Occurrence and ecological risks from fipronil in aquatic environments located within residential landscapes

Development of a Reversed-Phase UPLC Method for Assay of Fipronil Including Determination of Its Related Substances in Bulk Batches of Fipronil Drug Substance

BACKGROUND

Fipronil is a commonly used pesticide in the agricultural and animal health industries for the protection of crops and control of fleas, ticks, and chewing lice. It is difficult to obtain reproducible retention time and relative retention time (RRT) for a common hydrolytic degradation product of fipronil with the current European Pharmacopeia (EP) monograph for assay and estimation of related substances of fipronil. This situation causes misidentification, mislabeling, and/or false out-of-specification results for this hydrolytic degradation product of fipronil in bulk commercial batches during batch release and/or in the stability samples during the shelf life of a released batch.

OBJECTIVE

This study aimed to develop a reversed-phase ultra performance liquid chromatography (UPLC) method for assay and identification of fipronil including identification and estimation of its related substances in bulk drug substance batches of fipronil and provide consistent retention time of the hydrolytic degradation product.

METHODS

Fipronil and its related substances were separated by gradient elution on a Halo C18 column (50 mm × 2.1 mm id, 2.0 µm particle size) maintained at 40°C with 0.1% H3PO4 in H2O as mobile phase-A and acetonitrile-methanol (50 + 50, v/v) as mobile phase-B. Fipronil and its related substances were detected and quantified at 280 nm with a quantitation limit of 0.05% of the target (analytical) concentration.

RESULTS

The UPLC method was able to separate all analytes of interest by gradient elution with a total run time of 7 min (approximately 40% faster than EP).

CONCLUSION

In this paper, we report the development and validation of a fast, stability-indicating reversed-phase UPLC method for assay and estimation of related substances of fipronil in stability samples and bulk batches of fipronil.

HIGHLIGHTS

The new UPLC method is approximately 40% faster than the current Ph. Eur. monograph for fipronil assay and the new method provides reproducible retention of a common hydrolytic degradation product of fipronil.

Identify organic contaminants of high-concern based on non-targeted toxicity testing and non-targeted LC-HRMS analysis in tap water and source water along the Yangtze River

Many organic pollutants were detected in tap water (TW) and source water (SW) along the Yangtze River. However, the potential toxic effects and the high-concern organics (HCOs) which drive the effect are still unknown. Here, a non-targeted toxicity testing method based on the concentration-dependent transcriptome and non-targeted LC-HRMS analysis combining tiered filtering were used to reveal the overall biological effects and chemical information. Subsequently, we developed a qualitative pathway-structure relationship (QPSR) model to effectively match the biological and chemical information and successfully identified HCOs in TW and SW along the Yangtze River by potential substructures of HCOs. Non-targeted toxicity testing found that the biological potency of both TW and SW was stronger in the downstream of the Yangtze River, and disruption of the endocrine system and cancer were the main drivers of the effect. In addition, non-targeted LC-HRMS analysis combined with retention time prediction results identified 3220 and 631 high-confidence compound structures in positive and negative ion modes, respectively. Then, QPSR model was further implied and identified a total of 103 HCOs, containing 35 industrial chemicals, 30 PPCPs, 26 pesticides, and 12 hormones in TW and SW, respectively. Among them, the neuroactive and hormonal compounds oxoamide, 8-iso-16-cyclohexyl-tetranor prostaglandin E2, E Keppra, and Tocris-0788 showed the highest frequency of detection, which were identified in more than 1/3 of the samples. The strategy of combining non-targeted toxicity testing and non-targeted LC-HRMS analysis will support comprehensive biological effect assessment, identification of HCOs, and risk control of mixtures.

Effects of sublethal fipronil exposure on cross-generational functional responses and gene expression in Binodoxys communis

The effective systemic insecticide fipronil is widely used on a variety of crops and in public spaces to control insect pests. Binodoxys communis (Gahan) (Hymenoptera: Braconidae) is the dominant natural enemy of Aphis gossypii Glover (Homoptera: Aphididae), an important cotton pest, and has good efficiency in inhibiting aphid populations. The direct effects of environmental residues of sublethal fipronil doses on adult B. communis have not previously been reported. This study therefore aimed to evaluate the side effects and transcriptomic impacts of sublethal fipronil doses on B. communis. The results showed that exposure to the LC10 dose of fipronil significantly reduced the survival rate and parasitism rate of the F0 generation, but did not affect these indicators in the F1 generation. The LC25 dose did not affect the survival or parasitic rates of the F0 generation, but did significantly reduce the survival rate of F1 generation parasitoids. These results indicated that sublethal doses of fipronil affected B. communis population growth. Transcriptome analysis showed that differentially expressed genes (DEGs) in B. communis at 1 h after treatment were primarily enriched in pathways associated with fatty acid elongation, biosynthesis of fatty acids, and fatty acid metabolism. DEGs at 3 days after treatment were mainly enriched in ribosomal functions, glycolysis/gluconeogenesis, and tyrosine metabolism. Six DEGs (PY, ELOVL, VLCOAR, MRJP1, ELOVL AAEL008004-like, and RPL13) were selected for validation with real-time fluorescent quantitative PCR. This is the first report of sublethal, trans-generational, and transcriptomic side effects of fipronil on the dominant parasitoid of A. gossypii. The results of this study show that adaptation of parasitoids to high concentrations of pesticides may be at the expense of their offspring. These findings broaden our overall understanding of the intergenerational adjustments used by insects to respond to pesticide stress and call for risk assessments of the long-term impacts and intergenerational effects of other pesticides.

Fipronil disturbs the antigen-specific immune responses and GABAergic gene expression in the ovalbumin-immunized BALB/c mice

BACKGROUND

Fipronil (FPN) is a broad-spectrum pesticide and commonly known as low toxicity to vertebrates. However, increasing evidence suggests that exposure to FPN might induce unexpected adverse effects in the liver, reproductive, and nervous systems. Until now, the influence of FPN on immune responses, especially T-cell responses has not been well examined. Our study is designed to investigate the immunotoxicity of FPN in ovalbumin (OVA)-sensitized mice. The mice were administered with FPN by oral gavage and immunized with OVA. Primary splenocytes were prepared to examine the viability and functionality of antigen-specific T cells ex vivo. The expression of T cell cytokines, upstream transcription factors, and GABAergic signaling genes was detected by qPCR.

RESULTS

Intragastric administration of FPN (1-10 mg/kg) for 11 doses did not show any significant clinical symptoms. The viability of antigen-stimulated splenocytes, the production of IL-2, IL-4, and IFN-γ by OVA-specific T cells, and the serum levels of OVA-specific IgG1 and IgG2a were significantly increased in FPN-treated groups. The expression of the GABAergic signaling genes was notably altered by FPN. The GAD67 gene was significantly decreased, while the GABAR β2 and GABAR δ were increased.

CONCLUSION

FPN disturbed antigen-specific immune responses by affecting GABAergic genes in vivo. We propose that the immunotoxic effects of FPN may enhance antigen-specific immunity by dysregulation of the negative regulation of GABAergic signaling on T cell immunity.

