Evaluation of a lower tier exposure assessment model for veterinary medicines

The Use and Impact of Antibiotics in Plant Agriculture: A Review

Growers have depended on the specificity and efficacy of streptomycin and oxytetracycline as a part of their plant disease arsenal since the middle of the 20th century. With climate change intensifying plant bacterial epidemics, the established success of these antibiotics remains threatened. Our strong reliance on certain antibiotics for devastating diseases eventually gave way to resistance development. Although antibiotics in plant agriculture equal to less than 0.5% of overall antibiotic use in the United States, it is still imperative for humans to continue to monitor usage, environmental residues, and resistance in bacterial populations. This review provides an overview of the history and use, resistance and mitigation, regulation, environmental impact, and economics of antibiotics in plant agriculture. Bacterial issues, such as the ongoing Huanglongbing (citrus greening) epidemic in Florida citrus production, may need antibiotics for adequate control. Therefore, preserving the efficacy of our current antibiotics by utilizing more targeted application methods, such as trunk injection, should be a major focus. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Fate and transport of pharmaceuticals in water systems: A processes review

Pharmaceuticals are globally consumed by humans and animals to support daily health and to treat disease. Following consumption, they may reach the aquatic environment either directly through the discharge of untreated wastewater to water bodies, or indirectly via treated wastewater as a result of their incomplete removal from wastewater treatment plants. This paper reviews the processes that control the occurrence and fate of pharmaceuticals in water systems, including sorption, photodegradation, hydrolysis and biodegradation. The degree to which these four processes occur is influenced by pharmaceutical types and their chemical structure as well as environmental factors such as sunlight, water depth, organic matter content, water chemistry, sediment properties, and type and abundance of microorganisms. Depending on the complex interactions of these factors, pharmaceutical compounds may be mineralized, partially degraded, or remain intact because they are resistant to degradation. Kinetic rate parameters and the half-life of a variety of pharmaceutical products are provided herein for the above processes under different environmental conditions. Usually, photodegradation and biodegradation represent dominant reaction processes, while hydrolysis only affects some pharmaceuticals, particularly antibiotics. The identified sorption and reaction rate parameters can be incorporated into a concise modeling framework to assess and predict longitudinal concentration profiles of pharmaceutical products in the manmade and natural systems, particularly when large amounts of pharmaceuticals are discharged during abnormal events such as a virus outbreak. Finally, future research is suggested, including the fate of transformed products (intermediates) in water systems.

The effect of anaerobic pig slurry redox potentials on the degradation of veterinary medicines

Veterinary medicines are frequently used within intensive livestock husbandry and there has been a growing interest regarding their fate in the environment. However, research has seldom assessed the influence of pig slurry properties on the fate of veterinary medicines even though such an understanding is essential for a more robust environmental risk assessment. Changes within manure degradation rates have the potential to alter the concentration of antibiotics applied to land, and the outcome of the risk assessment. The aim of this work was to investigate whether commonly reported redox potentials affect the degradation rates of acetyl-salicylic acid, ceftiofur, florfenicol, oxytetracycline, sulfamethoxazole, and tylosin. The employed redox potentials were -100 mV (reduced), -250 mV (anaerobic) and -400 mV (very anaerobic). A compound specific relationship was observed where the degradation of ceftiofur, florfenicol, oxytetracycline and sulfamethoxazole was inhibited under reduced conditions over that of very anaerobic; the respective DT50 values were 0.7-1.84 h, 1.35-3.61 h, 22.2-49.8 h, 131-211 h and 35.4-94 h. In contrast, tylosin was found to degrade faster at reduced conditions over very anaerobic (DT50 6.88-19.4 h). The presented research demonstrates the importance of redox potential on degradation rates and suggests we need stringent and harmonized redox control to improve the environmental risk assessment of veterinary medicines. Environmental relevance and significance: Given the significant effect of anaerobic redox potentials on veterinary medicine fate tighter regulation is required in manure degradation trials.

Assessing the influence of pig slurry pH on the degradation of selected antibiotic compounds

Veterinary medicines are routinely used in animal husbandry and the environment may consequently be exposed to them via manure applications. This presents potential environmental and societal risks such as toxicological effects to aquatic/terrestrial organisms and the spread of antimicrobial resistance. Regulatory studies that assess the degradability of veterinary antibiotics during manure storage currently permit the use of just one manure per animal type although we speculate that heterogenic properties such as pH could be driving significant variability within degradation rates. To bridge this knowledge gap and assess degradation variability with pH, laboratory degradation studies were performed on a broad range of antibiotics (ceftiofur, florfenicol, oxytetracycline, sulfamethoxazole and tylosin) at three different environmentally relevant pH levels (5.5, 7, and 8.5). The effect of pig slurry pH on degradation rates was found to be significant and compound specific. Usually, acidic slurries were found to inhibit degradation when compared to neutral pH, for florfenicol, tylosin, and ceftiofur; the associated changes in DT50 (half-life) values were 2-209 h, 35.28-234 h, and 0.98-2.13 h, respectively. In some circumstances alkaline slurries were observed to enhance the degradation rate when compared to those for neutral pH, for tylosin, the respective changes in DT50 values were from 3.52 to 35.28 h. Comparatively, the degradation of sulfamethoxazole was enhanced by acidic conditions compared to neutral (DT50 20.6-31.6 h). Tentative identification of unknown transformation products (TPs) was achieved for sulfamethoxazole and florfenicol for the first time in pig slurries. These results reveal the importance of considering slurry pH when assessing the degradation of antibiotic compounds, which has implications for the acidification of manures and the environmental risk assessment for veterinary medicines. Environmental relevance and significance: Given the significant effect of pig slurry pH on degradation rates, manure degradation studies need to be harmonised and standardized, taking into account the influence of pH.

