Toxicity Of Mixtures Research Articles

Side effects of the addition of an adsorbent for the nitrification performance of a microbiome in the treatment of an antibiotic mixture

This work determined the effect of biochar (BC) as an adsorbent on the nitrifying microbiome in regulating the removal, transformation, fate, toxicity, and potential environmental consequences of an antibiotic mixture containing oxytetracycline (OTC) and sulfamethoxazole (SMX). Despite the beneficial role of BC as reported in the literature, the present study revealed side effects for the nitrifying microbiome and its functioning arising from the presence of BC. Long-term monitoring revealed severe disruption to nitratation via the inhibition of both nitrite oxidizers (e.g., Nitrospira defluvii) and potential comammox species (e.g., Ca. Nitrospira nitrificans). Byproducts (BPs) more toxic than the parent compounds were found to persist at a high relative abundance, particularly in the presence of BC. Quantitative structure–activity relationship modeling determined that the physicochemical properties of the toxic BPs significantly differed from those of OTC and SMX. The results suggested that the BPs tended to mobilize and accumulate on the surface of the solids in the system (i.e., the BC and biofilm), disrupting the nitrifiers growing at the interface. Collectively, this study provides novel insights, demonstrating that the addition of adsorbents to biological systems may not necessarily be beneficial; rather, they may generate side effects for specific bacteria that have important ecosystem functions.

Interactive Effects of Copper-Silver Mixtures at the Intestinal Epithelium of Rainbow Trout: An In Vitro Approach.

While metals are present in mixture in the environment, metal toxicity studies are usually conducted on an individual metal basis. There is a paucity of data in the existing literature regarding specific metal-metal interactions and their effect on metal toxicity and bioavailability. We studied interactions of a silver (Ag)-copper (Cu) mixture at the intestinal epithelium using an intestinal cell line derived from rainbow trout (Oncorhynchus mykiss), the RTgutGC. Exposures were conducted in media containing different chloride concentrations (low chloride, 1 mM; high chloride, 146 mM), thus resulting in different metal speciation. Cytotoxicity was evaluated based on two endpoints, cell metabolic activity and cell membrane integrity. The Ag-Cu mixture toxicity was assessed using two designs: independent action and concentration addition. Metal mixture bioavailability was studied by exposing cells to 500 nM of Ag or Cu as a single metal or a mixture (i.e., 500 nM of Cu plus 500 nM of Ag). We found an antagonistic effect in the low-chloride medium and an additive/synergistic effect in the high-chloride medium. We found that Cu dominates over Ag toxicity and bioavailability, indicating a competitive inhibition when both metals are present as free metal ions in the exposure media, which supports our hypothesis. Our study also suggests different mechanisms of uptake of free metal ions and metal complexes. The study adds valuable information to our understanding of the role of metal speciation on metal mixture toxicity and bioavailability. Environ Toxicol Chem 2024;43:105-114. © 2023 SETAC.

A novel method for predicting the emergence of toxicity interaction in ternary mixtures

The environment is teeming with a wide variety of pollutants, but the complexity and diversity of their combinations make it difficult to fully assess their toxicity interaction. A novel toxicity interaction prediction method (TIPM) based on the three-dimensional (3D) surface form of the concentration addition (CA) deviation model (dCA) was proposed to predict the emergence of toxicity interaction in ternary mixtures. Doxycycline hyclate (DH), bromoacetic acid (BAA) and iodoacetic acid (IAA) were used as target pollutants. The toxicity of binary and ternary mixtures designed by the direct equipartition ray design method (EquRay) and the uniform design ray method (UD-Ray) against Escherichia coli (E. coli) was determined by using a time-dependent microplate toxicity analysis (t-MTA) method. The toxicity interaction within mixtures was characterized qualitatively and quantitatively using dCA 3D surface modeling and the emergence of DH-MAA-IAA toxicity interaction was predicted by TIPM. The results showed that the dCA 3D surface model could well characterize the toxicity interactions of the mixtures, and toxicity interaction was closely related to the components’ concentration ratio (pi). TIPM could predict the emergence of DH-MAA-IAA toxicity interactions well based on the relationship. Due the model is only related to the toxicity interactions and pi value of a mixture, so it can be suggested to predict toxicity interaction within the more complex multicomponent mixtures, which provides a novel approach for the environmental risk assessment and prediction of hazardous substances.

