Chlorothalonil exposure compromised mouse oocyte in vitro maturation through inducing oxidative stress and activating MAPK pathway

Chlorothalonil (CTL) is widely used in agricultural production and antifoulant additive globally due to its broad spectrum and non-systemic properties, resulting in its widespread existence in foods, soil and water. Extensive evidence demonstrated that exposure to CTL induced adverse effects on organisms and in particular its reproductive toxicity has been attracted public concern. However, the influences of CTL on oocyte maturation is mysterious so far. In this study, we documented the toxic effects of CTL on oocyte in vitro maturation and the related underlying mechanisms. Exposure to CTL caused continuous activation of spindle assembly checkpoints (SAC) which in turn compromised meiotic maturation in mouse oocyte, featured by the attenuation of polar body extrusion (PBE). Detection of cytoskeletal dynamics demonstrated that CTL exposure weakened the acetylation level of α-tubulin and impaired meiotic spindle apparatus, which was responsible for the aberrant state of SAC. Meanwhile, exposure to CTL damaged the function of mitochondria, inducing the decline of ATP content and the elevation of reactive oxygen species (ROS), which thereby induced early apoptosis and DNA damage in mouse oocytes. In addition, exposure to CTL caused the alteration of the level of histone H3 methylation, indicative of the harmful effects of CTL on epigenetic modifications in oocytes. Further, the CTL-induced oxidative stress activated mitogen-activated protein kinase (MAPK) pathway and injured the maturation of oocytes. In summary, exposure to CTL damaged mouse oocyte in vitro maturation via destroying spindle assembly, inducing oxidative stress and triggering MAPK pathway activation.

Exposure and risk assessment for agricultural workers during chlorothalonil and flubendiamide treatments in pepper fields

Pesticides are indispensable tools in modern agriculture for enhancing crop productivity. However, the inherent toxicity of pesticides raises significant concerns regarding human exposure, particularly among agricultural workers. This study investigated the exposure and associated risks of two commonly used pesticides in open-field pepper cultivation, namely, chlorothalonil and flubendiamide, in the Republic of Korea. We used a comprehensive approach, encompassing dermal and inhalation exposure measurements in agricultural workers during two critical scenarios: mixing/loading and application. Results revealed that during mixing/loading, dermal exposure to chlorothalonil was 3.33 mg (0.0002% of the total active ingredient [a.i.]), while flubendiamide exposure amounted to 0.173 mg (0.0001% of the a.i.). Conversely, dermal exposure increased significantly during application to 648 mg (chlorothalonil) and 93.1 mg (flubendiamide), representing 0.037% and 0.065% of the total a.i., respectively. Inhalation exposure was also evident, with chlorothalonil and flubendiamide exposure levels varying across scenarios. Notably, the risk assessment using the Risk Index (RI) indicated acceptable risk of exposure during mixing/loading but raised concerns during application, where all RIs exceeded 1, signifying potential risk. We suggest implementing additional personal protective equipment (PPE) during pesticide application, such as gowns and lower-body PPE, to mitigate these risks.

Glutathione-dependent redox homeostasis is critical for chlorothalonil detoxification in tomato leaves

Glutathione plays a critical role in plant growth, development and response to stress. It is a major cellular antioxidant and is involved in the detoxification of xenobiotics in many organisms, including plants. However, the role of glutathione-dependent redox homeostasis and associated molecular mechanisms regulating the antioxidant system and pesticide metabolism remains unclear. In this study, endogenous glutathione levels were manipulated by pharmacological treatments with glutathione synthesis inhibitors and oxidized glutathione. The application of oxidized glutathione enriched the cellular oxidation state, reduced the activity and transcript levels of antioxidant enzymes, upregulated the expression level of nitric oxide and Ca2+ related genes and the content, and increased the residue of chlorothalonil in tomato leaves. Further experiments confirmed that glutathione-induced redox homeostasis is critical for the reduction of pesticide residues. RNA sequencing analysis revealed that miRNA156 and miRNA169 that target transcription factor SQUAMOSA-Promoter Binding Proteins (SBP) and NUCLEAR FACTOR Y (NFY) potentially participate in glutathione-mediated pesticide degradation in tomato plants. Our study provides important clues for further dissection of pesticide degradation mechanisms via miRNAs in plants.

Acute chlorothalonil exposure had the potential to influence the intestinal barrier function and micro-environment in mice

The intestinal barrier maintains intestinal homeostasis and metabolism and protects against harmful pollutants. Some environmental pollutants seriously affect intestinal barrier function. However, it remains unclear whether or how chlorothalonil (CTL) impacts the intestinal barrier function in animals. Herein, 6-week-old male mice were acutely exposed to different CTL concentrations (100 and 300 mg/kg BW) via intragastric administration once a day for 7 days. Histopathological examination revealed obvious inflammation in the mice' colon and ileum. Most notably, CTL exposure increased the intestinal permeability, particularly in the CTL-300 group. CTL exposure reduced the secretion of colonic epithelial mucus and changed the transcription levels of genes bound up with ion transport and ileal antimicrobial peptide (AMP) secretion, indicating intestinal chemical barrier damage. The results of terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay and Ki67 staining revealed abnormal apoptosis and increased intestinal epithelial cell proliferation, suggesting that CTL exposure led to cytotoxicity and inflammation. The results of 16S rRNA sequencing revealed that CTL exposure altered the intestinal microbiota composition and reduced its diversity and richness in the colon contents. Thus, acute CTL exposure affected the different intestinal barrier- and gut microenvironment-related endpoints in mice.

Detection of the fungicide transformation product 4-hydroxychlorothalonil in serum of pregnant women from Sweden and Costa Rica

BACKGROUND

4-hydroxychlorothalonil (HCT, R182281), a transformation product of the fungicide chlorothalonil, was recently identified in human serum and breast milk. There are indications that HCT may be more toxic and environmentally persistent than chlorothalonil.

OBJECTIVE

Our aim was to investigate serum concentrations of HCT in pregnant women in Sweden and Costa Rica.

METHODS

We developed a quantitative analytical method for HCT using liquid chromatography tandem mass spectrometry. We measured HCT in 1808 serum samples from pregnant women from the general population in Sweden (1997-2015) and in 632 samples from 393 pregnant women from an agricultural population in Costa Rica (2010-2011). In Swedish samples, we assessed time trends and investigated seasonality. In the Costa Rican samples, we evaluated variability between and within women and explanatory variables of HCT concentrations.

RESULTS

HCT was detected in all serum samples, and the limit of detection was 0.1 µg/L. The median HCT concentration in the Swedish samples was 4.1 µg/L (interquartile range [IQR] of 2.9 - 5.8 µg/L), and 3.9 times higher in the Costa Rican samples (median: 16.1 µg/L; IQR: 10.6 - 25.0 µg/L). We found clear seasonal variation with higher concentrations in the first half of each year among Swedish women. In the Costa Rican study, women working in agriculture and living near banana plantations had higher HCT concentrations, whilst higher parity and having a partner working in agriculture were associated with decreased HCT, and no clear seasonal pattern was observed.

IMPACT STATEMENT

For the first time, this study quantifies human exposure to the fungicide chlorothalonil and/or its transformation product 4-hydroxychlorothalonil (HCT, R182281) and finds higher serum concentrations in women from a tropical agricultural setting as compared with women from the general population in Sweden.

Effects of fungicide chlorothalonil on freshwater plankton communities: a microcosm study

Direct and indirect effects of the fungicide chlorothalonil on aquatic plankton community structure were investigated by exposing plankton to chlorothalonil concentrations of 0.010, 0.025, 0.100, 0.250 and 1.000 mg/L over 20 days in 18 microcosms (glass tanks having 8 L of pond water). Each treatment was executed in three replicates. Total phytoplankton and zooplankton abundance and chlorophyll-a concentrations in microcosms were measured 5, 10 and 20 days after pesticide exposure. Plankton community and taxa response to pesticide concentrations were analyzed using the similarity of percentages procedure (SIMPER) and one-way ANOVA test. The results of the study indicated that highest concentration levels of chlorothalonil exposure had a significant impact on phytoplankton and zooplankton taxa. Phytoplankton taxa Amphora sp. and Staurastrum sp. and zooplankton taxa Moina sp. and copepod Nauplius were highly sensitive to chlorothalonil exposure. Phytoplankton taxa Mougeotia sp. increased with increased chlorothalonil (0.1-1.0 mg/L) concentrations, and zooplankton taxa of Aeolosoma sp. showed no significant reduction of individuals in response to pesticide exposure. Results showed that pesticide residues have a direct and rapid impact on phytoplankton and zooplankton community structure. Changes in diversity and species composition induced by pesticides indicate the importance of considering indirect effects of pesticides on the ecological food chain in the aquatic environment.

