Identification and characterization of tebuconazole transformation products in soil by combining suspect screening and molecular typology

International audienceOnce released into the environment, pesticides generate transformation products (TPs) which may be of (eco-)toxicological importance. Past studies have demonstrated the difficulty to predict pesticide TP occurrence and their environmental risk by monitoring-driven approaches mostly used in current regulatory frameworks targeting only known toxicologically relevant TPs. We present a novel combined approach which identifies and categorizes known and unknown pesticide TPs in soil by combining suspect screening time-of-flight mass spectrometry with in silico molecular typology. This approach applies an empirical and theoretical pesticide TP library for compound identification by both non-target and target time-of-flight (tandem) mass spectrometry and structural elucidation through a molecular structure correlation program. In silico molecular typology was then used to group the detected TPs according to common molecular descriptors and to indirectly elucidate their environmental properties by analogy to known pesticide compounds having similar molecular descriptors. This approach was evaluated via the identification of TPs of the triazole fungicide tebuconazole occurring in a field dissipation study. Overall, 22 empirical and 12 yet unknown TPs were detected and categorized into three groups with defined environmental properties. This approach combining suspect screening time-of-flight mass spectrometry with molecular typology could be extended to other organic pollutants and used to rationalize the choice of TPs to be intensively studied towards a more comprehensive environmental risk assessment scheme

Lab to Field Assessment of the Ecotoxicological Impact of Chlorpyrifos, Isoproturon, or Tebuconazole on the Diversity and Composition of the Soil Bacterial Community

Pesticides are intentionally applied to agricultural fields for crop protection. They can harm non-target organisms such as soil microorganisms involved in important ecosystem functions with impacts at the global scale. Within the frame of the pesticide registration process, the ecotoxicological impact of pesticides on soil microorganisms is still based on carbon and nitrogen mineralization tests, despite the availability of more extensive approaches analyzing the abundance, activity or diversity of soil microorganisms. In this study, we used a high-density DNA microarray (PhyloChip) and 16S rDNA amplicon next-generation sequencing (NGS) to analyze the impact of the organophosphate insecticide chlorpyrifos (CHL), the phenyl-urea herbicide isoproturon (IPU), or the triazole fungicide tebuconazole (TCZ) on the diversity and composition of the soil bacterial community. To our knowledge, it is the first time that the combination of these approaches are applied to assess the impact of these three pesticides in a lab-to-field experimental design. The PhyloChip analysis revealed that although no significant changes in the composition of the bacterial community were observed in soil microcosms exposed to the pesticides, significant differences in detected operational taxonomic units (OTUs) were observed in the field experiment between pesticide treatments and control for all three tested pesticides after 70 days of exposure. NGS revealed that the bacterial diversity and composition varied over time. This trend was more marked in the microcosm than in the field study. Only slight but significant transient effects of CHL or TCZ were observed in the microcosm and the field study, respectively. IPU was not found to significantly modify the soil bacterial diversity or composition. Our results are in accordance with conclusions of the Environmental Food Safety Authority (EFSA), which concluded that these three pesticides may have a low risk toward soil microorganisms

A tiered-based approach to study the dissipation and adsorption of isoproturon, tebuconazole and chlorpyrifos in soil

International audienc

Evidence for the interest of suspect screening metabolomics to identify known and unkown pesticide metabolites in soil

International audienc

Evaluation of the environmental fate and ecotoxicological impact of the pesticide chlorpyrifos in soil for improvement of its environmental risk assessment

EABIOMEUBINRAPesticides protect crops from various pests but can also harm nontarget organisms. To minimize risks for the environment and human health, a huge amount of studies are carried out and evaluated during the authorization process of each pesticide. However, the prediction of the environmental fate and ecotoxicological impact of a pesticide remains difficult. Several 100 formerly used pesticides are now banned because unexpected risks emerged decades after their authorization. Risk assessment documents of the organophosphate insecticide chlorpyrifos (CHL) particularly lack information about its degradation and potential transformation products in soil, and its impact on non-target microorganisms supporting soil ecosystem services with impact at the global scale. Within the frame of a large European Marie Curie project, we studied the environmental fate of CHL in a lab-to-field dissipation study by (i) quantifying CHL and its main transformation product 3,5,6-trichloropyridinol (TCP), (ii) screening for known and new transformation products, and (iii) measuring its sorption to soil. Furthermore, the ecotoxicological impact of CHL on the soil bacterial community was estimated by (i) Illumina next-generation sequencing of 16S rDNA amplified from extracted soil DNA, and (ii) monitoring the adaptation of soil microorganisms to repeated CHL exposure by analysis of CHL mineralization. Main results are (i) the identification of known and one new transformation products of CHL, (ii) no effect of CHL on the diversity of the bacterial community in our lab-to-field experiment, (iii) but adaptation to repeated CHL exposure as shown by improved CHL mineralization and by microbial diversity analysis. For further research on CHL biodegradation and as potential candidates for bioremediation, we isolated a CHL-degrading bacterial consortium