Water quality deterioration remains a major stressor for macroinvertebrate, diatom and fish communities in German rivers

About 60 % of Europe's rivers fail to meet ecological quality standards derived from biological criteria. The causes are manifold, but recent reports suggest a dominant role of hydro-morphological and water quality-related stressors. Yet, in particular micropollutants and hydrological stressors often tend to be underrepresented in multiple-stressor studies. Using monitoring data from four Federal States in Germany, this study investigated the effects of 19 stressor variables from six stressor groups (nutrients, salt ions, dissolved oxygen/water temperature, mixture toxicity of 51 micropollutants, hydrological alteration and morphological habitat quality) on three biological assemblages (fishes, macroinvertebrates, benthic diatoms). Biological effects were analyzed for 35 community metrics and quantified using Random Forest (RF) analyses to put the stressor groups into a hierarchical context. To compare metric responses, metrics were grouped into categories reflecting important characteristics of biological communities, such as sensitivity, functional traits, diversity and community composition as well as composite indices that integrate several metrics into one single index (e.g., ecological quality class).Water quality-related stressors – but not micropollutants – turned out to dominate the responses of all assemblages. In contrast, the effects of hydro-morphological stressors were less pronounced and stronger for hydrological stressors than for morphological stressors. Explained variances of RF models ranged 23–64 % for macroinvertebrates, 16–40 % for benthic diatoms and 18–48 % for fishes. Despite a high variability of responses across assemblages and stressor groups, sensitivity metrics tended to reveal stronger responses to individual stressors and a higher explained variance in RF models than composite indices. The results of this study suggest that (physico-chemical) water quality deterioration continues to impact biological assemblages in many German rivers, despite the extensive progress in wastewater treatment during the past decades. To detect water quality deterioration, monitoring schemes need to target relevant physico-chemical stressors and micropollutants. Furthermore, monitoring needs to integrate measures of hydrological alteration (e.g., flow magnitude and dynamics). At present, hydro-morphological surveys rarely address the degree of hydrological alteration. In order to achieve a good ecological status, river restoration and management needs to address both water quality-related and hydro-morphological stressors. Restricting analyses to just one single organism group (e.g., macroinvertebrates) or only selected metrics (e.g., ecological quality class) may hamper stressor identification and its hierarchical classification and, thus may mislead river management.

Toxic metal mixtures in private well water and increased risk for preterm birth in North Carolina

BackgroundPrenatal exposure to metals in private well water may increase the risk of preterm birth (PTB) (delivery < 37 weeks’ gestation). In this study, we estimated associations between arsenic, manganese, lead, cadmium, chromium, copper, and zinc concentrations in private well water and PTB incidence in North Carolina (NC).MethodsBirth certificates from 2003–2015 (n = 1,329,071) were obtained and pregnancies were assigned exposure using the mean concentration and the percentage of tests above the maximum contaminant level (MCL) for the census tract of each individuals’ residence at the time of delivery using the NCWELL database (117,960 well water tests from 1998–2019). We evaluated associations between single metals and PTB using adjusted logistic regression models. Metals mixtures were assessed using quantile-based g-computation.ResultsCompared with those in other census tracts, individuals residing in tracts where > 25% of tests exceeded the MCL for lead (aOR 1.10, 95%CI 1.02,1.18) or cadmium (aOR 1.11, 95% CI 1.00,1.23) had an increased odds of PTB. Conversely, those residing in areas with > 25% MCL for zinc (aOR 0.77 (95% CI: 0.56,1.02) and copper (aOR 0.53 (95% CI: 0.13,1.34)) had a reduced odds of PTB. A quartile increase in the concentrations of a mixture of lead, cadmium, and chromium was associated with a small increased odds for PTB (aOR 1.02, 95% CI 1.01, 1.03). This metal mixture effect was most pronounced among American Indian individuals (aOR per quartile increase in all metals: 1.19 (95% CI 1.06,1.34)).ConclusionsIn a large study population of over one million births, lead and cadmium were found to increase the risk of PTB individually and in a mixture, with additional mixtures-related impacts estimated from co-exposure with chromium. This study highlights critical racial and ethnic health disparities in relation to private well water thereby emphasizing the urgent need for improved private well water quality to protect vulnerable populations.

