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Though phased out from use in the United States, environmental contamination by organochlorine pesticides (OCPs) remains a widespread issue, especially around intensive agricultural regions. OCPs, such as dichlorodiphenyltrichloroethane (DDT) and its primary metabolite, dichlorodiphenyldichloroethylene (DDE), have been detected in soils, sediments, surface waters, and biota decades after their discontinued use. As OCPs are persistent and can bioaccumulate in fats, these compounds can transfer and magnify across food webs. Freshwater predatory fish and birds can accumulate high OCP concentrations, leading to a myriad of deleterious impacts on organismal health. Studies have found evidence of reproductive disruption in predatory fish, such as the largemouth bass (LMB; Micropterus salmoides), associated with DDT and DDE exposure. DDE can act through estrogenic pathways and induce the expression of estrogenic signals in male animals; however, the molecular mechanism of disruption is unclear. Recently, metabolomics research has revealed corollary relationships between lipid signals and organic pollutant toxicity. Here, a two-month feeding experiment on LMB was conducted to assess the interactions of DDE (as p,p'-DDE) in food with gut and liver lipid signaling. Targeted lipidomic analysis revealed global alterations in the abundance of tissue lipids, especially cholesteryl esters and phospholipids, in LMB exposed to low levels of p,p'-DDE. Results from these studies indicate that p,p'-DDE may act through disruption of normal lipid homeostasis to cause toxicity in freshwater fish. [Display omitted] • This study examined the effects of p,p'-DDE on the largemouth bass lipidome. • p,p'-DDE alters the composition of phospholipids and cholesterol esters. • Fatty acid/steroid biosynthesis and phospholipid metabolism altered. [ABSTRACT FROM AUTHOR]

Sodium chloride (NaCl) is the most common de-icing agent used on roads and parking lots in North America. During the winter and spring, chloride (Cl−) is readily transported from paved surfaces to stormwater management facilities in a matter of hours to days. According to earlier studies, densimetric stratification in end-of-pipe stormwater management facilities such as wet stormwater management ponds (SWMPs) can result in latencies in Cl− transport to receiving waters. As a result, wet SWMPs may generate Cl− pulses in streams that exceed thresholds of acute toxicity to aquatic biota. This study identified the prevalence of this phenomenon at five headwater streams receiving discharge from wet SWMPs within the Greater Toronto Area over two years. All receiving streams in this study experienced exceedances of the chronic CWQG for Cl− downstream of the SWMP outlet, while only some experienced exceedances of the acute CWQG for Cl−. For most of the salting season, SWMP contributions exacerbate downstream Cl− concentrations, and occasionally are the primary driver of exceedances. Bottom-draw SWMPs were found to accumulate Cl− and flush rapidly following a rain or melt event. Top-draw SWMPs accumulated Cl− throughout the salting season and released diluted concentrations of Cl− near the end of the season. Streams with large upstream catchments diluted SWMP contributions and ameliorated downstream Cl− concentrations. [ABSTRACT FROM AUTHOR]

Demand for unconventional crude oils continues to drive the production of diluted bitumen (dilbit) within Western Canada, promoting increased transport volumes across the extensive 700,000 km pipeline system of Canada and the USA. Despite this vast extent of terrestrial transport, the current understanding of the behavior and fate of spilled dilbit within shallow groundwater systems is limited. To this end, oil spill experiments with a dilbit (Cold Lake Blend) and a physicochemically similar conventional heavy crude oil (Conventional Heavy Blend) were conducted for 104 days in large soil columns (1 m height × 0.6 m diameter) engineered to model contaminant transport in the unsaturated (vadose) zone. Around two-fold greater concentrations and 6–41 % faster rates of vadose zone transport of benzene, toluene, ethylbenzene and xylenes (BTEX) and polycyclic aromatic compounds (PACs) were observed in the dilbit- compared to conventional heavy crude-contaminated columns. As determined by Orbitrap mass spectrometry, the O x S x species abundances in the acid extractable organics (AEOs) fraction of column leachate from both oil types increased over time, ostensibly due to microbial degradation of petroleum. Bioaccumulation of petroleum constituents in fathead minnow (Pimephales promelas) larvae exposed to contaminated leachate was confirmed through the induction of developmental malformations lasting up to 34 days and increased abundance of cyp1a mRNA observed throughout the experiment. Toxicity was comparable between the two oils but could not be fully attributed to metals, BTEX, PACs or AEOs, implying the presence of uncharacterized teratogens capable of being transported within the vadose zone following terrestrial dilbit and conventional heavy crude oil surface spills. [Display omitted] • Vadose zone spill experiments carried out using large soil-filled columns. • Dilbit (DB) & conventional heavy crude (CC) had similar toxic effects over 104 d. • Higher BTEX & PAC concentrations and transfer rates in DB versus CC leachate. • O x S x species abundances in acid extractable organics (AEOs) increased over time. • Toxicity could not be fully attributed to metals, BTEX, PACs or AEOs. [ABSTRACT FROM AUTHOR]

