Occurrence, spatiotemporal distribution, and risk assessment of current-use pesticides in surface water: A case study near Taihu Lake, China

Oxidative stress and metal homeostasis alterations in Danio rerio (zebrafish) under single and combined carbamazepine, acetamiprid and cadmium exposures

Contaminants of emerging concern (CEC) are routinely detected in aquatic environments, especially pharmaceuticals, such as carbamazepine (CBZ), and neonicotinoid pesticides, like acetamiprid (ACT). CECs can interact with each other and with other legislated contaminants like Cd, resulting in unknown effects. Most studies evaluate only the effects of single contaminant exposures on aquatic biota. Therefore, the aim of the present study was to assess the effects of both single and combined CBZ, ACT and Cd exposures on zebrafish brain and liver oxidative stress parameters and metal homeostasis. The biomarkers catalase (CAT), glutathione-S-transferase (GST), total thiols (TOT), metallothionein (MT) and malondialdehyde (MDA) and the essential elements Ca, Cu, K, Na, Mg, Mn and Zn were evaluated after 96-hour static exposures. CBZ, ACT and Cd single (brain and liver) and combined (liver) treatments resulted in oxidative effects in both fish organs, also leading to metal (Ca, Mg, K, Mn, Zn and Cu) homeostasis alterations. ACT exposure resulted in the greatest adverse effects in the brain, while CBZ was the cause of major element homeostasis and oxidative stress alterations in the liver. Lower LPO levels were observed in the combined treatments compared to single treatments, suggesting interactions and contaminant effect attenuation. This study is the first to evaluate the initial effects of combined CBZ, ACT and Cd exposures in zebrafish, paving the way for further investigations concerning other biomarkers during longer exposure times.

Network Pharmacology Combined with Metabolomics Approach to Investigate the Toxicity Mechanism of Paclobutrazol

Paclobutrazol (PBZ) is a commonly used plant growth regulator (PGR) with good antibacterial activity. It has widespread applications in agricultural production. However, there is limited research reported on the potential risks of human health resulting from PBZ residues. In this study, using Sprague-Dawley rats, we carried out a systematic study on the hepatotoxicity and nephrotoxicity of PBZ in different doses (0.2, 0.5, and 1.0 g/kg). The metabolic profiles and network pharmacology were combined to construct a PBZ-endogenous substances-gene-hepatorenal diseases network to elucidate the underlying mechanism of PBZ's hepatorenal toxicity. At first, metabolomics analysis was done to investigate the metabolites and the related metabolic pathways associated with PBZ. Secondly, the network pharmacology approach was used in further exploration of the toxic targets. Additionally, molecular docking was carried out to investigate the interactions between PBZ and potential targets. The results indicated that PBZ showed obvious toxicity towards the liver and kidney of rats. The metabolomics analysis showed that PBZ mainly affected 4 metabolic pathways, including tryptophan metabolism, arachidonic acid metabolism, linoleic acid metabolism, and purine metabolism. Network pharmacology and molecular docking revealed that CYP1A2, CYP2A6, CYP2E1, MAOA, PLA2G2A, PTGS1, and XDH were critical targets for PBZ hepatorenal toxicity. This preliminary study revealed PBZ's hepatorenal toxicity and provided a theoretical basis for the rational and safe use of PBZ. Furthermore, it provided possible intervention targets for further research on how to avoid or reduce the damage caused by pesticides to the human body.

Ecological risk assessment for difenoconazole in aquatic ecosystems using a web-based interspecies correlation estimation (ICE)-species sensitivity distribution (SSD) model

Difenoconazole is a typical triazole fungicide that can inhibit demethylation during ergosterol synthesis. Due to its wide use, difenoconazole is frequently detected in surface water, paddy water, agricultural water, and other aquatic environments. Presently, an assessment of the ecological risk posed by difenoconazole in aquatic ecosystems is lacking. Here, a web-based interspecies correlation estimation (ICE)-species sensitivity distribution (SSD) model was first applied to assess the ecological risk of difenoconazole in aquatic environments. Meanwhile, maximum acceptable concentration (MAC), maximum risk-free concentration (MRFC), and risk quotient (RQ) values were used to evaluate the potential risk of difenoconazole to aquatic organisms. Our results showed that an aquatic MAC value of 0.31 μg/L was acceptable for difenoconazole in aquatic environments. Further, the detected concentration of difenoconazole was lower than the MRFC value of 0.09 μg/L indicating no risk to aquatic organisms. Assessment data suggested that difenoconazole exhibited potential risks to eight studied aquatic ecosystems (including surface water, paddy water, and agricultural water) in different countries (RQ > 1), indicating that difenoconazole overuse could cause adverse effects to aquatic organisms in these aquatic ecosystems. Thus, restricted use and rational use of difenoconazole are recommended.

