Pesticide Transformation Products Research Articles

Assessment of Environmental Pollution and Human Exposure to Pesticides by Wastewater Analysis in a Seven-Year Study in Athens, Greece.

Pesticides have been used in large amounts around the world for decades and are responsible for environmental pollution and various adverse effects on human health. Analysis of untreated wastewater can deliver useful information on pesticides’ use in a particular area and allow the assessment of human exposure to certain substances. A wide-scope screening method, based on liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry, was applied, using both target and suspect screening methodologies. Daily composite influent wastewater samples were collected for seven or eight consecutive days in Athens between 2014 and 2020 and analyzed for 756 pesticides, their environmental transformation products and their human metabolites. Forty pesticides were quantified at mean concentrations up to 4.9 µg/L (tralkoxydim). The most abundant class was fungicides followed by herbicides, insect repellents, insecticides and plant growth regulators. In addition, pesticide transformation products and/or metabolites were detected with high frequency, indicating that research should be focused on them. Human exposure was evaluated using the wastewater-based epidemiology (WBE) approach and 3-ethyl-carbamoyl benzoic acid and cis-1,2,3,6-tetrahydrophthalimide were proposed as potential WBE biomarkers. Wastewater analysis revealed the presence of unapproved pesticides and indicated that there is an urgent need to include more transformation products in target databases.

Modelling the Fate of Pesticide Transformation Products From Plot to Catchment Scale—State of Knowledge and Future Challenges

Transformation products (TP) of pesticides are found everywhere in the aquatic environment. Their dynamic formation and subsequent transport from agricultural fields to adjacent water bodies can be estimated by using environmental fate models, which is done in the registration process for plant protection products in the European Union. In this study, peer-reviewed applications of such models, the model complexity and their structure are documented and analysed. In total, 20 publications of 10 models – eight leaching models (GLEAMS, MACRO, RZWQM2, PEARL, PRZM, Pelmo, LEACHM, HYDRUS 1-D) and two catchment scale models (Zin-AgriTra, FRM) – were identified. The reviewed models greatly differ in their process complexity regarding the formation rate and the formation pathways of TPs.The major reason given for models failing to reproduce sampled TP concentrations in case studies was an erroneous substance transport, especially missing preferential flow simulation in soil. However, the contribution of TP formation processes to simulation uncertainty was not analysed at all in most of the studies. By comparing the structure of existing models, the state of knowledge on TP fate and requirements of TP fate assessment, the following recommendations were drawn: i) It is suggested that the models should be updated to reflect the current state of knowledge in process research, especially more complex transformation schemes and the formation of different TPs in different compartments, which was not included in most of the models. ii) Even though there are pesticide parent compound fate models at the catchment scale with a temporal resolution of one day, none of these models is able to simulate TP fate. Such models would enable scientists and authorities to estimate the environmental fate of TPs at the larger catchment scale or the regional scale. iii) To get over the assessment of the huge number of TPs formed in the environment, an integration of Quantitative Structure Properties Relationship models predicting TP fate characteristics, TP pathway prediction models and environmental fate models is suggested. This would allow for a largely automated and comprehensive assessment of the fate of a pesticide parent compound and all its TPs for regulatory purposes.

Identification of Pesticide Transformation Products in Surface Water Using Suspect Screening Combined with National Monitoring Data.

Pesticides are widespread anthropogenic chemicals and well-known environmental contaminants of concern. Much less is known about transformation products (TPs) of pesticides and their presence in the environment. We developed a novel suspect screening approach for not well-explored pesticides (n = 16) and pesticide TPs (n = 242) by integrating knowledge from national monitoring with high-resolution mass spectrometry data. Weekly time-integrated samples were collected in two Swedish agricultural streams using the novel Time-Integrating, MicroFlow, In-line Extraction (TIMFIE) sampler. The integration of national monitoring data in the screening approach increased the number of prioritized compounds approximately twofold (from 23 to 42). Ultimately, 11 pesticide TPs were confirmed by reference standards and 12 TPs were considered tentatively identified with varying levels of confidence. Semiquantification of the newly confirmed TPs indicated higher concentrations than their corresponding parent pesticides in some cases, which highlights concerns related to (unknown) pesticide TPs in the environment. Some TPs were present in the environment without co-occurrence of their corresponding parent compounds, indicating higher persistency or mobility of the identified TPs. This study showcased the benefits of integrating monitoring knowledge in this type of studies, with advantages for suspect screening performance and the possibility to increase relevance of future monitoring programs.

