Stephen A. Sassman

Agricultural Contributions of Antimicrobials and Hormones on Soil and Water Quality

Detection of many emerging chemicals of concern, including antimicrobials and steroid hormones, in the environment has increased in the past decade with the advancement of analytical techniques. There are several potential sources of these inputs, including municipal wastewater discharge, municipal biosolids, pharmaceutical production, and agriculture‐related activities. However, the heavy use of antibiotics in the livestock industry and the dramatic shift in recent years toward more highly concentrated animal feeding operations (CAFOs), thus a concomitant increase in the volume of animal wastes per unit of land, has drawn attention to the role of animal waste‐borne antimicrobials, antibiotic‐resistant bacteria, and steroid hormones on ecosystem and human health. Antimicrobials, although frequently detected, are typically present in water at concentrations in orders of magnitude below what would be considered inhibitory to most biota. Most antibiotics have a high affinity for soil and sediment, thus residual soil concentrations are usually much higher than noted in water but still often below concentrations of concern. The focal point with antibiotic use in animal production is the development of antibiotic‐resistant bacteria. Although there is a growing body of evidence of the presence of numerous antibiotic‐resistant genes in animal wastes, in soils where wastes are land applied, and in water bodies receiving runoff from manure‐amended fields or discharges from aquacultures, conclusive evidence of animal‐derived antibiotic‐resistant pathogens compromising human health is lacking. In contrast to antibiotics, hormones and related chemicals can cause significant biological responses at very low concentrations. CAFO discharges will include a variety of estrogens, natural and synthetic androgens and progesterones, and phytoestrogens associated with animal feed. Measurable concentrations of many of these hormones have been detected in soil, and ground and surface waters receiving runoff from fields fertilized with animal manure and downstream from farm animal operations. Overall, hormones appear to be moderately to highly sorbed and to dissipate quickly in an aerobic soil environment, but quantitative information on hormone persistence in manure‐applied fields and subsequent effects of hormone loads from CAFOs to the aquatic environment is lacking. Research directed toward evaluating the facilitated transport processes with regards to antimicrobial and hormone inputs from manure‐amended fields is in its infancy. With the advances in analytical techniques and what has already been learned with regards to transport of nutrients (nitrogen, phosphorus, and carbon) and pesticides from agricultural fields, a reasonable evaluation of CAFOs and associated activities (land application of animal wastes) should be forthcoming in the next decade. Meanwhile, implementation of management practices that optimize reduction in already regulated nutrient releases from CAFOs should also help to minimize the release of antimicrobials and hormones.

Hormone Discharges from a Midwest Tile-Drained Agroecosystem Receiving Animal Wastes

Manure is increasingly being viewed as a threat to aquatic ecosystems due to the introduction of natural and synthetic hormones from land application to agricultural fields. In the Midwestern United States, where most agricultural fields are tile-drained, there is little known about hormone release from fields receiving animal wastes. To this end, seven sampling stations (four in subsurface tile drains and three in the receiving ditch network) were installed at a Midwest farm where various types of animal wastes (beef, dairy, and poultry lagoon effluent, dairy solids, and subsurface injection of swine manure) are applied to agricultural fields. Water flow was continuously monitored and samples were collected for hormone analysis during storm events and baseline flow for a 15 month study period. The compounds analyzed included the natural hormones 17α- and 17β-estradiol, estrone, estriol, testosterone, and androstenedione and the synthetic androgens 17α- and 17β-trenbolone and trendione. Hormones were detected in at least 64% of the samples collected at each station, with estrone being detected the most frequently and estriol the least. Testosterone and androstendione were detected more frequently than synthetic androgens, which were detected in fewer than 15% of samples. Hormone concentrations in subsurface tile drains increased during effluent irrigation and storm events. Hormones also appeared to persist over the winter, with increased concentrations coinciding with early thaws and snowmelt from fields amended with manure solids. The highest concentration of synthetic androgens (168 ng/L) observed coincided with a snowmelt. The highest concentrations of hormones in the ditch waters (87 ng/L for total estrogens and 52 ng/L for natural androgens) were observed in June, which coincides with the early life stage development period of many aquatic species in the Midwest.