Unveiling the mechanism of imidacloprid removal by ferrate(VI): Kinetics, role of oxidation and adsorption, reaction pathway and toxicity assessment

Imidacloprid (IMI), an emerging pollutant, has high toxicity to non-target organisms. This paper presents the kinetics of IMI removal by ferrate(VI) at different pH (6.0-9.0), molar ratios ([ferrate(VI)]:[IMI]) and added Fe(III) ions. The apparent second-order rate constant (k_app) decreased with increase in pH from pH 6.0 to 9.0 (i.e., (1.2 ± 0.1) × 10² M^-1 s^-1 to (8.3 ± 0.3) M^-1 s^-1). The species-specific rate constants were obtained as k (HFeO₄^-) = 1.3 × 10² M^-1 s^-1 and k (FeO₄^2-) = 6.9 M^-1 s^-1. The decreases in the concentration of HFeO₄^- with increase in pH caused the observed pH dependence in k_app. At pH 7.0, the removal of IMI increased with the molar ratio from 1.0 to 10.0 with complete removal at the highest ratio. The variation in pH from 6.0 to 9.0 had no obvious effect on removal of IMI. Experiments indicate that IMI removal is mainly by ferrate(VI) oxidation and to a lesser extent by Fe(III) adsorption. Mineralization of IMI was also observed (20-26%). The addition of Fe(III) ions to ferrate(VI)-IMI at pH 7.0 and 8.0 resulted in enhanced removal of IMI, but the presence of Ca²⁺, SO₄^2-, HCO₃^-, and humic acid (HA) has negative effects. The presence of coexisting substances in river water slightly decreased IMI removal by ferrate(VI) by less than 10%. Identification of products and frontier electron density (FED) calculations demonstrated involvement of opening of the five-membered heterocyclic moiety of IMI by ferrate(VI). Toxicity assessment with NIH 3T3 fibroblasts and ECOSAR analysis indicated lower toxicity of oxidized products than parent IMI.

Removal of Tricyclazole and Total Organic Carbon in Real Pesticide Wastewater by Electro-Fenton

In this study, electro-Fenton (EF) was employed for the removal of tricyclazole (TC) and total organic carbon (TOC) in real pesticide wastewater (RPW). The central composite design (CCD) with three parameters, that is, current density, Fe2+ concentration, and electrolysis time, has been conducted to predict the TOC and TC removal efficiency. The high correlation of the quadratic models of 0.9842 and 0.9781 for TC and TOC removal, respectively, indicates the significance of the models. The obtained results revealed that the high-efficiency removal of both TC and TOC in RPW. Approximately 99.6% of TC was decomposed under the optimum conditions of a current density of 2.2 mA/cm2 and an Fe2+ concentration of 0.2 mM during 188 min with an operating cost of 121.392 $/kg TC or ∼2.692 $/m3, while 84.2% TOC was eliminated at a current density of 2.2 mA/cm2 and an Fe2+ concentration of 0.2 mM during 217 min with an operating cost of 3.019 $/kg TOC or 3.916 $/m3. Acute toxicity tests at optimal condition revealed moderate exhibition toxicity of treated wastewater against Daphnia magna with LC50 values of 3.12%, 2.05%, 1.84%, and 1.36% at 24 h, 48 h, 72 h, and 96 h, respectively. The removal of TC and TOC followed pseudo-first-order kinetic with an R2 of ∼0.993 and 0.923, respectively.

Acute toxicity of methomyl commercial formulation induces morphological and behavioral changes in larval zebrafish (Danio rerio)

The use of pesticides has continue grown over recent years, leading to several environmental and health concerns, such as the contamination of surface and groundwater resources and associated biota, potentially affecting populations that are not primary targets of these complex chemical mixtures. In this work, we investigate lethal and sublethal effects of acute exposure of methomyl commercial formulation in zebrafish embryo and larvae. Methomyl is a broad-spectrum carbamate insecticide and acaricide that acts primarily in acetylcholinesterase inhibition (AChE). Methomyl formulation 96 h-LC₅₀ was determined through the Fish Embryo Acute Toxicity Test (FET) and resulted in 1.2 g/L ± 0.04. Sublethal 6-day exposure was performed in six methomyl formulation concentrations (0.5; 1.0; 2.2; 4.8; 10.6; 23.3 mg/L) to evaluate developmental, physiological, morphological, behavioral, biochemical, and molecular endpoints of zebrafish early-development. Methomyl affected embryo hatching and larva morphology and behavior, especially in higher concentrations; resulting in smaller body and eyes size, failure in swimming bladder inflation, hypolocomotor activity, and concentration-dependent reduction of AChE activity; demonstrating methomyl strong acute toxicity and neurotoxic effect.