Involvement of toxic metals and PCBs mixture in the thyroid and male reproductive toxicity: In silico toxicogenomic data mining

Toxicological research is mostly limited to considering the effects of a single substance, even though the real exposure of people is reflected in their daily exposure to many different chemical substances in low-doses. This in silico toxicogenomic study aims to provide evidence for the selected environmental (organo)metals (lead, cadmium, methyl mercury) + polychlorinated biphenyls mixture involvement in the possible alteration of thyroid, and male reproductive system function, and furthermore to predict the possible toxic mechanisms of the environmental cocktail. The Comparative Toxicogenomic Database, GeneMANIA online software, and ToppGene Suite portal were used as the main tools for toxicogenomic data mining and gene ontology analysis. The results show that 35 annotated common genes between selected chemicals and endocrine system diseases can interact on the co-expression level. Our study highlighted the disruption of the cytokines, the cell's response to oxidative stress, and the influence of the transcription factors as the potential core of toxicological mechanisms of the discussed mixture's effects. The connected toxicological effects of the tested mixture were abnormal sperm cells, a disrupted level of testosterone, and thyroid hormones. The core mechanisms of these effects were inflammation, oxidative stress, disruption of androgen receptor signaling, and the alteration of the FOXO3-Keap-1/NRF2-HMOX1-NQO1 pathway signaling most likely controlled by the co-expression of overlapped genes among used chemicals. This in silico research can be used as a potential core for the determination of biomarkers that can be monitored in future further in vitro and in vivo experiments.

Combined cytotoxicity of phthalate esters on HepG2 cells: A comprehensive analysis of transcriptomics and metabolomics.

Phthalate esters (PAEs), widely used as plasticizers, may pose a potential environmental and human hazard. The aim of this study was to compare the cytotoxicity of di(2-ethylhexyl) phthalates (DEHP) and dibutyl phthalate (DBP)) after their exposure to HepG2 cells alone or in combination. HepG2 cells treated with individual/combined DEHP and DBP at a dose of 10-2 M for 24 h were selected for metabolome and transcriptome analysis. The results demonstrated that exposure to the mixtures of DEHP and DBP caused enhanced or reduced toxic effects regarding 8 pathways with 1065 downregulated genes and 643 upregulated genes, in comparison with those of single chemicals. The combined toxicity of mixture revealed both synergistic and antagonistic interactions between DEHP and DBP. Besides, combined exposure to DEHP and DBP promoted TCA cycle, pyrimidine, and purine metabolism, while an antagonistic effect on fatty acid derangement should require further investigation. To summarize, our results suggest that DEHP exposed alone or combined with DBP caused a variety of metabolic disorders, and the type of combination effects varied among metabolic pathways.

Micronuclei, Pesticides, and Element Mixtures in Mining Contexts: The Hormetic Effect of Selenium.

The contexts where there are mining and agriculture activities are potential sources of risk to human health due to contamination by chemical mixtures. These contexts are frequent in several Colombian regions. This study explored the potential association between the frequency of micronuclei and pesticides and elements in regions with ferronickel (Montelibano, Córdoba) and gold (Nechí, Antioquia) mining, and a closed native mercury mine (Aranzazu, Caldas), with an emphasis in the potential effect of selenium as a potential chelator. A cross-sectional study was carried out with 247 individuals. Sociodemographic, occupational, and toxicological variables were ascertained. Blood and urine samples were taken for pesticide analysis (5 organophosphates, 4 organochlorines, and 3 carbamates), 68 elements were quantified in hair, and micronuclei were quantified in lymphocytes. The mixtures of elements were grouped through principal component analysis. Prevalence ratios were estimated with robust variance Poisson regressions to explore associations. Interactions of selenium with toxic elements were explored. The highest concentrations of elements were in the active mines. The potentially most toxic chemical mixture was observed in the ferronickel mine. Pesticides were detected in a low proportion of participants (<2.5%), except paraoxon-methyl in blood (27.55%) in Montelibano and paraoxon-ethyl in blood (18.81%) in Aranzazu. The frequency of micronuclei was similar in the three mining contexts, with means between 4 to 7 (p = 0.1298). There was great heterogeneity in the exposure to pesticides and elements. The "hormetic effect" of selenium was described, in which, at low doses, it acts as a chelator in Montelibano and Aranzazu, and at high doses, it can enhance the toxic effects of other elements, maybe as in Nechí. Selenium can serve as a protective agent, but it requires adaptation to the available concentrations in each region to avoid its toxic effects.

