Toxicity Of Mixtures Research Articles

Prediction of toxicity and identification of key components for complex mixtures containing hormetic components

Mixtures containing hormetic components are likely to induce hormesis. However, due to the presence of stimulatory effects, predicting the toxicity of such mixtures and identifying their key components face challenges. This study investigated the complex relationship between the stimulatory effects of individual components and their mixtures, focusing on predicting mixture toxicity and identifying key components influencing this toxicity. Sixteen chemicals, commonly found in disinfectants and hand sanitizers, were selected to construct a complex mixture system containing hormetic components. Using Vibrio qinghaiensis sp.-Q67 as an indicator organism, the study employed microplate toxicity tests to collect toxicity data for individual chemicals and their mixtures. The independent action (IA) and back-propagation neural network (BPNN) methods were utilized to predict mixture toxicity, while global sensitivity analysis (GSA) identified key components affecting toxicity. Results revealed that six of the sixteen chemicals exhibited time-dependent hormesis. However, when combined into mixtures, the stimulatory effects observed in individual components tended to diminish or disappear, leading to higher overall toxicity, likely due to synergism. Traditional models like the IA significantly underestimated mixture toxicity, whereas the BPNN model demonstrated superior predictive performance. GSA identified five key components, and changes in the levels of some non-toxic components significantly altered the toxicity of the mixtures. Moreover, increasing the levels of certain key components could either increase or decrease the mixture's toxicity, making the strategy of reducing their concentration to control mixture toxicity ineffective. This study revealed the potential of neural networks in predicting the toxicity of mixtures containing hormetic components and the possible characteristics of the effects of key components on mixture toxicity.

Efficiently determining the toxicity of cryoprotectant mixtures through high throughput screening

Efficiently determining the toxicity of cryoprotectant mixtures through high throughput screening

Epigenetic dysregulation of H19/IGF2 in hepatic cells exposed to toxic metal mixtures in vitro

Exposure to mixtures of toxic metals is known to cause adverse health effects through epigenetic alterations. Here we aimed to examine the unexplored area of aberrant DNA methylation in the H19/IGF2 domain following combined toxic metal exposure. An in vitro epigenotoxicity assay using the human normal liver epithelial cell line THLE-3 was conducted. When THLE-3 cells were exposed to specific concentrations of either organic arsenic or MeHgCl, an increase in the H19 lncRNA levels and a marked reduction in the IGF2 mRNA levels were observed. In contrast, combined exposures coupled with CdCl2 resulted in the transcriptional repression of H19 and transcriptional activation of IGF2. It should be noted that the correlation between the dysregulated expression of H19/IGF2 and the hypermethylated CpG sites within the H19 differentially methylated region (DMR) was statistically significant. Furthermore, we performed transcriptomic analysis of the hepatocytes exposed to toxic metal combinations indicating enrichment of pro-inflammatory and anti-proliferative pathways compared to the unexposed cells. Our results suggest that hazardous metal mixtures may trigger epigenetic aberrations at the H19/IGF2 locus. We propose that altered CpG methylation in the H19 DMR could be a candidate biomarker for hepatic epigenotoxicity, in part, due to environmental exposure.

A comprehensive machine learning-based models for predicting mixture toxicity of azole fungicides toward algae (Auxenochlorella pyrenoidosa)

