binary indicator (presence or absence) of CAFOs within a buffer around individual residence based on several buffer sizes, and (2) four levels of exposure (no, low, medium, and high) based on the number of CAFOs within 15 km around each residence. We considered individual-level (sex, race/ethnicity, age, education) and community-level (median household income, urbanicity, and region) factors. Under all buffer sizes used to estimate CAFOs exposure, people living near CAFOs had significantly higher risk of cardiovascular mortality than other persons. Comparing those living near CAFOs to the no exposure group, odds ratios (ORs) for cardiovascular mortality were 1.01 (95% confidence interval (CI) 1.00, 1.03), 1.04 (1.03, 1.06), and 1.06 (1.05, 1.07) for low, medium, and high CAFOs exposure, respectively, indicating a trend of higher risk with higher exposure. Those in the high CAFOs exposure group had significantly higher risk of anemia and kidney disease mortality than those with no exposure. Results suggest higher mortality risk from CAFOs for some subpopulations, however differences were not statistically significant. Findings provide evidence of excess mortality risk from CAFOs in NC. These results have implications for future studies of environmental justice and CAFOs.

Asunto(s)

Crianza de Animales Domésticos , Exposición a Riesgos Ambientales/efectos adversos , Vivienda , Anemia/mortalidad , Alimentación Animal , Animales , Enfermedades Cardiovasculares/mortalidad , Ambiente , Contaminación Ambiental , Humanos , Enfermedades Renales/mortalidad , North Carolina/epidemiología , Pobreza , Justicia Social

RESUMEN

Despite increasing public concern about air and water pollution risks posed by concentrated animal feeding operation areas (CAFOs), there is little information about bioavailability and ecosystem impacts of agrochemicals used to increase productivity. In this study, we investigated the toxicity of wastewaters originating from beef cattle feeding operation on Daphnia pulex. Specifically, we assessed lethal and chronic sublethal exposure effects using various endpoints including survival, oxygen consumption, morphology, reproduction, and swimming behavior. Exposure assessments (acute and chronic) were performed with ten (10) surface water samples collected from on-site retention ponds designated as A, B, C, D, E, F, G, H, I, and R (reference site). Surface water samples were diluted to yield five concentrations (stock, 1 × , 2 × , 3 × , and 4 ×) as treatments and deionized water was used as control. Results showed site-specific and concentration-related effects on toxicity endpoints. Among treatments, significant (p < 0.05) increase in mortality rate (for A, E, F, and H) and decreasing total body length and width (for B, C, D, and G) of D. pulex were observed with increasing wastewater concentration. However, treatments did not have significant effect on swimming behavior (average speed) after exposure to the wastewater samples from all sites except for site E. Evidence from this study suggested that surface waters near beef cattle feed yards affected physiological responses in D. pulex and therefore may similarly affect organisms in the surrounding aquatic ecosystems.

Asunto(s)

Daphnia , Contaminantes Químicos del Agua , Agroquímicos , Animales , Bovinos , Ecosistema , Monitoreo del Ambiente , Agua , Contaminantes Químicos del Agua/toxicidad

RESUMEN

BACKGROUND: Several studies have reported environmental disparities regarding exposure to concentrated animal feeding operations (CAFOs). Public health implications of environmental justice from the intensive livestock industry are of great concern in North Carolina (NC), USA, a state with a large number and extensive history of CAFOs. OBJECTIVES: We examined disparities by exposure to CAFOs using several environmental justice metrics and considering potentially vulnerable subpopulations. METHODS: We obtained data on permitted animal facilities from NC Department of Environmental Quality (DEQ). Using ZIP code level variables from the 2010 Census, we evaluated environmental disparities by eight environmental justice metrics (i.e., percentage of Non-Hispanic White, Non-Hispanic Black, or Hispanic; percentage living below the poverty level; median household income; percentage with education less than high school diploma; racial residential isolation (RI) for Non-Hispanic Black; and educational residential isolation (ERI) for population without college degree). We applied two approaches to assign CAFOs exposure for each ZIP code: (1) a count method based on the number of CAFOs within ZIP code; and (2) a buffer method based on the area-weighted number of CAFOs using a 15 km buffer. RESULTS: Spatial distributions of CAFOs exposure generally showed similar patterns between the two exposure methods. However, some ZIP codes had different estimated CAFOs exposure for the different approaches, with higher exposure when using the buffer method. Our findings indicate that CAFOs are located disproportionately in communities with higher percentage of minorities and in low-income communities. Distributions of environmental justice metrics generally showed similar patterns for both exposure methods, however starker disparities were observed using a buffer method. CONCLUSIONS: Our findings of the disproportionate location of CAFOs provide evidence of environmental disparities with respect to race and socioeconomic status in NC and have implications for future studies of environmental and health impacts of CAFOs.