Environmental contamination by pet pharmaceuticals: A hidden problem

As the environmental risks of companion animal pharmaceuticals has been assumed to be low, currently, no data on the fate, behaviour or effect is required by the European Medicines Agency. This is in sharp contrast with what happens in farming animals, where ecotoxicological data is a pivotal part on the benefit-risk assessment for the marketing authorization of a new veterinary drug. Recently, concern about the environmental impacts from the indiscriminate prophylactic use of antiparasitic drugs in pets has arisen. Considering the notable increase of companion animals in Europe since 2010, our impression is that, effects and potential deleterious consequences of other therapeutic classes such as antimicrobials and psychotropic drugs are probably underrated. We believe that pets, as animals, should not be excluded from One Health's philosophy, and that authorities should incorporate environmental aspects in the benefit-risk assessment for drugs used in companion animals as well.

A strategy to determine the fate of active chemical compounds in soil; applied to antimicrobially active substances

Data on the fate of chemical substances in the environment after e.g. manure application is mandatory input for risk assessment in perspective of a more circular biobased economy. Such fate studies include a persistence study to determine a half-life value and a mobility study. It is recognized that not only the native substance should be considered, but that also degradation products should be included that might exert a similar effect as the native substance. We report a tiered fate study strategy that starts with a persistence study. For non-persistent substances a study is performed to determine if degradation products have a similar effect as the native compound. If so, a procedure using high resolution mass spectrometry is suggested to identify the potentially active degradation products. Based on the outcomes, substances are divided into three categories: (I) persistent, (II) degradable to inactive products or (III) degradable to active products. Even though the priority is with category I and III, for all substances and possible degradation products a mobility study is proposed. The fate strategy is successfully applied to ten antimicrobially active substances originating from the tetracyclines, sulfonamides, diaminopyrimidines, fluoroquinolones, macrolides and lincosamides. The fluoroquinolones, tetracyclines and trimethoprim were relatively persistent. The sulfonamides, macrolides and lincomycin (the latter also depending on soil type) degraded relatively quickly. Tylosin A proved to degrade to antimicrobially active degradation products which were tentitatively identified as tylosin C, tylosin A acid, tylosin B acid and tylosin C acid.

Pharmaceuticals and other contaminants in waters and sediments from Augusta Bay (southern Italy)

The contamination by pharmaceuticals products (PPs) in the marine environment is particularly relevant where wastewater treatment of urban areas on land is lacking. However, the number of studies focused on description of sources and fate of PP molecules in the marine environment remains still limited. In this study, the occurrence of 46 PPs was investigated in the marine and coastal-marine system (waters and sediments) of Augusta Bay (central Mediterranean Sea). This area is highly affected by industrial pollution and urban discharges (without wastewater treatment) and thus represents a 'natural laboratory' for exploring dynamics of multi-mixture contaminants in the marine environment. The study area is also part of the sub-region 'Central Mediterranean Sea' of the Marine Strategy Framework Directive and therefore offers an important reference site for exploring the distribution modes of PPs in the central Mediterranean Sea. In this work, samples of seawater, sediment, untreated wastewater, and marine receiving water were analysed using mass spectrometry with a target analysis for PPs and a suspect screening analysis for the presence of other contaminants. PPs concentration ranges were: 2426-67,155 ng/L for untreated wastewaters, 550-27,889 ng/L for marine receiving waters and 12-281 ng/L for seawaters. The highest concentrations were measured for the antibiotics, anti-inflammatories, cardiovascular and antihypertensive therapeutic classes. Likewise, sediments collected from untreated wastewater sewers resulted more contaminated. Ionic, non-ionic surfactants and personal care products were the most abundant compounds found in waters and sediments by suspect screening analysis. The risk associated with PPs contamination for aquatic organisms was relatively high in samples of marine receiving waters of the bay (with a risk quotient value up to 33,599). The levels of PPs in seawater and sediment compartments were generally not hazardous (RQ < 0.01), except for estrone with a calculated RQ = 2775.

Nano-immobilized flumequine with preserved antibacterial efficacy

Flumequine was nano-immobilized by self-assembly on iron oxide nanoparticles, called surface active maghemite nanoparticles (SAMNs). The binding process was studied and the resulting core-shell nanocarrier (SAMN@FLU) was structurally characterized evidencing a firmly immobilized organic canopy on which the fluorine atom of the antibiotic was exposed to the solvent. The antibiotic efficacy of the SAMN@FLU nanocarrier was tested on a fish pathogenic bacterium (Aeromonas veronii), a flumequine sensitive strain, in comparison to soluble flumequine and the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were assessed. Noteworthy, the MIC and MBC of soluble and nanoparticle bound drug were superimposable. Moreover, the interactions between SAMN@FLU nanocarrrier and microorganism were studied by transmission electron microscopy evidencing the ability of the complex to disrupt the bacterial wall. Finally, a preliminary in vivo test was provided using Daphnia magna as animal model. SAMN@FLU was able to protect the crustacean from the fatal consequences of a bacterial infection and showed no sign of toxicity. Thus, in contrast with the strength of the interaction, nano-immobilized FLU displayed a fully preserved antimicrobial activity suggesting the crucial role of fluorine in the drug mechanism of action. Besides the importance for potential applications in aquaculture, the present study contributes to the nascent field of nanoantibiotics.

