Impact of veterinary antibiotics in the environment

The focus of this dissertation is assessment of the potential impact of livestock production practices on terrestrial and aquatic ecosystems by studying the environmental fate and effects of two classes of veterinary antibiotics: macrolides (represented by tylosin) and sulfonamides (represented by sulfamethazine). These antibiotics are widely used in livestock production for disease treatment and prevention, as well as growth promotion. Each has also been widely detected in surface waters in the U.S. The work presented utilized laboratory experiments to study the fate (mobility, dissipation, binding, and degradation) in soil columns and aquatic microcosms, and bioavailability to benthic invertebrates. Additionally, methodologies were developed for using a passive sampling, or biomimetic, device to estimate bioavailability in aquatic ecosystems. Results suggest the potential persistence of some antibiotic residues in sediments, and the level of bioaccumulation in Lumbriculus variegatus, an aquatic oligochaete, indicates that uptake by sediment-dwelling invertebrates may be a concern

Preface of Veterinary Pharmaceuticals in the Environment

An important symposium was presented on Veterinary Pharmaceuticals in the Environment at the 233rd National Meeting of the American Chemical Society on March 25-26, 2007, in Chicago, IL. The excellence and timeliness of the presentations indicated the need for an ACS Symposium Series book addressing the environmental chemistry and toxicology of this group of emerging contaminants. The purpose of this symposium was to bring together scientists from academia, government, and industry to discuss and present data relevant to the significance of veterinary pharmaceuticals in the environment. A broad range of topics was covered, including environmental chemistry studies focusing on transport, mobility, sorption, persistence, and bioavailability of the compounds, as well as development of analytical techniques relevant to detection of the pharmaceuticals in environmental matrices, discussion of ecotoxicological studies of veterinary pharmaceuticals, and information relevant to ecological risk assessments. The primary classes of drugs addressed herein are veterinary antibiotics and syntheti

Identification of Tylosin Photoreaction Products and Comparison of ELISA and HPLC Methods for Their Detection in Water

Tylosin is a widely used macrolide antibiotic for therapeutics and growth promotion in swine, beef cattle, and poultry production. Through various routes such as manure application, emission, inappropriate disposal, etc., tylosin enters the environment. The fate of tylosin in the environment is not yet fully understood. In this study, two photoreaction products of tylosin in water were identified as isotylosin A alcohol (E,Z) and isotylosin A aldol (E,Z). Tylosin A, B, C, D, isotylosin A alcohol, and isotylosin A aldol were purified, and immunological cross-reactivities of these tylosin-related compounds were tested with a specificity of 26% for tylosin B, 19% for tylosin C, 106% for tylosin D, 121% for isotylosin A alcohol, and 46% for isotylosin A aldol, compared to 100% for tylosin A. Competitive direct enzyme-linked immunosorbent assay (ELISA) for tylosin detection in water was compared with a high-performance liquid chromatography (HPLC) method by analyzing the same water samples from a study of tylosin dissipation in water. ELISA kits detect the other tylosin-related compounds besides tylosin A, which can result in differences in tylosin determination in water

Phytoremediation—An Overview

The use of plants (directly or indirectly) to remediate contaminated soil or water is known as phytoremediation. This technology has emerged as a more cost effective, noninvasive, and publicly acceptable way to address the removal of environmental contaminants. Plants can be used to accumulate inorganic and organic contaminants, metabolize organic contaminants, and encourage microbial degradation of organic contaminants in the root zone. Widespread utilization of phytoremediation can be limited by the small habitat range or size of plants expressing remediation potential, and insufficient abilities of native plants to tolerate, detoxify, and accumulate contaminants. A better understanding and appreciation of the potential mechanisms for removing contaminants from the root zone and the interaction between plants, microorganisms, and contaminants will be useful in extending the application of phytoremediation to additional contaminated sites

Phytoremediation of Pesticide Wastes in Soil

Soils at agrochemical dealer sites often are contaminated with pesticide residues from decades of accidental and incidental spillage. We have determined that prairie grasses native to the Midwestern U.S. are suitable for phytoremediation because they are tolerant of most herbicides and of climatic extremes, such as heat, cold, drought, and flooding. A mixed stand of big bluestem, switch grass, and yellow indiangrass develops a rhizosphere with microflora that can readily detoxify pesticide residues. Specific atrazine-degrading bacteria or the free enzyme atrazine chlorohydrolase also can enhance the rate of biotransformation of atrazine in soil. Metolachlor degradation can be accelerated significantly by the prairie grass/rhizosphere effect. Several grasses used in filter strips have also been evaluated for their pesticidedegradation capabilities. The prairie grasses also have been demonstrated to reduce the rates of leaching of pesticides through intact soil columns, since less water leaches out of vegetated soil columns compared to non-vegetated soil columns. The evaluation of the degree of success of remediation has relied heavily on chemical residue analysis, but recent studies on biological endpoints have shown promise for providing more ecologically relevant indications of the potential exposure of organisms to pesticides in the soil. Earthworm 8-day bioaccumulation assays and root growth assays have shown the value of assessing the bioavailability of the residues. Mass balance experiments have utilized radiolabeled atrazine and metolachlor to ascertain the complete metabolism and binding profile of those two pesticides in phytoremediation studies.This article is from Zeitschrift für Naturforschung C 61 (2006): 213, doi:10.1515/znc-2006-3-410. Posted with permission.</p

The composition of Singaporean shopping centres

With its growing population but limited supply of land, Singapore has seen a huge increase in the number and size of shopping centres in recent years. This growth has led to two rather contradictory outcomes - more choice for retailers in their efforts to reach customers but also claims that too many of the centres contain the same types of retailers and contain no real differentiation in their&nbsp;offerings. This paper looks at this trend and reports on a survey of the composition of store types in a wide range of Singaporean shopping centres to consider whether or not these views are based on a full picture of the roles played by these shopping centres