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Capillary zone electrophoresis (CZE) was used to separate and determine simultaneously the p[K.sub.1], p[K.sub.2], and pI values of 12 environmentally relevant hydroxytriazines (hydroxymetabolites of atrazine, terbuthylazine, simazine, and propazine and four (arylamino)-s-triazines) and observe the effects of the alkylamino and arylamino substituents on the measured values. Capillary isoelectric focusing (CIEF) methods were developed to measure the pI of these compounds and compare those values with the CZE-measured pI's. CZE and CIEF can provide accurate pK and pI values reasonably fast, and pI values measured by the two techniques agree. Knowledge of the pK and pI values of hydroxytriazines is important for an understanding of the binding mechanisms of these molecules in environmental matrices. Because the hydroxy-triazines may exist as a myriad of species-neutral, charged, zwitterionic, and keto-enol tautomeric - depending on structure and pH, we briefly addressed the existence of these species relative to their electrophoretic analysis.

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of diclazuril (Clinacox® 0.5%) as a coccidiostat for chickens for fattening and chickens reared for laying. The additive currently on the market complies with the existing conditions of authorisation. The additive remains safe for the target species and the consumer under the authorised conditions of use. The additive is irritant to skin, eyes and respiratory tract but is not a skin sensitiser. Exposure by inhalation cannot be excluded. The FEEDAP Panel cannot conclude on the safety for the environment of diclazuril from Clinacox® 0.5% due to lack of data. Diclazuril from Clinacox® 0.5% at a concentration of 1 mg diclazuril/kg complete feed has the potential to control coccidiosis in chickens for fattening. This conclusion is extended to chickens reared for laying. Development of resistance to diclazuril of field Eimeria spp. strains isolated from chickens should be monitored., Competing Interests: If you wish to access the declaration of interests of any expert contributing to an EFSA scientific assessment, please contact interestmanagement@efsa.europa.eu., (© 2024 European Food Safety Authority. EFSA Journal published by Wiley‐VCH GmbH on behalf of European Food Safety Authority.)

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of the coccidiostat salinomycin sodium (Sacox®) for rabbits for fattening. The EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) concluded that the use of salinomycin sodium (SAL-Na) from Sacox® does not raise safety concerns for the target species, consumers, users and the environment with regard to the production strain. In the absence of adequate tolerance studies, the FEEDAP Panel could not conclude on the safety of SAL-Na from Sacox® for rabbits for fattening. The FEEDAP Panel concluded that the additive is safe for the consumer when it is used at the proposed maximum level of 25 mg SAL-Na/kg complete feed for rabbits and a withdrawal period of 1 day is respected. The following maximum residue limits (MRL) are proposed for the marker residue compound salinomycin (SAL): 0.2 and 0.03 mg SAL/kg for liver and kidney, respectively. The additive is not irritant to skin and eyes but should be considered a potential dermal and respiratory sensitiser. A risk for inhalation toxicity could not be excluded. The use of the SAL-Na from Sacox® in feed for rabbits for fattening up to the highest proposed level will not pose a risk for the terrestrial and aquatic compartment and ground water. The risk of secondary poisoning can be excluded for worm-eating birds and mammals, while it cannot be excluded for fish-eating birds and mammals. The FEEDAP Panel concludes that SAL-Na from Sacox® at the minimum concentration of 20 mg SAL-Na/kg complete feed has the potential to control coccidiosis in rabbits for fattening. Development of resistance to SAL-Na of field Eimeria spp. strains isolated from rabbits for fattening should be monitored., Competing Interests: If you wish to access the declaration of interests of any expert contributing to an EFSA scientific assessment, please contact interestmanagement@efsa.europa.eu., (© 2024 European Food Safety Authority. EFSA Journal published by Wiley‐VCH GmbH on behalf of European Food Safety Authority.)