Asunto(s)

Alimentación Animal , Benchmarking , Negro o Afroamericano , Animales , Exposición a Riesgos Ambientales , Hispánicos o Latinos , Humanos , North Carolina

RESUMEN

Phthalates (PAEs), bisphenol A (BPA), and oestrogenic compounds have become major concerns due to their endocrine-disrupting effect. However, few studies related to the occurrence of PAEs, BPA, and oestrogen in food and compost from different growth age livestock have been conducted. In this study, faeces, urine and food samples were collected from a typical livestock (cow) and a special livestock (pigeon) from concentrated animal feeding operations (CAFOs). The daily total oestrogen excretion of a single cow ranged from 192 µg/day to 671 µg/day, which was significantly higher than that of a single pigeon (0-0.01 µg/day). Conjugated oestrogens represented 22.0-46.0% of the total oestrogens excreted from cow faeces and 80.7-91.8% of those from cow urine, indicating that the form of the excreted oestrogens depends on the livestock species and type of excrement. BPA was all detected in all livestock manure and food, and the concentration in pigeon was 9.2-40.2 ng/g and 23.1 ng/g respectively, while that in cattle was 50.5-72.0 ng/g and 41.1 ng/g respectively. The results indicated that the food is significant sources of BPA entering the process of cow and pigeon breeding. Diethyl phthalate (DEP) was detected at high frequency in pigeon faeces samples, suggesting that pigeons were highly exposed to these plasticisers. The total oestradiol equivalent quantity (EEQt) of livestock origin in aquatic environments was estimated to be 2.99 ng/L, which was higher than the baseline hazard value (1 ng/L) (Xu et al., 2018). The study provides data on the emissions and sources of PAEs, BPA, and oestrogenic compounds from different livestock in CAFOs and demonstrates that food is a significant source of BPA entering livestock.

Asunto(s)

Alimentación Animal/análisis , Compuestos de Bencidrilo/análisis , Contaminantes Ambientales/análisis , Estrógenos/análisis , Contaminación de Alimentos/análisis , Fenoles/análisis , Ácidos Ftálicos/análisis , Animales , Bovinos , China , Heces/química , Femenino , Contaminación de Alimentos/estadística & datos numéricos , Humanos , Ganado , Estiércol/análisis , Plastificantes