This research comprehensively assesses phosphorus-based flame retardants (OPFRs) in seawater, sediment, and algae from the Romanian Black Sea coastline, evaluating their concentrations, distribution patterns, and potential environmental risks. OPFR concentrations ranged from 479 to 2229 ng/L in abiotic samples and 44 to 1953 ng/g dry weight in sediments, while algae samples showed concentrations between 273 and 10,301 ng/g dry weight. The most common OPFRs identified were tri-propyl phosphate (TPP), tri(2-chloroethyl) phosphate (TCEP), and tri(2-chloroisopropyl) phosphate (TCPP) in abiotic samples, with TCEP, diphenyl phosphate (DPHP), TPP, and TCPP dominating in algae. Notably, TPP reached concentrations of 1417 ng/L and 10,062 ng/g dry weight in algae. The environmental risk assessment indicated that these contaminants pose risks ranging from low to medium, highlighting a moderate concern for aquatic organisms. The findings underscore the need for ongoing monitoring and evaluation of OPFR levels in marine environments to inform management strategies and mitigate potential ecological impacts on the Black Sea ecosystem. [Display omitted] • Eleven OPFRs detected in Romanian Black Sea • TCPP, TCEP, and TPP dominant, with highest levels in algae • Similar concentrations in seawater and sediments; no global average for algae • Individual OPFRs pose low to medium risk; mixture risk needs study. • Understanding degradation & monitoring crucial for environmental implications [ABSTRACT FROM AUTHOR]

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Deltamethrin (DLM), in combination with the synergist piperonyl butoxide (PBO), is extensively used in pest control programs due to its potent pesticidal properties and appreciable safety margin. However, various research studies report their adverse effects on non-target organisms. In this study, we investigated the toxicity of DLM, PBO, and a DLM-PBO (3:1) combination on Labeo rohita (L. rohita) fish fingerlings. Fish behavior and mortality rates were recorded at different time intervals up to 96 h for concentrations of 0.003, 0.007, 0.015, 0.031, and 0.062 µg/mL, respectively. Biochemical, hematological, and histopathological studies were carried out. High-performance liquid chromatography (HPLC) was used to detect and quantify residues in fish samples. The LC50 values after 48 h for DLM, PBO, and DLM-PBO exposed fish fingerlings were found to be 0.028, 0.066, and 0.007 µg/mL, respectively. At a concentration of 0.003 µg/mL of DLM, PBO, and DLM-PBO, the treated fish fingerlings exhibited similar behavior to the control group. Hematological parameters, such as red blood cell (RBC) and white blood cell (WBC) counts, were reduced in the treated groups compared to the control. Biochemical parameters showed increased levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), while total serum protein levels decreased in DLM, PBO, and DLM-PBO treated fingerlings. Histopathological examination of liver, gill, and heart tissues revealed lesions with hydropic degeneration in the liver and fusions of gill lamellae in the treated tissues. Fish fingerlings exposed to the DLM-PBO combination appeared highly prone to toxicity compared to those treated with DLM and PBO separately. [Display omitted] • Combined DLM-PBO exposure was more toxic to L. rohita fingerlings than single exposures. • Notable tissue damage was observed, including hydropic degeneration and gill lamellae fusion. • Significant behavioral disruptions were evident at higher concentrations. • PBO accumulated more in fish tissues than DLM, highlighting differential bioaccumulation. • Findings suggest potential environmental risks of prolonged DLM use, emphasizing the need for careful management. [ABSTRACT FROM AUTHOR]

Endocrine disrupting compounds (EDCs) are commonly detected in aquatic environments and can endanger aquatic life. The responses of enzymatic biomarkers in asexual freshwater planarians (lactate dehydrogenase, glutathione S-transferase, glucose-6-phosphate dehydrogenase, and isocitric dehydrogenase) were evaluated after 7-day exposure to endocrine disruptors (bisphenol A [BPA], diethylstil-bestrol [DES], 17a-ethinylestradiol [EE2], and 17(3-estradiol [E2]). These biomarkers are ubiquitous enzymes and play crucial physiological roles in living organisms. In this study, EDCs influenced the non-specific enzyme activities of asexual planarians. However, the effects of EDCs on enzymatic biomarkers did not correspond with the order of their estrogenic potencies. Furthermore, exposure to EDCs for 7 days mostly slightly or significantly reduced the enzyme activities of planarians compared with those of their respective controls. Alterations in enzyme activities can affect the energy metabolism and health status of organisms. The environmental levels of E2, EE2, and DES can range from lower than their detectable limits to tens of ng L-1, and BPA levels in river water can be several μg L-1. These findings suggest that some aquatic animals might be affected by the current levels of BPA in hotspot pollution scenarios. [ABSTRACT FROM AUTHOR]

