Joint Toxicity Research Articles

Unraveling the complexities of Cd-aniline composite pollution: Insights from standalone and joint toxicity assessments in a bacterial community

Cadmium (Cd) and aniline frequently co-occur in industrial settings but have rarely been addressed as composite toxicants in terms of the overall toxicity despite extensive knowledge of the environmental impact of each individual pollutant. In this study, we attempt to assess the relation of individual and combined toxic effects of Cd and aniline using a bacterial consortium cultured from soils as a model system. Results showed that the consortial bacteria exhibited drastically stronger tolerance to stand-alone Cd and aniline in comparison to literature data acquired from single species studies. When occurring simultaneously, the joint toxicity displayed a concentration-dependent behavior that wasn't anticipated based on individual chemical tests. Specifically, additive effects manifested with Cd and aniline at their IC10s, but changed to synergistic when the concentrations increased to IC20, and finally transitioned into antagonistic at IC30s and beyond. In addition, co-occurring aniline appeared to have retarded the cellular accumulation of Cd while increasing the enzymatic activities of superoxide dismutase and catalase relative to that in Cd-alone treatments. Finally, the bacterial community experienced distinct compositional changes under solo and combined toxicities with several genera exhibiting inconsistent behavior between treatments of single and composite toxicants. Findings from this study highlight the complexity of bacterial response to composite pollutions and point to the need for more comprehensive references in risk and toxicology assessment at multi-chemical contamination sites.

Copper and zinc interact significantly in their joint toxicity to Chlamydomonas reinhardtii: Insights from physiological and transcriptomic investigations

Copper (Cu) and zinc (Zn) often discharge simultaneously from industrial and agricultural sectors and cause stress to aquatic biota. Although microalgae have been extensively investigated for their responses to Cu or Zn exposure, how they cope with the mixtures of two metals, especially at transcriptomic level, remains largely unknown. In this study, Chlamydomonas reinhardtii was exposed to environmentally relevant concentrations of two metals. It was found that Zn promoted the entry of Cu into the algal cells. With the increase of combined toxicity, extracellular polymeric substances (EPS) and cell wall functional groups immobilized significant amounts of Cu and Zn. Furthermore, C. reinhardtii adjusted resistance strategies internally, including starch consumption and synthesis of chlorophyll and lipids. Upon high level of Cu and Zn coexistence, synergistic effects were observed in lipid peroxidation and catalase (CAT) activity. Under 1.05 mg/L Cu + 0.87 mg/L Zn, 256 differentially expressed genes (DEGs) were mainly involved in oxidative phosphorylation, ribosome, nitrogen metabolism; while 4294 DEGs induced by 4.21 mg/L Cu + 3.48 mg/L Zn were mainly related to photosynthesis, citric acid cycle, etc. Together, this study revealed a more comprehensive understanding of mechanisms of Cu/Zn detoxification in C. reinhardtii, emphasizing critical roles of photosynthetic carbon sequestration and energy metabolism in the metal resistance.

Co-exposure of avermectin and imidacloprid induces DNA damage, pyroptosis, and immune dysfunction in epithelioma papulosum cyprini cells via ROS-mediated Keap1/Nrf2/TXNIP axis.

Pesticide mixtures can reduce pest resistance, however, their overuse severely threatens aquatic animal survival and public health. Avermectin (AVM) and imidacloprid (IMI) are potent insecticides often employed in agriculture. By inducing oxidative stress, these chemicals can induce cell death. Here, we evaluated the combined toxicity of AVM and IMI on EPC cells based on the concept of toxicity units (TU). We established EPC cell models exposed to AVM and IMI alone and in combination. The results showed that AVM and IMI had additive effects on the toxicity of EPC cells. Meanwhile, the co-exposure of AVM and IMI exacerbated oxidative stress and induced excessive production of reactive oxygen species (ROS), triggered Keap1/Nrf2/TXNIP axis, caused DNA damage and increased the expression of genes related to pyroptosis. In addition, co-exposure to AVM and IMI caused immunosuppression of EPC cells. The ROS inhibitor N-Acetyl-l-cysteine (NAC) can dramatically reverse these alterations brought on by AVM and IMI co-exposure. The findings above conclude that co-exposure to AVM and IMI causes DNA damage, pyroptosis, and immunosuppression in EPC cells through the ROS-mediated Keap1/Nrf2/TXNIP pathway. This study revealed the joint toxicity of AVM and IMI on EPC cells, and reminded people to consider its impact on aquatic animals when using pesticide mixtures.