Sorption and degradation in soils of veterinary ionophore antibiotics: Monensin and lasalocid

Monensin and lasalocid are polyether ionophores commonly used in the beef and poultry industries for the prevention of coccidial infections and promotion of growth. These ionophores can exhibit higher toxicity than many other antibiotics; thus, evaluating their fate in the environments associated with concentrated feed operations is important. Sorption of monensin and lasalocid was measured in eight soils of varying physiochemical composition. Organic carbon-normalized sorption coefficients (log Koc) ranged from 2.1 to 3.8 for monensin and from 2.9 to 4.2 for lasalocid and were inversely correlated to equilibrium soil-solution pH. Degradation of lasalocid and monensin in two contrasting soils with and without manure amendment was measured in moist soils at 23 degrees C and 0.03 MPa moisture potential. The half-life of both compounds in the fresh nonsterile soils was less than 4 d, for which monensin degraded slightly faster than lasalocid. Fresh liquid manure amendments did not significantly alter degradation of either compound. Based on parallel 60Co-sterilized soil experiments, some abiotic degradation of monensin was apparent, whereas lasalocid only degraded in the presence of microbes. Analysis of beef-derived lagoon effluent used for irrigation confirmed that monensin can be present at low-ppb to low-ppm concentrations in the aqueous and suspended solids fractions, respectively; however, subsequent analysis of drainage water in a nearby ditch suggested that attenuation by soil after land application will greatly reduce the amount entering surface waters.

Sorption of tylosin A, D, and A‐aldol and degradation of tylosin a in soils

Heightened concerns regarding the potential impact on soil and water quality of veterinary antibiotics warrant a better understanding of the environmental fate of antibiotics in soil. Sorption of the macrolides tylosin A (TA), tylosin D, and TA-aldol was measured in several soils and evaluated with respect to soil pH, organic matter content, percentage clay, and cation-exchange capacity (CEC). Tylosin and related compounds exhibit similar sorption characteristics and generally are strongly sorbed, with sorption being well and positively correlated to surface area, clay content, and CEC. Sorption coefficients normalized by CEC were within a narrow range (10(4.1+/-0.21 L/molc) for all but one soil; however, good extraction recoveries with only methanol for most soils suggested that hydrophobic processes also contribute to sorption. Aerobic degradation of TA over a three-month period in two freshly collected agricultural soils and 60Co-irradiated soils indicated that both abiotic and microbial processes contribute to TA transformation. The abiotic process was much slower and dominated in the first two weeks, followed by rapid microbial degradation within 3 d. Three primary degradation products were identified using liquid chromatography with full-scan mass spectrometry, with unconfirmed identifications of TA having the aldehyde group oxidized to an acid (m/z = 932) in both soils and tyslosin B (m/z = 772) as well as tylosin B having the aldehyde group oxidized to an acid (m/z = 788) in the sandy soil.

Assessing impacts of land-applied manure from concentrated animal feeding operations on fish populations and communities.

Concentrated animal feeding operation (CAFO) manure is a cost-effective fertilizer. In the Midwest, networks of subsurface tile-drains expedite transport of animal hormones and nutrients from land-applied CAFO manure to adjacent waterways. The objective of this study was to evaluate impacts of land-applied CAFO manure on fish populations and communities. Water chemistry including hormone, pesticide, and nutrient concentrations was characterized from study sites along with fish assemblage structure, growth, and endocrine disruption assessed in selected fish species. Although most CAFO water samples had hormone concentrations <1 ng/L, equivalent concentrations for 17β-E2 and 17α-TB peaked at >30 ng/L each during the period of spawning, hatching, and development for resident fishes. CAFO sites had lower fish species richness, and fishes exhibited faster somatic growth and lower reproductive condition compared to individuals from the reference site. Fathead minnows (Pimephales promelas) exposed to CAFO ditchwater during early developmental stages exhibited significantly skewed sex ratios toward males. Maximum observed hormone concentrations were well above the lowest observable effect concentrations for these hormones; however, complexities at the field scale make it difficult to directly relate hormone concentration and impacts on fish. Complicating factors include the consistent presence of pesticides and nutrients, and the difference in temperature and stream architecture of the CAFO-impacted ditches compared to the reference site (e.g., channelization, bottom substrate, shallow pools, and riparian cover).