Occurrence of pesticides and their transformation products in headwater streams: Contamination status and effect of ponds on contaminant concentrations

In France, more than 90% of monitored watercourses are contaminated with pesticides. This high contamination level increases at the head of agricultural watersheds, where dilution capacities are low and transport from treated lands is direct. Ponds, numerous around headwater streams, could provide additional protection against pesticide pollution. Because of their long hydraulic residence time and large water volumes, they mitigate pesticide concentrations between upstream and downstream rivers. However, pesticide transformation products may also be responsible for the degradation of environments, owing to their presence at high concentrations and their persistence, but related data are scarce, particularly because of their high level of molecular diversity. We first reported on the state of water contamination in agricultural headwater streams, based on high frequency water sampling. Analysis of 67 molecules (HPLC-ESI-MS/MS) showed pesticides and pesticide transformation product mixtures of up to 29 different compounds in one sample. Regardless of the sampling location, transformation products represented at least 50% of the detected compounds. Then, we demonstrated the capacity of a pond to reduce contaminant concentrations in downstream rivers for 90% of the detected compounds. Upstream from this pond, environmental quality or ecotoxicological standards were exceeded during sampling, with pesticide and transformation product sum concentrations of up to 27 μg/L. Downstream from the study pond, few exceedances were observed, with a maximum total concentration of 2.2 μg/L, reflecting significant water quality improvement.

Seasonal and spatial dynamics of selected pesticides and nutrients in a small lake catchment – Implications for agile monitoring strategies

Intensive anthropogenic pressure such as high inputs of nutrients and pesticides severely threaten most European water bodies. Small catchments ≤10 km2 are not monitored under the Water Framework Directive but play an important role in freshwater ecosystems. The high complexity in seasonal and spatial dynamics require more than a one-size-fits-all approach in water quality monitoring. Often located in rural areas with a high agricultural activity, small catchments often carry high amounts of nutrients, pesticides and their transformation products affecting drinking water resources. With a low-cost approach of a monthly sampling campaign over the course of one year combined with meaningful indicators for potential pollution sources within the catchment this study could elucidate catchment dynamics and two hotspots for pesticides and nutrients. Two different groups of pesticides were observed (I) pesticides on long-term use which were applied in high amounts over the last decades (e.g., chloridazon and its transformation products) and (II) pesticides on short-term use, newly introduced into the market. Especially transformation products of pesticides from group (I) together with nitrate showed a steady release from two fields into the receiving water bodies over the year, probably being stored in the soil layers over the years of application slowly leaching out. Pesticides from group (II) showed a strong seasonality, released from another hotspot area probably due to run-off shortly after application. Streamlining this knowledge into targeted measures and an agile monitoring strategy for the respective catchments may allow a sustainable improvement of water quality and a better ecosystem protection.

Inclusion of Pesticide Transformation Products Is Key to Estimating Pesticide Exposures and Effects in Small U.S. Streams.

Improved analytical methods can quantify hundreds of pesticide transformation products (TPs), but understanding of TP occurrence and potential toxicity in aquatic ecosystems remains limited. We quantified 108 parent pesticides and 116 TPs in more than 3 700 samples from 442 small streams in mostly urban basins across five major regions of the United States. TPs were detected nearly as frequently as parents (90 and 95% of streams, respectively); 102 TPs were detected at least once and 28 were detected in >20% samples in at least one region-TPs of 9 herbicides, 2 fungicides (chlorothalonil and thiophanate-methyl), and 1 insecticide (fipronil) were the most frequently detected. TPs occurred commonly during baseflow conditions, indicating chronic environmental TP exposures to aquatic organisms and the likely importance of groundwater as a TP source. Hazard quotients based on acute aquatic-life benchmarks for invertebrates and nonvascular plants and vertebrate-centric molecular endpoints (sublethal effects) quantify the range of the potential contribution of TPs to environmental risk and highlight several TP exposure-response data gaps. A precautionary approach using equimolar substitution of parent benchmarks or endpoints for missing TP benchmarks indicates that potential aquatic effects of pesticide TPs could be underestimated by an order of magnitude or more.