Acute aquatic toxicity of two commonly used fungicides to midwestern amphibian larvae

Fungicide usage has increased globally in response to the rise in fungal pathogens, especially in the agricultural sector. However, research examining the toxicity of fungicides is still limited for many aquatic species. In this study, we examined the acute toxicity of two widely used fungicides, chlorothalonil and pyraclostrobin, on six North American larval amphibian species across multiple families using 96-h LC50 tests. We found that pyraclostrobin was approximately 3.5x more toxic than chlorothalonil; estimated LC50 values ranged from 5-18 µg/L for pyraclostrobin and 15-50 µg/L for chlorothalonil. Comparing across amphibian groups, we found that salamanders were 3x more sensitive to pyraclostrobin than anuran species and equally as sensitive to chlorothalonil. Notably, our estimated LC50 values within the range of the expected environmental concentration for these fungicides suggesting environmental exposures could lead to direct mortality in these species. Given the widespread and increasing usage of fungicides, additional work should be conducted to assess the general risk posed by these chemicals to amphibian and their associated aquatic habitats.

High-intensity ultrasonication impact on the chlorothalonil fungicide and its reduction pathway in spinach juice

Among different novel technologies, sonochemistry is a sustainable emerging technology for food processing, preservation, and pesticide removal. The study aimed to probe the impact of high-intensity ultrasonication on chlorothalonil fungicide degradation, reduction pathway, and bioactive availability of spinach juice. The chlorothalonil fungicide-immersed spinach juice was treated with sonication at 360 W, 480 W, and 600 W, 40 kHz, for 30 and 40 min at 30 ± 1 °C. The highest reduction of chlorothalonil fungicide residues was observed at 40 min sonication at 600 W. HPLC-MS (high-performance liquid chromatography-mass spectroscopy) analysis revealed the degradation pathway of chlorothalonil and the formation of m-phthalonitrile, 3-cyno-2,4,5,6-tetrachlorobenamide, 4-dichloroisophthalonitrile, trichloroisophtalonitrile, 4-hydoxychlorothalonil, and 2,3,4,6-tetrachlorochlorobenzonitrile as degradation products. High-intensity sonication treatments also significantly increased the bioavailability of phenolic, chlorophyll, and anthocyanins and the antioxidant activity of spinach juice. Our results proposed that sonication technology has excellent potential in degrading pesticides through free radical reactions formation and pyrolysis. Considering future perspectives, ultrasonication could be employed industrially to reduce pesticide residues from agricultural products and enhance the quality of spinach juice.

Simultaneous electrochemical degradation of pesticides from the aqueous environment using Ti/SnO2-Sb2O3/PbO2/Bi electrode; process modeling and mechanism insight

In this work, modified Bi-PbO₂ electrode was fabricated and employed for simultaneous degradation of fenitrothion (FT), trifluralin (TF), and chlorothalonil (CT) from synthetic and pesticide wastewater through the anodic oxidation process. A novel high-performance liquid chromatography method was developed and optimized to identify the pesticides simultaneously. Quadratic models were developed to investigate the effects of main operating parameters and predict the degradation efficiencies of the treatment processes. The R² of the degradation efficiencies were obtained of 0.9847, 0.9910, and 0.9821 for FT, TF, and CT, respectively, which indicates the degree of conformity between the experimental and the actual values of degradation efficiencies, and the adjusted R² values for the degradation efficiency of FT, TF, and CT in proposed models were 0.9826, 0.9898, and 0.9796, and the values of the predicted R² were 0.9792, 0.9875, and 0.9755, respectively. The maximum degradation efficiencies of 99.7, 100, and 100% obtained for FT, TF, and CT, respectively, under the optimal operating condition of FT, TF, and CT concentration of 10.0, 6.0, and 8.0 mg L^-1, respectively, pH 6.0, the current density 6.0 mA cm^-2, and electrolysis time of 60 min. Chemical oxygen demand removal and energy consumption were 64.7% and 5.1 kWh m^-3. Eventually, the generated intermediates and other produced species of pesticides through the treatment process was evaluated using a gas chromatography-mass spectrometry method, and their degradation pathways were proposed.

Effects of plant morphology, vitamin C, and other co-present pesticides on the deposition, dissipation, and metabolism of chlorothalonil in pakchoi

Pesticide residues have been a focus of attention of food safety. Different varietal pakchoi plants grown in open fields were studied to understand effects of morphology, leaf wax content, and vitamin C on the deposition, dissipation, and metabolism of chlorothalonil. The loose pakchoi plants and flat leaves were conducive to pesticide deposition, but not plants with erect leaves. Chlorothalonil on nine varieties of pakchoi dissipated in the first-order kinetic with T1/2 s of 1.4 ~ 2.0 days. Vitamin C in pakchoi could promote the dissipation of chlorothalonil. Carbendazim could significantly promote the dissipation of chlorothalonil on pakchoi. Interestingly, four metabolites of chlorothalonil were identified in the pakchoi and the metabolic pathway was predicted by DFT calculations. The risk assessment showed that pakchoi were safe for consumption after 10 days of application of the recommended dose. This work provides important information for the understanding of deposition, dissipation, and metabolism of chlorothalonil in pakchoi.

Application of a new approach method (NAM) for inhalation risk assessment

The US Environmental Protection Agency (USEPA) and other regulatory authorities have been working to utilize in vitro studies with human cells and in silico modelling to reduce the use of vertebrate animals for evaluating chemical risk. Using the Source-to-Outcome framework, a novel mathematical procedure was developed to estimate the human equivalent concentration (HEC) for inhalation risk assessment based upon the relevant aerosol characterization, respiratory dosimetry modelling, and endpoints derived from an in vitro assay using human respiratory epithelial tissue. The procedure used the retained doses at the various areas of the inhalation tract estimated from a computational fluid-particle dynamics (CFPD) model coupled with a simple clearance model. The effect of exposure was derived from an in vitro assay. The magnitude of exposure and the particle size distributions (PSDs) of the external aerosol droplets were obtained from Unit Exposure values published by the USEPA and published monitoring studies, respectively. The Source-to-Outcome approach incorporates external and internal exposure metrics with the toxicity pathway. The information was then integrated to conduct a risk assessment for agricultural operators exposed to products containing chlorothalonil (CTN), a broad-spectrum fungicide. The HECs for three different PSDs considered in this work ranged from 0.043 to 0.112 mg-CTN/L for nasal and oral breathing. These were compared with the estimated average daily exposure concentration for six representative application scenarios. The resulting margins of exposure (MOEs) ranged from 230 to 70,000 depending on the application scenario. This New Assessment Method (NAM) that combined human in silico and human in vitro methods, eliminated the typical uncertainties associated with extrapolation from rodent studies, with their associated interspecies toxicokinetics and toxicodynamics differences. The intraspecies toxicodynamics and toxicokinetics, are still relevant and may need to be used in an inhalation risk assessment. The NAM presented in this work is not chemical-specific and may be applied to conduct an inhalation risk assessment for workers as well as bystanders who could be exposed to aerosol particles of any cytotoxic respiratory irritant.

Determination of chlorothalonil levels through inhibitory effect on papain activity at protein-decorated liquid crystal interfaces

A liquid crystal (LC)-based assay was developed to detect chlorothalonil (CHL). The detection principle is based on (i) the electrostatic interaction between the positively charged protein protamine (PRO) with the negatively charged phospholipid dioleoyl-sn-glycero-3-phospho-rac-(1-glycerol) sodium salt (DOPG) and (ii) the CHL-mediated inhibition of papain (PAP) activity. The aqueous/LC interface was decorated with a monolayer of DOPG and PRO that self-assembled via electrostatic interactions. PAP can hydrolyze PRO, resulting in the realignment of an LC by DOPG, inducing a shift in the LC response from bright to dark. The addition of CHL can inhibit the activity of PAP, leading to the attraction of PRO to DOPG and the consequent disruption of the LC orientation. The orientation change of the LC in the presence or absence of CHL can be observed from the changes in its optical appearance using a polarized light microscope. Under optimal conditions, the developed assay achieved a detection limit of 0.196 pg mL⁻¹ within a range of determination of 0.65–200 pg mL⁻¹. The selectivity of the assay was verified in the presence of carbendazim and imidacloprid. The practical application of the proposed assay was demonstrated by its use to determine the levels of CHL in food extracts and environmental samples, which yielded recoveries and relative standard deviations (RSD) in the ranges of 87.39–99.663% and 1.03–6.32%, respectively.

Virulence of native isolates of entomopathogenic fungi (Hypocreales) against the "sweetpotato whitefly" Bemisia tabaci (Hemiptera: Aleyrodidae), including the effects of temperature and fungicides

Hypocrella, Moelleriella and related species in the Hypocreales (Ascomycota, Sordariomycetes) cause epizootics of whiteflies and scale insects in nature. However, studies on their host specificity, virulence, infection cycles, optimal development under laboratory conditions, and compatibility with other control methods, are unexplored for most species. Under laboratory conditions, the virulence of several isolates of field-collected hypocrealean fungi (Hypocrella, Moelleriella, Regiocrella, and Verticillium) was determined on Bemisia tabaci eggs and 4th instar nymphs. In addition to virulence, the effect of temperature and two commercial fungicides on growth rates and germination of the isolates was evaluated. None of the isolates infected the eggs, while M. libera, M. ochracea, and M. turbinata caused high nymphal mortality. Moelleriella libera was the most virulent isolate. At all temperatures, M. libera, Regiocrella sp. (P17H20), and Verticillium cf. pseudohemipterigenum had the highest germination and growth rates. The optimal growth temperature depended on the isolate, but at 23 °C and 25 °C, the probability of spore germination was higher for most isolates. Finally, the fungicides azoxystrobin and chlorothalonil inhibited growth rates and conidial germination at 24 and 48 h of exposure. This research produces vital knowledge on the virulence and infection cycles of poorly studied native species of entomopathogenic fungi. In addition, the results provide information on the optimal temperature for development in laboratory conditions and susceptibility to fungicides, which could contribute to future biological control strategies.