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of monensin sodium (Coxidin®) as a coccidiostat for chickens for fattening, chickens reared for laying, turkeys for fattening and turkeys reared for breeding. The additive currently on the market complies with the existing conditions of authorisation. The FEEDAP Panel concluded that Coxidin® remains safe for turkeys for fattening (up to 16 weeks) and extends this conclusion to turkeys reared for breeding (up to 16 weeks). The Panel was not in the position to confirm that the current maximum authorised level of 125 mg monensin sodium/kg complete feed remains safe for chickens for fattening and chickens reared for laying. The use of monensin sodium from Coxidin® at the corresponding maximum authorised/proposed use levels in the target species is safe for the consumer. The existing maximum residue levels (MRLs) for poultry tissues ensure consumer safety. No withdrawal time is necessary. Both formulations of Coxidin® pose a risk by inhalation. The formulation with wheat bran as a carrier was neither irritant to the skin nor a skin sensitiser but it was irritant to the eyes. In the absence of data, no conclusions could be made on the potential of the formulation containing calcium carbonate to be irritant to skin and eyes and to be a skin sensitiser. The use of monensin sodium from Coxidin® in complete feed for the target species poses no risk for the terrestrial compartments and for sediment. No risk for groundwater is expected. For chickens for fattening the risk for aquatic compartment cannot be excluded, but no risks are expected for the other animal categories. There is no risk of secondary poisoning. Coxidin® is efficacious in controlling coccidiosis at a level of 100 mg/kg complete feed for chickens for fattening and at 60 mg/kg complete feed for turkeys for fattening. These conclusions are extended to chickens reared for laying and turkeys reared for breeding. The Panel noted that there are signs of development of resistance of Eimeria spp. to monensin sodium ., Competing Interests: If you wish to access the declaration of interests of any expert contributing to an EFSA scientific assessment, please contact interestmanagement@efsa.europa.eu., (© 2024 European Food Safety Authority. EFSA Journal published by Wiley‐VCH GmbH on behalf of European Food Safety Authority.)

Glyphosate currently is the most-widely used herbicide for weed control on railway tracks. However, railway companies look for non-chemical and chemical alternatives. Glyphosate has a low potential for leaching to groundwater and alternative herbicides should ideally share this behavior. We investigated the leaching of glyphosate and five potential alternatives in lysimeters filled with three different soils from railway tracks. Herbicides were applied in three consecutive years to 4-7 lysimeters. Leachate was collected and analysed for herbicides and major metabolites. Highest annual average concentrations of 23 μg/L were found for atrazine, which was selected as mobile reference compound. 2,4-D, flazasulfuron, and its major metabolite DTPU reached annual average concentrations of 0.60, 0.43, and 0.50 μg/L, respectively. Pelargonic-acid was detected in single samples shortly after application and heavy rainfall. Quizalofop-P, glyphosate, and metabolites were only sporadically found in leachate at annual average concentrations ≪0.1 μg/L. Highest leachate concentrations were generally observed in lysimeters with a high proportion of sandy fine material and little organic carbon, except for the quickly-degradable pelargonic-acid and 2,4-D that reached highest concentrations in lysimeters with high gravel content and thus small effective transport volume. After three years, up to 30, 6.5, and 0.56 % of the applied mass of flazasulfuron, atrazine, and 2,4-D, respectively, was recovered in leachate in form of the active substances and/or their metabolites (expressed in parent equivalents). Although recoveries of flazasulfuron exceeded those of atrazine, concentrations were lower due to the 100-fold lower application rate. From the perspective of groundwater protection, the currently used glyphosate still is by far the best (chemical) option while all tested possible glyphosate alternatives did show some potential for leaching which may, however, be manageable with certain restrictions (e.g., spot spraying). These findings are likely applicable to other uses in non-agricultural settings with gravel or paving stone surfaces., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: Although co-formulants constitute a substantial portion of the total plant protection product (PPP) mass applied to crops, data on residue formation and the behaviour of these substances on plants are scarce. In an earlier study we demonstrated that co-formulants commonly used in PPPs can form considerable residues, i.e., in the low to medium mg/kg range, but normally decline rapidly within few days. In the field trial reported here, we aimed to identify the major decline processes of co-formulants. Residues of co-formulants were therefore monitored in parsley and lettuce grown in an open field as well as under foil tunnels equipped with either an overhead or a drip irrigation system., Results: Dissipation of three anionic surfactants was markedly faster when crops (parsley and lettuce) were exposed to natural rainfall or irrigation from above compared to drip irrigation. In contrast, the decline of three volatile organic solvents was not affected by rain or irrigation, but was dependent on the crop, with much shorter half-lives in lettuce than in parsley. Furthermore, dilution through plant growth contributed significantly to the reduction of residues over time., Conclusion: In this work we substantiate earlier findings on the magnitude and dissipation of residues of anionic surfactants and solvents representing the most important co-formulant classes. The chosen experimental setup allowed differentiation between decline processes and we confirm that foliar wash-off is a major dissipation process for anionic surfactants. For volatile organic solvents, dissipation appears to depend on the properties not only of the substance but also of the plant (surface). © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry., (© 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.)