Evaluation and application of machine learning-based retention time prediction for suspect screening of pesticides and pesticide transformation products in LC-HRMS

Computational QSAR models have gradually been preferred for retention time prediction in data mining of emerging environmental contaminants using liquid chromatography coupled with mass spectrometry. Generally, the model performance relies on the components such as machine learning algorithms, chemical features, and example data. In this study, we evaluated the performances of four algorithms on three feature sets, using 321 and 77 pesticides as the training and validation sets, respectively. The results were varied with different combinations of algorithms on distinct feature sets. Two strategies including enhancing the complexity of chemical features and enlarging the size of the training set were proved to improve the results. XGBoost, Random Forest, and lightGBM algorithms exhibited the best results when built on a large-scale chemical descriptors, while the Keras algorithm preferred fingerprints. These four models have comparable prediction accuracies that at least 90% of pesticides in validation set can be successfully predicted with ΔRT <1.0 min. Meanwhile, a blended prediction strategy using average results from four models presented a better result than any single model. This strategy was used for assisting identification of pesticides and pesticide transformation products in 120 strawberry samples from a national survey of food contamination. Twenty pesticides and twelve pesticide transformation products were tentatively identified, where all pesticides and two pesticide transformation products (bifenazate diazene and spirotetramat-enol) were confirmed by standard materials. The outcome of this study suggested that retention time prediction is a valuable approach in compound identification when integrated with in silico MS2 spectra and other MS identification strategies.

The degradation dynamics and rapid detection of thiacloprid and its degradation products in water and soil by UHPLC-QTOF-MS

Thiacloprid is a neonicotinoid insecticide used to control sucking and chewing insects of fruits and vegetables. Hydrolysis, photolysis of thiacloprid in aqueous solutions, and soil degradation of three typical types of soil in China were studied. UHPLC-QTOF/MS was used to acquire high-resolution mass spectrometry information of thiacloprid’s degradation products in water and soil samples, and the UNIFI platform with integrated data processing function was used to find and identify degradation products. The degradation kinetics of thiacloprid was determined. Six transformation products (M271, M287, M269, M295, M279, M267) were found after the data processing workflow in the UNIFI platform by using the raw MSE data. The structure of putative transformation products can be inferred based on the accurate mass of fragment ions and the automated spectral interpretation tools in the UNIFI platform. The structure of M271 was validated to be thiacloprid amide by comparing the ESI-MS2 fragment ions in soil samples and thiacloprid amide standard. The TrendPlot function of UNIFI was used to demonstrate the kinetics of the transformation products. Reduction, hydrolysis, oxidation are the main reactions of thiacloprid in three tested soil in China and buffer solutions. This study provided a reference for the rapid identification of the transformation products of other pesticides in specific environmental conditions.

Neonicotinoids, fipronil, chlorpyrifos, carbendazim, chlorotriazines, chlorophenoxy herbicides, bentazon, and selected pesticide transformation products in surface water and drinking water from northern Vietnam

Studies on the occurrence of emerging pesticides in surface and drinking water in Vietnam are limited. In this study, lake water (n = 7), river water (n = 1), tap water (n = 46), and bottled water (n = 3) collected from Hanoi and other four provinces in northern Vietnam were analyzed for selected pesticides (including insecticides such as neonicotinoids, fipronil, and chlorpyrifos; fungicide carbendazim; herbicides such as atrazine, terbuthylazine, simazine, 2,4-dichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid, and bentazon) and some of their degradates by liquid chromatography-tandem mass spectrometry. Carbendazim (median: 86.7 ng/L) and triazines (49.3 ng/L) were the major pesticides found in lake water samples, followed by neonicotinoids and their degradation products (15.1 ng/L), chlorpyrifos and its degradate (13.4 ng/L), fipronil and its degradates (3.76 ng/L), chlorophenoxy acid herbicides (2.10 ng/L), and bentazon (0.62 ng/L). Triazines (164 ng/L) were the major pesticides in river water. Higher concentrations (median: 39.3 ng/L; range: 1.20–127) of selected pesticides were found in tap water from Hanoi than those from four other provinces studied (5.49 ng/L; 4.73–66.8 ng/L). Bottled water samples collected from Hanoi contained lower concentrations of pesticide residues (median: 3.54 ng/L, range: 2.18–8.09) than those of tap water samples. The calculated risks from pesticide exposure through ingestion of tap water by the general populations were low. However, fipronil concentrations in lake water exceeded the benchmark value recommended for freshwater in the United States or the Netherlands. Degradation of acetamiprid into desmethyl-acetamiprid was found in lake water.