RESUMEN

Nutrient pollution and greenhouse gas emissions related to crop agriculture and confined animal feeding operations (CAFOs) in the US have changed substantially in recent years, in amounts and forms. This review is intended to provide a broad view of how nutrient inputs-from fertilizer and CAFOs-as well as atmospheric NH3 and greenhouse gas emissions, are changing regionally within the US and how these changes compare with nutrient inputs from human wastewater. Use of commercial nitrogen (N) fertilizer in the US, which now exceeds 12,000,000 metric tonnes (MT) continues to increase, at a rate of 60,000 MT per year, while that of phosphorus (P) has remained nearly constant over the past decade at around 1,800,000 MT. The number of CAFOs in the US has increased nearly 10% since 2012, driven largely by a near 13% increase in hog production. The annualized inventory of cattle, dairy cows, hogs, broiler chickens and turkeys is approximately 8.7 billion, but CAFOs are highly regionally concentrated by animal sector. Country-wide, N applied by fertilizer is about threefold greater than manure N inputs, but for P these inputs are more comparable. Total manure inputs now exceed 4,000,000 MT as N and 1,400,000 MT as P. For both N and P, inputs and proportions vary widely by US region. The waste from hog and dairy operations is mainly held in open lagoons that contribute to NH3 and greenhouse gas (as CH4 and N2O) emissions. Emissions of NH3 from animal waste in 2019 were estimated at > 4,500,000 MT. Emissions of CH4 from manure management increased 66% from 1990 to 2017 (that from dairy increased 134%, cattle 9.6%, hogs 29% and poultry 3%), while those of N2O increased 34% over the same time period (dairy 15%, cattle 46%, hogs 58%, and poultry 14%). Waste from CAFOs contribute substantially to nutrient pollution when spread on fields, often at higher N and P application rates than those of commercial fertilizer. Managing the runoff associated with fertilizer use has improved with best management practices, but reducing the growing waste from CAFO operations is essential if eutrophication and its effects on fresh and marine waters-namely hypoxia and harmful algal blooms (HABs)-are to be reduced.

RESUMEN

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA), a bacterial pathogen, is a predominant cause of skin and soft tissue infections (SSTI) in the United States. Swine-production facilities have been recognized as potential environmental reservoirs of MRSA. To better understand how swine production may contribute to MRSA infection, we evaluated the association between MRSA infection among SSTI inpatients and exposure measures derived from national swine inventory data. METHODS: Based on adjusted odds ratios from logistic regression models, we evaluated the association between swine exposure metrics and MRSA infections among all Illinois inpatient hospitalizations for SSTI from January 2008 through July 2011. We also assessed if swine exposures had greater association with suspected community-onset MRSA (CO-MRSA) compared to suspected hospital-onset MRSA (HO-MRSA). Exposures were estimated using the Farm Location and Agricultural Production Simulator, generating the number of farms with greater than 1000 swine per residential ZIP code and the residential ZIP code-level swine density (swine/km2). RESULTS: For every increase in 100 swine/km2 within a residential ZIP code, the adjusted OR (aOR) for MRSA infection was 1.36 (95% CI: 1.28-1.45). For every additional large farm (i.e., >1000 swine) per ZIP code, the aOR for MRSA infection was 1.06 (95% CI: 1.04-1.07). The aOR for ZIP codes with any large farms compared to those with no large farms was 1.24 (95% CI: 1.19-1.29). We saw no evidence of an increased association for CO-MRSA compared to HO-MRSA with either continuous exposure metric (aORs=0.99), and observed inconsistent results across exposure categories. CONCLUSIONS: These publicly-available, ecological exposure data demonstrated positive associations between swine exposure measures and individual-level MRSA infections among SSTI inpatients. Though it is difficult to draw definitive conclusions due to limitations of the data, these findings suggest that the risk of MRSA may increase based on indirect environmental exposure to swine production. Future research can address measurement error related to these data by improving exposure assessment precision, increased specification of MRSA strain, and better characterization of specific environmental exposure pathways.

Asunto(s)

Crianza de Animales Domésticos , Staphylococcus aureus Resistente a Meticilina/aislamiento & purificación , Infecciones de los Tejidos Blandos/epidemiología , Infecciones Estafilocócicas/epidemiología , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Animales , Niño , Preescolar , Femenino , Humanos , Illinois/epidemiología , Lactante , Recién Nacido , Masculino , Persona de Mediana Edad , Densidad de Población , Factores de Riesgo , Infecciones de los Tejidos Blandos/microbiología , Infecciones Estafilocócicas/microbiología , Infecciones Cutáneas Estafilocócicas/epidemiología , Infecciones Cutáneas Estafilocócicas/microbiología , Sus scrofa , Adulto Joven