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety for the environment of diclazuril (Coxiril®) as a coccidiostat feed additive for chickens reared for laying and pheasants. In its previous assessments, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) could not reach a final conclusion on the risk resulting from the use of diclazuril in acid soil from Coxiril®. On the basis of the new data provided, the FEEDAP Panel updates the previous conclusions as follows: no risk is expected for the terrestrial compartment and for sediment when diclazuril is used in chickens reared for laying and to pheasants at the proposed condition of use (in both acidic and non-acidic soils). No concern for groundwater is expected for both acidic and non-acidic soils. Due to the lack of data, no conclusions can be drawn for the aquatic compartment. Diclazuril does not have the potential for bioaccumulation; therefore, a risk of secondary poisoning is unlikely., (© 2023 European Food Safety Authority. EFSA Journal published by Wiley‐VCH GmbH on behalf of European Food Safety Authority.)

Following a request from the European Commission, EFSA was asked to deliver a new scientific opinion on the coccidiostat halofuginone hydrobromide (STENOROL®) when used as a feed additive for chickens for fattening and turkeys for fattening/reared for breeding. The Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) concludes that the safety for turkeys for fattening established in its previous opinion can be extended to turkeys for breeding up to 12 weeks of age. Based on the new data provided on the safety for consumer, environment and efficacy, the Panel updates its previous conclusions as follows: halofuginone hydrobromide is not genotoxic. Applying an uncertainty factor of 100 to the lowest no observed adverse effect level (NOAEL) of 0.03 mg/kg body weight (bw) per day, an acceptable daily intake (ADI) of 0.3 μg halofuginone/kg bw is established. The chronic exposure of consumers to residues of halofuginone would amount to 6-19% of the ADI after 3 days of withdrawal. Therefore, the Panel considers that the additive is safe for the consumer of tissues obtained from chickens for fattening and turkeys for fattening fed the additive at a maximum level of 3 mg/kg complete feed at a 3-day withdrawal time. For control purposes, the Panel recommends the setting of the following maximum residue limits (MRLs): liver, 50 μg/kg; kidney, 40 μg/kg; muscle, 3 μg/kg; skin/fat, 10 μg/kg wet tissue. Based on an updated environmental risk assessment, no concern for groundwater is expected. Halofuginone is unlikely to bioaccumulate and the risk of secondary poisoning is not likely to occur. No safety concerns are expected for terrestrial and aquatic environments. The additive has the potential to control coccidiosis in chickens for fattening and turkeys for fattening/reared for breeding up to 12 weeks of age at a minimum level of 2 mg/kg complete feed., (© 2023 European Food Safety Authority. EFSA Journal published by Wiley‐VCH GmbH on behalf of European Food Safety Authority.)

Following a request from the European Commission, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP Panel) was asked to deliver a scientific opinion on the safety and efficacy of a copper(II)-betaine complex as nutritional feed additive for all animal species. Based on the results of a tolerance study carried out in chicken, the FEEDAP Panel concluded that the additive is safe for chickens for fattening when used up to the current maximum authorised levels of copper in feed; this conclusion was extrapolated to all animal species and categories at the respective maximum copper levels in complete feed authorised in the European Union. The FEEDAP Panel concluded that the use of the copper(II)-betaine complex in animal nutrition at the maximum copper levels authorised for the animal species poses no concern to the safety of consumers. Regarding the safety for the environment, the use of the additive in feed for terrestrial animals and land-based aquaculture is considered safe under proposed conditions of use. The data available do not allow the conclusion to be made on the safety of the additive for marine sediment when it is used in sea cages. The additive is not a skin irritant, but it is an irritant to the eyes. Due to the traces of nickel, the additive is considered to be a respiratory and skin sensitiser. The Panel could not conclude on the efficacy of the product., (© 2023 European Food Safety Authority. EFSA Journal published by Wiley‐VCH GmbH on behalf of European Food Safety Authority.)

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of a zinc(II)-betaine complex as nutritional additive for all animal species. The EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) concluded that the additive is safe for chickens for fattening. This conclusion could be extrapolated to all animal species and categories provided that the maximum authorised levels in the EU for total zinc in feed are not exceeded. The FEEDAP Panel concluded that the use of the zinc(II)-betaine complex in animal nutrition is of no concern for consumer safety provided that the maximum authorised total zinc levels in feed are respected. The additive is considered to be a skin and respiratory sensitiser due to the presence of nickel; it is irritant to the eyes, but not to the skin. The use of the additive in animal nutrition for terrestrial animals and land-based aquaculture at the proposed use levels is considered safe for terrestrial and aquatic ecosystems. The available data do not allow the conclusion to be made on the safety of the additive for the marine sediment when it is used in sea cages. Based on the deposition of zinc in edible tissues/organs in chickens for fattening, the FEEDAP Panel concluded that the additive is a source of bioavailable zinc, comparable to the standard inorganic zinc source, and therefore, the additive is efficacious in meeting the birds zinc requirements. This conclusion can be extrapolated to all animal species and categories., (© 2023 European Food Safety Authority. EFSA Journal published by Wiley‐VCH GmbH on behalf of European Food Safety Authority.)