Quantitative structure–activity relationships (QSARs) have been used to predict mixture toxicity. However, current research faces gaps in achieving accurate predictions of the mixture toxicity of azole fungicides. To address this gap, the application of machine learning (ML) algorithms has emerged as an effective strategy. In this study, we applied 12 algorithms, namely, k-nearest neighbor (KNN), kernel k-nearest neighbors (KKNN), support vector machine (SVM), random forest (RF), stochastic gradient boosting (GBM), cubist, bagged multivariate adaptive regression splines (Bagged MARS), eXtreme gradient boosting (XGBoost), boosted generalized linear model (GLMBoost), boosted generalized additive model (GAMBoost), bayesian regularized neural networks (BRNN), and recursive partitioning and regression trees (CART) to build ML models for 225 mixture toxicity of azole fungicides towards Auxenochlorella pyrenoidosa. A total of 36 single ML models and 12 consensus models were developed. The results indicated that models employing concentration addition (CA), independent action (IA), and molecular descriptors (MD) as variables demonstrated superior predictive abilities. The consensus model combining SVM and RF algorithms (labeled as CM0) demonstrated the highest level of accuracy in fitting the data, with a coefficient of determination of 0.980. Additionally, it showed strong predictive abilities when tested with external data, achieving an external R2 value of 0.945 and a Concordance Correlation Coefficient of 0.967. This study provides a positive contribution to the ecological risk assessment of a mixture of azole fungicides.

Structurally Selective Ozonolysis of p-Phenylenediamines and Toxicity in Coho Salmon and Rainbow Trout.

The tire-rubber-derived ozonation product of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-Q), was recently discovered to cause acute mortality in coho salmon (Oncorhynchus kisutch). para-Phenylenediamines (PPDs) with variable side chains distinct from 6PPD have been identified as potential replacement antioxidants, but their toxicities remain unclear under environmentally relevant ozone conditions. We herein tested the multiphase gas-surface ozone reactivity of four select PPDs [6PPD, N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N,N'-diphenyl-p-phenylenediamine (DPPD), and N-phenyl-N'-cyclohexyl-p-phenylenediamine (CPPD)] and evaluated the toxicity of their reaction mixtures in coho salmon, rainbow trout (Oncorhynchus mykiss), and fathead minnow (Pimephales promelas). 6PPD and IPPD were found to rapidly react with ozone, while no significant multiphase ozone reactivity was observed for DPPD or CPPD. The viability of coho salmon CSE-119 cells was strongly affected by the ozonolysis products of 6PPD but not by those of the other three PPDs. Acute mortality was only observed in juvenile rainbow trout that were exposed to oxidized 6PPD, suggesting a common mechanism of toxic action in the two salmonid fish species. This study reports the structurally selective ozone reactivity of PPDs and the unique toxicity of 6PPD ozonolysis mixtures, which demonstrates that other PPDs are potential alternative antioxidants.

Location-dependent effect of microplastic leachates on the respiration rate of two engineering mussel species.

Microplastics are ubiquitous in the world's oceans and pose serious environmental concerns, including their ingestion and the release of potentially toxic mixtures of intrinsic and extrinsic chemical compounds (i.e. leachates; MPLs). Mussels, as key intertidal bioengineers and filter-feeders are particularly susceptible to both exposure pathways. While the effects of microplastic ingestion have been widely investigated, research on the impacts of MPLs has only recently begun. This study examined the influence of MPLs derived from beached pellets collected in two separate regions, namely France and Portugal, on the respiration rates of two key ecosystem engineers, Mytilus edulis and Mytilus galloprovincialis. Possibly due to distinct mixtures of leached chemicals, unlike Portuguese-MPLs, exposure to French-MPLs significantly decreased the respiration rate of both mussel species. This research provides new insights into the physiological impacts of MPLs on bioengineer species, highlighting the importance of MP source and potential cascading effects at the ecosystem level. While we reported significant effects on mussel respiration after acute MPL exposure, future research should investigate long-term impacts and potential detoxification mechanisms to clarify the effects of MPs on mussel physiological performance and their potential consequences on specie fitness.