Metal Mixture Toxicity of Ni, Cu, and Zn in Freshwater Algal Communities and the Correlation of Single-Species Sensitivities Among Single Metals: A Comparative Analysis.

The effects assessment of metals is mainly based on data of single metals on single species, thereby not accounting for effects of metal mixtures or effects of species interactions. Both of these effects were tested in combination, thereby hypothesizing that the sensitivity of a community to synergistic mixture toxicity depends on the correlation of single-species sensitivities among the single metals. Single-metal and metal-mixture effects were tested in full concentration-response experiments (fixed ray of 1:1:3 and 5:1:13 mass ratio Ni:Cu:Zn) on eight single freshwater algal species and 14 algal communities of four species each. The mean correlation of single-species median effect concentrations among the single metals (Ni-Cu, Cu-Zn, and Zn-Ni) for all species in a community ( ) ranged from -0.4 to 0.9 among the communities; most of these (12/14) were positive. Functional endpoints (total biomass) were overall less sensitive than structural endpoints (Bray-Curtis similarity index) for communities with positively correlated single-species sensitivities among the single metals ( ), suggesting that such correlations indicate functional redundancy under metal-mixture stress. Antagonistic metal-mixture interactions were predominantly found in single species, whereas metal-mixture interactions were antagonistic and surprisingly synergistic for the communities, irrespective of the reference mixture model used (concentration addition or independent action). The mixture interactions close to the carrying capacity (day 7) of communities gradually shifted from antagonism to more noninteractions with increasing correlation of single-species sensitivities among the single metals. Overall, this suggests that functional redundancy under mixed-metal stress comes at the cost of reduced biodiversity and that synergisms can emerge at the community level without any synergisms on the single-species level. Environ Toxicol Chem 2023;42:2666-2683. © 2023 SETAC.

Laboratory Determination of Particulate-Matter-Bound Agrochemical Toxicity among Honeybees, Mason Bees, and Painted Lady Butterflies.

Pollinator population declines are global phenomena with severe consequences for native flora and agriculture. Many factors have contributed to pollinator declines including habitat loss, climate change, disease and parasitism, reductions in abundance and diversity of foraging resources, and agrochemical exposure. Particulate matter (PM) serves as a carrier of toxic agrochemicals, and pollinator mortality can occur following exposure to agrochemical-contaminated PM. Therefore, laboratory-controlled experiments were conducted to evaluate impacts of individual PM-bound agrochemicals. Honeybees (Apis mellifera), blue orchard mason bees (Osmia lignaria), and painted lady butterfly (Vanessa cardui) larvae were exposed to bifenthrin, permethrin, clothianidin, imidacloprid, abamectin, and ivermectin via suspended, airborne PM. Agrochemical concentrations in PM to which pollinators were exposed were based on concentrations observed in fugitive beef cattle feedyard PM including a "mean" treatment and a "max" treatment reflective of reported mean and maximum PM-bound agrochemical concentrations, respectively. In general, pollinators in the mean and max treatments experienced significantly higher mortality compared with controls. Honeybees were most sensitive to pyrethroids, mason bees were most sensitive to neonicotinoids, and painted lady butterfly larvae were most sensitive to macrocyclic lactones. Overall, pollinator mortality was quite low relative to established toxic effect levels derived from traditional pollinator contact toxicity tests. Furthermore, pollinator mortality resulting from exposure to individual agrochemicals via PM was less than that reported to occur at beef cattle feedyards, highlighting the importance of mixture toxicity to native and managed pollinator survival and conservation. Environ Toxicol Chem 2023;42:2642-2650. © 2023 SETAC.