Jasmonic acid promotes glutathione assisted degradation of chlorothalonil during tomato growth

Glutathione (GSH) biosynthesis and regeneration play a significant role in the metabolism of chlorothalonil (CHT) in tomatoes. However, the specific regulatory mechanism of GSH in the degradation of CHT remains uncertain. To address this, we investigate the critical regulatory pathways in the degradation of residual CHT in tomatoes. The results revealed that the detoxification of CHT residue in tomatoes was inhibited by buthionine sulfoximine and oxidized glutathione pretreatment, which increased by 26% and 46.12% compared with control, respectively. Gene silencing of γECS, GS, and GR also compromised the CHT detoxification potential of plants, which could be alleviated by GSH application and decreased the CHT accumulation by 33%, 25%, and 21%, respectively. Notably, it was found that the jasmonic acid (JA) pathway participated in the degradation of CHT regulated by GSH. CHT residues reduced by 28% after application of JA. JA played a role downstream of the glutathione pathway by promoting the degradation of CHT residue in tomatoes via nitric oxide signaling and improving the gene expression of antioxidant and detoxification-related enzymes. This study unveiled a crucial regulatory mechanism of GSH via the JA pathway in CHT degradation in tomatoes and offered new insights for understanding residual pesticide degradation.

Photochemical interactions between pesticides and plant volatiles

Among the numerous studies devoted to the photodegradation of pesticides, very scarce are those investigating the effect of plant volatiles. Yet, pesticides can be in contact with plant volatiles after having been spread on crops or when they are transported in surface water, making interactions between the two kinds of chemicals possible. The objectives of the present study were to investigate the reactions occurring on plants. We selected thyme as a plant because it is used in green roofs and two pesticides: the fungicide chlorothalonil for its very oxidant excited state and the insecticide imidacloprid for its ability to release the radical NO₂ under irradiation. Pesticides were irradiated with simulated solar light first in a solvent ensuring a high solubility of pesticides and plant volatiles, and then directly on thyme's leaves. Analyses were conducted by headspace gas chromatography-mass spectrometry (HS-GC-MS), GC-MS and liquid chromatography-high resolution mass spectrometry (LC-HRMS). In acetonitrile, chlorothalonil photosensitized the degradation of thymol, α-pinene, 3-carene and linalool with high quantum yields ranging from 0.35 to 0.04, and was photoreduced, while thymol underwent oxidation, chlorination and dimerization. On thyme's leave, chlorothalonil was photoreduced again and products arising from oxidation and dimerization of thymol were detected. Imidacloprid photooxidized and photonitrated thymol in acetonitrile, converting it into chemicals of particular concern. Some of these chemicals were also found when imidacloprid was irradiated dispersed on thyme's leaves. These results show that photochemical reactions between pesticides and the plants secondary metabolites can take place in solution as on plants. These findings demonstrate the importance to increase our knowledge on these complex scenarios that concern all the environmental compartments.

Selective, stepwise photodegradation of chlorothalonil, dichlobenil and dichloro- and trichloro-isophthalonitriles enhanced by cyanidin in water

Chlorothalonil, a widely used chloroisophthalonitrile fungicide, is highly toxic to aquatic organisms and amphibians. It is essential to understand the persistence and fate of chlorothalonil in aquatic environments. Cyanidin is one of the most common phytopolyphenolics in nature and is a strong antioxidant. This study was designed to understand fate of chlorothalonil and its analogs in surface water in the presence of cyanidin under sunlight and artificial lights. The photodegradation rates of chlorothalonil were increased by 9.6, 19, 26 and 9.1 fold, respectively, under solar, high-pressure mercury lamp (HPML), UV and Xenon lamp light irradiation, in comparison to the cyanidin-free control. Cyanidin also enhanced 2,5-dichloroisophthalonitrile and 2,4,5-trichloro isophthalonitrile (degradation products of chlorothalonil) for 20 and 4.7 fold under HPML irradiation compared to the absence of cyanidin. Chlorothalonil was transformed to 5-chloroisophthalonitrile quantitatively after stepwise dechlorination. The concentration profiles of chlorothalonil and its degradation products were well simulated in the cyanidin-triggered photoreductive dechlorination process, in which donation of hydrogen atom from cyanidin was also agreed by the density functional theory calculations. Cyanidin accelerated photolysis of dichlobenil for 4.3 fold as high as the cyanidin-free control under HPML irradiation. The results warrant an interest in further understanding photolysis of chloroarenes in natural waters and exploring the potential of using phytochemicals to abate chloroarenes-caused pollution.

Efficiency of mesoporous silica/carboxymethyl β-glucan as a fungicide nano-delivery system for improving chlorothalonil bioactivity and reduce biotoxicity

Understanding the lethal effects of pesticides nano formulations on the targeted organisms (pathogens) and the non-targeted organisms (fish, earthworms, etc) is essential in assessing the probable impact of new technologies on agriculture and environment. Here we evaluated the bioactivity and the biotoxicity of new type of fungicide smart-delivery formulation based on conjugating carboxymethylated-β-glucans on the mesoporous silica nanoparticles (MSNs) surface after loading chlorothalonil (CHT) fungicide in the MSNs pores. The obtained formulation has been characterized with FE-SEM, and HR-TEM. The CHT loading efficiency has been measured with TGA. The bioactivity of the obtained formulation (CHT@MSNs-β-glucans) has been tested against four pathogens, fusarium head blight (Fusarium graminearum), sheath rot (Sarocladium oryzae), rice sheath blight (Rhizoctonia solani), and soyabean anthracnose (Colletotrichum truncatum) compared with CHT WP 75% commercial formulation (CHT-WP) and technical CHT. The environmental biotoxicity of CHT@MSNs-β-glucans compared with CHT-WP has been tested toward earthworm (Eisenia fetida) and zebra fish (Danio rerio). The results showed that CHT@MSNs-β-glucans has an excellent bioactivity against the subjected pathogens with better inhabiting effects than CHT-WP. CHT@MSNs-β-glucans toxicity to Eisenia fetida was found 2.25 times lower than CHT-WP toxicity. The LC₅₀ of CHT@MSNs-β-glucans to zebra fish after the first 24h was 2.93 times higher than CHT-WP. After 96h of treatment, the LC₅₀ of CHT@MSNs-β-glucans was 2.66 times higher than CHT-WP. This work highlighted the necessity to increase the mandatory bioassays of nano formulations with the major non-target organisms in the environmental risk assessment of new pesticide formulations.

Small streams-large concentrations? Pesticide monitoring in small agricultural streams in Germany during dry weather and rainfall

Few studies have examined the exposure of small streams (< 30 km² catchment size) to agriculturally used pesticides, compared to large rivers. A total of 105 sites in 103 small agricultural streams were investigated for 76 pesticides (insecticides, herbicides, fungicides) and 32 pesticide metabolites in spring and summer over two years (2018 and 2019) during dry weather and rainfall using event-driven sampling. The median total concentration of the 76 pesticides was 0.18 µg/L, with 9 pesticides per sample on average (n = 815). This is significantly higher than monitoring data for larger streams, reflecting the close proximity to agricultural fields and the limited dilution by non-agricultural waters. The frequency of detection of all pesticides correlated with sales quantity and half-lives in water. Terbuthylazine, MCPA, boscalid, and tebuconazole showed the highest median concentrations. The median of the total concentration of the 32 metabolites exceeded the pesticide concentration by more than an order of magnitude. During dry weather, the median total concentration of the 76 pesticides was 0.07 µg/L, with 5 pesticides per sample on average. Rainfall events increased the median total pesticide concentration by a factor of 10 (to 0.7 µg/L), and the average number of pesticides per sample to 14 (with up to 41 in single samples). The concentration increase was particularly strong for 2,4-D, MCPA, terbuthylazine, and nicosulfuron (75 percentile). Metabolite concentrations were generally less responsive to rainfall, except for those of terbuthylazine, flufenacet, metamitron, and prothioconazole. The frequent and widespread exceedance of the regulatory acceptable concentrations (RAC) of the 76 pesticides during both, dry weather and rainfall, suggests that current plant protection product authorization and risk mitigation methods are not sufficient to protect small streams.