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety of sodium saccharin as a sensory feed additive (flavouring compound) for suckling and weaned piglets, fattening pigs, calves for rearing and for fattening. In a previous assessment, the Panel on Additives and Products or substances used in Animal Feed (FEEDAP Panel) could not conclude on the safety of the additive for the environment because concentrations of the additive or its degradation product 4-hydroxysaccharin in groundwater above 0.1 μg/L were likely to occur. In addition, regarding user safety, sodium saccharin was considered to be potentially harmful by inhalation or by contact to skin and eyes. In the current opinion, the applicant restricted the use to suckling and weaned piglets and up to a use level of 5 mg/kg complete feed. In relation to the user safety, the additive was neither a skin or eye irritant, nor a dermal sensitiser. In the absence of data, the FEEDAP Panel could not conclude on the potential of the additive to be toxic by inhalation. Regarding the safety of the additive for the environment, the new conditions of use describe a maximum use level of 5 mg sodium saccharin/kg feed. The applicant indicated that a restriction to a lower use level due to environmental safety would be accepted and submitted an environment risk assessment based on a use level of 1.13 mg sodium saccharin/kg feed. This use level cannot be considered safe. The estimated use level that would result in a concentration in groundwater below 0.1 μg/L is of 0.022 mg sodium saccharin/kg feed. The available data do not allow to conclude on the potential effect of the degradation product 4-hydroxysaccharin in ground water., (© 2023 Wiley‐VCH Verlag GmbH & Co. KgaA on behalf of the European Food Safety Authority.)

Background: The application of plant protection products (PPPs) leads to the formation of residues in treated crops. Even though PPPs contain considerable amounts of co-formulants, regulation and monitoring of residues normally focus on the active substances (a.s.) only. For our study we selected four commonly used co-formulants (three anionic surfactants and one organic solvent) and investigated the formation and decline of residues in vegetables and apples under field conditions. The aims were to characterize the behavior of co-formulant residues on crops and to provide a basis for future investigations on consumer exposure., Results: The development of robust and sensitive analytical methods allowed the quantification of residues in the low μg/kg-level. After treatment with PPPs, co-formulants were detected up to approximately 10 mg kg -1 in vegetables. In general, these residues declined fast with half-lives of a few days. Wash-off and volatilization were identified as important removal processes for anionic surfactants and the organic solvent, respectively. However, in specific crops (parsley and celery), organic solvent residues were still considerable (≈2 mg kg -1 ) 2 weeks after treatment. We further demonstrate that it is feasible to estimate co-formulant residues using publicly available data on pesticide a.s., Conclusion: To date no information on co-formulant residues in food is available. The findings from our field trials, as well as the presented approach for the prediction of residues, provide key elements for future consideration of consumer exposure to PPP co-formulants. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry., (© 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.)

The herbicide glyphosate is frequently detected in surface waters and its occurrence is linked to agricultural as well as urban uses. Elevated concentrations downstream of wastewater treatment plants (WWTPs) suggest that municipal wastewater is an important source of glyphosate in surface waters. We therefore conducted a study at a typical municipal WWTP in Switzerland to characterize the seasonality of glyphosate occurrence, the removal efficiency, and the processes involved in glyphosate removal. Glyphosate was present in raw (mechanically treated) wastewater during the whole study period (April to November). A lab incubation experiment with activated sludge indicated negligible degradation of glyphosate. Lack of degradation combined with strong adsorption lead to substantial enrichment of the compound in the sludge. Due to this enrichment and the long residence time of activated sludge (several days, compared to hours for wastewater itself), concentrations in treated wastewater show comparatively little variation, whereas concentrations in raw wastewater may fluctuate considerably. Overall removal efficiencies were in the range of 71-96%. This behavior could be described qualitatively using a numerical model that included input of glyphosate via raw wastewater, adsorption to activated sludge, and export via treated wastewater and excess sludge, but excluded degradation processes.