Simultaneous analysis of current-use pesticides and their transformation products in water using mixture-sorbent solid phase extraction and high-performance liquid chromatography-tandem mass spectrometry.

Pesticides have posed significant threats to aquatic ecosystems, yet little is known about their transformation products. The challenge is to simultaneously analyze various pesticides and transformation products in water as they have distinct physicochemical properties. A mix-mode solid phase extraction method was established to simultaneously analyze current-use pesticides and their transformation products using a mixture of hydrophile-lipophile balance, weak anion, and cation exchange resins (2:1:1, w/w/w) in combination with high-performance liquid chromatography and tandem mass spectrometry for chemical quantification. Neutral, acidic, and alkaline methanol were used as the elution solvent. Box-Behnken design was applied to optimize extraction conditions. Optimal conditions were as follows: sorbent mass, 200mg; volume of elution solvent, 5mL × 3; pH 4. The method was validated for compounds at concentrations from 20 to 1000ng/L in different types of water samples, with recovery being from 43.5 ± 3.1 to 141 ± 35%. Low method detection limits (0.02-5.6ng/L) implied that the developed method was sensitive. Finally, the method was applied to monitor current-use pesticides and their transformation products in natural waters. Frequent detection of transformation products of pesticides indicated that their contribution to aquatic risk should not be ignored.

Exploring QSAR models for assessment of acute fish toxicity of environmental transformation products of pesticides (ETPPs)

Environmental transformation products of pesticides (ETPPs) have a great deal of ecological impact owing to their ability to cause toxicity to the aquatic organisms, which can then be translated to the humans. The limited experimental data on biochemical and toxic effects of ETPPs, the high test costs together with regulatory limitations and the international push to reduce animal testing encourage greater dependence on predictive in silico techniques like quantitative structure-activity relationship (QSAR) models. The aim of the present work was to explore the key structural features, which regulate the toxicity towards fishes, for 85 ETPPs using a partial least squares (PLS) regression based chemometric model developed according to Organisation for Economic Co-operation and Development (OECD) guidelines. The model was extensively validated using both internal and external validation metrics, and the results so obtained justify the reliability and usefulness of the developed model (Q2 = 0.648, R2pred or Q2F1 = 0.734 and Q2F2 = 0.733). From the developed model, we can conclude that lipophilicity, polarity, presence of branching and the functional form of O-atom in the transformed structures of pesticides are the important features that are to be considered during ecotoxicity assessment of ETPPs. The information obtained from the descriptors of the developed model could be utilized in the future for assessing ETPPs with the benefit of providing an early warning of their potentially detrimental effect on fishes for regulatory purposes.

A strategy for an initial assessment of the ecotoxicological effects of transformation products of pesticides in aquatic systems following a tiered approach