Rapid Surface-Enhanced Raman Spectroscopy Detection of Chlorothalonil in Standard Solution and Orange Peels with Pretreatment of Ultraviolet Irradiation

At present, the detection of chlorothalonil is generally based on chromatography and immunoassay; both of which are time-consuming and costly. In this study, Surface-enhanced Raman Spectroscopy (SERS) has been successfully utilized in the detection of chlorothalonil coupled with photochemistry and meanwhile, gold nanoparticles were prepared to enhance the Raman signal. Two Raman peaks (2246 cm^- 1 and 2140 cm^- 1) of chlorothalonil were appeared after ultraviolet (UV) irradiation compared to the original solution. Chlorothalonil generated excited and weakened C≡N bonds in its structure by absorbing UV energy, thus leading to two kinds of corresponding peaks. These two kinds of peaks were both selected as analytical peaks in chlorothalonil detection. Different light sources and solvents were made different contributions to the final spectra. Chlorothalonil methanol solution under 302 nm wavelength irradiation was performed the best. The 2246 cm^- 1 sharp peak represented to the normal C≡N bond appeared at first, which overall trend was significantly increased followed by a gradual decrease. The 2140 cm^- 1 broad peak represented to the weakened C≡N bond appeared later, which overall trend was increased as the irradiation time passing by and then kept stable. Natural bond orbital (NBO) analysis indicates that the downshift of C≡N bond from 2246 cm^- 1 to 2140 cm^- 1 is due to the increase of electronic populations of π* orbital of C≡N bond transited from π orbital excited by UV irradiation. The positively charged C≡N bond had more chance to approach negatively charged gold nanoparticles. The detection limit of chlorothalonil was as low as 0.1 ppm in the standard solution. Orange peels spiked with chlorothalonil oil were also detected in this paper to confirm the practical operability of this method. The SERS method may be further developed as a rapid detection of pesticides that contains a triple bond by utilizing photochemistry.

Fucoidan ameliorates acute and sub-chronic in vivo toxicity of the fungicide cholorothalonil in Oreochromis niloticus (Nile tilapia)

Fucoidans are sulfated glycans from marine algae that have both anti-cancer and anti-microbial properties. Chlorothalonil is a fungicide and insecticide commonly used in agriculture. Chlorothalonil is relatively toxic to fish and can potentially affect the aquaculture practices. In this study, we determined whether fucoidan administration would offer any protection from acute and subchronic toxicity of chlorothalonil on Nile tilapia. First, we tested the effect of chlorothalonil (20 to 140 μg/L, water-applied) on Nile tilapia in an acute exposure (six days). Survival analysis was performed, together with assessment of histopathology, oxidative stress (i.e., antioxidant status, hydrogen peroxide levels, malondialdehyde and nitric oxide levels) and immunohistochemistry to measure indicators of hepatic damage (i.e., caspase 3, p53, mini-chromosome maintenance proteins (MCM), and glutathione peroxidase). Chlorothalonil induced mild to severe histopathological alterations that were dose-dependent in various tissues of Nile tilapia. Chlorothalonil also induced oxidative stress as indicated by elevated biochemical markers. The highest recorded mortalities were associated with p53 expression. Additional feeding experiments were conducted with fucoidan (8 g/kg diet), following acute (40 μg/L for seven days) and sub-chronic (20 μg/L for six weeks) chlorothalonil application in Nile tilapia. Many of these same biochemical biomarkers of stress, oxidative damage response, and tissue pathology (evidence for hepatic neoplasm) were ameliorated by fucoidan, suggesting a protective effect of the compound. Agrochemicals are ubiquitous on a global scale, and the use of fucoidan as a feed additive may be beneficial for protecting aquatic animal health and aquaculture species from the impacts of chemical run-off.

In situ monitoring of chlorothalonil and lambda-cyhalothrin by polyethylene passive samplers under fields and greenhouse conditions

Sampling is a critical step in pesticide atmospheric analysis. Passive sampling offers advantages of inexpensive and convenient air monitoring. Polyethylene films (PE) were used as a passive sampler at multiple heights in greenhouse and agricultural field for 15 days to trap atmospheric chlorothalonil and lambda-cyhalothrin in the months of May and July. Among the two PE film thicknesses (20 and 80 μm), 20 μm PE was the most effective at absorbing target pesticides from air and attains equilibrium stage earlier than 80 μm PE film. After approximately 240 h of PE exposure in greenhouse and fields, chlorothalonil and lambda-cyhalothrin reached an equilibrium stage of partitioning between air and PE. Atmospheric concentrations of chlorothalonil (p < 0.01) and lambda-cyhalothrin (p < 0.001) at 1.5 m height were higher with the concentrations of 1855.59 ± 243.85 ng/m3 and 3682.11 ± 316.71 ng/m3, respectively, in the month of May as compared to the other three respective heights. The concentrations of chlorothalonil in air at 2 m height (1587.27 ± 284.19 ng/m3) were slightly higher than 0.5 m (1392.28 ± 205.09 ng/m3). Atmospheric concentrations of lambda-cyhalothrin at 2 m (3178.26 ± 299.29 ng/m3) were significantly lower than the other heights (p < 0.05). The greenhouse air concentrations of chlorothalonil and lambda-cyhalothrin in the months of May (1855.59 ± 243.85 and 3682.11 ± 316.71 ng/m3, respectively) and July (1749.33 ± 378.61 and 3445.08 ± 390.32 ng/m3, respectively) were higher than fields. The results indicate the usability of PE films to monitor chlorothalonil and lambda-cyhalothrin and potential other semi-volatile pesticides in agricultural fields.

[Membrane sampling for the determination of chlorothalonil in the air of workplaces-solvent analysis-Gas Chromatography]

Objective: To establish a method for the determination of chlorothalonil in air by filtration membrane sampling, solvent elution and gas chromatography. Methods: PTFE filter was used for sampling, eluted with dichloromethane, separated by DB-5 capillary column, and determined by FID. Results: The standard curve was used for quantitative detection, and the correlation of chlorothalonil in the range of 15 μg/ml-300 μg/ml, R(2)=0.9999. The detection limit of this method was 1.70 μg/ml and the lower quantitative limit was 5.70 μg/ml. The minimum detected concentration was 0.045 mg/m(3) (75L air sample was collected) . The recovery rate was 90.14%-91.81%. The precision of the same batch was 1.5%-1.8%, and that of different batches was 2.3%-3.8%. The sampling efficiency can reach above 95%; The samples can be stored for 14 days at room temperature. Conclusion: The results show that the method of filtration membrane sampling-solvent elude-gas chromatography is suitable for the determination of chlorothalonil in the air.

Simultaneous and ultrasensitive detection of three pesticides using a surface-enhanced Raman scattering-based lateral flow assay test strip

Chlorothalonil (CHL), imidacloprid (IMI) and oxyfluorfen (OXY) are commonly used in combination to increase crop yield. However, these three pesticides are toxic to aquatic organisms and do not easily degrade. In this study, a surface-enhanced Raman scattering-based lateral flow assay (SERS-LFA) test strip was prepared by combining antibodies with SERS nanotags, and then competitive immune binding was used to detect the three pesticides simultaneously. Moreover, the two-way binding effect of ssDNA-streptavidin bound to Ag^4-NTP@AuNPs and Ag^4-NTP@AuNPs with antibodies was used to further amplify the detection signal. Under the optimal conditions, the SERS-LFA test strips exhibited high sensitivity, a low detection limit, short detection time, high specificity and low cost. Furthermore, the detection range was within the values prescribed by international detection standards. By measuring the intensity of the SERS signal on the test line of the paper strip, accurate quantitative analysis was achieved. The practical application of the proposed system was demonstrated by simultaneous detection of CHL, IMI and OXY in environmental and food samples with satisfactory results.

Resveratrol relieves chlorothalonil-induced apoptosis and necroptosis through miR-15a/Bcl2-A20 axis in fish kidney cells

Chlorothalonil (CT) is a commonly used fungicide and its excessive application seriously threatens aquatic life and human health. Resveratrol (RSV) is a natural polyphenol and can be used as a therapeutic and preventive agent for the treatment of various diseases. To explore the toxic mechanism of CT exposure on fish kidney cell, as well as the alleviation effect of RSV, we established CT poisoning and/or RSV treatment fish kidney cell models. Ctenopharyngodon idellus kidney (CIK) cell line was treated with CT (5 μg/L) and/or RSV (10 μM) for 48 h. The results showed that CT exposure activated cytochromeP450s (CYPs) including CYP1A1, CYP1B1 and CYP1C, caused malondialdehyde (MDA) accumulation, inhibited glutathione (GSH) levels and glutathione peroxidase (GPX) activities, increased the expression of miR-15a and downregulated BCL2 and TNFα-induced protein 3 (TNFAIP3, A20), triggered mitochondrial pathway mediated apoptosis and receptor interacting serine/threonine kinase (RIP)-dependent necroptosis in CIK cells. However, cell death under CT exposure could be relieved by RSV treatment through inhibiting the expression of CYP1 family genes and restoring miR-15a/BCL2-A20 axis disorders. Overall, we conclude that RSV could relieve CT-induced apoptosis and necroptosis through miR-15a/Bcl2-A20 axis in CIK cells. These results enrich the toxicological mechanisms of the CT and confirm that RSV can be used as a potential antidote for CT poisoning.

Patterns of pesticide usage in agriculture in rural Tanzania call for integrating agricultural and public health practices in managing insecticide-resistance in malaria vectors

BACKGROUND

Unrestricted use of pesticides in agriculture is likely to increase insecticide resistance in mosquito vectors. Unfortunately, strategies for managing insecticide resistance in agriculture and public health sectors lack integration. This study explored the types and usage of agricultural pesticides, and awareness and management practices among retailers and farmers in Ulanga and Kilombero districts in south-eastern Tanzania, where Anopheles mosquitoes are resistant to pyrethroids.

METHODS

An exploratory sequential mixed-methods approach was employed. First, a survey to characterize pesticide stocks was conducted in agricultural and veterinary (agrovet) retail stores. Interviews to assess general knowledge and practices regarding agricultural pesticides were performed with 17 retailers and 30 farmers, followed by a survey involving 427 farmers. Concurrently, field observations were done to validate the results.