A critical review on organic micropollutants contamination in wastewater and removal through carbon nanotubes

The prevalence of organic micropollutants (OMPs) in various environmental compartments is posing a serious health risks to all kinds of lives on the planet. The levels of OMPs such as polyaromatic hydrocarbons, antibiotics, pesticides, contraceptive medicines, and personal care products in water bodies are increasing with each passing day. It is an urgent need of time to limit the release of OMPs into the environment, and to remove the prevailing OMPs for sustainable environmental management. The majority of the conventional means of water decontamination are either inefficient or expensive. However, due to nanosize, high surface area, and hollow and layered structure, carbon nanotubes (CNTs) serve as excellent sorbents for the removal of a diverse range of OMPs. The occurrence of emerging OMPs and their detrimental effects on human and animal health are collected and discussed in this review. The characteristics and efficacy of various CNTs (pristine and modified) for the efficient removal of different OMPs, and the removal mechanisms have been reviewed and discussed. The literature demonstrated that adsorption of OMPs onto CNTs is very complicated and rely on multiple factors including the properties of adsorbent and the adsorbate as well as solution chemistry. It was found that H-bonding, electrostatic interactions, van der Waals forces, hydrophobic interactions, H-π bongs, and π-π interactions were the major mechanisms responsible for the adsorption of OMPs onto various kinds of CNTs. Despite of higher affinities for OMPs, hydrophobicity and higher costs restrain the practical application of CNTs for wastewater treatment on large scale. However, continuous production may lead to the development of cost-effective, efficient and eco-friendly CTNs technology for wastewater treatments in future.

Biologically safe colloidal suspensions of naked iron oxide nanoparticles for in situ antibiotic suppression

A category of naked maghemite nanoparticles (γ-Fe₂O₃), named surface active maghemite nanoparticles (SAMNs), is characterized by biological safety, high water colloidal stability and a surface chemistry permitting the binding of ligands. In the present study, the interaction between SAMNs and an antibiotic displaying chelating properties (oxytetracycline, OxyTC) was extensively structurally and magnetically characterized. OxyTC emerged as an ideal probe for providing insights into the colloidal properties of SAMNs. At the same time, SAMNs turned out as an elective tool for water remediation from OxyTC. Therefore, a dilute colloidal suspension of SAMNs was used for the removal of OxyTC in large volume tanks where, to simulate a real in situ application, a population of zebrafish (Danio rerio) was introduced. Interestingly, SAMNs led to the complete removal of the drug without any sign of toxicity for the animal model. Moreover, OxyTC immobilized on SAMNs surface resulted safe for sensitive Escherichia coli bacteria strain. Thus, SAMNs were able to recover the drug and to suppress its antibiotic activity envisaging their feasibility as competitive option for water remediation from OxyTC in more nature related scenarios. The present contribution stimulates the use of novel smart colloidal materials to cope with complex environmental issues.

Quantitative risk model to estimate the level of antimicrobial residues that can be transferred to soil via manure, due to oral treatments of pigs

Veterinary antimicrobials can spread via manure onto agricultural fields, representing an emission of these products or their active metabolites into the environment. This causes concerns regarding the role of antimicrobial residues in the development, selection and spread of resistance. Aiming to approach this issue quantitatively, first a literature review was performed on the bioavailability and extent of in vivo biotransformation of twelve antimicrobials commonly used in pigs orally, and on the level of their persistence in manure. This information was then used in a model estimating the level of each of these administered antimicrobials that is present in manure at the end of common storage durations in pits and, thus, readily applied onto soil. From the studied antimicrobials, the highest level of residues in stored manure was estimated for doxycycline (55% of the initial amount of doxycycline administered orally to pigs after six months of manure storage), as a combining result of its high use in pigs, low bioavailability and high stability in manure. Other antimicrobials (e.g. amoxicillin) are readily degraded and therefore pose less threat. The results of this study highlight the importance of rational antimicrobial use and of further research on pharmacokinetics of antimicrobials and their degraded products in different environmental compartments, to efficiently control the spread of residues and/or resistance genes from manure to these matrices.

Flexing the PECs: Predicting environmental concentrations of veterinary drugs in Canadian agricultural soils

Veterinary drugs administered to food animals primarily enter ecosystems through the application of livestock waste to agricultural land. Although veterinary drugs are essential for protecting animal health, their entry into the environment may pose a risk for nontarget organisms. A means to predict environmental concentrations of new veterinary drug ingredients in soil is required to assess their environmental fate, distribution, and potential effects. The Canadian predicted environmental concentrations in soil (PECsoil) for new veterinary drug ingredients for use in intensively reared animals is based on the approach currently used by the European Medicines Agency for VICH Phase I environmental assessments. The calculation for the European Medicines Agency PECsoil can be adapted to account for regional animal husbandry and land use practices. Canadian agricultural practices for intensively reared cattle, pigs, and poultry differ substantially from those in the European Union. The development of PECsoil default values and livestock categories representative of typical Canadian animal production methods and nutrient management practices culminates several years of research and an extensive survey and analysis of the scientific literature, Canadian agricultural statistics, national and provincial management recommendations, veterinary product databases, and producers. A PECsoil can be used to rapidly identify new veterinary drugs intended for intensive livestock production that should undergo targeted ecotoxicity and fate testing. The Canadian PECsoil model is readily available, transparent, and requires minimal inputs to generate a screening level environmental assessment for veterinary drugs that can be refined if additional data are available. PECsoil values for a hypothetical veterinary drug dosage regimen are presented and discussed in an international context. Integr Environ Assess Manag 2017;13:331-341. © 2016 Her Majesty the Queen in Right of Canada. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of SETAC. Reproduced with the permission of the Minister of Health.