Assessment of Joint Toxicity of Arsenate and Lead by Multiple Endpoints in Chlamydomonas reinhardtii.

In aquatic ecosystems, arsenate (As(V)) and lead (Pb(II)) frequently coexist but their joint toxicity on microalgae remains unknown. In this study, Chlamydomonas reinhardtii was exposed to various levels of combined As(V) and Pb(II) treatments. The cell growth, respiration, pigment synthesis, polysaccharides and protein secretion as well as As speciation of C. reinhardtii were analyzed. The low-level coexistence of As(V) and Pb(II) had a stimulatory effect, as indicated by enhanced cell proliferation. In the middle-level coexistence, the cells resisted the toxicity by significant increasing protein secretion. Under high-level coexistence, the presence of Pb(II) inhibited the efflux of As and caused the decline of cell numbers and occurrence of cell lysis, indicating that the interaction mode between As(V) and Pb(II) switched to synergistic. Taken together, the above findings may deepen the understanding of detoxification mechanisms of algae upon exposure to combined metal(loid)s in aqueous environments.

A refined toxicokinetic model for quantifying the interaction between Cd and Cu in zebrafish larvae

The interaction between metals is ubiquitous, but there is still a lack of quantitative models considering the interaction between metals, which leads to the deviations in predicting the joint toxicity of metals. The present study estimated the uptake rate constants (kin) and elimination rate constants (kout) and elucidated how the presence of one metal (Cu or Cd) affects the absorption and excretion of another metal (Cd or Cu) in zebrafish larvae. The results showed that Cd and Cu inhibited each other in the process of absorption and excretion by comparing separately kin and kout of Cd or Cu with the other metal Cu or Cd mixed concentrations increased, thereby affecting the Cd and Cu bioaccumulation in the zebrafish larvae. Then the interactions between Cd and Cu in the uptake and elimination processes were quantified to obtain a refined toxicokinetic model. Verification with independent experiment data showed that the refined toxicokinetic model could significantly improve the prediction of the Cd or Cu bioaccumulation in the zebrafish larvae. This study contributes to understand the toxicokinetic process of the Cd-Cu mixture in the zebrafish larvae, and the developed model could be used to predict the toxicity of the metal mixtures.

Ecological effects and molecular mechanisms of single and coexisting PFOS and Cu exposure on submerged macrophytes and periphytic biofilms in aquatic environments

Perfluorooctane sulfonate (PFOS) is an accumulative emerging persistent organic pollutant that coexists with copper (Cu) in aquatic environments and is a severe threat to human health. PFOS has genotoxicity, male reproductive toxicity, neurotoxicity, developmental toxicity and endocrine disrupting effects, and is considered to be a kind of environmental pollutant with systemic multi-organ toxicity. However, the combined effects of PFOS and Cu on aquatic organisms have not been analyzed previously. In this study, we investigate the response of Vallisneria Natans (V. natans) and biofilms to single and combined treatments of PFOS and Cu at environmental concentrations (1.0, 10.0, and 100.0 μg·L−1). Results indicate that single and combined treatment triggered the reactive oxygen species (ROS) metabolism with increased activities of GSH, MDA, CAT, TSOD and an antagonistic joint toxicity. Meanwhile, transcriptomic analyses showed that the peroxidase (PER), 9 glutaredoxin (GRX), and 39 glutathione S-transferase (GST) expression of genes related to ROS detoxification was up-regulated. In addition, single and combined exposure induced the up-regulation of the transport channel genes which encode aquaporins, rapid-type anion channels, and copper-exporting P-type ATPase transporters, promoting the uptake of PFOS and Cu in V. natans, Enhancing detoxification and mitigating the effects of Cu and PFOS exposure. Moreover, PFOS and Cu changed the structural characteristics of extracellular polysaccharides in biofilms, synthesizing large amounts of β-D-glucopyranose PS, α-D-glucopyranose PS. And the community diversity and species evenness changed, with Rhizobiaceae, Chloroplast, and Weeksellaceae being the dominant phylum. This study provides insights into the molecular mechanism of joint toxicity of PFOS and Cu by Transcriptomics and PCR analysis on the submerged macrophyte and their periphyton biofilms.