Difenoconazole has a widespread agricultural use to control fungal diseases in crops, including rice. In edge-of-field surface waters the residues of this lipophilic fungicide may be toxic to both pelagic and benthic organisms. To allow an effect assessment we mined the regulatory and open literature for aquatic toxicity data. Since published sediment toxicity data were scarce we conducted 28 d sediment-spiked toxicity test with 8 species of benthic macroinvertebrates. Ecotoxicological threshold levels for effects were assessed by applying the species sensitivity distribution approach. Based on short-term L(E)C 50 's for aquatic organisms from water-only tests an acute Hazardous Concentration to 5% of the species (HC 5) of 100 µg difenoconazole/L was obtained, while the HC 5 based on chronic NOEC values was a factor of 104 lower (0.96 µg difenoconazole/L). For benthic macroinvertebrates the chronic HC 5 , based on 28d-L(E)C 10 values, was 0.82 mg difenoconazole/kg dry weight sediment. To allow a risk assessment for water- and sediment-dwelling organisms, exposure concentrations were predicted for the water and sediment compartment of an edge-of-field pond bordering rice paddies treated with difenoconazole using the Chinese Top-Rice modelling approach, the Chinese Nanchang exposure scenario and the Equilibrium Partitioning theory. It appeared that in the vast majority of the 20 climate years simulated, potential risks to aquatic and sediment organisms cannot be excluded. Although the HC 5 values based on laboratory toxicity data provide one line of evidence only, our evaluation suggests population- and community-level effects on these organisms due to chronic risks in particular. • Ecotoxicological threshold levels on pelagic and benthic aquatic organisms of the fungicide difenoconazole were assessed by applying the species sensitivity distributions. • Sediment-spiked toxicity tests were conducted with 8 benthic test species, since sediment toxicity data for difenoconazole were hardly available in the open and regulatory literature. • Based on hazardous concentrations for 5% of the pelagic aquatic species tested, the acute to chronic ratio was high (factor of 104). • The Top-Rice modelling approach and our estimates of threshold levels for effect suggest high chronic risks to pelagic organisms in edge-of-field ponds bordering rice paddies. • Preliminary sediment exposure estimates and results of our sediment-spiked toxicity tests indicate potential risks on sediment-dwelling macroinvertebrates in these ponds. [ABSTRACT FROM AUTHOR]

The ability to employ waste products, such as vegetable scraps, as raw materials for the synthesis of new promising adsorbing materials is at the base of the circular economy and end of waste concepts. Dextrin-based nanosponges (D_NS), both cyclodextrin (CD) and maltodextrin (MD), have shown remarkable adsorption abilities in the removal of toxic compounds from water and wastewater, thus representing a bio-based low-cost solution which is establishing itself in the market. Nevertheless, their environmental safety for either aquatic or terrestrial organisms has been overlooked, raising concern in terms of potential hazards to natural ecosystems. Here, the environmental safety (ecosafety) of six newly synthesized batches of D_NS was determined along with their full characterization by means of dynamic light scattering (DLS), thermogravimetric analysis (TGA), Fourier transformed infrared spectroscopy with attenuated total reflection (FTIR-ATR) and transmission electron microscopy (SEM). Ecotoxicity evaluation was performed using a battery of model organisms and ecotoxicity assays, such as the microalgae growth inhibition test using the freshwater Raphidocelis subcapitata and the marine diatom Dunaliella tertiolecta , regeneration assay using the freshwater cnidarian Hydra vulgaris and immobilization assay with the marine brine shrimp Artemia franciscana. Impact on seedling germination of a terrestrial plant of commercial interest, Cucurbita pepo was also investigated. Ecotoxicity data showed mild to low toxicity of the six batches, up to 1 mg/mL, in the following order: R. subcapitata > H. vulgaris > D. tertiolecta > A. franciscana > C. pepo. The only exception was represented by one batch (NS-Q+_BDE_(GLU2) which resulted highly toxic for both freshwater species, R. subcapitata and H. vulgaris. Those criticalities were solved with the synthesis of a fresh new batch and were hence attributed to the single synthesis and not to the specific D_NS formulation. No effect on germination of pumpkin but rather more a stimulative effect was observed. To our knowledge this is the first evaluation of the environmental safety of D_ NS. As such we emphasize that current formulations and exposure levels in the range of mg/mL do not harm aquatic and terrestrial species thus representing an ecosafe solution also for environmental applications. [Display omitted] • Dextrin-based materials represent a promising bio-based sustainable solution. • As dextrin-based materials applications and market increase, a significant environmental release is expected. • Environmental safety has been overlooked for both aquatic and terrestrial organisms. • Preliminary ecotoxicity data indicate them as ecosafe for natural ecosystems. [ABSTRACT FROM AUTHOR]