Results of extended plant tests using more realistic exposure scenarios for improving environmental risk assessment of veterinary pharmaceuticals

BACKGROUND

Residues of veterinary medicinal products (VMPs) enter the environment via application of manure onto agricultural areas where in particular antibiotics can cause phytotoxicity. Terrestrial plant tests according to OECD guideline 208 are part of the environmental risk assessment of VMPs. However, this standard approach might not be appropriate for VMPs which form non-extractable residues or transformation products in manure and manure-amended soil. Therefore, a new test design with a more realistic exposure scenario via manure application is needed. This paper presents an extended plant test and its experimental verification with the veterinary antibiotics florfenicol and tylosin tartrate. With each substance, plant tests with four different types of application were conducted: standard tests according to OECD 208 and three tests with application of test substance via spiked manure either without storage, aerobically incubated, or anaerobically incubated for different time periods.

RESULTS

In standard tests, the lowest NOEC was <0.06 mg/kg dry soil for florfenicol and 16.0 mg/kg dry soil for tylosin tartrate. Pre-tests showed that plant growth was not impaired at 22-g fresh manure/kg dry soil, which therefore was used for the final tests. The application of the test substances via freshly spiked as well as via aerobically incubated manure had no significant influence on the test results. Application of florfenicol via anaerobically incubated manure increased the EC10 by a factor up to 282 and 540 for half-maximum and for maximum incubation period, respectively. For tylosin tartrate, this factor amounted to 64 at half-maximum and 61 at maximum incubation period. The reduction of phytotoxicity was generally stronger when using cattle manure than pig manure and particularly in tests with cattle manure phytotoxicity decreased over the incubation period.

CONCLUSIONS

The verification of the extended plant test showed that seedling emergence and growth are comparable to a standard OECD 208 test and reliable effect concentrations could be established. As demonstrated in the present study, phytotoxicity of veterinary antibiotics can be significantly reduced by application via incubated manure compared to the standard plant test. Overall, the presented test design proved suitable for inclusion into the plant test strategy for VMPs.

Assessment of the biodegradability of selected sulfa drugs in two polluted rivers in Poland: Effects of seasonal variations, accidental contamination, turbidity and salinity

The aim of our study was to assess the aerobic biodegradation of four selected sulfonamides (sulfanilamide, sulfamethoxazole, sulfadiazine and sulfathiazole) using water samples drawn from highly polluted rivers. Additionally, we aimed to identify the factors that have a significant effect on the process efficiency. The 19 water samples were collected from Brynica and Czarna Przemsza rivers (in Poland) at the same location at approximately monthly intervals. A characteristic feature of the results is the presence of significant differences between the rates of sulfonamides biodegradation in particular samples. The sulfonamide most resistant to biodegradation was sulfamethoxazole, whereas sulfathiazole was most biodegradable. Seasonal variations and related microbial population changes had the most significant effects on sulfonamides biodegradation, e.g., the studied process was highly inhibited during wintertime. A decrease in the biodegradation rate in the river water could be caused by an accidental water pollution by industrial wastewater with heavy metals, an increase in salinity and a decrease in pH, and turbidity.

Effect of ions on sorption of tylosin on clay minerals

Tylosin sorption on three ion-exchanged montmorillonites indicated that hydrogen bond interactions were more important than cation exchange in the montmorillonite interlayer.

Occurrence and transformation of veterinary pharmaceuticals and biocides in manure: a literature review

The spread of veterinary medicinal products (VMPs) and biocides via manure onto agriculturally used areas represents a very important emission into the environment for these product groups. Within this literature study, publicly available transformation studies with liquid manure are summarized. Transformation studies were evaluated regarding the transformation fate of tested substances, the origin and characteristics of used manure, the experimental setup, and the measured parameters. As main topics within the 42 evaluated transformation studies, the high dependency of transformation on temperature, redox potential, dry matter content, and other parameters is reported. Test duration throughout the studies ranged from 2 to 374 days and study temperature ranged from 5 to 55 °C. Only seven publications gave information on the redox potential of the manure. Further, the characterization of the matrix in many cases was inadequate due to missing parameters such as dry matter content or pH. Only three publications studied transformation of biocides. To allow for a consistent assessment of studies within the registration process, a harmonized internationally accepted and validated test method is needed. Additionally, monitoring data of VMPs in manure were collected from literature and evaluated regarding the origin and characteristics of the manure, the minimum/maximum found concentrations, and the percentage of identified compounds. Within the 27 evaluated publications, 1568 manure samples were analyzed and 39 different active substances for VMPs and 11 metabolites and transformation products of VMPs could be found in manure. Most often, the samples were analyzed for sulfonamides, tetracyclines, and fluoroquinolones. Not one study searched for biocides or worked with a non-target approach. For sulfadiazine and chlortetracycline, concentrations exceeding the predicted environmental concentrations were found.