Pesticide residues in tropical agricultural soils: Distribution, seasonality, and earthworm ecological risk

Soil contamination by pesticide residues is associated with agricultural intensification in tropical regions and endangers human health and the environment. A mixture of pesticide residues and their degradation products persist in agricultural soils and represent a risk to soil organisms. In this study, we aimed to investigate the concentration and distribution of organochlorine (OC) and organophosphate (OP) pesticide residues in agricultural soils where the industrial cultivation of maize and soybeans is intensively carried out, at three depths (0–5, 5–15, and 15–30 cm) and during two seasons (rainy and dry). Likewise, we performed the ecological risk assessment of those found pesticide residues on two earthworm species, Eisena fetida, and Aporrectoda calagionsa. We calculated the Toxicity-Exposure Ratio (TER) using Predicted no Effect Concentrations (PNEC) and measured concentrations in soils, for identifying the risk of pesticide residues separately. The Risk Quotient (RQ) method was used to evaluate the ecological risk of pesticide residue mixtures in soils from each cropping system. Endrin ketone and dieldrin were the pesticide residues with the highest frequency of detection. The highest concentration in the study was found in a soil sample from maize crops in the dry season at 15–30 cm depth (2917 ng/g). The pesticide mixture from soil samples belonging to maize (0–5 cm) and soybean (5–15 cm) crops in dry season posed the highest ecological risk for A. caliginosa with 100 %, and a maximum RQ of 82.2. Endrin ketone is the OC that contributed most to the overall toxicity of the pesticide mixture in soil samples from maize crop and dieldrin in soil samples from soybean crop. Among OP, disulfoton contributed most to RQsite in soybean crop and methyl parathion in maize crop. Results pointed out the need to apply alternatives to remediate obsolete pesticide residues and restrict the use of methyl parathion and disulfoton in maize and soybean crops, to reduce the ecological risk that represent for earthworms.

Acute toxicity of binary and ternary mixtures of La, Ce and Dy on Daphnia magna: Toxicity patterns depend on the ratios of the components and the concentration gradient

Rare earth elements (REEs) have raised significant environmental contamination concerns, yet the combined toxicity of REE mixtures remains inadequately understood. In this study, acute toxicity of individual, binary and ternary mixtures of lanthanum (La), cerium (Ce), and dysprosium (Dy) on neonatal Daphnia magna was investigated. Dy exhibited the greatest toxicity on neonatal Daphnia magna, followed by La and Ce. The concentration addition (CA) model was superior to the independent action (IA) model for predicting the toxicity of binary mixtures. The CA model indicated additive effects for LaCe mixture and antagonistic effects for LaDy and CeDy mixtures. In contrast, IA model suggested synergistic interactions for LaCe and LaDy mixtures, with antagonistic effects for CeDy mixture when considering dissolved concentration and synergistic effects when considering free-ion concentration. The nonadditive interactions and deviation parameters from the prediction of binary mixture toxicity were assessed by using MixTox model. The ternary mixture of LaCeDy exhibited antagonistic effects on Daphnia magna, and IA model slightly outperformed CA model. Overall, the type of combined toxicity in REE mixtures is influenced by constituents in the mixture and concentration levels. These findings provide scientific basis for the toxicological assessment, risk evaluation and pollution control of REE mixtures. Environmental implicationRare earth elements (REEs) level is increasing in water environment due to wide use and exploitation. However, currently, we know little about the difference of REEs toxicity and combined toxicity of mixture to aquatic organism, which limited the assessment of toxicity and hazard risk of REEs in natural water. Here, this study demonstrates the acute toxicity of individual, binary and ternary mixtures of lanthanum, cerium, and dysprosium on neonatal Daphnia magna according to the measured data and predicted model, identifying the influence factors for combined toxicity. This discovery offers new insights for the assessment and prediction of REEs toxicity.