Joint toxicity of cadmium and fenpyroximate on two earthworms: Interspecific differences, subcellular partitioning and biomarker responses

Cadmium (Cd) and fenpyroximate are common soil contaminants found together in the field, but their combined toxicity to terrestrial invertebrates has not been studied. Therefore, earthworms Aporrectodea jassyensis and Eisenia fetida were exposed into Cd (5, 10, 50 and 100 μg/g) and fenpyroximate (0.1, 0.5, 1, and 1.5 μg/g) and their mixture, and multiple biomarker responses (mortality, catalase (CAT), superoxide dismutase (SOD), total antioxidant activity (TAC), lipid peroxidation (MDA), protein content, weight loss and subcellular partitioning) were determined to estimate health status and mixture effect. MDA, SOD, TAC, and weight loss were significantly correlated with Cd in total internal and debris (p < 0.01). Fenpyroximate altered the subcellular distribution of Cd. It appears that maintaining Cd in a non-toxic form was the earthworms' primary Cd detoxification strategy. CAT activity was inhibited by Cd, fenpyroximate, and their combined presence. BRI values for all treatments indicated a major and severe alteration in earthworm's health. The combined toxicity of Cd and fenpyroximate was greater than the toxicity of either substance alone. According to EAI, all combined treatments exhibited a clear antagonistic effect. In general, the sensitivity of A. jassyensis was greater than that of E. fetida.

Joint toxicity mechanisms of perfluorooctanoic acid and sulfadiazine on submerged macrophytes and periphytic biofilms

Hazardous chemicals, such as perfluoroalkyl substances (PFASs) and antibiotics, coexist in aquatic environments and pose a severe threat to aquatic organisms. However, research into the toxicity of these pollutants on submerged macrophytes and their periphyton is still limited. To assess their combined toxicity, Vallisneria natans (V. natans) was exposed to perfluorooctanoic acid (PFOA) and sulfadiazine (SD) at environmental concentrations. Photosynthetic parameters such as chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids were lower in the SD exposure group, indicating that SD had a significant effect on the photosynthesis of aquatic plants. Single and combined exposures effectively induced antioxidant responses, with increases in superoxide dismutase, peroxidase activities, and ribulose-1,5-bisphosphate carboxylase concentrations, as well as malondialdehyde content. Accordingly, antagonistic toxicity was assessed between PFOA and SD. Furthermore, metabolomics revealed that V. natans improved stress tolerance through changes in enoic acid, palmitic acid, and palmitoleoyloxymyristic acid related to the fatty acid metabolism pathway responding to the coexisting pollutants. Additionally, PFOA and SD in combination induced more effects on the microbial community of biofilm. The alternation of α- and β-D-glucopyranose polysaccharides and the increased content of autoinducer peptides and N-acylated homoserine lactones indicated that PFOA and SD changed the structure and function of biofilm. These investigations provide a broader perspective and comprehensive analysis of the responses of aquatic plants and periphyton biofilms to PFAS and antibiotics in the environment.

Co-exposure of polycarbonate microplastics aggravated the toxic effects of imidacloprid on the liver and gut microbiota in mice

The joint toxicity of microplastics (MPs) and pesticides may be different from MPs or pesticides individually, however, the information about the combined toxicity of MPs and pesticides is not well understood. Herein, we investigated the joint toxicity of polycarbonate (PC) MPs and imidacloprid (IMI) on mice. After orally exposure for 4 weeks, PC and/or IMI lowered the body weight gain of mice. Single exposure of IMI induced the tissue damage in liver by disturbing the redox homeostasis, and PC significantly aggravated the imbalance of redox homeostasis by facilitating the accumulation of IMI in liver. Additionally, compared to single exposure of PC or IMI, PC+IMI exposure caused more severe damage to the gut microstructure and microbial diversity. Several key metabolic pathways, especially the lipid metabolism, were significantly affected. Overall, these findings provide new insight into understanding the potential risk of co-exposure of microplastics and pesticides to animal and human health.