In order to conduct a fast and comprehensive toxicity screening of pesticide transformation products (TPs), this study used a tiered approach by a combination of in silico and experimental methods to determine the probability to be of relevance for risk assessment. The six pesticides Boscalid, Penconazole, Diuron, Terbutryn, Octhilinone (OIT), and Mecoprop were used as model compounds. Identification of corresponding environmental known and unknown TPs were done by literature analysis and photolysis experiments in combination. Aquatic solutions of the pesticides were photolysed to generate TPs which can be expected in the aquatic environment. The resulting mixtures were screened for TPs by high resolution LC-MS/MS. The herein developed approach was conducted at three different tiers: Literature review and in silico methods were used to predict exemplary the environmental bacterial toxicity and the genotoxicity of every single TP at tier I. In case of indications to be toxic, experiments at tier II were applied. Hereby, the photolytic mixtures containing parent compound and TPs were used for the consecutive toxicity test. Microtox assay for the parent compounds and the photolytic mixture was conducted to determine the acute and chronic toxicity and the growth inhibition of V. fischeri. Umu-tests were conducted to determine primary DNA damage. At tier III, single substance standards were used to conduct toxicity tests in case of toxic indication by previous tiers and availability of analytical standard. Identification of TPs revealed 45 known environmental TPs that originated from the six pesticides. The number of substances that need to be assessed was therefore more than sevenfold. By the tiered approach, it was possible to assess toxicological effects on environmental bacteria of 94% of the selected TPs. For 20% we found strong evidence to be toxic to environmental bacteria, as they were assessed at least at two tiers. For further 44% of the TPs we found slight evidence, as they could be assessed at one tier. Contrary, this approach turned out to be unsuitable to assess genotoxic effects of TPs neither by in silico tools nor by experiments. The number of substances that could probably pose a risk onto environment was quadrupled in comparison to the consideration of solely the parent compounds. Thus, this study demonstrates that the conducted screening approach allows for easy and fast identification of environmental relevant TPs. However, the study presented was a very first screening. Its applicability domain needs to be assessed further. For this purpose as a very next step the approach suggested here should be verified by applying additional endpoints and including additional parent compounds.

The potential endocrine disruption of pesticide transformation products (TPs): The blind spot of pesticide risk assessment

The ecological and health risk assessment of environmental pesticide residues have attracted ever-growing attention; however, their transformation products (TPs) have seldom been considered. Herein, we examined the endocrine-disrupting effects of 4 widely used pesticides as pyriproxyfen (Pyr), malathion (ML), benalaxyl (BX), and fenoxaprop-ethyl (FE), together with their 21 TPs through in vitro and in silico approaches, and found approximately 50% of the TPs exhibited stronger endocrine-disrupting effects than their corresponding parent compounds. Specifically, Pyr and 9 TPs (five TPs of Pyr, one of ML, one of BX, and two of FE) exhibited estrogen-disrupting effects, which were also confirmed by results of E-screen and pS2 expression assays, and molecular docking showed that certain hydroxylated TPs could well mimic the binding mode of estrogen with ERα. Meanwhile, two TPs of Pyr, ML and its TP demonstrated weak glucocorticoid antagonistic activities partially contributed by hydrogen bonds. We also discovered that in H295R cells, all the endocrine disruptors increased hormone secretion and the related gene expression levels. Conclusively, since an increasing number of pesticide TPs have been being detected in various environmental media, a more comprehensive understanding of the ecological risk of pesticide TPs is imperative for risk assessments more extensively and regulatory policy-making on pesticide restriction in the future.

Suspect and Nontarget Screening for Contaminants of Emerging Concern in an Urban Estuary.

This study used suspect and nontarget screening with high-resolution mass spectrometry to characterize the occurrence of contaminants of emerging concern (CECs) in the nearshore marine environment of Puget Sound (WA). In total, 87 non-polymeric CECs were identified; those confirmed with reference standards (45) included pharmaceuticals, herbicides, vehicle-related compounds, plasticizers, and flame retardants. Eight polyfluoroalkyl substances were detected; perfluorooctanesulfonic acid (PFOS) concentrations were as high as 72-140 ng/L at one location. Low levels of methamphetamine were detected in 41% of the samples. Transformation products of pesticides were tentatively identified, including two novel transformation products of tebuthiuron. While a hydrodynamic simulation, analytical results, and dilution calculations demonstrated the prevalence of wastewater effluent to nearshore marine environments, the identity and abundance of selected CECs revealed the additional contributions from stormwater and localized urban and industrial sources. For the confirmed CECs, risk quotients were calculated based on concentrations and predicted toxicities, and eight CECs had risk quotients >1. Dilution in the marine estuarine environment lowered the risks of most wastewater-derived CECs, but dilution alone is insufficient to mitigate risks of localized inputs. These findings highlighted the necessity of suspect and nontarget screening and revealed the importance of localized contamination sources in urban marine environments.