Single and mixture toxicity evaluation of avobenzone and homosalate to male zebrafish and H295R cells

Avobenzone and homosalate are widely used in sunscreens to provide ultraviolet (UV) protection, either as single compounds or in combination. Some UV filters exhibit estrogenic or anti-androgenic activities, however, studies regarding their interactions and toxicity in mixtures are limited. In this study, the effect of the toxicity of a binary mixture comprising avobenzone (0.72 μg L−1) and homosalate (1.02 and 103 μg L−1) on steroid hormone biosynthesis were investigated using male zebrafish and human adrenocortical carcinoma (H295R) cells. In fish exposed to homosalate, a significant decrease in the gonadosomatic index, testosterone level, and transcription of several genes (e.g, hsd3b2, cyp17a1, and hsd17b1) and a significant increase in the hepatosomatic index, liver steatosis, 17β-estradiol level, and transcription of vtg gene were observed. These results suggest that estrogenic and anti-androgenic effects of homosalate were mediated by the steroidogenic pathway. The presence of 0.72 μg L−1 of avobenzone augmented the anti-androgenic responses in male fish. The testosterone level in the H295R cells were significantly decreased after they were exposed to homosalate alone or in combination with avobenzone, which is consistent with observations in male zebrafish. Further studies need to be conducted to understand the endocrine disrupting properties of long-term exposure to substances typically used in sunscreens.

Assessment of the contribution of surfactants to mixture toxicity in French surface waters

Surfactants are widely used ‘down-the-drain’ chemicals with the potential to occur at high concentrations in local water bodies and to be part of unintentional environmental mixtures. Recently, increased regulatory focus has been placed on the impacts of complex mixtures in aquatic environments and the substances that are likely to drive mixture risk. This study assessed the contribution of surfactants to the total mixture pressure in freshwater ecosystems. Environmental concentrations, collated from existing French monitoring data, were combined with estimated ecotoxicological thresholds to calculate hazard quotients (HQ) for each substance, and hazard indices (HI) for each mixture. Two scenarios were investigated to correct for concentrations below the limit of quantification (LOQ) in the dataset. The first (best-case) scenario assumed all values <LOQ = 0, hence unquantified chemicals were not accounted for in the mixture. The second (worst-case) scenario considered values <LOQ = LOQ, whereby the uncertainty associated with unquantified chemicals was accounted for. When the first scenario was applied (<LOQ = 0), the HIs of the surfactants within the mixture were below 1 for almost all (233/234) mixtures. The median HI for the surfactants was 0.03, whereas the median HI for non-surfactants was 0.5. In the second scenario (<LOQ = LOQ), the surfactants within the mixture exceeded the HI of 1 in all mixtures. Detailed evaluation of the results demonstrated that these exceedances were primarily driven by laurylpyridinium, while other surfactants displayed HIs between 0 and 0.5 and non-surfactants displayed a median HI of 243. Across both scenarios, this study found that the relative contribution of the investigated surfactants to the total mixture pressure in French surface waters was measurable but low compared to non-surfactant substances in the mixture. This indicates that mixture risks of surfactants are of minor importance in these aquatic environments.

Unraveling the combined toxicity and removal mechanisms of fluoxetine and sertraline co-contaminants by the freshwater microalga Chlorella pyrenoidosa

Selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine (FLX) and sertraline (SER), are among the most widely detected pharmaceuticals in aquatic environments, and they usually occur as mixtures. However, little is known about the combined toxicity of SSRI mixtures to microalgae and the associated removal mechanisms. This study investigated the combined toxicity of FLX and SER to the growth, photosynthetic activity, and antioxidant system of Chlorella pyrenoidosa and their removal mechanisms. The results showed that FLX and SER strongly inhibited microalgal growth with 96 h EC50 values of 493 and 61.1 μg/L, respectively. Additionally, the combined toxicity of FLX and SER towards microalgal growth exhibited an additive effect. After 4 days of short-term exposure, FLX, SER, and their mixtures caused photosynthetic damage and oxidative stress in microalgae, and the mixture's toxicity was stronger than those of individuals. However, the adverse effects on microalgal growth, photosynthetic activity, and antioxidant system were alleviated with increasing exposure time. Meanwhile, C. pyrenoidosa efficiently removed FLX (67.59%–99.08%) and SER (94.92%–99.11%) individually after 11 days of cultivation. Biodegradation (59.25%–86.21%) was the prominent removal mechanism of FLX, while both biodegradation (48.08%–88.17%) and bioaccumulation (4.74%–43.38%) contributed significantly to SER removal. The co-existence of FLX and SER lowered the removal rate and biodegradation amount of both compounds. Besides, SER inhibited C. pyrenoidosa's N-demethylation and O-dealkylation of FLX, while co-existing with FLX inhibited the excretion of the N-deamination product of SER from microalgal cells. Furthermore, the principal component analysis indicated that the removal performance of FLX, SER, and their mixtures correlated strongly to the microalgae's physiological and biochemical states. These results highlighted the significance of co-contamination during ecological risk assessments and microalgae-based bioremediation of SSRIs.

Assessing the Toxicity of Sea Salt to Early Life Stages of Freshwater Mussels: Implications for Sea Level Rise in Coastal Rivers.

Sea levels across the planet are rising, particularly along the eastern coast of the United States. Climate-induced sea level rise can result in the inundation and intrusion of seawater into freshwater drainages. This would alter salinity regimes and lead to the salinization of coastal freshwater ecosystems. Increased salinity levels in freshwater can negatively affect freshwater-dependent species, including native mussels belonging to the order Unionida, which are highly sensitive to changes in water quality. Sea salt is largely made up of sodium and chloride ions, forming sodium chloride, a known toxicant to freshwater mussels. However, sea salt is a mixture that also contains other major ions, including potassium, sulfate, calcium, strontium, and magnesium, among others. Freshwater mussels exposed to sea salt would be exposed to each of the sea salt ions at the same time, resulting in a mixture toxicity effect. The mixture toxicity of these ions on early life stages of freshwater mussels is largely unknown because most research to date has evaluated individual salt ions in relative isolation. Therefore, we conducted acute toxicity tests on early life stages (glochidia and juvenile) of three freshwater mussel species that inhabit Atlantic Slope drainages (nonsalinity-adapted Atlanticoncha ochracea, salinity-adapted A. ochracea, Sagittunio nasutus, and Utterbackiana implicata). Glochidia and juveniles of each species were exposed to a control and six concentrations of Instant Ocean® Sea Salt (IOSS), a synthetic sea salt that closely resembles the ionic composition of natural sea salt. Exposure concentrations were 1 part(s) per thousand (ppt), 2 ppt, 8.5 ppt, 12.5 ppt, 17 ppt, and 34 ppt. We calculated the median effect concentration (EC50) for each of the eight acute toxicity tests and found that glochidia were more sensitive than juveniles to IOSS. At hour 24 EC50s for the glochidia ranged from 0.38 to 3.6 ppt, with the most sensitive freshwater mussel being the nonsalinity-adapted A. ochracea, exhibiting an EC50 of 0.38 ppt (95% confidence interval [CI] 0.33-0.44). Juvenile freshwater mussels exhibited EC50s at hour 96 ranging from 5.0 to 10.4 ppt, with the least sensitive freshwater mussel being the nonsalinity-adapted A. ochracea, exhibiting an EC50 of 10.4 ppt (95% CI 9.1-12.0). Our results show that acute exposure to sea salt adversely affects freshwater mussel viability, particularly glochidia. This information can be used to enhance freshwater mussel conservation strategies in regions that are or will be impacted by climate-induced sea level rise and associated freshwater salinization. Environ Toxicol Chem 2023;42:2478-2489. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

A novel mixture sampling strategy combining latin hypercube sampling with optimized one factor at a time method: A case study on mixtures of antibiotics and pesticides