Study on the characterization of pesticide modes of action similarity and the multi-endpoint combined toxicity of pesticide mixtures to Caenorhabditis elegans

With the widespread use of pesticides, the coexistence of multiple low-residue pesticides in environmental media has increased significantly, and the “cocktail” effect caused by this phenomenon has garnered increasing attention. However, owing to the scarcity of information regarding the modes of action (MOAs) of chemicals, the application of concentration addition (CA) models for evaluating and predicting the toxicity of mixture with similar MOAs is limited. Additionally, the joint toxicity laws of complex mixture systems to different toxicity endpoints in organisms remain unclear, and effective methods to test the mixture toxicity on lifespan and reproductive inhibition are lacking. Therefore, in this study, the similarity of pesticide MOAs was characterized using molecular electronegativity-distance vector (MEDV-13) descriptors based on eight pesticides (aldicarb, methomyl, imidacloprid, thiamethoxam, dichlorvos, dimethoate, methamidophos and triazophos). Additionally, the methods of lifespan and reproduction inhibition microplate toxicity analysis of elegans (EL-MTA and ER-MTA) were established to test the lifespan and reproduction inhibition toxicity of Caenorhabditis elegans. Finally, a unified scale synergistic-antagonistic heatmap (SAHscale) method was proposed to explore the combined toxicity of the mixtures on the lifespan, reproduction, and mortality of nematodes. The results showed that the MEDV-13 descriptors could effectively characterize the similarity in MOAs. The lifespan and reproductive ability of Caenorhabditis elegans were significantly inhibited when the pesticide exposure concentration was one order of magnitude lower than the lethal dose. The sensitivity of lifespan and reproductive endpoints to mixtures was dependent on the concentration ratio. The same rays in the mixture had consistent toxicity interactions on the lifespan and reproductive endpoints of Caenorhabditis elegans. In conclusion, we demonstrated the feasibility of MEDV-13 in characterizing the similarity of MOAs, and provided a theoretical basis for exploring the mechanism of chemical mixtures by studying their apparent toxicity of mixtures on nematode lifespan and reproduction endpoints.

Estimating the aquatic risk from exposure to up to twenty-two pesticide active ingredients in waterways discharging to the Great Barrier Reef

Pesticides decrease the quality of water reaching the Great Barrier Reef (GBR), Australia. Up to 86 pesticide active ingredients (PAIs) were monitored between July 2015 to end of June 2018 at 28 sites in waterways that discharge to the GBR. Twenty-two frequently detected PAIs were selected to calculate their combined risk when they co-occur in water samples. Species sensitivity distributions (SSDs) for the 22 PAIs to fresh and marine species were developed. The SSDs, the multi-substance potentially affected fraction (msPAF) method, Independent Action model of joint toxicity and a Multiple Imputation method were combined to convert measured PAI concentration data to estimates of the Total Pesticide Risk for the 22 PAIs (TPR22) expressed as the average percentage of species affected during the wet season (i.e., 182 days). The TPR22 and percent contribution of active ingredients of Photosystem II inhibiting herbicides, Other Herbicides, and Insecticides to the TPR22 were estimated. The TPR22 ranged from <1 % to 42 % of aquatic species being affected. Approximately 85 % of the TPR22 estimates were >1 % — meaning they did not meet the Reef 2050 Water Quality Improvement Plan's pesticide target for waters entering the GBR. There were marked spatial differences in TPR22 estimates — regions dominated by grazing had lower estimates while those with sugar cane tended to have higher estimates. On average, active ingredients of PSII herbicides contributed 39 % of the TPR22, the active ingredients of Other Herbicides contributed ~36 % and of Insecticides contributed ~24 %. Nine PAIs (diuron, imidacloprid, metolachlor, atrazine, MCPA, imazapic, metsulfuron, triclopyr and ametryn) were responsible for >97 % of TPR22 across all the monitored waterways.

Rapid and versatile colorimetric sensor based on luminescent bacterium for water comprehensive toxicity detection