RESULTS

Lambda-cyhalothrin, cypermethrin (both pyrethroids) and imidacloprids (neonicotinoids) were the most common agricultural insecticides sold to farmers. The herbicide glyphosate (amino-phosphonates) (59.0%), and the fungicides dithiocarbamate and acylalanine (54.5%), and organochlorine (27.3%) were also readily available in the agrovet shops and widely used by farmers. Although both retailers and farmers had at least primary-level education and recognized pesticides by their trade names, they lacked knowledge on pest control or proper usage of these pesticides. Most of the farmers (54.4%, n = 316) relied on instructions from pesticides dealers. Overall, 93.7% (400) farmers practised pesticides mixing in their farms, often in close proximity to water sources. One-third of the farmers disposed of their pesticide leftovers (30.0%, n = 128) and most farmers discarded empty pesticide containers into rivers or nearby bushes (55.7%, n = 238).

CONCLUSION

Similarities of active ingredients used in agriculture and malaria vector control, poor pesticide management practices and low-levels of awareness among farmers and pesticides retailers might enhance the selection of insecticide resistance in malaria vectors. This study emphasizes the need for improving awareness among retailers and farmers on proper usage and management of pesticides. The study also highlights the need for an integrated approach, including coordinated education on pesticide use, to improve the overall management of insecticide resistance in both agricultural and public health sectors.

Particle Size Characterization of Agricultural Sprays Collected on Personal Air Monitoring Samplers

Potential inhalation exposure of agricultural workers and bystanders to aerosolized particles emitted by typical agricultural spray nozzles is influenced by the particle size distribution (PSD) of the spray. However, inhalation risk assessments do not currently factor in the human-relevant PSD that may be inhaled during pesticide handling activities. This study was conducted to characterize the PSD of aerosols collected with OSHA Versatile Sampler (OVS) tubes, which are monitoring devices commonly used for inhalation risk assessment in worker exposure studies. An Oxford Lasers N60V particle size analyzer was used for characterizing the spray PSD emitted from various agricultural nozzles. Side-by-side air sampling with OVS tubes and Respicon TM particle samplers was conducted to characterize the size distribution of aerosols collected on the OVS tubes during spraying of a diluted chlorothalonil formulation. Based on this comparison, OVS tubes captured the inhalable fraction (mass median diameter (D50) = 100 μm), with approximately 40% of the total inhalation concentration contributing to systemic exposure (D50 = 10 μm) regardless of nozzle spray quality. In addition, nozzles with fine and medium spray produced higher airborne concentrations compared to nozzles with coarse spray. Thus, the use of modern low-drift nozzles (e.g., air-induction nozzles) that emit larger spray droplets can substantially reduce the airborne concentration levels within inhalable particle size fractions. While the concentrations within these airway fractions (e.g., respirable, thoracic, inhalable) increased from extremely coarse to very fine spray nozzles, the relative proportion of each fraction within the total inhalable concentration remained constant regardless of spray quality or nozzle type. Such information on the PSD of pesticide applications can be used to refine inhalation risk assessments for agricultural workers and bystanders.

A common fungicide impairs stream ecosystem functioning through effects on aquatic hyphomycetes and detritivorous caddisflies

Fungicides can reach streams through runoff or adhered to leaf litter, and have the potential to adversely affect processes such as litter decomposition and associated communities. This study investigated the effects of chlorothalonil, a widely used fungicide, on litter decomposition, detritivorous invertebrates (larvae of the insect Sericostoma pyrenaicum) and aquatic hyphomycetes (AHs), using stream microcosms. We considered the single and combined effects of two exposure modes: waterborne fungicide (at two concentrations: 0.125 μg L^-1 and 1.25 μg L^-1) and litter previously sprayed with the fungicide (i.e., pre-treated litter, using the application dose concentration of 1250 μg L^-1). We also assessed whether fungicide effects on invertebrates, AHs and decomposition varied among litter types (i.e., different plant species), and whether plant diversity mitigated any of those effects. Invertebrate survival and AH sporulation rate and taxon richness were strongly reduced by most combinations of fungicide exposure modes; however, invertebrates were not affected by the low waterborne concentration, whereas AHs suffered the highest reduction at this concentration. Total decomposition was slowed down by both exposure modes, and microbial decomposition was reduced by litter pre-treatment, while the waterborne fungicide had different effects depending on plant species. In general, with the exception of microbial decomposition, responses varied little among litter types. Moreover, and contrary to our expectation, plant diversity did not modulate the fungicide effects. Our results highlight the severity of fungicide inputs to streams through effects on invertebrate and microbial communities and ecosystem functioning, even in streams with well-preserved, diverse riparian vegetation.

Dissipation of chlorothalonil in the presence of chlortetracycline and ciprofloxacin and their combined effects on soil enzyme activity

The long-term application of substantial amounts of fungicides and antibiotic-polluted organic manure (OM) in greenhouse has caused the co-existence of fungicides and antibiotics in soils. However, little is known about the effects of antibiotics on the persistence of fungicides in soils or their combined effects on soil enzyme activity. In this study, fungicide chlorothalonil (CTL) alone and in combination with antibiotic chlortetracycline (CTC) or ciprofloxacin (CIP) were repeatedly added to OM-amended soil to investigate the changes in the residual characteristics of CTL and in soil dehydrogenase and urease activity. The results showed that CTL rapidly dissipated in soils with the corresponding half-lives of 0.9-3.2, which initially increased, then decreased and finally stabilized with an increased treatment frequency. The dissipation of CTL was inhibited by CTC and CIP during the first several treatments. The soil dehydrogenase and urease activity in CTL-treated soils was inhibited during the first six treatments and then recovered afterwards. Compared with the OM-amended soil+CTL treatment, the OM-amended soil+CTL+CTC and OM-amended soil+CTL+CIP treatments had stronger inhibitory effects on soil enzyme activity during the first six repeated treatments but exhibited slight stimulating effects afterwards. Therefore, the results obtained in this study suggested that the long-term co-existence of CTL, CTC, and CIP altered the dissipation characteristics of CTL in soil and affected the soil enzyme activity levels. The prudent application of large and frequent of fungicides and OM-containing antibiotic residues in greenhouses should therefore be carefully considered in order to reduce the long-term combined pollution in soils.

Detection of pesticide in water using two-dimensional fluorescence correlation spectroscopy and N-way partial least squares

To determine the concentration of carbaryl and chlorothalonil in water, the potential of two-dimensional (2D) fluorescence correlation spectra with N-way partial least squares (N-PLS) was investigated. A total of 40 mixture solutions of carbaryl and chlorothalonil were prepared and 27 of them were used to form a calibration set. The excitation-emission matrix (EEM) fluorescence spectra of all samples were measured. Under the excitation perturbation, 2D fluorescence correlation spectra of all samples were calculated and formed a 2D correlation spectral matrix. And N-PLS models for determination of carbaryl and chlorothalonil in water were built based on 2D correlation fluorescence spectral matrix and traditional EEM spectral matrix, respectively. Finally, the performances of N-PLS models using both methods were compared. For chlorothalonil, the root mean square error of calibration (RMSEC) were 3.43 × 10^-6 g L^-1 and 5.08 × 10^-6 g L^-1, the root mean square errors of prediction (RMSEP) were 5.86 × 10^-6 g L^-1 and 8.99 × 10^-6 g L^-1 for 2D correlation spectra and EEM spectra, respectively. For carbaryl, the RMSEC were 5.24 × 10^-7 g L^-1 and 6.18 × 10^-7, the RMSEP were 9.20 × 10^-7 g L^-1 and 9.63 × 10^-7 g L^-1 for 2D correlation spectra and EEM spectra, respectively. From the results of this study, it may conclude that 2D fluorescence correlation spectra is superior over the traditional EEM fluorescence spectra in terms of predictability and can be used as an alternative method for detection of organic pollutants in environment.

Low doses of carbendazim and chlorothalonil synergized to impair mouse spermatogenesis through epigenetic pathways

Pesticides have been extensively produced and used to help the agricultural production which leads to the contamination of the environment, soil, groundwater sources, and even foodstuffs. Fungicides carbendazim (CBZ) and chlorothalonil (Chl) are widely applied in agriculture and other aspects. CBZ or Chl have been reported to disrupt spermatogenesis and decrease semen quality. However, it is not understood the effects of pubertal exposure to low doses of CBZ and Chl together, and the underlying mechanisms. Therefore, the aim of current investigation was to explore the negative impacts of pubertal exposure to low doses of CBZ and Chl together on spermatogenesis and the role of epigenetic modifications in the process. We demonstrated that CBZ and Chl together synergize to decrease sperm motility in vitro (CBZ 1.0 + Chl 0.1, CBZ 10.0 + CHl 1.0, CBZ 100.0 + Chl 10 μM in incubation medium for 24 h) and sperm concentration and motility in vivo with ICR mice (CBZ 0.1 + Chl 0.1, CBZ 1.0 + CHl 1.0, CBZ 10.0 + Chl 10 mg/kg body weight; oral gavage for five weeks). CBZ + Chl significantly increase reactive oxygen species (ROS) and apoptosis by the increase in the protein level of caspase 8 in vitro. Moreover, CBZ + Chl synergized to disrupt mouse spermatogenesis with the disturbance in sperm production proteins and sperm proteins (VASA, A-Myb, STK31, AR, Acrosin). CBZ + Chl synergized to decrease the protein level of estrogen receptor alpha and the protein level of DNA methylation marker 5 mC in Leydig cells, and to increase the protein levels of histone methylation marker H3K9 and the methylation enzyme G9a in germ cells. Therefore, greater attention should be paid to the use of CBZ and Chl as pesticides to minimise their adverse impacts on spermatogenesis.