RESUMEN

Driven by the growing demand for food products of animal origin, industrial livestock and poultry production has become increasingly popular and is on the track of becoming an important source of environmental pollution in China. Although concentrated animal feeding operations (CAFOs) have higher production efficiency and profitability with less resource consumption compared to the traditional family-based and "free range" farming, they bring significant environmental pollution concerns and pose public health risks. Gaseous pollutants and bioaerosols are emitted directly from CAFOs, which have health implications on animal producers and neighboring communities. A range of pollutants are excreted with the animal waste, including nutrients, pathogens, natural and synthetic hormones, veterinary antimicrobials, and heavy metals, which can enter local farmland soils, surface water, and groundwater, during the storage and disposal of animal waste, and pose direct and indirect human health risks. The extensive use of antimicrobials in CAFOs also contributes to the global public health concern of antimicrobial resistance (AMR). Efforts on treating the large volumes of manure generated in CAFOs should be enhanced (e.g., by biogas digesters and integrated farm systems) to minimize their impacts on the environment and human health. Furthermore, the use of veterinary drugs and feed additives in industrial livestock and poultry farming should be controlled, which will not only make the animal food products much safer to the consumers, but also render the manure more benign for treatment and disposal on farmlands. While improving the sustainability of animal farming, China also needs to promote healthy food consumption, which not only improves public health from avoiding high-meat diets, but also slows down the expansion of industrial animal farming, and thus reduces the associated environmental and public health risks.

Asunto(s)

Agricultura , Contaminantes Atmosféricos/análisis , Ganado , Aves de Corral , Animales , China , Salud Ambiental , Contaminación Ambiental , Humanos , Salud Pública

RESUMEN

The paper examines the relationship between farm animal welfare, industrial farm animal production, and human health consequences. The data suggest that when the animal welfare of land-based farm animals is compromised, there are resulting significant negative human health consequences due to environmental degradation, the use of non-therapeutic levels of antibiotics for growth promotion, and the consequences of intensification. This paper accepts that even if meat and fish consumption is reduced, meat and fish will be part of the diet of the future. Industrial production modified from the current intensified systems will still be required to feed the world in 2050 and beyond. This paper identifies the concept of sustainable intensification and suggests that if farm animal welfare is improved, many of the human health consequences of intensified industrial production can be eliminated or reduced. In water-based farm animal production, many new systems are resulting in a product that actually protects the environment and can be done at industrial levels without the use of antibiotics.

Asunto(s)

Crianza de Animales Domésticos/estadística & datos numéricos , Bienestar del Animal/normas , Animales Domésticos/fisiología , Estado de Salud , Animales , Acuicultura , Humanos

RESUMEN

Recent literature suggests that Ca supplements have adverse effects on cardiovascular health. The effects of a Ca-rich supplement administered alone or in combination with short-chain fructo-oligosaccharides (scFOS) on serum lipids in postmenopausal women were examined using secondary data from a 24-month double-blind randomised controlled study. A total of 300 postmenopausal women were randomly assigned to daily supplements of 800 mg of Ca (2·4 g Aquamin) (Ca), 800 mg of Ca with 3 g of scFOS (CaFOS) or control (maltodextrin) (MD). A full lipid profile, body composition, blood pressure and a range of cytokines were measured at baseline and after 24 months. Intention-to-treat ANCOVA assessed treatment effects between the groups. A significant time-by-treatment effect was observed for LDL and total cholesterol for the Ca and CaFOS groups, with both groups having lower LDL and total cholesterol concentrations compared with MD after 24 months. The control group had mean (5·2 mmol/l) total cholesterol concentrations above the normal range (≤ 5 mmol/l) at 24 months, whereas values remained within the normal range in the treatment groups. There was no significant treatment effect on HDL-cholesterol, TAG, body composition, blood pressure or cytokine concentrations at 24 months, with the exception of IL-4, where there was a significant increase in the CaFOS group compared with the placebo. This study demonstrates a lipid-lowering effect of both the Ca-rich supplement alone and the supplement with scFOS. At the 4-year follow-up, there was no significant difference between the groups for reported diagnosed cardiovascular conditions.