Background: Imazaquin is a chiral herbicide which displays high mobility in soils. Like other imidazolinones, imazaquin is available for use only as racemic mixture of its enantiomers. In this work, several clay materials were assayed as adsorbents of imazaquin, and then the most suitable material was selected to prepare a clay-based slow release imazaquin nanoformulation containing exclusively the biologically active R-enantiomer. Next, laboratory experiments were conducted to illustrate the benefits of using the clay-based R-imazaquin formulation over the free (non-supported) racemic herbicide or the free pure R-imazaquin enantiomer regarding its leaching behavior and bioefficacy., Results: The clay material selected as a carrier for R-imazaquin, hexadecyltrimethylammonium-saturated montmorillonite (SA-HDTMA), combined a high affinity for the herbicide and a high stability of the clay-herbicide adsorption complex. In a simulated scenario of high water input shortly after herbicide application, the clay-based R-imazaquin formulation displayed reduced leaching and increased bioefficacy compared to free racemic imazaquin and free R-imazaquin., Conclusion: The new clay-R-imazaquin formulation prepared, besides avoiding the environmental impact caused by the application of the less active S-enantiomer, reduced the herbicide leaching losses and prolonged the herbicidal activity, by increasing the residence time of the herbicide in the topsoil. © 2018 Society of Chemical Industry., (© 2018 Society of Chemical Industry.)

Many pesticides show a pronounced biphasic degradation in soil, typically with a faster initial phase, followed by a slower decline. For chiral compounds, a biphasic decline of the total concentration may result from enantioselective degradation. In this study with the chiral herbicide imazamox, biphasic degradation was observed in most of the 18 soils investigated. In neutral soils, degradation was, in fact, enantioselective with faster degradation of (+)-imazamox. In slightly acidic soils, differences between enantiomers were not pronounced, and in strongly acidic soils, degradation was again enantioselective, but with reversed preference. Additional experiments with pure enantiomers indicated no interconversion. Enantioselective degradation thus contributed to the biphasic decline of the total concentration in certain soils. However, this was not the only factor since degradation of the individual enantiomers was biphasic in itself. In addition to the observed correlation between enantioselectivity and pH, degradation was generally faster in neutral than in acidic soils with half-lives ranging from only 2 to >120 days. Half-lives were also determined for two known metabolites and a further chiral metabolite, the structure of which was characterized by high resolution tandem mass spectrometry. As for the parent compound, half-lives of the metabolites varied considerably in the different soils.

Imazamox is a chiral herbicide that, in laboratory experiments in the dark, exhibits pronounced enantioselective biodegradation in certain soils. Imazamox also shows rapid photodegradation. However, which processes are predominant in the field is not clear. We conducted a set of soil incubation experiments under natural sunlight (and corresponding dark controls), using enantioselective LC-MS/MS analysis as a probe to distinguish biodegradation and photodegradation. Under dark conditions, imazamox was degraded enantioselectively. In contrast, degradation was nonenantioselective and 2× faster when the soil was exposed to sunlight, suggesting that biodegradation (in the dark) and photodegradation (under sunlight) were the predominant degradation processes. We also investigated the effectiveness of strategies that were proposed to exclude photodegradation in field studies, covering of soil with sand or irrigation after herbicide application. The sand cover did not prevent photodegradation. On the contrary, degradation was 10× faster than in the dark and nonenantioselective. Computer simulations supported the explanation that imazamox was transported upward by capillary flow due to evaporation onto the sand surface, where it was rapidly photodegraded. Irrigation postponed but not completely prevented photodegradation. For mobile substances susceptible to photodegradation, upward transport to the soil surface thus needs to be considered when deriving rates for biodegradation from field studies.

Occurrence and fate of glyphosate, a widely used herbicide, and its main metabolite AMPA was investigated in Lake Greifensee, Switzerland. Monthly vertical concentration profiles in the lake showed an increase of glyphosate concentrations in the epilimnion from 15 ng/L in March to 145 ng/L in July, followed by a sharp decline to <5 ng/L in August. A similar pattern was observed for AMPA. Concentrations of glyphosate and AMPA in the two main tributaries generally were much higher than in the lake. Simulations using a numerical lake model indicated that a substantial amount of glyphosate and AMPA dissipated in the epilimnion, mainly in July and August, with half-lives of only ≈2-4 days which is ≫100 times faster than in the preceding months. Fast dissipation coincided with high water temperatures and phytoplankton densities, and low phosphate concentrations. This indicates that glyphosate might have been used as an alternative phosphorus source by bacterio- and phytoplankton. Metagenomic analysis of lake water revealed the presence of organisms known to be capable of degrading glyphosate and AMPA.