Dissipation and adsorption of isoproturon, tebuconazole, chlorpyrifos and their main transformation products under laboratory and field conditions

EABIOMEUBINRAAssessment of dissipation constitutes an integral part of pesticides risk assessment since it provides an estimate of the level and the duration of exposure of the terrestrial ecosystem to pesticides. Within the frame of an overall assessment of the soil microbial toxicity of pesticides, we investigated the dissipation of a range of dose rates of three model pesticides, isoproturon IPU), tebuconazole (TCZ), and chlorpyrifos CHL), and the formation and dissipation of their main transformation products following a tiered lab-to-field approach. The adsorption of pesticides and their transformation products was also determined. IPU was the least persistent pesticide showing a dose-dependent increase in its persistence in both laboratory and field studies. CHL dissipation showed a dose-dependent increase under laboratory conditions and an exact opposite trend in the field. TCZ was the most persistent pesticide under lab conditions showing a dose-dependent decrease in its dissipation, whereas in the field TCZ exhibited a biphasic dissipation pattern with extrapolated DT90s ranging from 198 to 603.4 days in the x1 and x2 dose rates, respectively. IPU was demethylated to mono- (MD-IPU) and di-desmethyl-isoproturon (DD-IPU) which dissipated following a similar pattern with the parent compound. CHL was hydrolyzed to 3,5,6-trichloro-2-pyridinol (TCP) which dissipated showing a reverse dose-dependent pattern compared to CHL. Pesticides adsorption affinity increased in the order IPU < TCZ < CHL. IPU transformation products showed low affinity for soil adsorption, whereas TCP was weakly adsorbed compared to its parent compound. The temporal dissipation patterns of the pesticides and their transformation products will be used as exposure inputs for assessment of their soil microbial toxicity. (C) 2016 Published by Elsevier B.V

New paradigms for European pesticide policy to reduce pressure on the environment

National audienceDespite their benefits for humanity, pesticides pose serious threats to environmental and human health. Those pesticides deemed to be most persistent and dangerous have thus been subject to a series of bans, including several hundred formerly authorized and widely used pesticides that are banned in Europe today, following the emergence of unexpected and unacceptable risks decades after their market introduction. In particular, pesticide transformation products, which form in the environment via abiotic or biotic processes, can pose higher risks to the environment than the parent compound itself. The nature and chemistry of these products is however largely unknown. The safe use of pesticides is one of the biggest challenges of agricultural intensification. Here we argue that a paradigm shift in European pesticide policy is required to reduce pressure on the environment. I will constructively discuss the process of pesticide environmental risk assessment including major weaknesses in pesticide policy. I will present a new method combining suspect screening and molecular typology for environmental risk assessment of pesticides, which has the potential to detect and identify unknown transformation products. Furthermore, in silico molecular typology allows evaluating environmental parameters of transformation products for their potential inclusion in environmental risk studies in the post-registration assessment

Identification and characterization of tebuconazole transformation products in soil by combining suspect screening and molecular typology

Pesticides generate transformation products (TPs) when they are released into the environment. These TPs may be of ecotoxicological importance. Past studies have demonstrated how difficult it is to predict the occurrence of pesticide TPs and their environmental risk. The monitoring approaches mostly used in current regulatory frameworks target only known ecotoxicologically relevant TPs. Here, we present a novel combined approach which identifies and categorizes known and unknown pesticide TPs in soil by combining suspect screening time-of-flight mass spectrometry with in silico molecular typology. We used an empirical and theoretical pesticide TP library for compound identification by both non-target and target time-of-flight (tandem) mass spectrometry, followed by structural proposition through a molecular structure correlation program. In silico molecular typology was then used to group TPs according to common molecular descriptors and to indirectly elucidate their environmental parameters by analogy to known pesticide compounds with similar molecular descriptors. This approach was evaluated via the identification of TPs of the triazole fungicide tebuconazole occurring in soil during a field dissipation study. Overall, 22 empirical and 12 yet unknown TPs were detected, and categorized into three groups with defined environmental properties. This approach combining suspect screening timeof-flight mass spectrometry with molecular typology could be extended to other organic pollutants and used to rationalize the choice of TPs to be investigated towards a more comprehensive environmental risk assessment scheme

New approach to identify and categorize pesticide metabolites in soil combining suspect screening metabolomics with in silico molecular typology. 5th International Conference on Environmental Pollution and Remediation (ICEPR)

New approach to identify and categorize pesticide metabolites in soil combining suspect screening metabolomics with in silico molecular typology. 5th International Conference on Environmental Pollution and Remediation (ICEPR). 5th International Conference on Environmental Pollution and Remediation (ICEPR