Integrated Chemical and Ecotoxicological Assessment of Metal Contamination in the Andong Watershed: Identifying Key Toxicants and Ecological Risks

This study employed an integrated field monitoring approach, combining chemical analysis and ecotoxicity testing of multiple environmental matrices—water, sediment, and sediment elutriates—to comprehensively assess the environmental health of the Andong watershed, located near a Zn smelter and mining area. The primary objectives were to evaluate the extent of metal contamination, identify key toxicants contributing to ecological degradation, and trace the sources of these pollutants. Our findings revealed severe metal contamination and significant ecotoxicological effects both in proximity to and downstream from industrial sites. Specifically, Cd, Zn, and Pb were strongly linked to the smelter, while Hg, Ni, Cu, and As were predominantly associated with mining activities in the tributaries. To further assess toxicity of field-collected sediment and their elutriates, a logistic regression analysis was employed to estimate benchmark values for distinguishing between toxic and non-toxic samples, using the sum of toxic units for sediment elutriates and the mean probable effect level (PEL) quotient for sediment toxicity. These models demonstrated greater predictive accuracy than conventional benchmarks for determining toxicity thresholds. Our results highlight that integrating chemical and ecotoxicological monitoring with site-specific concentration–response relationships enhances the precision of ecological risk assessments, facilitating more accurate identification of key toxicants driving mixture toxicity in complex, pollution-impacted aquatic ecosystems.

Bioavailability of trace metals in sediments from Daya bay nature reserve: Spatial variation, controlling factors and the exposure risk assessment for aquatic biota

Determining the ecological risk and environmental significance of trace metal bioavailability is critical for the sustainability of the marine environment and bioresources. The spatial variation, controlling factors and ecological risks of the bioavailability of trace metals (V, Cr, Ni, Cu, Zn, As, Cd and Pb) in Daya Bay sediments were analyzed using BCR sequential extraction and diffusive gradient in thin films (DGT). Differences in concentration distributions between the anthropogenic impact zone (AIZ) and the marine disturbance zone (MDZ) revealed the accumulation of anthropogenic metals in sediments, and that the ocean dynamic conditions promoted the release of bioavailable metals from nature sediments. Fine-grained sediments rich in organic matter possessed more bioavailable metals on the surface. The negative correlations between salinity and the non-residual fractions (F123) suggests that salinity has the potential to inhibit the bioavailability of trace metals. Risk assessment based on total concentrations and acid soluble fractions (F1) showed that Cd was the dominant contributing element to the potential ecological risks with 55.8 %. The evaluation via DGT-labile concentrations indicated that Cu was the element of priority concern for aquatic exposure risk with a risk probability of 7.45 %, and the joint risk probability for metal mixture toxicity was 12.27 %. The exposure risk for aquatic biota was shown as molluscs (9.37 %) > algae (6.82 %) > crustaceans (6.21 %) > invertebrates (6.07 %) > fish (2.61 %). The results provide new clues for risk assessment and management of trace metals in coastal sediments.

Joint Toxicity and Interaction of Carbon-Based Nanomaterials with Co-Existing Pollutants in Aquatic Environments: A Review.

This review paper focuses on the joint toxicity and interaction of carbon-based nanomaterials (CNMs) with co-existing pollutants in aquatic environments. It explores the potential harmful effects of chemical mixtures with CNMs on aquatic organisms, emphasizing the importance of scientific modeling to predict mixed toxic effects. The study involved a systematic literature review to gather information on the joint toxicity and interaction between CNMs and various co-contaminants in aquatic settings. A total of 53 publications were chosen and analyzed, categorizing the studies based on the tested CNMs, types of co-contaminants, and the used species. Common test models included fish and microalgae, with zebrafish being the most studied species. The review underscores the necessity of conducting mixture toxicity testing to assess whether the combined effects of CNMs and co-existing pollutants are additive, synergistic, or antagonistic. The development of in silico models based on the solid foundation of research data represents the best opportunity for joint toxicity prediction, eliminating the need for a great quantity of experimental studies.