Structural elucidation of sulfaquinoxaline metabolism products and their occurrence in biological samples using high-resolution Orbitrap mass spectrometry

Four previously unreported metabolism products of sulfaquinoxaline (SQX), a widely used veterinary medicine, were isolated and analyzed using liquid chromatography coupled to high-resolution Orbitrap mass spectrometry. Metabolites were structurally elucidated, and a fragmentation pathway was proposed. The combination of high-resolution MS(2) spectra, linear ion trap MS(2), in-source collision-induced dissociation (CID) fragmentation, and photolysis were used to analyze SQX and its metabolites. All metabolism products identified showed a similar fragmentation pattern to that of the original drug. Differential product ions were produced at m/z 162 and 253 which contain the radical moiety with more 16 Da units than sulfaquinoxaline. This occurs by a hydroxyl attachment to the quinoxaline moiety. With the exception of two low-intensity compounds, all the mass errors were below 5.0 ppm. The distribution of these metabolites in some animal species are also presented and discussed.

Quantitative modelling to estimate the transfer of pharmaceuticals through the food production system

Use of pharmaceuticals in animal production may cause an indirect route of contamination of food products of animal origin. This study aimed to assess, through mathematical modelling, the transfer of pharmaceuticals from contaminated soil, through plant uptake, into the dairy food production chain. The scenarios, model parameters, and values refer to contaminants in emission slurry production, storage time, immission into soil, plant uptake, bioaccumulation in the animal's body, and transfer to meat and milk. Modelling results confirm the possibility of contamination of dairy cow's meat and milk due the ingestion of contaminated feed by the cattle. The estimated concentration of pharmaceutical residues obtained for meat ranged from 0 to 6 ng kg(-1) for oxytetracycline, from 0.011 to 0.181 μg kg(-1) for sulfamethoxazole, and from 4.70 to 11.86 μg kg(-1) for ketoconazole. The estimated concentrations for milk were: zero for oxytetracycline, lower than 40 ng L(-1) for sulfamethoxazole, and from 0.98 to 2.48 μg L(-1) for ketoconazole. Results obtained for the three selected pharmaceuticals indicate a minor risk for human health. This study showed that supply chain modelling could be an effective tool in assessing the indirect contamination of feedstuff and animal products by residues of pharmaceuticals. The model can easily be adjusted to other contaminants and supply chain and, in this way, present a valuable tool to underpin decision making.

Adsorption Behaviors of Oxytetracycline onto Sediment in the Weihe River, Shaanxi, China

Adsorption behaviors of oxytetracycline onto sediment in the Weihe River were described. The impact factors in the processes of adsorption, such as contact time, solution pH, temperature, and ionic strength, were determined by experiments. The experimental results were analyzed by kinetic and isotherm models. The adsorption kinetics was found to follow a pseudo-first-order model. The equilibrium adsorption data fitted well with the Langmuir and Freundlich isotherm models. However, the Langmuir isotherm was more suitable to describe the adsorption. Thermodynamics parameters such as Gibbs-free energy change (ΔG°), enthalpy change (ΔH°), and entropy change (ΔS°) were calculated. Results showed that the adsorption was feasible, spontaneous, entropy increasing, and endothermic in nature, which reached equilibrium in about 24 hours. The adsorption capacity did not cause obvious change at solution pH 4.0–7.0, and both decreased in solution pH 7.0–10.0 and 4.0–2.0. The presence of electrolytes such as NaCl in aqueous solution had a significant negative effect on the adsorption. The mechanisms controlling the adsorption were supposed to be chemisorption.

Environmental Risk Assessment of antimicrobials applied in veterinary medicine-A field study and laboratory approach

The fate and environmental risk of antimicrobial compounds of different groups of veterinary medicine pharmaceuticals (VMP's) have been compared. The aim was to demonstrate a correlation between the physical and chemical properties of active compounds and their metabolism in target animals, as well as their fate in the environment. In addition, the importance of techniques for manure management and agricultural practice and their influence on the fate of active compounds is discussed. The selected active compounds are shown to be susceptible to at least one environmental factor (sun, water, bacterial or fungal degradation) to which they are exposed during their life cycle, which contributes to its degradation. Degradation under a number of environmental factors has also to be considered as authentic information additional to that observed in the limited conditions in laboratory studies and in Environmental Risk Assessment calculations.

An approach for mapping the vulnerability of European Union soils to antibiotic contamination

Release of antibiotics into the environment through the agricultural reuse of animal manure is considered a cause of chronic environmental exposure that often leads to adverse ecotoxicological effects, as well as to the introduction of antibiotic-resistant bacteria into the environment. The vulnerability of soil to antibiotic contamination plays a major role in determining the extent of the contamination and the likelihood of the emergence of antibiotic resistance and the appearance of ecotoxicological effects. It depends on soil characteristics, which vary across Europe, and antibiotic characteristics, which vary across drug classes. Understanding how soil vulnerability varies geographically for different veterinary medicinal products would be very useful for resource allocation among surveillance programmes. This paper performs risk analysis of the EU region for 12 antimicrobials using a spatial assessment performed in four steps. First, antibiotic release was estimated based on livestock density. Then exposure was estimated based on antimicrobial soil contamination. Third, consequences were modelled based on soil uses. Finally, risk was estimated by combining release, exposure and consequences using spatial multicriteria decision analysis. A final risk value for soil vulnerability was calculated for each antibiotic studied and displayed in chloropletic maps (ArcGIS 9.3). Furthermore, the Getis-Ord Gi statistic was used to identify clusters of areas at high risk for antibiotic soil contamination. Enrofloxacin was the highest-risk antibiotic in the European Union, followed by tetracyclines, tylosin and sulfodiazine. The highest risk values were found in Belgium, Ireland, Netherlands, Switzerland, Denmark, Germany and the UK. The results suggest that this methodology can be used successfully for evaluating the contamination potential of antibiotics over large areas with limited input data. This work is a preliminary step towards prioritising the use of veterinary medicinal products (VMPs), orientating monitoring studies and antimicrobial surveillance programmes, and informing sustainable decision-making for interventions designed to mitigate the risk of VMPs.