Glyphosate is currently one of the most important herbicides worldwide. Its unique properties provide for a wide range of uses in agriculture but also in non-agricultural areas. At the same time, its zwitterionic nature prevents the inclusion in multi-residue analytical methods for environmental monitoring. Consequently, despite its extensive use, data on occurrence of glyphosate in the aquatic environment is still scarce. Based on existing methods, we developed a simplified procedure for the determination of glyphosate and its main metabolite aminomethylphosphonic acid (AMPA) in water samples using derivatization with fluorenylmethyl chloroformate FMOC-Cl, combined with on-line solid phase extraction and liquid chromatography-tandem mass spectrometry (LC-MS/MS) detection. This method was extensively tested on over 1000 samples of surface water, groundwater, and treated wastewater and proved to be simple, sensitive, and reliable. Limits of quantification of 0.005 μg/L were routinely achieved. Glyphosate and AMPA were detected in the vast majority of stream water samples in the area of Zurich, Switzerland, with median concentrations of 0.11 and 0.20 μg/L and 95th percentile concentrations of 2.1 and 2.6 μg/L, respectively. Stream water data and data from treated wastewater indicated that non-agricultural uses may significantly contribute to the overall loads of glyphosate and AMPA in surface waters. In the investigated groundwater samples, selected specifically because they had shown presence of other herbicides in previous monitoring programs, glyphosate and AMPA were generally not detected, except for two monitoring sites in Karst aquifers, indicating that these compounds show much less tendency for leaching.

Background: Convincing experimental evidence suggests increased sorption of pesticides on soil over time, which, so far, has not been considered in the regulatory assessment of leaching to groundwater. Recently, Beulke and van Beinum (2012) proposed a guidance on how to conduct, analyse and use time-dependent sorption studies in pesticide registration. The applicability of the recommended experimental set-up and fitting procedure was examined for two fungicides, penflufen and fluxapyroxad, in four soils during a 170 day incubation experiment., Results: The apparent distribution coefficient increased by a factor of 2.5-4.5 for penflufen and by a factor of 2.5-2.8 for fluxapyroxad. The recommended two-site, one-rate sorption model adequately described measurements of total mass and liquid phase concentration in the calcium chloride suspension and the calculated apparent distribution coefficient, passing all prescribed quality criteria for model fit and parameter reliability., Conclusion: The guidance is technically mature regarding the experimental set-up and parameterisation of the sorption model for the two moderately mobile and relatively persistent fungicides under investigation. These parameters can be used for transport modelling in soil, thereby recognising the existence of the experimentally observed, but in the regulatory leaching assessment of pesticides not yet routinely considered phenomenon of time-dependent sorption. © 2016 Society of Chemical Industry., (© 2016 Society of Chemical Industry.)

Pesticide transport from seed dressings toward subsurface tile drains is still poorly understood. We monitored the neonicotinoid insecticides imidacloprid and thiamethoxam from sugar beet seed dressings in flow-proportional drainage water samples, together with spray applications of bromide and the herbicide S-metolachlor in spring and the fungicides epoxiconazole and kresoxim-methyl in summer. Event-driven, high first concentration maxima up to 2830 and 1290 ng/L for thiamethoxam and imidacloprid, respectively, were followed by an extended period of tailing and suggested preferential flow. Nevertheless, mass recoveries declined in agreement with the degradation and sorption properties collated in the groundwater ubiquity score, following the order bromide (4.9%), thiamethoxam (1.2%), imidacloprid (0.48%), kresoxim-methyl acid (0.17%), S-metolachlor (0.032%), epoxiconazole (0.013%), and kresoxim-methyl (0.003%), and indicated increased leaching from seed dressings compared to spray applications. Measured concentrations and mass recoveries indicate that subsurface tile drains contribute to surface water contamination with neonicotinoids from seed dressings.

Metabolism of chiral pesticides in crops is typically studied using achiral analytical methods and, consequently, the stereoisomer composition of residues is unknown. In this study, we developed an enantioselective GC-MS/MS method to quantify residues of the fungicides fenpropidin, fenpropimorph, and spiroxamine in plant matrices. In field trials, the fungicides were applied to grapevines, sugar beets, or wheat. Fenpropidin was metabolized with no or only weak enantioselectivity. For fenpropimorph, slightly enantioselective metabolism was observed in wheat but more pronounced in sugar beets. This enantioselectivity was due to different rates of metabolism and not due to interconversion of enantiomers. The four stereoisomers of spiroxamine were also metabolized at different rates, but selectivity was only found between diastereomers and not between enantiomers. trans-Spiroxamine was preferentially degraded in grapes and cis-spiroxamine in wheat. These findings may affect the consumer dietary risk assessment because toxicological end points were determined using racemic test substances.