Determining bad actors: A linear mixed effects model approach to elucidate behavioral toxicity of metal mixtures in drinking water

Mixtures of chemical contaminants can pose a significant health risk to humans and wildlife, even at levels considered safe for each individual chemical. There is a critical need to develop statistical methods to evaluate the drivers of toxic effects in chemical mixtures (i.e., bad actors) from exposure studies. Here, we develop a hierarchical modeling framework to disentangle the toxicity of complex metal mixtures from a screening study of 92 drinking well water samples containing multiple metal elements from Maine and New Hampshire, USA. In order to screen for neurodevelopmental impacts from exposure to these drinking water samples, we use a larval zebrafish (Danio rerio) behavioral assay. Zebrafish are an advantageous toxicological model organism due to combining the complexity of a vertebrate organism and higher-throughput exposure methods. We formulate a linear mixed modeling approach that captures intrinsic complexity in a common larval behavioral assay in order to improve its sensitivity and rigor and identify drivers of behavioral toxicity from the metal mixtures within the drinking water samples. Our analysis identifies lead (Pb), cadmium (Cd), nickel (Ni), copper (Cu), barium (Ba), and uranium (U) as metals that consistently impact larval locomotor activity, individually and across nine pairs of those metals. Our model also elucidates three distinct clusters of metal mixture components that drive behavioral effects: (Ba:Cu:U), (Ni:Pb:U), (Ba:Pb:U). Having identified a set of “bad-actor” metals from the water samples, we conduct exposure experiments for each individual metal (Pb, Cd, Ni, Cu, and Ba) at levels considered safe by the US Environmental Protection Agency drinking water regulatory limits and validate Pb, Ni, Cu, and Ba as behavioral toxicants at these concentrations. Collectively, our modeling approach estimates the impact of metal elements on a complex behavioral outcome in a statistically robust manner and establishes an approach to capture “bad actors” and key chemical interactions in a complex mixture.

Phthalates Disrupt Female Reproductive Health: A Call for Enhanced Investigation into Mixtures.

Daily exposure to a mixture of phthalates is unavoidable in humans and poses a risk to reproductive health because they are known endocrine-disrupting chemicals. Specific to female reproductive health, the literature has linked phthalate exposure to impairments in ovarian function, uterine function, pregnancy outcomes, and endocrine signaling in the hypothalamus-pituitary-ovarian axis. However, limitations to these studies are that they primarily focus on single phthalate exposures in animal models. Thus, the effects of real life exposures to mixtures of phthalates and the clinical and translational impacts on reproductive function in women are largely unknown. This review summarizes recent literature specifically investigating associations between phthalate mixture exposures and clinical reproductive outcomes and reproductive disease states in women. Because these studies are scarce, they are supplemented with literature utilizing single phthalate analyses in women and mechanistic basic science studies using phthalate mixture exposures. Main findings from the literature suggest that elevated phthalate exposure is associated with altered menstrual cyclicity, altered pubertal timing, disrupted ovarian folliculogenesis and steroidogenesis, ovarian disorders including primary ovarian insufficiency and polycystic ovary syndrome, uterine disorders including endometriosis and leiomyomas, poor in vitro fertilization outcomes, and poor pregnancy outcomes. There is an urgent need to better incorporate phthalate mixtures in epidemiology (mixture analyses) and basic science (direct exposures) study designs. Further, as exposure to multiple phthalates is ubiquitous, elucidating the mechanism of phthalate mixture toxicities is paramount for improving women's reproductive health.

Association between the levels of toxic heavy metals and schizophrenia in the population of Guangxi, China: A case-control study