Toxicity assessment of carvacrol and its acetylated derivative in early staged zebrafish (Danio rerio): Safer alternatives to fipronil-based pesticides?

Fipronil is a broad-spectrum pesticide presenting high acute toxicity to non-target organisms, particularly to aquatic species. Natural compounds stand out as promising alternatives to the use of synthetic pesticides such as fipronil. Thus, our study aimed to compare the toxicity of carvacrol (natural), acetylcarvacrol (semisynthetic), and fipronil (synthetic) to early staged zebrafish. We conducted a series of toxicity assays at concentrations ranging from 0.01 μM to 25 μM for fipronil and 0.01 μM to 200 μM for carvacrol and acetylcarvacrol, depending on the assay, after 7-days post-fertilization (dpf). The potency (EC50) of fipronil was ∼1 μM for both deformities and mortality at 7 dpf, whereas EC50 was >50 μM for carvacrol and >70 μM for acetylcarvacrol. Fipronil at 0.1 and 1 μM caused a decrease in body length and swim bladder area of larvae at 7dpf, but no difference was observed for either carvacrol or acetylcarvacrol. Based upon the visual motor response test, fipronil induced hypoactivity in larval zebrafish at 1 μM and acetylcarvacrol induced hyperactivity at 0.1 μM. Anxiolytic-type behaviors were not affected by any of these chemicals. All chemicals increased the production of reactive oxygen species at 7 dpf, but not at 2 dpf. Genes related to swim bladder inflation, oxidative stress, lipid metabolism, and mitochondrial activity were measured; only fipronil induced upregulation of atp5f1c. There were no changes were observed in oxygen consumption rates of fish and apoptosis. Taken together, our data suggest that carvacrol and its derivative may be safer replacements for fipronil due to their lower acute toxicity.

Colorimetric and ratiometric supramolecular AIE fluorescent probe for the on-site monitoring of fipronil

The overuse of fipronil (FPN, a broad-spectrum insecticide) in agriculture has brought great concerns for environmental pollution and food safety. The development of a rapid, reliable, and portable analytical method for the on-site monitoring of FPN is therefore of great significance but is full of challenge. Herein, a novel supramolecular probe using human serum albumin (HSA) as the host and an aggregation-induced emission-active fluorescence probe LIQ-TPA-TZ as the guest was developed for the colorimetric and ratiometric detection of FPN, displaying fast response (30 s), high sensitivity (LOD ∼ 0.05 μM), and good selectivity and anti-interference performance. Moreover, portable paper-based test strips could be facilely obtained and utilized for the determination of FPN, showing colorimetric changes from yellow to orange. This supramolecular probe also demonstrated great potential in real applications for choosing the best cleaning method to reduce the residue rate of FPN on apples. This study provides a versatile tool for the fast and real-time analysis of FPN, which greatly benefits the on-site determination of pesticides with the use of simple testing apparatus.

Mortality and toxicity of a commercial formulation of cypermethrin in Physalaemus gracilis tadpoles

This study evaluated the lethal, sublethal, and toxic of a commercial formulation of cypermethrin in the anuran species Physalaemus gracilis. In the acute test, concentrations of 100-800 μg L-1 were tested over 96 h. In the chronic test, cypermethrin concentrations recorded in nature (1, 3, 6, and 20 μg L-1) were tested for mortality and then used for the micronucleus test and erythrocyte nuclear abnormalities over a 7-days period. The LC50 determined for P. gracilis for the commercial cypermethrin formulation was 273.41 μg L-1. In the chronic test, a mortality of more than 50% was observed at the highest concentration (20 μg L-1), as it caused half of the tadpoles studied to die. The micronucleus test showed significant results at concentrations of 6 and 20 μg L-1 and recorded the presence of several nuclear abnormalities, indicating the genotoxic potential of the commercial cypermethrin formulation for P. gracilis. Cypermethrin presented a high risk to the species, indicating that it has the potential to cause several problems in the short and long term and to affect the dynamics of this ecosystem. Therefore, it can be concluded that the commercial formulation of cypermethrin had toxicological effects on P. gracilis.

Influence of dissolved organic carbon on multimedia distribution and toxicity of fipronil and its transformation products in lotic waterways

Environmental fate and ecological impacts of fipronil and its transformation products (FIPs) in aquatic environment have caused worldwide attention, however, the influence of dissolved organic carbon (DOC) on multimedia distribution, bioavailability, and toxicity of FIPs in field waterways was largely unknown. Here, we collected 11 companion water and sediment samples along a lotic stream in Guangzhou, South China. FIPs were ubiquitous with total water concentrations ranging from 1.22 to 43.2 ng/L (14.8 ± 12.9 ng/L) and fipronil sulfone was predominant in both water and sediment. More than 70% of FIPs in aqueous phase were bound to DOC and the K_DOC values of FIPs were approximately 1-2 orders of magnitude higher than K_d-s/K_OC, emphasizing the significance of DOC in phase partitioning and transport of FIPs in aquatic environment. Water and sediment samples were more toxic to Chironomus dilutus than Hyallela azteca, and FIPs (especially fipronil sulfone) pronouncedly contributed toxicity to C. dilutus. Toxic units (TU) based on freely dissolved concentrations in water determined by solid phase microextraction significantly improved toxicity estimation of FIPs to the invertebrates compared to TUs based on aqueous concentrations. The present study highlights the significance of DOC association on fate and ecological risk of hydrophobic insecticides in lotic ecosystem.

Prioritizing Pesticides of Potential Concern and Identifying Potential Mixture Effects in Great Lakes Tributaries Using Passive Samplers

To help meet the objectives of the Great Lakes Restoration Initiative with regard to increasing knowledge about toxic substances, 223 pesticides and pesticide transformation products were monitored in 15 Great Lakes tributaries using polar organic chemical integrative samplers. A screening-level assessment of their potential for biological effects was conducted by computing toxicity quotients (TQs) for chemicals with available US Environmental Protection Agency (USEPA) Aquatic Life Benchmark values. In addition, exposure activity ratios (EAR) were calculated using information from the USEPA ToxCast database. Between 16 and 81 chemicals were detected per site, with 97 unique compounds detected overall, for which 64 could be assessed using TQs or EARs. Ten chemicals exceeded TQ or EAR levels of concern at two or more sites. Chemicals exceeding thresholds included seven herbicides (2,4-dichlorophenoxyacetic acid, diuron, metolachlor, acetochlor, atrazine, simazine, and sulfentrazone), a transformation product (deisopropylatrazine), and two insecticides (fipronil and imidacloprid). Watersheds draining agricultural and urban areas had more detections and higher concentrations of pesticides compared with other land uses. Chemical mixtures analysis for ToxCast assays associated with common modes of action defined by gene targets and adverse outcome pathways (AOP) indicated potential activity on biological pathways related to a range of cellular processes, including xenobiotic metabolism, extracellular signaling, endocrine function, and protection against oxidative stress. Use of gene ontology databases and the AOP knowledgebase within the R-package ToxMixtures highlighted the utility of ToxCast data for identifying and evaluating potential biological effects and adverse outcomes of chemicals and mixtures. Results have provided a list of high-priority chemicals for future monitoring and potential biological effects warranting further evaluation in laboratory and field environments. Environ Toxicol Chem 2023;42:340-366. Published 2022. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Fipronil and its metabolites in chicken feather: residue analysis, depletion study, and application analysis of pollution sources in laying hens