Effect of temperature, pH and illumination on abiotic degradation of oxytetracycline in sterilized swine manure

Tetracyclines such as oxytetracycline (OTC) are widely used veterinary chemicals. They are often poorly absorbed with a significant fraction being excreted in manure that can subsequently result in environmental contamination. In many countries throughout South East Asia swine manure is not composted, but sun-dried. Using sunlight to heat manure has been suggested as an effective and low-cost strategy to reduce OTC contamination, but this has previously been unexplored. Such conditions have also been shown to reduce bacterial numbers in manure meaning abiotic OTC degradation processes may become more significant. This work investigated for the first time, the role of temperature, illumination and pH in the abiotic degradation of OTC in sterilized swine manure. OTC loss from laboratory-based experiments simulating conditions likely to be experienced in sun-drying were assessed using simple first order and availability-adjusted loss models. ANOVA results suggested that neither model was superior to the other. In addition, pH and light had little influence. Temperature was shown to be the main factor influencing OTC loss. Kinetic results showed reductions in OTC concentrations of 65 % after 100 h at 40°C based on the availability-adjusted loss model, regardless of pH and illumination. Such temperatures are likely to be attained during the process of sun-drying. Therefore this may be a useful and practical means of reducing OTC contamination in manure.

Effects of the presence of sulfonamides in the environment and their influence on human health

World production and consumption of pharmaceuticals has been steadily increasing. Anti-infectives have been particularly important in modern therapy of microbial infection. Sulfonamides have been widely used for a long time as anti-infectives and are still widely prescribed today. This review presents the most common types of sulfonamides used in healthcare and veterinary medicine and discusses the problems connected with their presence in the biosphere. Based on the analysis of over 160 papers, it was found that small amounts of sulfonamides present in the environment were mainly derived from agricultural activities. These drugs have caused changes in the population of microbes that could be potentially hazardous to human health. This human health hazard could have a global range, and administrative activities have been ineffective in risk reduction.

Occurrence and distribution of antibiotics in coastal water of the Bohai Bay, China: impacts of river discharge and aquaculture activities

The presence of 21 antibiotics in six different groups was investigated in coastal water of the Bohai Bay. Meantime, to illuminate the potential effects caused by the river discharge and aquaculture activities, wastewater from three breeding plants and surface water from six rivers flowing into the Bohai Bay were also analyzed for the selected antibiotics. The result revealed that measured antibiotics in the North Bobai Bay were generally higher than those in the South, highlighting the remarkable effects of high density of human activities on the exposure of antibiotics in environment. The antibiotics found in the six rivers were generally higher than those in the Bohai Bay reflecting the important antibiotics source of river discharge. This study reveals that the high consumption of some antibiotics in aquaculture activities may pose high ecological risk to the bay.

Integron prevalence and diversity in manured soil

The levels of integron abundance and diversity in soil amended with pig slurry were studied. Real-time PCR illustrated a significant increase in class 1 integron prevalence after slurry application, with increased prevalence still evident at 10 months after application. Culture-dependent data revealed 10 genera, including putative human pathogens, carrying class 1 and 2 integrons.

Veterinary medicines and the environment

Veterinary medicines may be emitted either directly or indirectly into the environment, following its use. As veterinary medicines are biologically active compounds, there is a concern that their occurrence in the environment may have an adverse impact on aquatic and terrestrial organisms. This chapter reviews the major sources by which veterinary medicines enter the environment, the fate, behaviour and occurrence of veterinary medicines in the environment and the potential effects on environmental and human health. Finally, gaps in the current knowledge are identified and recommendations provided on priorities for future research.

Sequestration of manure-applied sulfadiazine residues in soils

It is not the total but the (bio)accessible concentration of veterinary medicines that determines their toxicity in the environment. We elucidate the changes in (bio)accessibility of manure-applied sulfadiazine (SDZ) with increasing contact time in soil. Fattening pigs were medicated with 14C-labeled SDZ, and the contaminated manure (fresh and aged) was amended to 2 soil types (Cambisol, Luvisol) and incubated for 218 days at 10 degrees C in the dark. Antibiotic residues of different bioaccessibility were approached by sequential extractions with 0.01 M CaCl2 (CaCl2 fraction), methanol (MeOH fraction), and finally acetonitrile/water (residual fraction, microwave extraction at 150 degrees C). In each fraction, total radioactivity, SDZ, and its major metabolites were quantified. The results showed that both SDZ and,to a lesser extent 4-hydroxysulfadiazine (4-OH-SDZ) were rapidly reformed from N-acetylsulfadiazine (N-ac-SDZ) during the first 2-4 weeks after fresh manure application, i.e., the N-acetylated metabolite does not sequester in soil to a significant extent Yet, the water and methanol extractable SDZ and 4-OH-SDZ also dissipated rapidly (DT50 = 6.0-32 days) for the fresh manure treatment with similar rate constants for both soil types. In the residual fractions, however, the concentrations of both compounds increased with time. We conclude that the residual fraction comprises the sequestered pool of SDZ and its hydroxylated metabolite. There they are entrapped and may persist in soil for several years. Including the residual fraction into fate studies thus yields dissipation half-lives of SDZ which exceed those previously reported for sulfonamides by a factor of about 100.