Haloxyfop-methyl is a chiral herbicide that was first introduced as racemate and later replaced by "haloxyfop-P-methyl", mainly consisting of the R-enantiomer, which carries the herbicidal activity. We studied the ester cleavage of haloxyfop-methyl and further degradation and chiral inversion of the acid enantiomers in three different soils using enantioselective gas chromatography-mass spectrometry. Our results confirm the rapid ester hydrolysis of haloxyfop-methyl with half-lives of a few hours and indicate that hydrolysis is weakly enantioselective. Further degradation of haloxyfop was slower with half-lives of several days. In all three soils, S-haloxyfop was rapidly converted to R-haloxyfop. In sterile soil, no degradation and no inversion were observed, indicating that both processes are biologically mediated. In soil where 50% of the water had been replaced by deuterium oxide, significant H-D exchange in haloxyfop was observed, pointing to a reaction mechanism involving abstraction of the proton at the chiral center of the molecule.

Haloxyfop-methyl is a chiral herbicide against grasses in dicotyledonous crops. In plants and soil, haloxyfop-methyl is rapidly hydrolyzed to haloxyfop-acid, whose R-enantiomer carries the actual herbicidal activity. In soil, S-haloxyfop-acid is converted within less than 1 day and almost completely into R-haloxyfop-acid. In this study, we investigated the possible interconversion of the enantiomers of haloxyfop-methyl and haloxyfop-acid in blackgrass and garden cress. Racemic or enantiopure haloxyfop-methyl was applied to the leaves of plants grown in agar. The metabolism was followed during 4 days using enantioselective GC-MS. In contrast to soils, no interconversion was observed in plants, and metabolism was nonenantioselective. These findings are consistent with the fact that after pre-emergence application to soil and uptake by roots, the observed herbicidal effect is basically independent of the enantiomer composition of the applied substance, whereas after postemergence application, the efficacy clearly is different for the two enantiomers.

A sensitive and selective analytical method, based on online solid phase extraction coupled to LC-MS/MS, was developed and validated to determine traces of several recently introduced fungicides in surface water and wastewater. The list of target analytes included eight succinate dehydrogenase inhibitors (bixafen, boscalid, fluopyram, flutolanil, fluxapyroxad, isopyrazam, penflufen, and penthiopyrad), and two other fungicides with different modes of action, fenpyrazamine and fluopicolide. Detection and quantification limits in various matrices were in the range of 0.1 to 2 and 0.5 to 10 ng/L, respectively. Moderate signal suppression was observed in surface water (≤15%) and wastewater (≤25%) and was well compensated by the selected internal standard. The intra- and inter-day precisions were generally <10 and <20%, respectively. The applicability of the method was demonstrated in a study on the occurrence of fungicides in the river Glatt, Switzerland, that drains a catchment area of 419 km(2) with a substantial proportion of agricultural land. Of the studied compounds, only boscalid and fluopicolide were detected in flow-proportional weekly composite samples, generally at low concentrations up to 15 and 5 ng/L, respectively. While fluopicolide was detected in only 30% of the samples above the LOD of 0.5 ng/L, boscalid was detected in all samples analyzed between March and October 2012.

δ-Hexachlorocyclohexane (δ-HCH), one of the prevalent isomers of technical HCH, was enantioselectively dehydrochlorinated by the dehydrochlorinases LinA1 and LinA2 from Sphingobium indicum B90A to the very same δ-pentachlorocyclohexene enantiomer. Racemic δ-pentachlorocyclohexene, however, was transformed with opposite enantioselectivities by the two enzymes. A transformation pathway based on an anti-1,2-elimination, followed by a syn-1,4-elimination and a subsequent syn-1,2-elimination is postulated.

Beflubutamid is a chiral soil herbicide currently marketed as racemate against dicotyledonous weeds in cereals. Biotests have shown that (-)-beflubutamid is at least 1000× more active than (+)-beflubutamid. Potential substitution of the racemate by (-)-beflubutamid should therefore be further considered. Here, we investigated the degradation behavior in soils and formation and degradation of two chiral metabolites. Laboratory incubation experiments were performed with an alkaline and an acidic soil. The compounds were analyzed by enantioselective GC-MS. Degradation rate constants were determined by kinetic modeling. In the alkaline soil, degradation of beflubutamid was slightly enantioselective, with slower degradation of the herbicidally active (-)-enantiomer. In the acidic soil, however, both enantiomers were degraded at similar rates. In contrast, degradation of a phenoxybutanamide metabolite was highly enantioselective. Chiral stability of beflubutamid and its metabolites was studied in separate incubations with the pure enantiomers in the same soils. In these experiments, (-)-beflubutamid was not converted to the nonactive (+)-enantiomer and vice versa. Significant enantiomerization was, however, observed for the major metabolite, a phenoxybutanoic acid. With regard to biological activity and behavior in soils, enantiopure (-)-beflubutamid definitively has the potential to substitute for the racemic herbicide.