A method based on a multi-mechanism impurity adsorption and ultra-performance liquid chromatography-tandem mass spectrometry was established to detect fipronil and four of its metabolites in chicken feathers. This method was successfully applied to the depletion study of fipronil in feathers of laying hens. Fipronil and two metabolites were found in feathers during treatment. Fipronil concentrations in feathers increased during medication and then regularly decreased during withdrawal, and they were still detected on the 14th day after withdrawal. High residue concentrations were also present in feathers on day 23 of the experimental period. Pollution sources of fipronil can be inferred on the basis of the residue ratio of fipronil metabolites from different pollution modes. Result shows that feathers were an effective matrix for residue monitoring and risk analysis of fipronil in animals and the environment.

Embryonic toxicity of Imidacloprid: Impact on hatchability, survivability, swimming speed and cardiac function of catfish, Clarias gariepinus

Imidacloprid is a systemic insecticide that belongs to the neonicotinoid class of chemicals that act on the central nervous system of insects. Imidacloprid is used to control sucking insects, chewing insects such as termites, soil insects, and fleas on pets, as well as to treat structures, crops, soil, and seeds. As a result of these factors, this pesticide may end up in the aquatic environment via municipal discharges and runoff. Although the presence of imidacloprid in aquatic environments has been underreported as widespread, the toxic effects of this pesticide may have serious implications on aquatic organisms, particularly at environmentally relevant concentrations and demand more attention. Given this knowledge, the goal of this study was to investigate the effects of imidacloprid on Clarias gariepinus embryonic development. Clarias gariepinus embryos (3 h post-fertilization) were exposed to environmentally relevant concentrations of imidacloprid (10, 30, 100, and 500 µg/L) until 48 h post-fertilization using a modified fish embryo acute toxicity test (OECD TG 236). A stereomicroscope was used to assess hatchability, deformity, heart rate, and swimming speed as endpoints. According to our results of the developmental acute toxicity test, imidacloprid significantly reduced the hatching rate and heartbeats of C. gariepinus embryos. It also influenced the swimming kinematics of exposed embryos and caused teratogenic effects such as yolk sac rupture, pericardial oedema, lordosis, an abnormally shaped head, and altered epiboly. Our results allow us to conclude that imidacloprid is a toxic pesticide in the early life stages of C. gariepinus due to its high teratogenic potential.

Nontarget Identification of Novel Per- and Polyfluoroalkyl Substances in Cord Blood Samples

Per- and polyfluoroalkyl substances (PFASs) can penetrate the placental barrier and reach embryos through cord blood, probably causing adverse birth outcomes. Therefore, novel PFASs identification in cord blood and their relationships with birth outcomes are essential to evaluate prenatal exposure risk of PFASs. Herein, 16 legacy and 12 novel PFASs were identified in 326 cord blood samples collected from pregnant women in Jinan, Shandong, China. The presence of perfluoropolyether carboxylic acids, hydrogen-substituted polyfluoroetherpropane sulfate, and 3:3 chlorinated polyfluoroalkyl ether alcohol in cord blood was reported for the first time. Two extensive OECD (Organization for Economic Co-operation and Development)-defined PFASs named fipronil sulfone and 2-chloro-6-(trifluoromethyl)pyridine-3-ol were also identified. Quantification results showed that the emerging and OECD-defined PFASs separately accounted for 9.4 and 9.7% of the total quantified PFASs, while the legacy PFOA, PFOS, and PFHxS were still the most abundant PFASs with median concentrations of 2.12, 0.58, and 0.37 ng/mL, respectively. Several PFASs (C₉-C₁₂ PFCAs, C₆-C₈ PFSAs, and 6:2 Cl-PFESA) showed significantly higher levels for older maternities than younger ones. PFHxS levels were positively associated with birth weight and ponderal index (p < 0.05). The results provide comprehensive information on the presence and exposure risks of several novel PFASs during the early life stage.

Determination of 52 hidden chemical pesticides in biopesticide products by GC-MS/MS and LC-MS/MS

Addition of chemical pesticides in biopesticides are expected to be common, due to effect of pest control during plant protection. These hidden chemical pesticides may cause various food safety problems if consumed. The purpose of our study was to develop a method to determine 52 hidden chemical pesticides in three formulation biopesticide products. Optimizations of different parameters, such as the instrument analysis condition for target, the extraction, and the composition of clean-up materials were carried out. The developed method used acetonitrile as an extraction solvent for all biopesticide formulations. The composition of adsorbents was based on QuEChERS, called QuSEL which was a needle filter head, containing PSA, GCB, and MgSO₄. Fifty-two chemical pesticides residues were then analyzed by GC-MS/MS and LC-MS/MS. The present results showed good linearity by correlation coefficients of more than 0.99 for all analyses. The LOQ ranged from 5.0 to 20.0 μg kg^-1. Recoveries of 32 chemical pesticides ranged from 71.9% to 118.4% at the spiked level of 10, 50, and 100 μg kg^-1, and 20 chemical pesticides ranged from 75.3% to 119.8% at the spiked level of 5, 25, and 50 μg kg^-1. The developed method was applied for biopesticide products, and 9 samples were positive in 20 samples.

Occurrence and ecological risk assessment of neonicotinoids and related insecticides in the Bohai Sea and its surrounding rivers, China

Systemic insecticides like neonicotinoids and the phenylpyrazole insecticide fipronil are the most widely applied insecticides around the world. Multiple studies analyzed insecticide residues in freshwater systems, but data on seawater contamination levels are scarce. This study investigates the spatiotemporal distribution and ecological risk assessment of fipronil, neonicotinoids, sulfoxaflor and selected transformation products (TPs) in the Chinese Bohai Sea and its surrounding rivers. Well-established neonicotinoids (acetamiprid, clothianidin, imidacloprid, thiacloprid and thiamethoxam) and TPs of fipronil and imidacloprid were frequently detected (detection frequency (DF): 42-100%) in freshwater. The median total insecticide concentration in freshwater was significantly higher in summer (72.4 ng•L-1) than in fall (23.4 ng•L-1), with major contributions from neonicotinoids, suggesting that pollution originates mostly from diffuse sources. In 2018, acetamiprid, desnitro-imidacloprid, fipronil-desulfinyl and thiacloprid were abundant in seawater (DF: 47-100%), indicating a high stability of acetamiprid and thiacloprid and a rapid photodegradation of fipronil and imidacloprid in surface waters. These results indicate that the continued use of these parent compounds may lead to their accumulation and/or of their TPs in shallow coastal seas. Consequently, this may lead to their transport to open seas, increasing their potential risk to marine organisms. Similarities between contaminant fingerprints in freshwater and seawater strongly suggest riverine discharges as main pollution source of adjacent coastal areas. This is the first study to perform an ecological risk assessment of fipronil, neonicotinoids, sulfoxaflor and selected TPs on marine ecosystems. Fipronil and its TPs demonstrated to be environmentally relevant with potential high risks for aquatic species. Our study provides novel insights into the fate and ecological risk of fipronil, neonicotinoids, sulfoxaflor and their TPs to marine species in shallow coastal seas.