Immunomodulatory effect of mancozeb, chlorothalonil, and thiophanate methyl pesticides on macrophage cells

Mancozeb (MZ), chlorothalonil (CT), and thiophanate methyl (TM) are pesticides commonly used in agriculture due to their efficacy, low acute toxicity to mammals, and short environmental persistence. Although the toxic effects of these pesticides have been previously reported, studies regarding their influence on the immune system are limited. As such, this study focused on the immunomodulatory effect of MZ, CT, and TM pesticides on macrophage cells. RAW 264.7 cells were exposed to a range of concentrations (0.1-100 μg/mL) of these pesticides. CT exposure promoted an increase in reactive oxygen species (ROS) and nitric oxide (NO) levels. The MTT and ds-DNA assay results demonstrated that MZ, CT, and TM exposure induced macrophage proliferation. Moreover, MZ, CT, and TM promoted cell cycle arrest at S phase, strongly suggesting macrophage proliferation. The levels of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α, and IFN-γ) and caspases (caspase 1, 3, and 8) in macrophages exposed to MZ, CT, and TM pesticides increased, whereas the anti-inflammatory cytokine levels decreased. These results suggest that MZ, CT, and TM exert an immunomodulatory effect on the immune system, inducing macrophage activation and enhancing the inflammatory response.

Influence of chlorothalonil and carbendazim fungicides on the transformation processes of urea nitrogen and related microbial populations in soil

To improve crop yielding, a large amount of fungicides is continuously applied during the agricultural management, while the effects of fungicides residues on microbial processing of N in soil need further study. In the present study, two broad spectrum fungicides, chlorothalonil and carbendazim, were applied at the rates of 5, 10, and 50 mg of active ingredient (A.I.) per kg of dry soil combined with urea with 200 mg of N per kg of dry soil under laboratory conditions. The results showed that chlorothalonil obviously retarded the hydrolysis of urea, whereas carbendazim accelerated it in 4 days after the treatments (P < 0.05). Chlorothalonil reduced denitrification, nitrification, and N₂O production (P < 0.05), but not for carbendazim. Further analysis on N-associated microbial communities showed chlorothalonil reduced nitrosomonas populations at the rates of 10 and 50 mg of A.I. per kg and autotrophic nitrifying bacterial populations at three application rates (P < 0.05), but Carbendazim decreased nitrosomonas populations only at the rate of 50 mg of A.I. per kg and also autotrophic nitrifying bacterial populations at three rates and heterotrophic nitrifying bacterial populations at the rates of 10 and 50 mg of A.I. per kg. The reasons for this difference were ascribed to arrest urea hydrolysis and impediment of denitrification and nitrification processes by chlorothalonil. In conclusion, to improve crop yielding, chlorothalonil might be more beneficial to conserve soil N by improving soil N fertility, compared with carbendazim.

Low dose chlorothalonil impairs mouse spermatogenesis through the intertwining of Estrogen Receptor Pathways with histone and DNA methylation

Recently, environment contaminants including pesticides, fungicides, mycotoxin and others chemicals have been suggested to be responsible for the decline in the human spermatozoa quality especially motility and the increase in infertility rate. Chlorothalonil is used widely for protection of vegetables and crops because it is a broad spectrum fungicide. It has been reported that chronic occupational exposure to fungicides was associated with poor spermatozoa morphology in young men. The pubertal period is very important for the male reproductive system development due to spermatogonial cell proliferation, the expansion of meiotic and haploid germ cells. Although some investigations have studied the male reproductive toxicity of chlorothalonil, almost no studies focused on spermatogenesis. The aim of our current investigation was to explore the impacts of chlorothalonil on spermatogenesis and the underlying mechanisms. It demonstrates: i) chlorothalonil decreased boar spermatozoa motility in vitro and increased the cell apoptosis; ii) chlorothalonil inhibited mouse spermatogenesis in vivo; iii) chlorothalonil disturbed spermatogenesis through the disruption of estrogen receptor signalling; iv) chlorothalonil disrupted histone methylation and DNA methylation which might be through estrogen signalling pathways. Due to the over use or incorrect use, chlorothalonil might cause serious problems to human health, especially spermatogenesis. Therefore we strongly recommend that greater attention should be paid to this fungicide to minimise its impact on human health especially spermatogenesis.

Use of ozone and detergent for removal of pesticides and improving storage quality of tomato

The efficiencies of two conventional domestic procedures (immersion in pure water and detergent solution at 0.25 and 1%) and two treatments using ozone (immersion in water with bubbling O₃ and immersion in ozonated water, both at 1 and 3 mg L^-1) were evaluated for the removal of residues of the fungicides azoxystrobin, chlorothalonil and difenoconazole in tomatoes. The fungicides were sprayed on the fruits at the recommended concentration for the crop. The residues in the tomatoes and in the washing solutions were determined by extraction with low-temperature partition techniques and analysis by gas chromatography. More concentrated solutions were more effective in removing pesticide residues. The water bubbled with ozone at 3 mg L^-1 was the most efficient treatment for the removal of fungicides, reaching a reduction of 70-90% of the residues. However, the treatments with the lowest concentration of ozone had lower loss of fruit mass during storage.

Fate and effects of two pesticide formulations in the invertebrate Folsomia candida using a natural agricultural soil

Degradation rates of two widely used pesticides were assessed, and acute and chronic effects on a standard invertebrate species investigated. An herbicide (Montana®) and fungicide (Bravo500®) formulations were investigated and results were compared to the isolated active substances of each formulation (glyphosate and chlorothalonil, respectively). Tests were performed using the invertebrate Folsomia candida as test species and an agricultural natural soil. Degradation rate tests were determined under aerobic conditions at 20 ± 2 °C, using an ecologically relevant concentration of 5 mg (a.i.) kg^-1 of soil for both chemicals. Results demonstrated degradation half-lives (DT50) of 2.2 days for Montana® and 2.8 days when pure glyphosate was tested. Values of 1.1 and 2.9 days were registered for Bravo500® and its active substance chlorothalonil, respectively. There were no effects on survival for the tested concentrations of both forms of the herbicide (up to 17.3 mg kg^-1). However, reproduction was affected, but only by the herbicide formulation, with an estimated EC50 value of 4.63 mg (a.i.) kg^-1. Effects were most unlikely related to glyphosate. For chlorothalonil, both tested forms affected survival and reproduction. The estimated LC50 values were 117 mg (a.i.) kg^-1 and 73.5 mg (a.i.) kg^-1, and the EC50 41.3 mg (a.i.) kg^-1 and 14.9 mg kg^-1 for the formulation and the active ingredient, respectively. The effects of the active ingredient were significantly stronger, indicating the major influence of the active substance in the effects caused also by the formulation. Overall results demonstrate the importance of evaluating the effects of the formulated chemicals, as they are applied in the field, and not only their isolated active ingredients.

Chlorothalonil tolerance of indole producing bacteria associated to wheat (Triticum turgidum L.) rhizosphere in the Yaqui Valley, Mexico

Chlorothalonil is a commonly used fungicide to control the karnal bunt caused by Tilletia indica Mitra in wheat production from the Yaqui Valley, Mexico. Here, the effect of Chlorothalonil on the growth of 132 bacterial strains associated with wheat rhizosphere from the Yaqui Valley was evaluated, as well as their ability to produce indoles. Thirty-three percent of the evaluated strains were inhibited by Chlorothalonil, being Bacillus and Paenibacillus the most inhibited genera, observing an inhibition >50% of their strains. In addition, 49% of the inhibited strains showed the ability to produce indoles (>5 μg/mL), where the genus Bacillus was the most abundant (80%). The remaining strains (67%) were tolerant to the evaluated fungicide, but only 37% of those showed the ability to produce indoles, which could be considered as Plant Growth Promoting Rhizobacteria (PGPR). These results showed that Chlorothalonil is not only an antifungal compound but also inhibits the growth of bacterial strains with the ability to produce indoles. Thus, the intensive application of fungicides to agro-systems needs more validation in order to develop sustainable agricultural practices for food production.