Global sensitivity analysis in conjunction with quantitative high-throughput screening presents a novel technique for identifying the key components that induce the toxicities of mixtures. However, the mixtures currently designed with this method suffer from unequal frequency sampling, repeated mixtures, and only odd factor levels being considered. Accordingly, we use latin hypercube sampling to generate the starting points of the trajectories to achieve equal frequency sampling and non-repeated mixtures, as well as apply different one factor at a time methods for factors with odd and even levels to achieve suitability for factors with both odd and even levels. This method is called LHS-OAT. LHS-OAT was successfully applied to design 110 equal-frequency and non-repeated mixtures consisting of six antibiotics and four pesticides. It was found that four factors, roxithromycin (A5), tetracycline (A6), dichlorvos (P1), and demeton-S (P3), induce the toxicities of mixtures, and A5 and P1 in the Shaying River Basin have risk quotients ≥ 1. Additionally, we developed the toxicity deviation ratio to correct the risk quotients of interacting mixtures for effective risk assessments. This study provides a rational and effective method for mixture design that accurately identifies the important factors that induce the toxicities of mixtures.

Lethal and sublethal effects towards zebrafish larvae of microcystins and other cyanopeptides produced by cyanobacteria

Cyanobacterial blooms affect aquatic ecosystems across the globe and one major concern relates to their toxins such as microcystins (MC). Yet, the ecotoxicological risks, particularly non-lethal effects, associated with other co-produced secondary metabolites remain mostly unknown. Here, we assessed survival, morphological alterations, swimming behaviour and cardiovascular functions of zebrafish (Danio rerio) upon exposure to cyanobacterial extracts of two Brazilian Microcystis strains. We verified that only MIRS-04 produced MCs and identified other co-produced cyanopeptides also for the MC non-producer NPCD-01 by LC-HRMS/MS analysis. Both cyanobacterial extracts, from the MC-producer and non-producer, caused acute toxicity in zebrafish with LC50 values of 0.49 and 0.98 mgdw_biomass/mL, respectively. After exposure to MC-producer extract, additional decreased locomotor activity was observed. The cyanopeptolin (micropeptin K139) contributed 52% of the overall mortality and caused oedemas of the pericardial region. Oedemas of the pericardial area and prevented hatching were also observed upon exposure to the fraction with high abundance of a microginin (Nostoginin BN741) in the extract of the MC non-producer. Our results further add to the yet sparse understanding of lethal and sublethal effects caused by cyanobacterial metabolites other than MCs and the need to better understand the underlying mechanisms of the toxicity. We emphasize the importance of considering mixture toxicity of co-produced metabolites in the ecotoxicological risk assessment of cyanobacterial bloom events, given the importance for predicting adverse outcomes in fish and other organisms.

Biodegradation of commercial textile reactive dye mixtures by industrial effluent adapted bacterial consortium VITPBC6: a potential technique for treating textile effluents.

Textile industries release major fraction of dyestuffs in effluents leading to a major environmental concern. These effluents often contain more than one dyestuff, which complicates dye degradation. In this study ten reactive dyes (Reactive Yellow 145, Reactive Yellow 160, Reactive Orange 16, Reactive Orange 107, Reactive Red 195, Reactive Blue 21, Reactive Blue 198, Reactive Blue 221, Reactive Blue 250, and Reactive Black 5) that are used in textile industries were subjected to biodegradation by a bacterial consortium VITPBC6, formulated in our previous study. Consortium VITPBC6 caused single dye degradation of all the mentioned dyes except for Reactive Yellow 160. Further, VITPBC6 efficiently degraded a five-dye mixture (Reactive Red 195, Reactive Orange 16, Reactive Black 5, Reactive Blue 221, and Reactive Blue 250). Kinetic studies revealed that the five-dye mixture was decolorized by VITPBC6 following zero order reaction kinetic; Vmax and Km values of the enzyme catalyzed five-dye decolorization were 128.88mg L-1day-1 and 1003.226mg L-1 respectively. VITPBC6 degraded the dye mixture into delta-3,4,5,6-Tetrachlorocyclohexene, sulfuric acid, 1,2-dichloroethane, and hydroxyphenoxyethylaminohydroxypropanol. Phytotoxicity, cytogenotoxicity, microtoxicity, and biotoxicity assays conducted with the biodegraded metabolites revealed that VITPBC6 lowered the toxicity of five-dye mixture significantly after biodegradation.