Determination of Fipronil and Fipronil-Sulfone in Surface Waters of the Guandu River Basin by High-Performance Liquid Chromatography with Mass Spectrometry

Fipronil (FIP) is a broad-spectrum insecticide used in the industrial, residential and agricultural sectors, which presents environmental and human health risks. Studies report its presence in aquatic environments in several countries, but in Brazil reports are scarce. The aim of this work was to evaluate the presence of fipronil and fipronil sulfone in surface waters through a validated analytical method by LC-MS according to INMETRO and USEPA in eight sampling sites in two seasons (summer and autumn, 2020) in Guandu River basin, in the state of Rio de Janeiro. FIP was quantified in the concentration range of 0.132-2.44 μg/L, while FIP-S was detected in most samples. This is the first study on the occurrence of FIP and FIP-S in the Guandu River basin, presenting values high enough to justify the need for monitoring studies in a region of great importance for the city of Rio de Janeiro.

Exposure to Fipronil Insecticide in the Sixth Total Diet Study — China, 2016–2019

What is already known about this topic?

What is added by this report?

What are the implications for public health practice?

Neurotoxicity of fipronil affects sensory and motor systems in zebrafish

Fipronil is a phenylpyrazole insecticide that may selectively inhibit gamma-aminobutyric acid receptors in insects. Although fipronil is the most widely used insecticide in aquatic environments, few studies have evaluated its neurotoxicity for the sensory and motor systems of aquatic vertebrates. We assessed the effects of acute fipronil exposure on the survival rate, number of hair cells of lateral lines, and neurotoxicity for zebrafish (Danio rerio). In addition, heat maps and the speed and distance of the swimming trajectory were compared between zebrafish subjected to the sham and fipronil treatments. Western blotting and immunohistochemistry were conducted separately to compare expressions of oxidative stress, inflammation, apoptosis, and neurotoxicity related proteins in the brain tissue between adult zebrafish with sham and fipronil treatments. Our results indicated that the survival rates and the speed and distance of the swimming trajectory significantly decreased for adult zebrafish exposed to fipronil. The results also suggested that the number of hair cells of lateral lines significantly reduced for zebrafish embryos exposed to fipronil. In histopathology and Western blotting tests, substantial oxidative stress, inflammation, and apoptosis were observed in the brain tissue of adult zebrafish exposed to fipronil. Our results revealed that fipronil toxicity may impair sensory and motor systems in zebrafish because of damage to lateral hair cells and brain tissue through oxidative stress, inflammation, and apoptosis, which in turn result in a significantly reduced survival rate and impaired locomotion. The behavioral responses of zebrafish exposed to fipronil toxicity should be determined for better understanding the reliability of behavioral biomarkers in the risk assessment of environmental toxicology.

Multibiomarker responses and bioaccumulation of fipronil in Prochilodus lineatus exposed to spiked sediments: Oxidative stress and antioxidant defenses

Fipronil is a current use pesticide, widely used in many crops, commonly adsorbed to sediments of aquatic environments. The purpose of this study was to evaluate the biomarker responses and fipronil distribution pattern in different matrixes (fish, sediment and water) after juveniles P. lineatus exposure at two environmental concentrations (5.5 and 82 μg kg^--1) of fipronil-spiked sediments. The levels of oxidized proteins (PO), lipid peroxidation (LPO), and enzymatic activity of superoxide dismutase (SOD), reduced glutathione content (GSH), antioxidant capacity against peroxyls (ACAP) and acetylcholinesterase (AChE) were evaluated in liver, gills and brain. Concentrations of fipronil and its metabolites (f. desulfinyl, f sulphpHide and f. sulfone) were quantified by GC-ECD. F. desulfinyl was the major metabolite found in all matrixes, followed by f. sulphide in sediments, while f. sulfone was mainly accumulated in fish. Fipronil promoted oxidative stress in P. lineatus, as evidenced by the increases in LPO and PO levels and the decrease brain AChE activity. Fish exposed at both concentrations showed significant decrease in antioxidant capacity. Alterations in the antioxidant defenses system was evidenced in all organs. These results suggest that the occurrence of fipronil in aquatic environments can generate oxidative stress at different levels in P. lineatus, showing that this species is highly sensitive to the deleterious effects of fipronil and metabolites.

The effects of fipronil exposure on oxidative stress, non-specific immunity, autophagy, and apoptosis in the common carp

The increase in the area treated with the insecticide fipronil has caused concern for aquatic organisms such as fish. Here, we assessed the effect of fipronil on carp indexes of non-specific immunity, oxidative stress, autophagy, and apoptosis following exposure to 0.074 mg/L and 0.185 mg/L of fipronil in the aqueous environment for 1 day, 3 days, 5 days, and 7 days. It was found that glutathione (GSH), malonaldehyde (MDA), and superoxide dismutase (SOD) in gills were significantly reduced (P < 0.05). The increase in exposure time increases the impact on GSH, SOD, and MDA parameters in the liver and intestine. Liver acid phosphatase (ACP), alkaline phosphatase (AKP), and lysozyme (LZM) activity levels increased significantly in the treatment group on the first day after exposure, except for the 0.074 mg/L group of ACP (P < 0.05). The mRNA expression levels of autophagy-related genes ATG12, ATG5, ATG16L, LC3-II, and BECN1 were generally elevated in the liver and intestine during the initial exposure period (P < 0.05), while mTOR was significantly reduced on the first and third days after treatment (P < 0.05). From the results of Western blotting (WB), we can see that the amount of LC3-II was significantly higher than that of LC3-I at 1, 3, and 5 days of exposure (P < 0.05). Furthermore, the apoptosis-related gene Bcl-2 reached its peak in the liver, intestine, and gill on the first day, and caspase3 was significantly downregulated throughout the exposure period (P < 0.05). The results showed that fipronil was potentially harmful to carp and should be used moderately to reduce the damage to aquatic ecosystems. This study complements the mechanism theory of fipronil on fish toxicology and has a certain value for human health risk assessment.