Residue behavior and dietary risk assessment of chlorothalonil and its metabolite SDS-3701 in water spinach to propose maximum residue limit (MRL)

Dietary risk assessment generally combines food consumption data and the concentration of pesticide by using the risk quotient (RQ) method. Chlorothalonil is the second popular fungicide in the world, and its residue and risk assessment in water spinach remain unknown. In this paper, the field trials of chlorothalonil in water spinach were operated under good agricultural practice (GAP) in China to human health protective. The dissipation experiments demonstrated that chlorothalonil was rapidly degraded in water spinach, with the half-lives of 1.8-3.2 days, and the amount of its metabolite SDS-3701 (4-hydroxy-2,5,6-trichloroisophthalonitrile) taken up through the water spinach roots from the soil was minor. The terminal experiments disclosed that the average residues of chlorothalonil and SDS-3701 in water spinach were below 6.59 mg/kg and 0.01 mg/kg, respectively. The results suggested the chronic dietary risk probability of chlorothalonil was 51.95-59.15% in terms of all registered crops, and the acute dietary risk probability of chlorothalonil was 12.30%-63.01% in water spinach, highlighting that the dietary risk of chlorothalonil in water spinach under GAP was acceptable. MRL of chlorothalonil was proposed as 7 mg/kg for water spinach and 5 days was recommended as a safe pre-harvest interval (PHI) for chlorothalonil application in water spinach field.

Micropollutants related to human activity in groundwater resources in Barbados, West Indies

Several micropollutants, including caffeine, artificial sweeteners, pharmaceuticals, steroid hormones and a current-use pesticide were analyzed in water samples collected from five groundwater pumping stations in Barbados. The presence of caffeine and three artificial sweeteners (i.e. acesulfame, sucralose, saccharin) in groundwater samples indicated that groundwater was being contaminated by infiltration of wastewater into the karst aquifer. An estrogen (i.e. estrone), three pharmaceuticals (i.e. carbamazepine, trimethoprim, ibuprofen) and a transformation product of the fungicide, chlorothalonil (i.e. 4-hydroxychlorothalonil) were also detected at ng/L concentrations in groundwater collected from two or more pumping sites. The concentrations of carbamazepine and trimethoprim were correlated with the concentrations of caffeine (R² values of 0.70 to 0.80), indicating pharmaceutical contamination of groundwater by infiltration from domestic wastewater. The concentrations of caffeine were generally higher in groundwater samples collected in June during the wet season relative to the concentrations in samples collected in February during the dry season, indicating that infiltration of contaminants is higher during periods of heavy rainfall. Rapid rates of degradation and relatively slow rates of infiltration may explain why several target analytes were not detected in groundwater. Elevated concentrations of 4-hydroxychlorothalonil > 0.1 μg/L in samples collected at two of the monitoring sites warrant further studies on the sources and the distribution of this compound and other pesticides used in agriculture and for turf-treatment (e.g. golf courses). Overall, more data are needed in order to implement mitigation strategies that are effective in reducing chemical contamination in groundwater in Barbados.

From laboratory to the field: Validating molecular markers of effect in Folsomia candida exposed to a fungicide-based formulation

Under controlled laboratory conditions, toxicity data tend to be less variable than in more realistic in-field studies and responses may thus differ from those in the natural environment, creating uncertainty. The validation of data under environmental conditions is therefore a major asset in environmental risk assessment of chemicals. The present study aimed to validate the mode of action of a commercial fungicide formulation in the soil invertebrate F. candida, under more realistic exposure scenarios (in-field bioassay), by targeting specific molecular biomarkers retrieved from laboratory experiments. Organisms were exposed in soil cores under minimally controlled field conditions for 4 days to a chlorothalonil fungicide dosage causing 75% reduction of reproduction in a previous laboratory experiment (127 mg a.i. kg^-1) and half this concentration (60 mg a.i. kg^-1). After exposure, organisms were retrieved and RNA was extracted from each pool of organisms. According to previous laboratorial omics results with the same formulation, ten genes were selected for gene expression analysis by qRT-PCR, corresponding to key genes of affected biological pathways including glutathione metabolism, oxidation-reduction, body morphogenesis, and reproduction. Six of these genes presented a dose-response trend with higher up- or down-regulation with increasing pesticide concentrations. Highly significant correlations between their expression patterns in laboratory and in-field experiments were observed. This work shows that effects of toxicants can be clearly demonstrated in more realistic conditions using validated biomarkers. Our work outlines a set of genes that can be used to assess the early effects of pesticides in a realistic agricultural scenario.

Chlorothalonil inhibits mouse ovarian development through endocrine disruption

Although many studies have investigated the toxic effects and even the reproductive toxicity of chlorothalonil, almost no studies have focused on the ovary, the organ of oocyte development. Puberty is a critical window for development of the female reproductive system. Therefore, this investigation aimed to explore the effects and underlying mechanisms of chlorothalonil at low doses on peripubertal mouse ovarian development. Chlorothalonil is frequently used in horticulture with short intervals between applications, therefore, vegetables and fruits may be potential sources of chlorothalonil contamination. For the first time, this study demonstrated that chlorothalonil inhibited ovarian development during puberty in mice, and at levels currently assumed to have no adverse health consequences for humans. Chlorothalonil exposure inhibited mouse ovarian development by increasing the number of primary follicles and decreasing the number of mature follicles. It acted by decreasing the levels of hormone production proteins, such as FSH receptor and estrogen receptor alpha, while increasing the levels of DNA repairing marker RAD51 and cell apoptosis. These results suggest that chlorothalonil may disrupt endocrine function and inhibit murine ovarian development. Therefore it may pose a potential health risk to female reproductive systems in other species, especially to the ovary.

Modelling the behavior of pesticide residues in tomatoes and their associated long-term exposure risks

This study is focused on the dissipation behavior of 7 fungicides and 5 insecticides applied in tomatoes after a third spraying at recommended and double doses by considering 6 kinetic models which allow estimating the pesticides half-lives (t_1/2). Except studying the pesticides dissipation, another scope of our manuscript was investigating the risk to human health after application of different pesticide treatments in tomatoes. The pesticides analysis in tomatoes at harvest showed that the residues were below the maximum residue level (MRL), with the exception of chlorotalonil (included in Group 2B - "Possibly carcinogenic to humans") and bifenthrin for recommended dose treatments, while for double dose treatments, the MRLs was exceeded for 7 pesticides, once again including chlorotalonil. For recommended dose treatments, the 1st order kinetic model is confirmed only for metalaxyl-M. The values of pesticides t_1/2 ranged from 0.006 days (for chlorothalonil) to 48.59 days (for myclobutanil). For double dose treatments, the 1st order kinetic model is confirmed for deltamethrin and triadimenol. In this case, the values of pesticides t_1/2 ranged from 0.32 to 10.67 days. Further, consumers' exposure was estimated by calculating the long-term risk based on hazard quotient (HQ). The results indicated that the risks generated by pesticide residues in tomatoes applied in recommended or double doses are in an acceptable limit, except for chlorothalonil which may pose a threat for children health. However, if we consider the cumulative hazard index (HI) values which were higher than 1, consumption of tomatoes containing pesticides residues may cause harmful non-carcinogenic health effects.

Nylon 6,6 modified screen printed carbon electrodes as electrochemical sensors for rapid chlorothalonil determination in water samples using differential pulse cathodic stripping voltammetry

A newly developed electrochemical sensor for chlorothalonil based on nylon 6,6 film deposited onto screen printed electrode (SPE) with electrochemical modulation of pH at the electrode/solution interface was studied for the first time. Differential pulse cathodic stripping voltammetry (DPCSV) was used to carry out the electrochemical and analytical studies. Experimental parameters such as accumulation potential, initial potential, accumulation time and pH of Britton-Robinson buffer have been optimized. Chlorothalonil gave optimum analytical signal in a medium of 0.04 M Britton-Robinson buffer at pH 6.0. A well-defined reduction peak was observed, at E_p= -0.851 and -0.938 V vs. Ag/AgCl (3.0 M KCl) for both bare SPE and modified SPE, respectively. The peak currents of modified SPE were significantly increased as compared to bare SPE. At the modified SPE, a linear relationship between the peak current and chlorothalonil concentration was obtained in the range from 0.1 to 2.8 × 10^-6 M with a detection limit of 1.53 × 10^-8 M (S/N= 3). The practical applicability of the newly developed method has been demonstrated on analyses of real water samples. The newly developed sensor shows good reproducibility with RSD of 3.92%. The nylon 6,6 modified SPE showed itself as promising sensor with good selectivity for chlorothalonil determination.

Chlorothalonil: an effective bacteriostatic agent for bud induction of Acacia auriculiformis under open condition (non-axenic)

BACKGROUND

Open tissue culture technique could be simplified by using different bacteriostatic agents. There is a great difference in the bacteriostatic effects of different antimicrobial agents on various explants. However, there is no report about the effective bacteriostatic agent for open tissue culture of Acacia auriculiformis.

RESULTS

We carried out the bud induction trials under open conditions to screen out an effective antibacterial agent for open tissue culture of A. auriculiformis. The results showed that the suitable type and concentration of bacteriostatic agent was 0.2 g L^-1 Chlorothalonil, and the suitable explant type was middle shoot section with leaves (the shoot section with third to fifth axillary bud). The treatment of 0.8 g L^-1 Carbendazim for 3 min was the most suitable strategy for explants disinfection, and October was the best time for explants collection. The suitable bud induction medium was 1/8 MS + agar 7 g L^-1 + Chlorothalonil 0.2 g L^-1 + 6-BA 1.5 mg L^-1, and the bud induction rate was 99.54%.