The relationship between body levels of heavy metals and the risk of schizophrenia remains unclear. This study investigates the relationship between plasma levels of toxic heavy metals and the risk of schizophrenia among adults in Guangxi, China. Plasma concentrations of lead (Pb), cadmium (Cd), arsenic (As), and chromium (Cr) were measured using inductively coupled plasma mass spectrometry (ICP-MS). To evaluate both the single and combined effects of metal exposure on the risk of schizophrenia, we employed multivariate logistic regression, Bayesian Kernel Machine Regression (BKMR), and generalized Weighted Quantile Sum (gWQS) models. Additionally, we employed the Comparative Toxicogenomics Database (CTD) to analyze the mechanistic pathways through which metal mixtures may induce schizophrenia. Relative mRNA expression levels were measured using Real-Time Quantitative Reverse Transcription Polymerase Chain Reaction (RT-qPCR). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were conducted to predict potential biological functions. In logistic regression models, compared to the lowest exposure group (Q1), the odds ratios (ORs) for Pb in groups Q2, Q3, and Q4 were 2.18 (95% CI: 1.20–3.94), 4.74 (95% CI: 2.52–8.95), and 3.62 (95% CI: 1.80–7.28), respectively. Both BKMR and gWQS models indicated a positive correlation between the combined effects of toxic heavy metal mixtures and the risk of schizophrenia, with Pb demonstrating the most substantial impact, particularly in older adults and females. Elevated levels of tumor necrosis factor (TNF) and interleukin-1 beta (IL-1β) were observed in patients with schizophrenia, while the expression of tumor protein p53 (TP53) was significantly reduced. These findings underscore the critical need to avoid exposure to toxic heavy metals to prevent schizophrenia, highlighting significant public health implications.

Combined environmental relevant exposure to perfluorooctanoic acid and zinc sulfate enhances apoptosis through binding with endogenous antioxidants in Daphnia magna

Perfluorooctanoic acid (PFOA) is a long-chain legacy congener of the per- and polyfluoroalkyl substances (PFAS) family, notorious as a "forever chemical" owing to its environmental persistence and toxic nature. Essential elements such as zinc (Zn) can cause toxic effects when they change their metal speciation and become bioavailable, such as zinc sulfate (ZnSO4). Combined toxicity assessment is a realistic approach and a challenging task to evaluate chemical interactions and associated risks. Therefore, the present study aims to elucidate the acute mixture toxicity (12–48 h) of PFOA and ZnSO4 in Daphnia magna at environment-relevant concentrations (ERCs, low dose: PFOA 10 μg/L ZnSO4 20 μg/L; high dose: PFOA 20 μg/L ZnSO4 50 μg/L) in terms of developmental impact, apoptosis induction, and interaction with major endogenous antioxidants. Our results showed that deformity rates significantly increased (p < 0.05) with increasing exposure duration and exposure concentrations, compared to the control group. Further, lack of antenna, tale degeneration, and carapace alterations were the most commonly observed deformities following combined exposure to PFOA and ZnSO4, and these malformations were particularly pronounced after 48 h of exposure. Acridine orange (AO) staining was employed to examine apoptosis in D. magna, and apoptotic cells in terms of bright green fluorescence were detected in the abdominal claw carapace, heart, and post-abdominal area following exposure to a high dose of PFOA and ZnSO4. The molecular docking results revealed that both PFOA and ZnSO4 showed strong binding affinities with endogenous antioxidants CAT and GST, where PFOA was more strongly bound with CAT and GST with higher docking scores of −9.59 kcal/mol and −7.49 kcal/mol than those with ZnSO4 (−6.70 kcal/mol and −6.55 kcal/mol, respectively). In conclusion, the mixture exposure to PFOA and ZnSO4 at the environmental level induce developmental impacts and apoptosis through binding with major endogenous antioxidants in D. magna.