In this study, a high-efficiency colorimetric sensor for water toxicity assessment was successfully constructed by the visual analysis with naked eyes and the high-throughput measurement with a microplate reader. The bioluminescent Photobacterium phoshoreum T3 spp. (T3) and Prussian blue (PB) were used as model bacterium and indicator of the colorimetric sensor, respectively. In order to accurately detect acute toxicities of wastewater, the experimental conditions, concentrations of cells, K3[Fe(CN)6] and NaCl, reaction temperature and time, were optimized to be OD600 = 2, 8 mM, 1.2%, 26.5 °C and 25 min, respectively. Then several samples of simulated wastewater containing Hg2+, Cd2+, Zn2+, 3,5-dichlorophenol (DCP) and formaldehyde (HCHO) were tested. The composite biotoxicity of dry battery leachate and real water sample was also evaluated. The IC50 values of Hg2+, Cd2+, Zn2+ and DCP obtained were 3.60, 1.56, 0.96 and 11.77 mg L−1, respectively. Moreover, a toxic unit (TU) model was applied to evaluate the binary complex toxicity of Hg2+ + Cd2+, Hg2+ + Zn2+ and DCP + Zn2+, which showed antagonistic effects. The work demonstrates that the promising high-efficiency sensor can detect quickly and sensitively the single and joint toxicities of multi-pollutants in water, which possesses extensive potentials in field of toxicity detection.

Single and joint toxic effects of thyroid hormone, levothyroxine, and amiodarone on embryo-larval stages of zebrafish (Danio rerio).

This study evaluates single and joint endocrine disruptor toxicities of thyroid hormone, levothyroxine, and amiodarone in the embryo-larval stages of Danio rerio. Single toxicity experiments were carried out in concentrations based on the environmental concentration and increasing concentrations of 10, 100, and 1000 times the environmental concentration. Joint toxicity experiments evaluated the combined effects of these compounds. Toxic effects were examined during zebrafish embryonic development, and the parameters analyzed were apical sublethal, teratogenicity, mortality endpoints, and morphometry. Thyroid hormone exhibited the highest toxicity. However, the results showed that the environmental concentrations for all 3 compounds had low risk in relation to the parameters studied, such as teratogenic effects and morphometry. The larvae were more affected than embryos, where embryos needed higher concentrations in all experiments, possibly due to the absence of the chorion. The same type of effects were observed in the joint toxicity test, except that a possible antagonistic effect was detected. However, high concentrations showed stronger effects of these toxic compounds on fish development.

Toxicity interaction of polystyrene nanoplastics with sulfamethoxazole on the microalgae Chlamydomonas reinhardtii: A closer look at effect of light availability

The coexistence of nanoplastics and antibiotics in the aquatic environment has raised a complicated risk for ecosystems and human health. How the environmental factors e.g., light, regulate the interaction between nanoplastics and antibiotics and the resulting combined toxicity is poorly understood. Here, we investigated the individual and combined toxicity of polystyrene nanoplastics (nPS, 100 mg L1) and sulfamethoxazole (SMX, 2.5 and 10 mg L−1) toward the microalgae Chlamydomonas reinhardtii under low (LL, 16 μmol m−2·s−1), normal (NL, 40 μmol m−2·s−1), and high light (HL, 150 μmol m−2·s−1) in terms of cellular responses. Results indicated that the joint toxicity of nPS and SMX commonly exhibited a strong antagonistic/mitigative effect under LL/NL at 24 h, and under NL at 72 h. nPS could adsorb more SMX under LL/NL at 24 h (1.90/1.33 mg g−1) and under NL at 72 h (1.01 mg g−1), thereby alleviating SMX toxicity to C. reinhardtii. However, the self-toxicity of nPS had a negative influence on the degree of antagonism between nPS and SMX. The experimental results coupled with computational chemistry further revealed that the adsorption capacity of SMX on nPS was stimulated by low pH under LL/NL at 24 h (∼7.5), while by less co-existing saline ions (0.83 ppt) and algae-derived dissolved organic matter (9.04 mg L−1) under NL at 72 h. nPS toxicity that was responsible for the toxic action modes was mainly attributed to the shading effect induced by hetero-aggregation and hindrance of light transmittance (>60%), as well as being regulated by additives leaching (0.49–1.07 mg L−1) and oxidative stress. Overall, these findings provided a critical basis for the risk assessment and management of multiple pollutants in the complex natural environment.