Effects of agricultural conditions on the leaching behaviour of veterinary antibiotics in soils

Antibiotics may be released to soils during the application of manure as fertiliser to land. The compounds may subsequently be transported to and contaminate groundwater and surface waters. This paper describes a series of lysimeter-based studies to explore the leaching behaviour of three veterinary antibiotics (sulfachloropyridazine, oxytetracycline and tylosin) under different conditions that could occur in the agricultural environment. The specific objectives were to: (1) explore the influence of slurry amendment and incorporation on leaching; (2) assess the effects of climate on leaching behaviour; and (3) evaluate the predictive capability of a leaching model used in the regulatory assessment of veterinary medicines. Sulfachloropyridazine was detected sporadically in leachate at concentrations up to 0.66 microg L(-1) under typical irrigation conditions and more frequently at concentrations up to 8.5 microg L(-1) under extreme irrigation conditions. Incorporation and timing of rainfall had no effect on leaching behaviour. Oxytetracycline and tylosin were not detected in any leachate samples. These differences in behaviour were explained by the sorption and persistence characteristics of the compounds. Comparison of the experimental measurements with simulations from the leaching model indicated that the model greatly underestimates the transport of antibiotics to groundwater which raises questions over the application of these models in the regulatory risk assessment process.

A preliminary investigation on the occurrence and distribution of antibiotics in the Yellow River and its tributaries, China

This study investigated the residues of antibiotics present in the Yellow River and its tributaries. Ofloxacin, norfloxacin, roxithromycin, erythromycin, and sulfamethoxazole, were found in the river with mean concentrations from 25 to 152 ng/L, and in certain tributaries from 44 to 240 ng/L. The other four analytes were all below the limits of quantification. The results indicated that the detected antibiotics in the middle and lower Yellow River were primarily from its tributaries and ambient wastewater discharge. The concentrations of the antibiotics detected in the river were greater than that in other rivers in Europe. The antibiotics in the river and its tributaries at ng/L concentrations found in this study are unlikely to induce lethal toxicity to aquatic organism but could cause chronic ecological effects.

Simulating sulfadimidine transport in surface runoff and soil at the microplot and field scale

To prevent residues of veterinary medicinal products (VMPs) from contaminating surface waters and ground water, an environmental impact assessment is required before a new product is allowed on the market. Physically based simulation models are advocated for the calculation of predicted environmental concentrations at higher tiers of the assessment process. However, the validation status of potentially useful models is poor for VMP transport. The objective of this study was to evaluate the dual-permeability model MACRO for simulation of transport of sulfonamide antibiotics in surface runoff and soil. Special focus was on effects of solute application in liquid manure, which may alter the hydraulic properties at the soil surface. To this end we used data from a microplot runoff experiment and a field experiment, both conducted on the same clay loam soil prone to preferential flow. Results showed that the model could accurately simulate concentrations of sulfadimidine and the nonreactive tracer bromide in runoff and in soil from the microplot experiments. The use of posterior parameter distributions from calibrations using the microplot data resulted in poor simulations for the field data of total sulfadimidine losses. The poor results may be due to surface runoff being instantly transferred off the field in the model, whereas in reality re-infiltration may occur. The effects of the manure application were reflected in smaller total and micropore hydraulic conductivities compared with the application in aqueous solution. These effects could easily be accounted for in regulatory modeling.

Laboratory study of oxytetracycline degradation kinetics in animal manure and soil

Oxytetracycline (OTC) is a major member of tetracyclines, which are widely administered to animals in confined feeding operations. To diminish the contamination of OTC in the environment, which results from the application of OTC-containing manure as fertilizer in agricultural lands, OTC degradation kinetics in manure and soil under laboratory aerobic conditions was investigated. OTC degradation kinetics was found to be described well by the previously developed availability-adjusted first-order model at all moistures and low temperatures (<or=25 degrees C). OTC degradation increased with increasing moisture from 60 to 100%. However, OTC became very persistent in water-saturated manure. Increasing temperature greatly accelerated OTC degradation, and thermal degradation became noticeable at high temperatures (>or=35 degrees C) in manure. At 25 degrees C, OTC half-life was determined to be 8.1 days in manure with moisture at 80%, 33 days in manure-amended soil (amendment ratio at 5%), and 56 days in non-amended soil with both moistures at 20%, demonstrating that OTC may become persistent in the environment once it is released from manure into soil. No pronounced effect of coexistent antibiotics on OTC degradation in manure was observed.

The dissipation and transport of veterinary antibiotics in a sandy loam soil

The environmental fate of the antibiotics sulfachloropyridazine and oxytetracycline was investigated in a sandy loam soil. Liquid pig manure was fortified with the compounds and then applied to soil plots to investigate leaching, dissipation and surface run-off under field conditions. Additionally, as the macrolide antibiotic tylosin had been administered to the pigs from which the slurry had been sourced, this was also analysed for in the samples collected. Sulfachloropyridazine dissipated rapidly with DT(50) and DT(90) values of 3.5 and 18.9 days but oxytetracycline was more persistent with DT(50) and DT(90) values of 21.7 and 98.3 days. Both sulfachloropyridazine and oxytetracyline were detected in surface run-off samples at maximum concentrations of 25.9 and 0.9microg/l respectively but only sulfachloropyridazine was detected in soil water samples at a maximum concentration of 0.78microg/l at 40cm depth 20 days after treatment. Tylosin was not detected in any soil or water samples. The results indicated that tylosin, when applied in slurry, posed very little risk of accumulating in soil or contaminating ground or surface water. However, tylosin may pose a risk if used to treat animals on pasture and risks arising from transformation products of tylosin, formed during slurry storage, cannot be ruled out. Oxytetracycline posed a very low risk of ground or surface water contamination but had the potential to persist in soils and sulfachloropyridazine posed a moderate risk of contaminating ground or surface water but had low potential to accumulate in soils. These findings were consistent with the sorption and persistence characteristics of the compounds and support a number of broad-scale monitoring studies that have measured these antibiotic classes in the environment.