Effects of the insecticide fipronil in freshwater model organisms and microbial and periphyton communities

Fipronil is a broad-spectrum insecticide whose release in the environment damages many non-target organisms. This study evaluated the toxicity of fipronil at two biological levels using in vivo conditions and environmentally relevant concentrations: the first based on two model organisms (aquatic invertebrate Daphnia magna and the unicellular freshwater alga Chlamydomonas reinhardtii) and a second based on three natural communities (river periphyton and freshwater and soil microbial communities). The physicochemical properties of fipronil make it apparently unstable in the environment, so its behaviour was followed with high performance liquid chromatography (HPLC) under the different test conditions. The most sensitive organism to fipronil was D. magna, with median lethal dose (LC₅₀) values from 0.07 to 0.38 mg/L (immobilisation test). Toxicity was not affected by the media used (MOPS or river water), but it increased with temperature. Fipronil produced effects on the photosynthetic activity of C. reinhardtii at 20 °C in MOPS (EC₅₀ = 2.44 mg/L). The freshwater periphyton presented higher sensitivity to fipronil (photosynthetic yield EC₅₀ of 0.74 mg/L) in MOPS and there was a time-dependent effect (toxicity increased with time). Toxicity was less evident when periphyton and C. reinhardtii tests were performed in river water, where the solubility of fipronil is poor. Finally, the assessment of the metabolic profiles using Biolog EcoPlates showed that bacteria communities were minimally affected by fipronil. The genetic identification of these communities based on 16S rRNA gene sequencing revealed that many of the taxa are specialists in degrading high molecular weight compounds, including pesticides. This work allows us to better understand the impact of fipronil on the environment at different levels of the food chain and in different environmental conditions, a necessary point given its presence in the environment and the complex behaviour of this compound.

Short-term effects of pesticide fipronil on behavioral and physiological endpoints of Daphnia magna

Fipronil (FIP) is an organic pesticide with many practical uses. Although some results indicated toxic effects in some terrestrial and aquatic animal species, little is known on its influence on behavioral and physiological endpoints of cladocerans. The aim of our study was to determine the short-term effects of FIP at concentrations of 0.1 μg/L, 1 μg/L, 10 μg/L, and 100 μg/L on Daphnia magna sublethal indices: behavioral (swimming speed, distance traveled) and physiological endpoints (heart rate, post-abdominal claw activity and thoracic limb movements). The results showed that FIP induced reduction of swimming speed and distance traveled in a concentration- and time-dependent manner at all the concentrations used. The lowest concentration of the insecticide temporarily stimulated post-abdominal claw activity after 24 h and thoracic limb activity after 48 h; however, the highest concentrations reduced all the studied physiological endpoints. IC50 values showed that thoracic limb activity, swimming speed, and distance traveled were most sensitive to FIP after 24-h exposure. The most sensitive parameter after 48 h and 72 h was swimming speed and post-abdominal claw activity, respectively. The study indicated that (i) behavioral and physiological endpoints of Daphnia magna are reliable and valuable sublethal indicators of toxic alterations induced by FIP; however, they respond with different sensitivity at various times of exposure, (ii) FIP may alter cladoceran behavior and physiological processes at concentrations detected in the aquatic environment; therefore, it should be considered as an ecotoxicological hazard to freshwater cladocerans.

Fiproles as a proxy for ecological risk assessment of mixture of fipronil and its degradates in effluent-dominated surface waters

Environmental risk assessment of complex chemical mixtures has increasingly been prioritized as a management goal, especially in the regulatory sector. Although fipronil and its three degradates (-sulfone, -sulfide and -desulfinyl) have been frequently quantified in waterways, little information is available about the likelihood and magnitude of ecological risk posed by these chemical mixtures - collectively known as fiproles - in surface water. In the present study, a probabilistic risk assessment of mixtures of fipronil and its three degradates was conducted for three effluent-dominated southern California rivers: Los Angeles River (LAR), San Gabriel River (SGR) and Santa Clara River (SCR), California, USA. The assessments, which used fiproles as an integrated proxy, were based on three levels of toxicity endpoints: median lethal concentration (LC50), half-maximal effective concentration (EC50), and lowest observed effect concentration (LOEC), to gain comprehensive assessment information. Probabilistic approaches based on species sensitivity distribution (SSD) and exposure concentration distribution (ECD) were developed with the log-logistic model by pooling the toxicity and occurrence data, respectively. The 5th percentile hazardous concentrations (HC5s) were calculated to be at low parts per billion levels, enabling these values to be used to estimate the chemical-specific benchmarks for components that lack ecotoxicity data. The single substance potentially affected fraction (ssPAF) of fiproles revealed risk levels for the three rivers in descending order: LAR ≥ SGR > SCR. The overall risk probability estimated from the joint probability curve (JPC) by Monte Carlo simulation was 1.13 ± 0.20% (LC50), 9.31 ± 1.46% (EC50), and 6.58 ± 1.43% (LOEC) for the three rivers collectively. These results derived from the fiproles indicates that fipronil and its degradates pose risks to the aquatic organisms in the surface water of the three rivers. The present study provides a methodology for the use of a proxy in the risk assessment of chemical mixtures.

A mixture of fipronil and fungicides induces alterations on behavioral and oxidative stress parameters in zebrafish

Pesticide commercial mixtures, including the insecticide fipronil and the fungicides pyraclostrobin and methyl-thiophanate, have been used in concomitant pest control, facilitating agricultural management. Their widespread use can lead to soil and water contamination and potentially induce damages in the ecosystem, producing toxic effects in non-target organisms. Despite their toxicological potential, their effects on behavioral and biochemical parameters are not well understood. Here we investigated the effects of the mixture of fipronil and fungicides (MFF) pyraclostrobin and methyl- thiophanate on behavioral and biochemical parameters of oxidative stress in adult zebrafish. Animals exposed to the highest MFF tested concentration showed a decrease in the total distance traveled and in the number of crossings in the different zones of the tank. Furthermore, animals exposed to highest MFF tested concentration spent more time in water surface. In addition, our data showed that the exposure to this preparation promoted a decrease in non-protein thiol content as well as in catalase activity. Finally, pesticide exposure induced an increase in the superoxide dismutase/catalase ratio. Our results indicate that alterations in behavioral and oxidative parameters are involved in MFF toxicity in zebrafish. The antioxidant mechanisms analyzed were altered in concentrations that did not affect zebrafish behavior. Therefore, the assessment of oxidative stress parameters in zebrafish brains could be very useful to detect the early effects of environmental exposure to the MFF.

In vitro biotransformation of pharmaceuticals and pesticides by trout liver S9 in the presence and absence of carbamazepine

The aim of the present study was to develop (i) a technique for identifying metabolites of organic contaminants by using an in vitro system of trout S9 and liquid chromatography-high-resolution mass spectrometry-based identification method and (ii) to apply this technique to identify the interactive potential of carbamazepine on the formation rate of other metabolites. The pharmaceuticals carbamazepine and propranolol and the pesticides azoxystrobin, diazinon, and fipronil were selected as test contaminants. As a result, a total of ten metabolites were identified for the five parent substances, six of which were confirmed using reference standards. Metabolic reactions included hydroxylation, epoxidation, S-oxidation, and dealkylation. The metabolic transformation rate ranged from 0.2 to 3.5 pmol/mg protein/min/μmol substrate. In the binary exposure experiment with increasing carbamazepine concentration, the formation rates of diazinon and fipronil metabolites (MDI2 and MFP2, respectively) increased, while formation of metabolites of propranolol and azoxystrobin (MPR1, MPR2, MPR3, and MAZ1) slowed down. Meanwhile, S9 pre-exposed to carbamazepine produced diazoxon, a toxic metabolite of diazinon, and pyrimidinol, a less toxic metabolite, more rapidly. These results suggest that carbamazepine, a perennial environmental pollutant, might modulate the toxicity of other substances such as diazinon but further in vivo studies are needed.