Enhanced toxicity of 2,2-bis(chloromethyl) trimethylene bis[bis(2-chloroethyl) phosphate] (V6) by nanopolystyrene particles towards HeLa cells

2,2-bis(chloromethyl) trimethylene bis[bis(2-chloroethyl) phosphate] (V6) has been widely used as an additive in a variety of plastics due to its extremely low toxicity. However, we showed in the study that once mixed with nanopolystyrene particles (NPs), the nontoxic V6 could exhibit significant toxicity to HeLa cells. The enhanced toxicity was much higher than the toxicity of NPs alone and was related to the size of NPs. The mixture of V6 and small polystyrene NPs (10 nm and 15 nm in radius) showed obvious toxicity to HeLa cells. The toxicity increased with the concentrations of both V6 and NPs. On the contrary, the mixture of V6 and larger NPs (25 nm, 50 nm, 100 nm, and 500 nm in radius) showed almost no toxicity even at extremely high concentrations (NPs: 100 mg/L; V6: 50 mg/L). The small NPs could enter the cells and accumulated in cytoplasm. However, the larger NPs did not distribute inside the cells. NPs efficiently adsorbed V6 on the surface. The mechanism of the enhanced toxicity was attributed to the increased intracellular reactive oxygen species (ROS) production and the regulation of gene expression concerning apoptosis and ROS scavenging. Our study not only showed that a safe chemical V6 could be turned to be toxic by NPs, but also pointed out a potential risk caused by the joint toxicity of ‘safe’ chemicals and plastic particles with small size.

The effect of silica-magnetite nanoparticles on the ecotoxicity of the antibiotic ciprofloxacin.

The increase in the production and application of engineered nanomaterials, including nanoparticles (NPs), leads to their discharge into the environment, where they can interact with coexisting antibiotics from wastewater, causing a complicated joint effect on organisms that need to be studied. Herein, a typical engineered nanomaterial, silica-magnetite NPs modified with tetraethoxysilane and 3-aminopropyltriethoxysilane (MTA-NPs, 1-2g/L), and common antibiotic ciprofloxacin (CIP, 0-5mg/L) were selected as the analytes. Their joint toxicity to a model of ciliates infusoria, Paramecium caudatum was specifically investigated. The impact of CIP, MTA-NPs, and humic acids (HA) was tracked for 24h, individually and collectively, on the mortality of infusoria. The addition of MTA-NPs and HA at the studied concentrations leads to 40% mortality of organisms. The combined presence of the MTA-NPs at a concentration of 1.5-2mg/L and HA at a concentration of 20-45mg/L has a multiplier effect and allows to reduce the mortality rate of ciliates > 30% due to the enhanced removal of CIP. That finding demonstrated a clearly detoxifying role of dissolved organic matter (here, humic substances) in case of complex water pollution where pharmaceuticals and nanomaterials are presented.

Toxicity effects of polystyrene nanoplastics and arsenite on Microcystis aeruginosa

Despite the increasing research on the fate of nanoplastics (NPs, <100 nm) in freshwater systems, little is known about the joint toxic effects of metal(loid)s and NPs modified with different functional groups on microalgae. Here, we explored the joint toxic effects of two types of polystyrene NPs [one modified with a sulfonic acid group (PSNPs-SO3H), and one without this functional group (PSNPs)] and arsenic (As) on the microalgae Microcystis aeruginosa. The results highlighted that PSNPs-SO3H showed a smaller hydrodynamic diameter and greater potential to adsorb positively charged ions than PSNPs, contributing to the more severe growth inhibition, while both of them produced oxidative stress. Metabolomics further revealed that the fatty acid metabolism of the microalgae was significantly up-regulated under both NPs exposure, while PSNPs-SO3H down-regulated the tricarboxylic acid cycle (TCA cycle) of the microalgae. As uptake by algae was significantly reduced by 82.58 % and 59.65 % in the presence of 100 mg/L PSNPs and PSNPs-SO3H, respectively. The independent action model showed that the joint toxicity of both NPs with As was assessed as antagonistic. In addition, PSNPs and PSNPs-SO3H had dissimilar effects on the composition of the microalgae extracellular polymeric substances (EPS), resulting in different uptake and adsorption of As, thereby affecting the physiology and biochemistry of algae. Overall, our findings propose that the specific properties of NPs should be considered in future environmental risk assessments.