Aquatic hazard and risk posed by four pesticides detected in waterways discharging to the Great Barrier Reef, Australia: Part 2. Hazard and risk assessment

Pesticide active ingredients (PAIs) are regularly detected in the rivers, creeks, wetlands, and inshore waterways that discharge to the Great Barrier Reef (GBR) lagoon. Pesticide active ingredients detected above ecologically protective concentrations may pose a hazard and risk to aquatic species. The ability to assess this hazard and risk is reliant on the availability of water quality guidelines, which are only available for a limited number of PAIs detected in GBR catchment waterways. Unendorsed guideline values, known as ecotoxicity threshold values (ETVs) were developed in part one of this study for active ingredients in two fungicides (4-hydroxychlorothalonil (fungicide degradate) and carbendazim) and two insecticides (dimethoate and methoxyfenozide) that are commonly detected in GBR catchment waterways. In the current study, the hazard and risk posed by these PAIs was assessed by comparing the ETVs to environmental monitoring data from the Great Barrier Reef Catchment Loads Monitoring Program. Exceedances of the concentrations that should protect 99 % of aquatic species (i.e., PC99) were observed for all four pesticides. Detected concentrations of 4-hydroxychlorothalonil, carbendazim and methoxyfenozide exceeded the PC95 ETV, however no exceedances of the PC95 were observed for dimethoate. The hazard quotient (HQ) method was used to identify high hazard sites across the GBR catchment area. In total, six sites were identified as having concentrations that exceeded the PC95 ETVs. For 4-hydroxychlorothalonil, the risk to aquatic species based on the 95th percentile concentrations ranged from 3 to 13 %, 1 to 8 % for carbendazim and 2 to 8 % for methoxyfenozide. Detected concentrations of carbendazim were two orders of magnitude higher than concentrations that are reported to induce behavioural effects in some fish species. Considering that detected concentrations of three of the four PAIs individually pose a potential risk to aquatic species, their contributions to pesticide mixture toxicity should be further assessed.

Combined toxicity of perfluoroalkyl substances and microplastics on the sentinel species Daphnia magna: Implications for freshwater ecosystems

Persistent chemicals from industrial processes, particularly perfluoroalkyl substances (PFAS), have become pervasive in the environment due to their persistence, long half-lives, and bioaccumulative properties. Used globally for their thermal resistance and repellence to water and oil, PFAS have led to widespread environmental contamination. These compounds pose significant health risks with exposure through food, water, and dermal contact. Aquatic wildlife is particularly vulnerable as water bodies act as major transport and transformation mediums for PFAS. Their co-occurrence with microplastics may intensify the impact on aquatic species by influencing PFAS sorption and transport. Despite progress in understanding the occurrence and fate of PFAS and microplastics in aquatic ecosystems, the toxicity of PFAS mixtures and their co-occurrence with other high-concern compounds remains poorly understood, especially over organisms’ life cycles.Our study investigates the chronic toxicity of PFAS and microplastics on the sentinel species Daphnia, a species central to aquatic foodwebs and an ecotoxicology model. We examined the effects of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and polyethylene terephthalate microplastics (PET) both individually and in mixtures on Daphnia ecological endpoints. Unlike conventional studies, we used two Daphnia genotypes with distinct histories of chemical exposure. This approach revealed that PFAS and microplastics cause developmental failures, delayed sexual maturity and reduced somatic growth, with historical exposure to environmental pollution reducing tolerance to these persistent chemicals due to cumulative fitness costs. We also observed that the combined effect of the persistent chemicals analysed was 59% additive and 41% synergistic, whereas no antagonistic interactions were observed. The genotype-specific responses observed highlight the complex interplay between genetic background and pollutant exposure, emphasizing the importance of incorporating multiple genotypes in environmental risk assessments to more accurately predict the ecological impact of chemical pollutants.

Benzo(a)anthracene Targeting SLC1A5 to Synergistically Enhance PAH Mixture Toxicity.