Sulfadimethoxine degradation kinetics in manure as affected by initial concentration, moisture, and temperature

Sulfadimethoxine is a widely used sulfonamide veterinary antibiotic and could be a source of agricultural contamination. Therefore, information is needed about its degradation kinetics in manure under aerobic conditions. Based on the analysis of first-order kinetics and the assumption that sulfadimethoxine availability for degradation in manure could be limiting, a new kinetic model was developed and was found to fit the degradation kinetics well. The degradation rate in sterile manure was found to be much lower than in nonsterile manure, indicating that biodegradation was significant. In biologically active manure, the degradation rate constant decreased with increasing initial concentration of sulfadimethoxine, implying that the activity of the degrading microorganisms was inhibited. Increasing moisture or temperature was found to increase sulfadimethoxine degradation in manure. Mixing manure containing high levels of sulfadimethoxine with manure containing lower levels may result in more rapid degradation, thus greatly diminishing sulfadimethoxine contamination in manure and significantly reducing sulfadimethoxine inputs into the environment. During treatment, keeping the manure moist and storing in a moderately warm place under aerobic conditions may also help to diminish sulfadimethoxine contamination.

Tracking Oxytetracyline Mobility Across Environmental Interfaces by Second Harmonic Generation

This work examines the binding behavior of the antibiotic oxytetracycline (OTC) to mineral oxide/water interfaces in the presence and absence of organic functional groups using the interface-specific technique second harmonic generation (SHG). Studies show that OTC binding to fused quartz, methyl ester, carboxylic acid, and alkyl interfaces is fully reversible and highly dependent on solution pH, with appreciable adsorption occurring only at pH 8. Relative surface coverage at pH 8 is highest for the polar organic-functionalized surfaces, and surface saturation occurs for the methyl ester-functionalized fused quartz/water interface at 2 x 10(-5) M. Adsorption isotherm measurements indicate that the binding process is controlled by hydrogen bonding and hydrophobic interactions, with free energies of adsorption on the order of -40 kJ/mol for all interfaces studied. The results indicate that OTC transport in the environment will depend heavily on soil pH and composition and have implications for the development of bacterial antibiotic resistance.

A global perspective on the use, sales, exposure pathways, occurrence, fate and effects of veterinary antibiotics (VAs) in the environment

Veterinary antibiotics (VAs) are widely used in many countries worldwide to treat disease and protect the health of animals. They are also incorporated into animal feed to improve growth rate and feed efficiency. As antibiotics are poorly adsorbed in the gut of the animals, the majority is excreted unchanged in faeces and urine. Given that land application of animal waste as a supplement to fertilizer is often a common practice in many countries, there is a growing international concern about the potential impact of antibiotic residues on the environment. Frequent use of antibiotics has also raised concerns about increased antibiotic resistance of microorganisms. We have attempted in this paper to summarize the latest information available in the literature on the use, sales, exposure pathways, environmental occurrence, fate and effects of veterinary antibiotics in animal agriculture. The review has focused on four important groups of antibiotics (tylosin, tetracycline, sulfonamides and, to a lesser extent, bacitracin) giving a background on their chemical nature, fate processes, occurrence, and effects on plants, soil organisms and bacterial community. Recognising the importance and the growing debate, the issue of antibiotic resistance due to the frequent use of antibiotics in food-producing animals is also briefly covered. The final section highlights some unresolved questions and presents a way forward on issues requiring urgent attention.

Uptake of veterinary medicines from soils into plants

Medicines play an important role in the treatment and prevention of disease. Whereas the side effects on human and animal health resulting directly from treatment have been widely documented, only recently have the occurrence and fate of medicines in the environment and the potential consequences for human health been recognized as an issue warranting consideration. Medicines have been shown to be released to soils and to persist in the environment. This study was performed to investigate the potential for a range of veterinary medicines to be taken up from soil by plants used for human consumption and to assess the potential significance of this exposure route in terms of human health. Soil analyses indicated that, for selected substances, measurable residues of these are likely to occur in soils for at least 5 months following application of manure containing these compounds. Experimental studies on the uptake of veterinary medicines into carrot roots (tubers) and lettuce leaves showed that only florfenicol, levamisole, and trimethoprim were taken up by lettuces, whereas diazinon, enrofloxacin, florfenicol, and trimethoprim were detected in carrot roots. Measured concentrations in plant material were used to model potential adult human exposure to these compounds. Although exposure concentrations were appreciable in a few instances, accounting for approximately 10% of the acceptable daily intake values (ADI), all were lower than the ADI values, indicating that, at least for compounds with properties similar to those considered here, there is little evidence of an appreciable risk. This exposure route may, however, be important when veterinary medicines have a very low ADI, at which they elicit subtle effects over prolonged periods, or when exposure is occurring via a number of routes at once. Although degradation products (produced in the soil or the plant) were not measured, it is possible for some substances that these could increase the risks to consumers.