Mixture effects of thiamethoxam and seven pesticides with different modes of action on honey bees (Aplis mellifera)

Even though honey bees in the field are routinely exposed to a complex mixture of many different agrochemicals, few studies have surveyed toxic effects of pesticide mixtures on bees. To elucidate the interactive actions of pesticides on crop pollinators, we determined the individual and joint toxicities of thiamethoxam (THI) and other seven pesticides [dimethoate (DIM), methomyl (MET), zeta-cypermethrin (ZCY), cyfluthrin (CYF), permethrin (PER), esfenvalerate (ESF) and tetraconazole (TET)] to honey bees (Aplis mellifera) with feeding toxicity test. Results from the 7-days toxicity test implied that THI elicited the highest toxicity with a LC50 data of 0.25 (0.20–0.29) μg mL−1, followed by MET and DIM with LC50 data of 4.19 (3.58–4.88) and 5.30 (4.65–6.03) μg mL−1, respectively. By comparison, pyrethroids and TET possessed relatively low toxicities with their LC50 data from the range of 33.78 (29.12–38.39) to 1125 (922.4–1,442) μg mL−1. Among 98 evaluated THI-containing binary to octonary mixtures, 29.59% of combinations exhibited synergistic effects. In contrast, 18.37% of combinations exhibited antagonistic effects on A. mellifera. Moreover, 54.8% pesticide combinations incorporating THI and TET displayed synergistic toxicities to the insects. Our findings emphasized that the coexistence of several pesticides might induce enhanced toxicity to honey bees. Overall, our results afforded worthful toxicological information on the combined actions of neonicotinoids and current-use pesticides on honey bees, which could accelerate farther comprehend on the possible detriments of other pesticide mixtures in agro-environment.

Integrating FTIR 2D correlation analyses, regular and omics analyses studies on the interaction and algal toxicity mechanisms between graphene oxide and cadmium.

Graphene oxide (GO, a popular 2D graphene-based nanomaterial) has developed quickly and has received considerable attention for its applications in environmental protection and pollutant removal. However, significant knowledge gaps still exist about the interaction characteristic and joint toxicity mechanism of GO and cadmium (Cd) on aquatic organisms. In this study, GO showed a high adsorption capacity (120. 6mg/g) and strong adsorption affinity (KL = 0.85L/mg) for Cd2+. Integrating multiple analytical methods (e.g., electron microscopy, Raman spectra, and 2D correlation spectroscopy) revealed that Cd2+ is uniformly adsorbed on the GO surface and edge mainly through cation-π interactions. The combined ecological effects of GO and Cd2+ on Chlorella vulgaris were observed. Cd2+ induced more severe growth inhibition, photosynthesis toxicity, ultrastructure damage and plasmolysis than GO. Interestingly, we found that GO nanosheets could augment the algal toxicity of Cd2+ (e.g., chlorophyll b, mitochondrial membrane damage, and uptake). Transcriptomics and metabolomics further explained the underlying mechanism. The results indicated that the regulation of PSI-, PSII-, and metal transport-related genes (e.g., ABCG37 and ZIP4) and the inhibition of metabolic pathways (e.g., amino acid, fatty acid, and carbohydrate metabolism) were responsible for the persistent phytotoxicity. The present work provides mechanistic insights into the roles of coexisting inorganic pollutants on the environmental fate and risk of GO in aquatic ecosystems.

Unraveling the joint toxicity of transition-metal dichalcogenides and per- and polyfluoroalkyl substances in aqueous mediums by experimentation, machine learning and molecular dynamics.

The environmental fate of transition-metal dichalcogenides (TMDCs) may be further complicated by interacting with existing pollutants, especially per- and polyfluoroalkyl substances (PFAS). However, due to their sheer volume, it is impossible to explore all possible interactions by simply utilizing experimental methods. Herein, we used two model TMDC nanosheets, molybdenum disulfide (MoS2) and tungsten disulfide (WS2), and seven PFAS to explore their interactions and subsequent impacts on model cell lines and zebrafish. Utilizing experimental methods and machine learning approaches, we showed that TMDCs-PFAS interactions can pose unique challenges due to their interaction-specific toxicity niches towards cell lines. Further in vivo experiments, together with molecular dynamics simulation, suggested that TMDCs-PFAS interactions in aqueous environments significantly increased their bioaccumulation in zebrafish towards different target organs, mostly due to the differences in loading PFAS. Such enhanced bioaccumulation increased the oxidative stress in zebrafish liver and intestine, as demonstrated by the increased reactive oxygen species (ROS) level and other enzyme activities, which eventually led to obvious histopathological alterations in the liver and intestine. Our study highlights the importance of exploring interactions between emerging and existing contaminants with state-of-art techniques in aqueous environments and its significance in safeguarding aquatic environment health.