Occurrence of imidacloprid and its transformation product (imidacloprid-nitroguanidine) in rivers during an irrigating and soil puddling duration

Liquid chromatography/triple quadrupole mass spectrometry is a promising technique to detect trace contaminants in water environments. This technique requires reference standard reagents to develop selected reaction monitoring (SRM) conditions, but emerging contaminants like pesticide transformation products are often commercially unavailable in markets. Thus in this study, high resolution mass spectrometry was coupled with sensitive triple quadrupole mass spectrometry to develop SRM conditions by using environmental samples instead of reference standard reagents. The SRM conditions for imidacloprid-nitroguanidine (1-((6-chloropyridin-3-yl)methyl)-2-nitroguanidine), an transformation product of a neonicotinoid, were successfully developed by using a concentrated paddy water sample. Prior to its synthesis, imidacloprid-nitroguanidine was verified to be present in actual river water samples. Without such verification, the synthesis of imidacloprid-nitroguanidine could be meaningless if its concentrations in samples were below detection limit. After that, it was eventually synthesized to acquire its calibration curve. In the sampling site, imidacloprid has been applied to nursery boxes of rice seedling. Rice seedlings raised in nursery boxes were transplanted to paddy fields along with the soil in boxes. Imidacloprid-nitroguanidine was detected in the soil and its penetration into river water may cause pollution. Obvious pollution was observed before the rice plantation began because of irrigating and soil puddling in paddy fields, which indicates that monitoring of transformation product in soil must be started before rice plantation begins.

New relevant pesticide transformation products in groundwater detected using target and suspect screening for agricultural and urban micropollutants with LC-HRMS

Groundwater is a major drinking water resource, but its quality is threatened by a broad variety of anthropogenic micropollutants (MPs), originating from agriculture, industry, or households, and undergoing various transformation processes during subsurface passage. To determine a worst-case impact of pesticide application in agriculture on groundwater quality, a target and suspect screening for more than 300 pesticides and more than 1100 pesticide transformation products (TPs) was performed in 31 Swiss groundwater samples which predominantly originated from areas with intensive agriculture. To assess additional urban contamination sources, more than 250 common urban MPs were quantified. Most of the screened pesticide TPs were experimentally observed by the pesticide producers within the European pesticide registration. To cover very polar pesticide TPs, vacuum-assisted evaporative concentration was used for enrichment, followed by liquid chromatography high-resolution tandem mass spectrometry (LC-HRMS/MS). Based on intensity, isotope pattern, retention time, and in silico fragmentation, the suspect hits were prioritised and verified. We identified 22 suspects unequivocally and five tentatively; 13 TPs are reported here for the first time to be detected in groundwater. In 13 out of 31 groundwater samples, the total concentration of the 20 identified and quantified suspects (1 pesticide and 19 pesticide TPs) exceeded the total concentration of the 519 targets (236 pesticides and TPs; 283 urban MPs) for which we screened. Pesticide TPs had higher concentrations than the parent pesticides, illustrating their importance for groundwater quality. The newly identified very polar chlorothalonil TP R471811 was the only compound detected in all samples with concentrations ranging from 3 to 2700 ng/L. Agricultural MP concentration and detection frequency correlated with agricultural land use in the catchment, except for aquifers, where protective top layers reduced MP transport from the surface. In contrast to agricultural MPs, urban MPs displayed almost no correlation with land use. The dominating entry pathway of urban MPs was river bank filtration.

Evaluation of the behaviour of propoxycarbazone herbicide in soils and water under different conditions. Post-targeted study

The aim of this study is to understand the levels and behaviour of the herbicide propoxycarbazone in environmental compartments, which are poorly characterized considering degradation products that might reach either surface water as groundwater or soil samples. To this end, an analytical method, based on ultra-high performance liquid chromatography (UHPLC) coupled with Orbitrap mass spectrometry (MS), has been developed to determine the parent compound and its transformation products in soils and water. In addition, a set of laboratory trials has been designed to address the dissipation process of propoxycarbazone formulation in both environmental substrates. The study revealed that the dissipation in water followed a first order kinetics and a non-linear “First Order Multi Compartment” model (FOMC) to soil.Relevant advances have been also achieved in terms of the analytical methodology, as far as the UHPLC-Orbitrap-MS technique allows the development of a retrospective screening of pesticide transformation products in water and soils. For this purpose, an accurate-mass database has been built and used for the post-run screening analysis with 9 transformation products. Photodegradation presumably plays an important role in the dissipation of propoxycarbazone. The results of UHPLC-Orbitrap-MS revealed that four transformation products were formed during the degradation process of the herbicide.