CONCLUSIONS

Our results revealed that Chlorothalonil is an effective bacteriostatic agent for bud induction of A. auriculiformis under open condition. These results would be very helpful for further establishment of open tissue culture technology for A. auriculiformis.

larvae reared in vitro

Chlorothalonil is a broad-spectrum fungicide and diflubenzuron is an insect growth regulator used to control many insect larvae feeding on agricultural, forest and ornamental plants. Honey bee larvae may be exposed to both via contaminated pollen, in the form of beebread, added to their diet by their adult nurse sisters. In this study, we determined how single (acute: 72 h mortality) and repeated (chronic: mortality until emergence as adults) exposure to chlorothalonil and diflubenzuron in their diet affected honey bee larvae reared in vitro. The tested doses of chlorothalonil (20, 100, or 200 mg/L) did not impact 72 h larval mortality acutely relative to that of the solvent control. The 72 h mortality of larvae exposed to 1.6 mg/L and higher doses of diflubenzuron acutely in their diet (47.2-63.9% mortality) was significantly higher than that of larvae fed the solvent control, with no predictable dose dependent pattern observed. In the chronic toxicity tests, consuming an artificial diet with 30 or 100 mg/L chlorothalonil and 0.8, 1.3 or 2 mg/L diflubenzuron significantly lowered the survival of honey bee larvae over that of larvae feeding on the solvent control diet. We calculated risk quotients (RQs) for both compounds using the data we generated in our experiments. Collectively, the RQs suggest that neither compound is likely to affect larval mortality directly at field relevant doses given that pollen composes only a fraction of the total larval diet. Nevertheless, our data do not preclude any sublethal effects that chronic exposure to either compound may cause.

The influence of chlorothalonil on the activity of soil microorganisms and enzymes

As one of the most widely used pesticides in agriculture, chlorothalonil can pose threat to soil ecosystems. Therefore, the impact of this substance on the development of microbiological and biochemical properties of the soil as well as on the growth of spring wheat was evaluated. The study was conducted with two soils (loamy sand with pH_KCl 5.6 and sandy loam with pH_KCl 7.00), to which fungicide was used in the following doses: 0.00, 0.166 (recommended dose), 1.660, and 16.60 mg kg^-1 dry matter of soil (DM of soil). In addition, we determined the effectiveness of fertilizing substances (Lignohumat Super and Bioilsa N 12.5) in the restoration of soil homeostasis and chlorothalonil degradation in the soil. Chlorothalonil caused modifications in the count and biological diversity of soil microorganisms. It stimulated the growth of heterotrophic bacteria and actinobacteria, and inhibited the growth of fungi. This pesticide was a potent inhibitor of dehydrogenase, catalase and acid phosphatase activities. It showed variable effects on urease and alkaline phosphatase. The fungicide also a reduction the yield of dry matter of the aboveground parts of spring wheat. It should, however, be noted that these changes in the soil environment occurred after the introduction of higher doses of chlorothalonil. The fertilizing substances used contributed to enhanced microbial and biochemical activities of soils, while they did not significantly affect plant yields. The Bioilsa N 12.5 preparation was effective in chlorothalonil degradation, while Lignohumat Super reduced the degradation rate of the tested fungicide. Based on the conducted experiment, an ecological risk assessment of chlorothalonil was made by estimating the changes occurring in the soil environment evaluated through the microbiological and biochemical analyses of the soil.

Bioaugmentation of chlorothalonil-contaminated soil with hydrolytically or reductively dehalogenating strain and its effect on soil microbial community

Although bioaugmentation of pollutant-contaminated sites is a great concern, there are few reports on the relationships among indigenous microbial consortia, exogenous inocula, and pollutants in a bioaugmentation process. In this study, bioaugmentation with Pseudochrobactrum sp. BSQ1 and Massilia sp. BLM18, which can hydrolytically and reductively dehalogenate chlorothalonil (TPN), respectively, was studied for its ability to remove TPN from soil; the alteration of the soil microbial community during the bioaugmentation process was investigated. The results showed that TPN (50 mg/kg) was completely removed in both bioaugmentation treatments within 35 days with half-lives of 6.8 and 9.8 days for strains BSQ1 and BLM18 respectively. In high concentration of TPN-treated soils (100 mg/kg), the bioaugmentation with strains BSQ1 and BLM18 respectively reduced 76.7% and 62.0% of TPN within 35 days. The TPN treatment significantly decreased bacterial richness and diversity and improved the growth of bacteria related to the elimination of chlorinated organic pollutants. However, little influence on soil microbial community was observed for each inoculation treatment (without TPN treatment), showing that TPN treatment is the main force for the shift in indigenous consortia. This study provides insights into the effects of halogenated fungicide application and bioaugmentation on indigenous soil microbiomes.

Spatial distribution and seasonal variation of four current-use pesticides (CUPs) in air and surface water of the Bohai Sea, China

Current-use pesticides (CUPs) are widely used in agriculture, and some are listed as persistent organic pollutants (POPs) due to their bioaccumulative and toxic properties. China is one of the largest producers and users of pesticides in the world. However, very limited data are available about the environmental fates of CUPs. Four CUPs (trifluralin, chlorothalonil, chlorpyrifos, and dicofol) in surface seawater and low atmospheric samples taken during research cruises on the Bohai Sea in August and December 2016 and February 2017 were analyzed, we added the spring data sampled in May 2012 to the discussion of seasonal variation. In our study, chlorpyrifos was the most abundant CUPs in the gas phase with a mean abundance of 59.06±126.94pgm^-3, and dicofol had the highest concentration dissolved in seawater (mean: 115.94±123.16pgL^-1). The concentrations of all target compounds were higher during May and August due to intensive use and relatively high temperatures in the spring and summer. Backward trajectories indicated that air masses passing through the eastern coast of the Bohai Sea contained high concentrations of pollutants, while the air masses from the Bohai and Yellow Seas were less polluted. The high concentration of pollutants in seawater was not only influenced by high yields from the source region of production or usage, but also by input from polluted rivers. Volatilization from surface water was found to be an important source of trifluralin and chlorpyrifos in the air. Air-sea gas exchange of chlorothalonil underwent strong net deposition (mean FRs: 51.67), which was driven by higher concentrations in air and indicates that the Bohai Sea acted as a sink for chlorothalonil.

Some adverse actions of chlorothalonil at sublethal levels in rat thymic lymphocytes: Its relation to Zn2

Chlorothalonil, a polychlorinated aromatic fungicide, is considered non-toxic to small mammals. However, chlorothalonil inactivates sulfhydryl enzymes and depletes cellular glutathione. Chlorothalonil increases intracellular Zn²⁺ concentration ([Zn²⁺]i) in mammalian cells possibly because intracellular Zn²⁺ is released via zinc-thiol/disulfide interchange. The effects of chlorothalonil at sublethal concentrations on the cellular content of nonprotein thiols ([NPT]i) and [Zn²⁺]i were examined using flow cytometry in rat thymocytes. Low concentrations (0.3-1 μM) of chlorothalonil increased, but high concentrations (3-10 μM) decreased [NPT]i. These effects of chlorothalonil were partly attenuated by an intracellular Zn²⁺ chelator. Chlorothalonil at 0.3-10 μM increased [Zn²⁺]i in a concentration-dependent manner, which was largely dependent on the release of intracellular Zn²⁺. Both the decrease in [NPT]i and increase in [Zn²⁺]i increase the vulnerability of cells to oxidative stress. Chlorothalonil at 1-10 μM potentiated the cytotoxicity of H₂O₂ (300 μM). It was also the case for 10 μM pentachloronitrobenzene, but not 10 μM pentachlorophenol. In conclusion, chlorothalonil at low (sublethal) micromolar concentrations is cytotoxic to mammalian cells under oxidative stress.

Probiotic strain Stenotrophomonas acidaminiphila BJ1 degrades and reduces chlorothalonil toxicity to soil enzymes, microbial communities and plant roots

Chlorothalonil, a non-systemic and broad-spectrum fungicide, is widely used to control the pathogens of agricultural plants. Although microbial degradation of chlorothalonil is known, we know little about the colonization and degradation capacity of these microbes in the natural and semi-natural soil environments. Therefore, we studied the colonization and detoxification potential of a chlorothalonil degrading Stenotrophomonas acidaminiphila probiotic strain BJ1 in the soil under green conditions. The results from polymerase chain reaction-denaturing gradient gel electrophoresis demonstrated that probiotic strain BJ1 successfully colonized the soil by competing with the native biota. Moreover, the bacterial inoculation stimulated some members of indigenous soil microbial communities. Meantime, the degradation half-life of chlorothalonil decreased from 9.0 to 4.9 days in the soil environment. Moreover, the results from enzymatic activities and micronucleus test of Vicia faba root tips showed that the probiotic strain BJ1 reduced the ecotoxicity and genotoxicity of chlorothalonil in the soil. We suggest that probiotic strains like BJ1 could potentially alleviate the toxic effects of pesticides on soil microbes and plant roots under greenhouse conditions.

UV characterization and photodegradation mechanism of the fungicide chlorothalonil in the presence and absence of oxygen

An experimental and theoretical study of the UV spectrum of chlorothalonil (CT) was carried out and the vibrationally resolved HOMO→LUMO transition is presented for the first time. The fluorescence spectrum has also been recorded. Furthermore, preparative photolysis allowed a detailed study of the photoproducts formed with recognition of different isomers. In the presence of oxygen only the first reductive dechlorination-decyanation occurred, while in its absence a successive dechlorination-decyanation takes place.