Anthropogenic contaminants of high concern: Existence in water resources and their adverse effects

Existence of anthropogenic contaminants (ACs) in different environmental matrices is a serious and unresolved concern. For instance, ACs from different sectors, such as industrial, agricultural, and pharmaceutical, are found in water bodies with considerable endocrine disruptors potency and can damage the biotic components of the environment. The continuous ACs exposure can cause cellular toxicity, apoptosis, genotoxicity, and alterations in sex ratios in human beings. Whereas, aquatic organisms show bioaccumulation, trophic chains, and biomagnification of ACs through different entry route. These problems have been found in many countries around the globe, making them a worldwide concern. ACs have been found in different environmental matrices, such as water reservoirs for human consumption, wastewater treatment plants (WWTPs), drinking water treatment plants (DWTPs), groundwaters, surface waters, rivers, and seas, which demonstrate their free movement within the environment in an uncontrolled manner. This work provides a detailed overview of ACs occurrence in water bodies along with their toxicological effect on living organisms. The literature data reported between 2017 and 2018 is compiled following inclusion-exclusion criteria, and the obtained information was mapped as per type and source of ACs. The most important ACs are pharmaceuticals (diclofenac, ibuprofen, naproxen, ofloxacin, acetaminophen, progesterone ranitidine, and testosterone), agricultural products or pesticides (atrazine, carbendazim, fipronil), narcotics and illegal drugs (amphetamines, cocaine, and benzoylecgonine), food industry derivatives (bisphenol A, and caffeine), and personal care products (triclosan, and other related surfactants). Considering this threatening issue, robust detection and removal strategies must be considered in the design of WWTPs and DWTPs.

Mixed-chemical exposure and predicted effects potential in wadeable southeastern USA streams

Complex chemical mixtures have been widely reported in larger streams but relatively little work has been done to characterize them and assess their potential effects in headwater streams. In 2014, the United States Geological Survey (USGS) sampled 54 Piedmont streams over ten weeks and measured 475 unique organic compounds using five analytical methods. Maximum and median exposure conditions were evaluated in relation to watershed characteristics and for potential biological effects using multiple lines of evidence. Results demonstrate that mixed-contaminant exposures are ubiquitous and varied in sampled headwater streams. Approximately 56% (264) of the 475 compounds were detected at least once across all sites. Cumulative maximum concentrations ranged 1,922-162,346ngL^-1 per site. Chemical occurrence significantly correlated to urban land use but was not related to presence/absence of wastewater treatment facility discharges. Designed bioactive chemicals represent about 2/3rd of chemicals detected, notably pharmaceuticals and pesticides, qualitative evidence for possible adverse biological effects. Comparative Toxicogenomics Database chemical-gene associations applied to maximum exposure conditions indicate >12,000 and 2,900 potential gene targets were predicted at least once across all sites for fish and invertebrates, respectively. Analysis of cumulative exposure-activity ratios provided additional evidence that, at a minimum, transient exposures with high probability of molecular effects to vertebrates were common. Finally, cumulative detections and concentrations correlated inversely with invertebrate metrics from in-stream surveys. The results demonstrate widespread instream exposure to extensive contaminant mixtures and compelling multiple lines of evidence for adverse effects on aquatic communities.

The Terminalia laxiflora modulates the neurotoxicity induced by fipronil in male albino rats

The extensive use of fipronil (FPN) may trigger hazards to more than insects. The present investigation was carried out to evaluate the abrogating role of Terminalia laxiflora (TL) methanol extract (TLE) against the neurotoxic effects provoked by FPN. Fourty male albino rats were assigned into four equal groups. The first group served as control, the second one was orally administered FPN (10.5 mg/kg BW), the third group was given combination of FPN and TLE) (100 mg/kg BW), and the fourth one was orally given TLE. Our findings highlighted the efficacy of TLE as a neuroprotectant through a significant reduction in malondialdehyde (MDA) content by 25.8%, elevations of the reduced glutathione (GSH) level, catalase (CAT,) and superoxide dismutase (SOD) activities by 30.9, 41.2, and 48.2% respectively. Consequently, the relative mRNA levels of both Bax and caspase-3 were down-regulated by 40.54% and caspase-3 by 30.35% compared with the control group. Moreover, restoration of the pathological tissue injuries were detected. In conclusion, TLE proved to be a potent neuroprotective agent against the FPN-induced toxicity.

Maternal exposure to fipronil results in sulfone metabolite enrichment and transgenerational toxicity in zebrafish offspring: Indication for an overlooked risk in maternal transfer?

Ecotoxicological studies show the association between pesticide pollution and transgenerational toxicity in aquatic organisms. However, a less considered risk is that many pesticides can be metabolized and transferred to offspring as new toxicants. In this study, we used zebrafish to evaluate the maternal transfer risk of fipronil (FIP), which is a great threat to aquatic organisms with toxic metabolite formation. After 28-day exposure to environmentally relevant concentrations (1.0, 5.0 and 10.0 μg/L) of FIP in adult female zebrafish (F0), the toxicants off-loading and transgenerational toxicity in offspring were studied. High burdens of FIP and its sulfone metabolite were found in both F0 and the embryos (F1), resulting in increased CYP450 activity. The residual levels of the metabolite were higher than those of the parent compound. Chiral analysis further showed a preferential accumulation of S-enantiomer of FIP in both F0 and F1. Maternal exposure to FIP increased the malformation rate and decreased the swim speed in larvae. Additionally, after exposure, the levels of thyroid hormones (THs), including triiodothyronine (T3) and thyroxine (T4), decreased in both generations, particularly in the F1. Gene transcription expression along the hypothalamic-pituitary-thyroid (HPT) axis was also significantly affected. Maternal exposure to FIP increased sulfone metabolite enrichment and cause multiple toxic effects in F1. Findings from this study highlight the key role of biologically active product formation in the maternal transfer of pollutants and associated risk assessment.