Studies on the behavior and ecotoxicity of pesticides and their transformation products in a river.

To clarify the properties of pesticide transformation products (TPs) for which the risk to aquatic organisms should be evaluated, I monitored the concentrations of paddy pesticides and their TPs in the Sakura River, Japan, during the rice-growing season in 2007-2010. I also conducted algal growth inhibition tests of herbicides and their TPs using a diatom and a green alga and acute toxicity tests of insecticides and their TPs using a caddisfly and a daphnid. Moreover, on the basis of the results of pesticide monitoring and toxicity tests, I attempted to evaluate the risk of these compounds to the riverine organisms as well as the risk of mixtures of insecticides and their TPs for caddisflies and cladocerans. The TPs were detected in the river water depending on the half-lives of the parent compounds and of the TPs in water and soil. The toxicities of the parent compound and its TPs may be related to their hydrophobicities and chemical structures. Some toxic and persistent TPs that formed rapidly in water and soil posed a risk to the organisms over a long period. The physicochemical properties and chemical structures of a parent compound and its TPs can be key factors in evaluating the pesticide TP risk to aquatic organisms in rivers.

Investigation of Chlorpyrifos and Its Transformation Products in Fruits and Spices by Combining Electrochemistry and Liquid Chromatography Coupled to Tandem Mass Spectrometry

The identification of transformation products (TPs) of pesticides in food is a crucial task difficult to tackle, due to the lack of standards. In this work, we present a novel methodology to synthesize five main TP standards of the insecticide chlorpyrifos (CPF) and to investigate their occurrence in selected fruits and spices. TPs were electrochemically (EC) synthesized using a boron-doped diamond electrode (BDD) and identified by EC coupled online to mass spectrometry, LC-MS/MS, and high-resolution mass spectrometry. CPF and its TPs were analyzed in the food samples by LC-MS/MS on multiple reaction monitoring (MRM) after dispersive solid-phase extraction. A good recovery of 83–103% for CPF and 65–85% for TPs was obtained. Matrix effects, which cause signal suppression, ranged between 81 to 95% for all targeted analytes. The limit of detection and quantification for CPF were 1.6–1.9 and 4.9–5.7 μg/kg, respectively. Among investigated samples, CPF was determined in fresh lemon (104 μg/kg), fenugreek seed (40 μg/kg), and black pepper (31 μg/kg). CPF content in all samples was lower than the EU maximum residue level (MRL). The most frequently detected TPs were diethylthiophosphate and diethylphosphate. Other TPs, CPF oxon and trichloropyridinol, were also detected. Hence, EC is a versatile tool to synthesize TP standards which enables the determination of contaminants and residues in foodstuffs even if no commercial standards are available.

Removals of pesticides and pesticide transformation products during drinking water treatment processes and their impact on mutagen formation potential after chlorination

Removal efficiencies of 28 pesticide transformation products (TPs) and 15 parent pesticides during steps in drinking water treatment (coagulation–sedimentation, activated carbon adsorption, and ozonation) were estimated via laboratory-scale batch experiments, and the mechanisms underlying the removal at each step were elucidated via regression analyses. The removal via powdered activated carbon (PAC) treatment was correlated positively with the log Kow at pH 7. The adjusted coefficient of determination (r2) increased when the energy level of the highest occupied molecular orbital (HOMO) was added as an explanatory variable, the suggestion being that adsorption onto PAC particles was largely governed by hydrophobic interactions. The residual error could be partly explained by π-π electron donor–acceptor interactions between the graphene surface of the PAC particles and the adsorbates. The removal via ozonation correlated positively with the energy level of the HOMO, probably because compounds with relatively high energy level HOMOs could more easily transfer an electron to the lowest unoccupied molecular orbital of ozone. Overall, the TPs tended to be more difficult to remove via PAC adsorption and ozonation than their parent pesticides. However, the TPs that were difficult to remove via PAC adsorption did not induce strong mutagenicity after chlorination, and the TPs that were associated with strong mutagenicity after chlorination could be removed via PAC adsorption. Therefore, PAC adsorption is hypothesized to be an effective method of treating drinking water to reduce the possibility of post-chlorination mutagenicity associated with both TPs and their parent pesticides.