For many chiral pesticides, little information is available on the properties and fate of individual stereoisomers. A basic data set would, first of all, include stereoisomer-specific analytical methods and data on the biological activity of stereoisomers. The herbicide beflubutamid, which acts as an inhibitor of carotenoid biosynthesis, is currently marketed as racemate against dicotyledonous weeds in cereals. Here, we present analytical methods for enantiomer separation of beflubutamid and two metabolites based on chiral HPLC. These methods were used to assign the optical rotation and to prepare milligram quantities of the pure enantiomers for further characterization with respect to herbicidal activity. In addition, sensitive analytical methods were developed for enantiomer separation and quantification of beflubutamid and its metabolites at trace level, using chiral GC-MS. In miniaturized biotests with garden cress, (-)-beflubutamid showed at least 1000× higher herbicidal activity (EC50, 0.50 μM) than (+)-beflubutamid, as determined by analysis of chlorophyll a in 5-day-old leaves. The agricultural use of enantiopure (-)-beflubutamid rather than the racemic compound may therefore be advantageous from an environmental perspective. In further biotests, the (+)-enantiomer of the phenoxybutanoic acid metabolite showed effects on root growth, possibly via an auxin-type mode of action, but at 100× higher concentrations than the structurally related herbicide (+)-mecoprop.

α-, β, γ-, and δ-Hexachlorocyclohexane (HCH), the four major isomers of technical HCH, are susceptible to biotic transformations, whereby only α- and γ-HCH undergo complete mineralization. Nevertheless, LinA and LinB catalyzing HCl elimination and hydrolytic dehalogenations, respectively, as initial steps in the mineralization also convert β- and δ-HCH to a variety of mainly hydroxylated metabolites. In this study, we describe the isolation of two minor components of technical HCH, ε-HCH, and heptachlorocyclohexane (HeCH), and we present data on enzymatic transformations of both compounds by two dehydrochlorinases (LinA1 and LinA2) and a haloalkane dehalogenase (LinB) from Sphingobium indicum B90A. In contrast to reactions with α-, γ-, and δ-HCH, both LinA enzymes converted ε-HCH to a mixture of 1,2,4-, 1,2,3-, and 1,3,5-trichlorobenzenes without the accumulation of pentachlorocyclohexene as intermediate. Furthermore, both LinA enzymes were able to convert HeCH to a mixture of 1,2,3,4- and 1,2,3,5-tetrachlorobenzene. LinB hydroxylated ε-HCH to pentachlorocyclohexanol and tetrachlorocyclohexane-1,4-diol, whereas hexachlorocyclohexanol was the sole product when HeCH was incubated with LinB. The data clearly indicate that various metabolites are formed from minor components of technical HCH mixtures. Such metabolites will contribute to the overall toxic potential of HCH contaminations and may constitute serious, yet unknown environmental risks and must not be neglected in proper risk assessments.

Artificial sweeteners are consumed in substantial quantities as sugar substitutes and were previously shown to be ubiquitously present in the aquatic environment. The sweetener saccharin is also registered as additive in piglet feed. Saccharin fed to piglets was largely excreted and, consequently, found in liquid manure at concentrations up to 12 mg/L, where it was stable during 2 months of storage. Saccharin may thus end up in soils in considerable quantities with manure. Furthermore, other studies showed that saccharin is a soil metabolite of certain sulfonylurea herbicides. Sweeteners may also get into soils via irrigation with wastewater-polluted surface water, fertilization with sewage sludge (1-43 μg/L), or through leaky sewers. In soil incubation experiments, cyclamate, saccharin, acesulfame, and sucralose were degraded with half-lives of 0.4-6 d, 3-12 d, 3-49 d, and 8-124 d, respectively. The relative importance of entry pathways to soils was compared and degradation and leaching to groundwater were evaluated with computer simulations. The data suggest that detection of saccharin in groundwater (observed concentrations, up to 0.26 μg/L) is most likely due to application of manure. However, elevated concentrations of acesulfame in groundwater (up to 5 μg/L) may result primarily from infiltration of wastewater-polluted surface water through stream beds.