Human exposure to polycyclic aromatic hydrocarbons (PAHs) as mutagenic and carcinogenic pollutants in the environment often occurs in the form of mixtures. Although the mixture effects of PAHs have been previously recognized, the toxicological mechanisms to explain them still remain quite unclear. This study combined metabolomics and chemical proteomics methods to comprehensively understand the mixture effects of a PAH mixture including benzo(a)anthracene (BaA), benzo(b)fluoranthene (BbF), benzo(a)pyrene (BaP), and chrysene (CHR). Among them, BaA has shown a strong synergistic effect with other PAHs. Interestingly, BaA alone is not a potent oxidative stress inducer in liver cells but dose-dependently amplifies oxidative damage caused by the PAH mixture. Global metabolomics analysis results revealed damage to the antioxidant glutathione synthesis, which was caused by the glutamine depletion caused by BaA in the mixture. Subsequently, the label-free chemical proteomics and cellular thermal shift analysis (CETSA) demonstrated that the PAH mixture altered the thermal shift of glutamine transporter SLC1A5. Furthermore, Western blotting and the isothermal titration calorimetry (ITC) interaction measurements showed nanomolar KD values between BaA and SLC1A5. Overall, this study showed that BaA synergistically contributed to PAH mixture induced oxidative damage by targeting SLC1A5 to inhibit glutamate transport into cells, resulting in the inhibition of glutathione synthesis.

Single and mixture toxicity of benzophenone-3 and its metabolites on Daphnia magna

Benzophenone-3 (BP-3) is one of the organic ultraviolet (UV) filters widely used in personal care products, resulting in its ubiquitous occurrence in aquatic systems. This study discovered the potential risks of benzophenone-3 and its metabolites (BP-1 and BP-8) in aquatic environments. This study investigated the toxicity of three single BPs and their mixtures' effects on the survival of Daphnia magna. All three BP types were found to have toxic effects on D. magna, with median effective concentration (EC50) values of 22.55 mg/L for BP-1, 1.89 mg/L for BP-3, and 2.36 mg/L for BP-8, after 48 h of exposure. When the three BPs were binary and ternary mixtures, the EC50 values fell within 2.74–32.26 mg/L. Binary and tertiary mixtures of the three BPs indicated no strong synergistic or antagonistic effects. The mixture toxicity predictions using the classical mixture concept of concentration addition and measured toxicity data showed good predictability. The ecological risks of BPs were assessed using the maximum measured environmental concentrations of BPs collected from a river in Taiwan, divided by their respective predicted no-effect concentration (PNEC) values derived from the assessment factor (AF) method. The result showed a low ecological risk for the sum of three BPs. However, BP-3 had the highest potential risk, while BP-1 was the lowest among the three BPs. Therefore, BP-3 should pay attention to long-term environmental monitoring and management. This study provides valuable information for establishing scientifically-based water quality criteria for BPs and evaluating and managing the potential risk of BPs in the aquatic environment.

Cocktail effects of clothianidin and imidacloprid in zebrafish embryonic development, with high and low concentrations of mixtures.

There is growing concern that sprayed neonicotinoid pesticides (neonics) persist in mixed forms in the environmental soil and water systems, and these concerns stem from reports of increase in both the detection frequency and concentration of these pollutants. To confirm the toxic effects of neonics, we conducted toxicity tests on two neonics, clothianidin (CLO) and imidacloprid (IMD), in embryos of zebrafish. Toxicity tests were performed with two different types of mixtures: potential mixture compounds and realistic mixture compounds. Potential mixtures of CLO and IMD exhibited synergistic effects, in a dose-dependent manner, in zebrafish embryonic toxicity. Realistic mixture toxicity tests that are reflecting the toxic effects of mixture in the aquatic environment were conducted with zebrafish embryos. The toxicity of the CLO and IMD mixture at environmentally-relevant concentrations was confirmed by the alteration of the transcriptional levels of target genes, such as cell damage linked to oxidative stress response and thyroid hormone synthesis related to zebrafish embryonic development. Consequently, the findings of this study can be considered a strategy for examining mixture toxicity in the range of detected environmental concentrations. In particular, our results will be useful in explaining the mode of toxic action of chemical mixtures following short-term exposure. Finally, the toxicity information of CLO and IMD mixtures will be applied for the agricultural environment, as a part of chemical regulation guideline for the use and production of pesticides.