Quantitative Detection of Fipronil and Fipronil-Sulfone in Sera of Black-Tailed Prairie Dogs and Rats after Oral Exposure to Fipronil by Camel Single-Domain Antibody-Based Immunoassays

The insecticide fipronil can be metabolized to its sulfone in mammalian species. Two camel single-domain antibodies (VHHs) F1 and F6, selective to fipronil and fipronil-sulfone, respectively, were generated and used to develop enzyme linked immunosorbent assays (ELISAs) for the detection of the two compounds in the sera of black-tailed prairie dogs and rats. The limits of detection of fipronil and fipronil-sulfone in the rodent sera by the corresponding ELISAs were 10 and 30 ng mL-1, and the linear ranges were 30-1000 and 75-2200 ng mL-1. ELISAs showed a good recovery for fipronil and fipronil-sulfone cospiked in the control sera of the black-tailed prairie dogs (90-109%) and rats (93-106%). The VHH-based ELISAs detected fipronil and fipronil-sulfone in the sera of the rodents that received a repeated oral administration of fipronil. The average concentration of fipronil-sulfone was approximately 3.2-fold higher than fipronil in the prairie dog sera (1.15 vs 0.36 μg mL-1) and rat sera (1.77 vs 0.53 μg mL-1). ELISAs agreed well with a liquid chromatography-mass spectrometry method for the quantification of both fipronil and fipronil-sulfone in real serum samples. Fipronil-sulfone was identified as the predominant metabolite of fipronil in the black-tailed prairie dog and rat sera.

Effects of short-term, sublethal fipronil and its metabolite on dragonfly feeding activity

Dragonflies, Sympetrum spp., are indispensable to agriculture and are a central element of culture in Japan. However, S. frequens populations in rice paddy fields have declined in recent decades. Dragonfly larvae are predatory aquatic insects that feed on other organisms found in habitats with slow-moving or standing water. The increasing use of fipronil and neonicotinoid insecticides in agriculture is also increasing exposure to Sympetrum spp. in larval stages through paddy soil and water. The role of fipronil insecticides in the decline of dragonflies is of concern, and we here examine the sublethal effects of this insecticide on the feeding behaviors of two Sympetrum spp. Based on the quantity of prey items consumed and the time to capture prey items, feeding inhibition was determined to be a potential mechanism of the decline of Sympetrum spp. following 48-h exposure to fipronil and fipronil sulfone. Prey consumption by S. infuscatum was significantly reduced for fipronil sulfone at all concentrations (0.01-1000 μg/L). S. frequens exposed to 1, 10, 100 and 1000 μg/L fipronil sulfone had significantly longer prey capture times. Fipronil sulfone was 2.8, 9.7 and 10.5 times more toxic to S. infuscatum than fipronil in terms of acute toxicity, feeding inhibition and delayed toxicity, respectively. In addition, fipronil sulfone was 6.6, 2.9 and 9.1 times more toxic, respectively, to S. frequens than fipronil. Our findings suggest that sublethal effects on feeding inhibition lead to severe mortality at realistic paddy soil and water concentrations. Our results provide the first demonstration that short-term exposure to fipronil and fipronil sulfone can consequently cause significant harm to dragonfly larvae survival due to feeding inhibition. These findings have implications for current pesticide risk assessment and dragonfly protection.

The impacts of modern-use pesticides on shrimp aquaculture: An assessment for north eastern Australia

The use of pyrethroid and neonicotinoid insecticides has increased in Australia over the last decade, and as a consequence, increased concentrations of the neonicotinoid insecticide imidacloprid have been measured in Australian rivers. Previous studies have shown that non-target crustaceans, including commercially important species, can be extremely sensitive to these pesticides. Most shrimp farms in Australia are predominantly located adjacent to estuaries so they can obtain their required saline water, which support multiple land uses upstream (e.g. sugar-cane farming, banana farming, beef cattle and urbanisation). Larval and post-larval shrimp may be most susceptible to the impacts of these pesticides because of their high surface area to volume ratio and rapid growth requirements. However, given the uncertainties in the levels of insecticides in farm intake water and regarding the impacts of insecticide exposure on shrimp larvae, the risks that the increased use of new classes of pesticide pose towards survival of post-larval phase shrimp cannot be adequately predicted. To assess the potential for risk, toxicity in 20day past hatch post-larval Black Tiger shrimp (Penaeus monodon) to modern use insecticides, imidacloprid, bifenthin, and fipronil was measured as decreased survival and feeding inhibition. Post-larval phase shrimp were sensitive to fipronil, bifenthrin, and imidacloprid, in that order, at concentrations that were comparable to those that cause mortality other crustaceans. Bifenthrin and imidacloprid exposure reduced the ability of post-larval shrimp to capture live prey at environmentally realistic concentrations. Concentrations of a broad suite of pesticides were also measured in shrimp farm intake waters. Some pesticides were detected in every sample. Most of the pesticides detected were measured below concentrations that are toxic to post-larval shrimp as used in this study, although pesticides exceed guideline values, suggesting the possibility of indirect or mixture-related impacts. However, at two study sites, the concentrations of insecticides were sufficient to cause toxicity in shrimp post larvae, based on the risk assessment undertaken in this study.

The effects of fipronil and the photodegradation product fipronil desulfinyl on growth and gene expression in juvenile blue crabs, Callinectes sapidus, at different salinities

Endocrine disrupting compounds (EDCs) are now widely established to be present in the environment at concentrations capable of affecting wild organisms. Although many studies have been conducted in fish, less is known about effects in invertebrates such as decapod crustaceans. Decapods are exposed to low concentrations of EDCs that may cause infertility, decreased growth, and developmental abnormalities. The objective herein was to evaluate effects of fipronil and its photodegradation product fipronil desulfinyl. Fipronil desulfinyl was detected in the eggs of the decapod Callinectes sapidus sampled off the coast of South Carolina. As such, to examine specific effects on C. sapidus exposed in early life, we exposed laboratory-reared juveniles to fipronil and fipronil desulfinyl for 96h at three nominal concentrations (0.01, 0.1, 0.5μg/l) and two different salinities (10, 30ppt). The size of individual crabs (weight, carapace width) and the expression of several genes critical to growth and reproduction were evaluated. Exposure to fipronil and fipronil desulfinyl resulted in significant size increases in all treatments compared to controls. Levels of expression for vitellogenin (Vtg), an egg yolk precursor, and the ecdysone receptor (EcR), which binds to ecdysteroids that control molting, were inversely correlated with increasing fipronil and fipronil desulfinyl concentrations. Effects on overall growth and on the expression of EcR and Vtg differ depending on the exposure salinity. The solubility of fipronil is demonstrated to decrease considerably at higher salinities. This suggests that fipronil and its photodegradation products may be more bioavailable to benthic organisms as salinity increases, as more chemical would partition to tissues. Our findings suggest that endocrine disruption is occurring through alterations to gene expression in C. sapidus populations exposed to environmental levels of fipronil, and that effects may be dependent upon the salinity at which exposure occurs.