Asunto(s)

Calcio de la Dieta/uso terapéutico , Enfermedades Cardiovasculares/prevención & control , Suplementos Dietéticos , Hipolipemiantes/uso terapéutico , Minerales/uso terapéutico , Oligosacáridos/uso terapéutico , Rhodophyta/química , Anciano , Conservadores de la Densidad Ósea/efectos adversos , Conservadores de la Densidad Ósea/uso terapéutico , Calcio de la Dieta/efectos adversos , Enfermedades Cardiovasculares/sangre , Enfermedades Cardiovasculares/epidemiología , Enfermedades Cardiovasculares/etiología , Colesterol/sangre , LDL-Colesterol/sangre , Suplementos Dietéticos/efectos adversos , Método Doble Ciego , Fenómenos Fisiológicos Nutricionales del Anciano , Femenino , Estudios de Seguimiento , Humanos , Hipolipemiantes/efectos adversos , Hipolipemiantes/química , Análisis de Intención de Tratar , Persona de Mediana Edad , Minerales/efectos adversos , Peso Molecular , Irlanda del Norte/epidemiología , Oligosacáridos/efectos adversos , Oligosacáridos/química , Osteoporosis Posmenopáusica/sangre , Osteoporosis Posmenopáusica/epidemiología , Osteoporosis Posmenopáusica/prevención & control , Pacientes Desistentes del Tratamiento , Factores de Riesgo

RESUMEN

The objective of this study was to compare the personal respiratory exposures of poultry workers in three different types of layer housing under commercial production conditions. Workers were randomly assigned to each of conventional cage, enriched cage, and aviary barns in a crossover repeated-measures design for three observation periods over the hens' lifetime. Inhalable and fine particulate matter (PM) and endotoxin in both size fractions were assessed by personal and area samplers over the work shift. Concentrations of inhalable PM, PM2.5 (PM with an aerodynamic diameter <2.5 µm), and endotoxin in both size fractions were higher in aviary than either the conventional or enriched barns. Geometric means (95% confidence intervals [CIs]) of inhalable PM and endotoxin for the aviary, conventional, and enriched barns were 8.9 (6.8-11.5) mg/m(3) and 7517.9 (5403.2-10,460.2) EU/m(3), 3.7 (2.8-4.8) mg/m(3) and 1655.7 (1144.6-2395.2) EU/m(3), 2.4 (1.8-3.3) mg/m(3) and 1404.8 (983.3-2007.0) EU/m(3), respectively. Area samplers recorded a lower mean inhalable PM concentration and higher PM2.5 concentration than personal samplers. Ammonia concentrations were low throughout three monitoring seasons. These findings show that the aviary barns pose higher respiratory exposures to poultry workers than either conventional or enriched barns.

Asunto(s)

Contaminantes Ocupacionales del Aire/análisis , Agricultores , Vivienda para Animales , Exposición Profesional/análisis , Aerosoles/análisis , Contaminación del Aire Interior/análisis , Amoníaco/análisis , Animales , Pollos , Endotoxinas/análisis , Femenino , Humanos , Tamaño de la Partícula , Aves de Corral , Distribución Aleatoria

RESUMEN

The rapid increase in obesity prevalence in the United States in the last 20 years is unprecedented and not well explained. Here, we explore a hypothesis that the obesity epidemic may be driven by population-wide chronic exposures to low-residue antibiotics that have increasingly entered the American food chain over the same time period. We propose this hypothesis based on two recent bodies of published reports - (1) those that provide evidence for the spread of antibiotics into the American food chain, and (2) those that examine the relationship between the gut microbiota and body physiology. The livestock use of antimicrobial agents has sharply increased in the US over the same 20-year period of the obesity epidemic, especially with the expansion of intensified livestock production, such as the concentrated animal feeding operations. Observational and experimental studies support the idea that changes in the intestinal microbiota exert a profound effect on body physiology. We propose that chronic exposures to low-residue antimicrobial drugs in food could disrupt the equilibrium state of intestinal microbiota and cause dysbiosis that can contribute to changes in body physiology. The obesity epidemic in the United States may be partly driven by the mass exposure of Americans to food containing low-residue antimicrobial agents. While this hypothesis cannot discount the impact of diet and other factors associated with obesity, we believe studies are warranted to consider this possible driver of the epidemic.