Metallomics analysis of metal exposure and cognitive function in older adults: A combined epidemiological and bioinformatics study

Dementia is a significant cause of elderly disability and Alzheimer's disease (AD) is the most prevalent form of dementia. As an early stage of AD, the mechanism related to mild cognitive impairment (MCI) and heavy metals is still unclear. This study utilized a cross-sectional design and enrolled 514 older adults in Bejing, China. Cognitive function was assessed by the Mini-Mental State Examination (MMSE) and fourteen blood metals were measured by inductively coupled plasma mass spectrometry (ICP-MS). In the adjusted single-metal models, we observed that copper [Cu, β (95% CI): 3.73 (−6.42, −1.03)] and lead [Pb, β (95% CI): 0.79 (−1.26, −0.32)] demonstrated negative associations with cognitive function, while selenium [Se, β (95% CI): 2.97 (1.23, 4.70)] was beneficial to cognition. Our findings were robust in secondary analysis using multi-metal models, which included generalized linear models (GLM), Bayesian kernel machine regression (BKMR), and quantile g-computation (qgcomp). Moreover, the toxic metal mixture (Cu and Pb) exhibited a significant negative association with MMSE scores and the inclusion of Se in the metal mixture attenuated the neurotoxicity of Cu–Pb mixture. The in silico analysis was used to examine the potential molecular mechanisms (genes, biological processes, pathways, and illnesses) of interaction among metal mixtures. We identified 20 cognition-related genes that are associated with both Cu–Pb and Se. Among these genes, eight (APOE, APP, BAX, BDNF, CASP3, HMOX1, TF, and TPP1) exhibited opposite effects on protein activity, mRNA expression, or protein expression in response to Se and Cu/Pb exposure, which could be the key genes accounting for the anti-neurotoxic effects of Se. Our findings support that Se can attenuate the neurotoxicity of exposure to single Cu or Pb, and Cu–Pb mixture. More research is needed to confirm our findings and gain knowledge about the molecular mechanisms of combined metal exposure on cognitive function.

P17-05: Mixture toxicity of pharmaceuticals and microplastics toward Daphnia magna

P17-05: Mixture toxicity of pharmaceuticals and microplastics toward Daphnia magna

Toxicity of spray adjuvants and tank mix combinations used in almond orchards to adult honey bees (Apis mellifera).

Commercial beekeepers transporting honey bees across the United States to provide almond pollination services have reported honey bee deaths, possibly due to pesticide applications made during crop bloom. Pesticides are often applied as "tank mixes", or mixtures of fungicides and insecticides combined into a single application. Spray adjuvants are often added to tank mixes to improve the application characteristics of a pesticide and include spreaders, stickers, or surfactants. The goal of this research was to determine toxicity of adjuvants to adult worker honey bees, both when applied alone and in adjuvant-pesticide tank mixtures. Field-relevant combinations of formulated products were applied to 3-day-old adult worker honey bees using a Potter Spray Tower, and mortality was assessed 48 h following exposure. Adjuvants tested included Activator-90, Attach, Choice Weather Master, Cohere, Dyne-Amic, Induce, Kinetic, LI 700, Liberate, Nu-Film P, PHT Latron B-1956, and Surf-90; fungicides tested include Luna Sensation (Fluopyram and Trifloxystrobin), Pristine (Pyraclostrobin and Boscalid), Tilt (Propiconazole), and Vangard (Cyprodinil), and insecticides tested include Altacor (Chlorantraniliprole), Intrepid 2F (Methoxyfenozide), and a positive control Mustang Maxx (Zeta-cypermethrin). Results demonstrated that exposure to some adjuvants causes acute honey bee mortality at near-field application rates, both when applied alone and in combination with pesticides. Some adjuvant-pesticide combinations demonstrated increased toxicity compared with the adjuvant alone, while others demonstrated decreased toxicity. A better understanding of adjuvant and adjuvant-pesticide tank mixture toxicity to honey bees will play a key role in informing "Best Management Practices" for pesticide applicators using spray adjuvants during bloom when honey bee exposure is likely.