Optimization of fipronil degradation by heterogeneous photocatalysis: Identification of transformation products and toxicity assessment

In this work it was studied the degradation of the insecticide fipronil (FIP) by heterogeneous photocatalysis induced by TiO₂ P25. Using chemometric methods (Factorial Design and Response Surface Methodology), it was possible to evaluate the role of interaction between pH of the reaction medium, the reaction time and concentration of TiO₂, optimizing the conditions for degradation using artificial radiation. Under the optimized conditions (79.4 mg L^-1 TiO₂ and 66.3 min of reaction time for 1.1 mg L^-1 of FIP, at pH 5.6-5.8 (natural pH of the irradiated suspension)), 90.9% of FIP degradation was achieved at a degradation rate of 1.54 × 10^-2 m² kJ^-1 in terms of accumulated UVA radiation, corresponding to a pseudo-first order rate constant of 1.34 × 10^-2 min^-1 and a half-life of 51.7 min. Under the same conditions, these assays were extended to the use of solar radiation, when the degradation rate was 14% higher, with half-life of 45 min, suggesting that in both cases FIP degradation was successful. Four by-products of FIP photocatalytic degradation could be separated, identified, and their formation and consumption followed by UHPLC-Q-TOF. Although the same intermediates have been obtained using both irradiation sources, a faster degradation of the transformation products (TPs) was observed under solar irradiation due to its expressive photonic flux covering the UVA and UVB. It is noteworthy that both the untreated effluent and the identified compounds have low toxicity with respect to V. fischeri, suggesting that the heterogeneous photocatalysis may be a good alternative for treatment of wastewaters containing FIP and its TPs, mainly when solar radiation is the source of radiation, since under this condition the power consumption during the treatment can be significantly reduced.

A statistical assessment of pesticide pollution in surface waters using environmental monitoring data: Chlorpyrifos in Central Valley, California

Pesticides are routinely monitored in surface waters and resultant data are analyzed to assess whether their uses will damage aquatic eco-systems. However, the utility of the monitoring data is limited because of the insufficiency in the temporal and spatial sampling coverage and the inability to detect and quantify trace concentrations. This study developed a novel assessment procedure that addresses those limitations by combining 1) statistical methods capable of extracting information from concentrations below changing detection limits, 2) statistical resampling techniques that account for uncertainties rooted in the non-detects and insufficient/irregular sampling coverage, and 3) multiple lines of evidence that improve confidence in the final conclusion. This procedure was demonstrated by an assessment on chlorpyrifos monitoring data in surface waters of California's Central Valley (2005-2013). We detected a significant downward trend in the concentrations, which cannot be observed by commonly-used statistical approaches. We assessed that the aquatic risk was low using a probabilistic method that works with non-detects and has the ability to differentiate indicator groups with varying sensitivity. In addition, we showed that the frequency of exceedance over ambient aquatic life water quality criteria was affected by pesticide use, precipitation and irrigation demand in certain periods anteceding the water sampling events.

Influence of Three Citrus Herbicides on Potential Production of Sorghum bicolor 'Topper 76-6' as a Bioenergy Crop

Planting bioenergy crops on land previously used for citrus production may offer an alternative source of revenue for growers looking for alternative-to-citrus crops. However, residual herbicides used in citrus production may adversely affect alternative crops. This study evaluated effects of three herbicides (bromacil, norflurazon, and simazine) commonly used in citrus production on the bioenergy crop Sorghum bicolor 'Topper 76-6'. Plants were exposed to herbicides in soil for 1-5 weeks and observations of effects on photosynthetic quantum yield, leaf greenness, height, and biomass were made. Results indicate that concentrations of bromacil and norflurazon greater than 0.09 and 0.07 mg/kg and simazine >0.46 mg/kg will impair growth and development in similar soils. Concentrations below these may also be toxic.

Fipronil and two of its transformation products in water and European eel from the river Elbe

Fipronil is an insecticide which, based on its mode of action, is intended to be predominantly toxic towards insects. Fipronil bioaccumulates and some of its transformation products were reported to be similar or even more stable in the environment and to show an enhanced toxicity against non-target organisms compared to the parent compound. The current study investigated the occurrence of Fipronil and two of its transformation products, Fipronil-desulfinyl and Fipronil-sulfone, in water as well as muscle and liver samples of eels from the river Elbe (Germany). In water samples total concentrations of FIP, FIP-d and FIP-s ranged between 0.5-1.6ngL(-1) with FIP being the main component in all water samples followed by FIP-s and FIP-d. In contrast, FIP-s was the main component in muscle and liver tissues of eels with concentrations of 4.05±3.73ngg(-1) ww and 19.91±9.96ngg(-1) ww, respectively. Using a physiologically based toxicokinetic (PBTK) model for moderately hydrophobic organic chemicals, the different distributions of FIP, FIP-d and FIP-s in water and related tissue samples could be attributed to metabolic processes of eels. The measured concentrations in water of all analytes and their fractional distribution did not reflect the assumed seasonal application of FIP and it seems that the water was constantly contaminated with FIP, FIP-d and FIP-s.

Coupling coagulation, flocculation and decantation with photo-Fenton process for treatment of industrial wastewater containing fipronil: Biodegradability and toxicity assessment

This work reports the treatment of wastewater containing the insecticide fipronil, integrating coagulation, flocculation and decantation in the photo-Fenton process. Under the best concentration of the coagulant - Fe(3+) (56 mg L(-1)), the suspended solids and total fipronil concentrations decreased respectively from 7000 and 20.9 mg L(-1) to 590 and 2.2 mg L(-1), but without reduction in dissolved organic carbon - DOC (1760 mg C L(-1)) and acute toxicity to Artemia salina (100%). Subsequently, the photo-Fenton process was applied as alternative of pre- or complete treatment, taking into account toxicity and biodegradability (given by biochemical oxygen demand after five days - BOD5/chemical oxygen demand - COD ratio) assessment. The best DOC and COD removal were reached with 60 and 6723 mg L(-1) of Fe(2+) and H2O2, respectively. Under these conditions, after 60 min of irradiation, 57% of DOC and 74% of COD were removed, with a decrease in acute toxicity to A. salina from 100% to 13% and an increase in the BOD5/COD ratio from 0.052 to 1.0. With these parameters, the integration of coagulation/flocculation/decantation and photo-Fenton processes may be an alternative to the pre- or complete treatment of wastewater containing fipronil.

Enantioselective Metabolism of Flufiprole in Rat and Human Liver Microsomes

The enantioselective metabolism of flufiprole in rat and human liver microsomes in vitro was investigated in this study. The separation and determination were performed using a liquid chromatography system equipped with a triple-quadrupole mass spectrometer and a Lux Cellulose-2 chiral column. The enantioselective metabolism of rac-flufiprole was dramatically different in rat and human liver microsomes in the presence of the β-nicotinamide adenine dinucleotide phosphate regenerating system. The half-lives (t1/2) of flufiprole in rat and human liver microsomes were 7.22 and 21.00 min, respectively, for R-(+)-flufiprole, whereas the values were 11.75 and 17.75 min, respectively, for S-(-)-flufiprole. In addition, the Vmax of R-(+)-flufiprole was about 3-fold that of S-(-)-flufiprole in rat liver microsomes, whereas its value in the case of S-(-)-flufiprole was about 2-fold that of R-(+)-flufiprole in human liver microsomes. The CLint of rac-flufiprole also showed opposite enantioselectivy in rat and human liver microsomes. The different compositions and contents of metabolizing enzyme in the two liver microsomes might be the reasons for the difference in the metabolic behavior of the two enantiomers.