Environmental pollution poses risks to ecosystems. Among these risks, one finds neurotoxicity and damage to the lateral line structures of fish, such as the neuromast and its hair cells. Zebrafish (Danio rerio) is recommended as model species to be used in ecotoxicological studies and environmental biomonitoring programs aimed at assessing several biomarkers, such as ototoxicity. However, little is known about the history of and knowledge gaps on zebrafish ototoxicity. Thus, the aim of the current study is to review data available in the scientific literature about using zebrafish as animal model to assess neuromast toxicity. It must be done by analyzing the history and publication category, world production, experimental design, developmental stages, chemical classes, neuromasts and hair cell visualization methods, and zebrafish strains. Based on the results, number, survival and fluorescence intensity of neuromasts, and their hair cells, were the parameters oftentimes used to assess ototoxicity in zebrafish. The wild AB strain was the most used one, and it was followed by Tübingen and transgenic strains with GFP markers. DASPEI was the fluorescent dye most often applied as method to visualize neuromasts, and it was followed by Yo-Pro-1 and GFP transgenic lines. Antibiotics, antitumorals, metals, nanoparticles and plant extracts were the most frequent classes of chemicals used in the analyzed studies. Overall, pollutants can harm zebrafish's mechanosensory system, as well as affect their behavior and survival. Results have shown that zebrafish is a suitable model system to assess ototoxicity induced by environmental pollution. [Display omitted] • State-of-the-art review of zebrafish neuromast ecotoxicity. • Chemicals induce citotoxicity and reduce hair cells. • Ototoxicity mechanisms in zebrafish neuromasts/hair cells discussed. • Zebrafish: great model for environmental ototoxicity. [ABSTRACT FROM AUTHOR]

The phytotoxicity and degradation of ofloxacin (OFX) in duckweed Spirodela polyrhiza based system was estimated in this study. For that, OFX was added in an environmentally relevant range (0.01–1.0 mg L−1) in medium (Hoagland nutrient) and toxicity biomarkers, i.e. changes in plant biomass, relative growth rate (RGR), photopigment (Chl- a , Chl- b and carotenoids), protein content, antioxidative enzymes (catalase, CAT; superoxide dismutase, SOD; and ascorbate peroxidases, APX) in fronds were estimated. The batch-scale setups (250 ml) was prepared in triplicate for each concentration of OFX and reared in growth chambers (Algae Tron AG 230) for 7 d. Results suggested that the high concentrations of OFX caused a reduction in biomass (4.8–41.3%), relative root growth (RGR), protein (4.16–11.28%) and photopigment contents. The fronds in OFX spiked setups showed an increased level of antioxidative enzymes: CAT (0.230–0.338 mmol H2O2 mg−1 protein), APX (0.043–0.074 mmol ascorbate mg−1 protein), and SOD (0.267–0.317 U mg−1 protein) than control. At the end (7 d), the residual OFX content in the medium was also estimated, and results suggested a significant (p < 0.05) reduction (93.73–98.36%) in OFX content than control setup (54.76–75.53%) at the end of the experimentation. The trend of residual OFX suggested phytodegradation as a significant mechanism of antibiotic degradation other than hydrolysis and photodegradation processes. This study indicates that duckweed can be an effective bio-tool for the removal of environmental relevant concentration of the antibiotics from the wastewater. Image 1 • To our best knowledge, this is first study on toxicity and removal of ofloxacin (OFX) by duckweed (DW) Spirodela polyrhiza. • Phototoxicity biomarkers (Chl a , Chl b , carotenoids, etc.) and antioxidative enzymes (CAT, SOD and APX) indicates the sensitivity towards OFX. • Reduction in OFX content (93.73–98.36%) in DW setups suggested the role of phytodegradation apart from other mechanisms in antibiotic removal. [ABSTRACT FROM AUTHOR]

Abstract Neonicotinoids are the most widely used insecticides in the world. They are preferentially toxic to insects while displaying a low toxicity toward vertebrates, and this selective toxicity has resulted in the rapid and ubiquitous use of these compounds. However, neonicotinoids have been detected in agricultural surface waters and are known to cause adverse effects in non-target aquatic organisms. A wide range of toxicity has been reported for aquatic crustaceans, but most of the studies focus on the acute effects of imidacloprid, and few data are available regarding chronic effects of other neonicotinoids or neonicotinoid replacements (e.g., butenolides). The objective of this study was to assess the acute and chronic toxicity of six neonicotinoids (imidacloprid, thiamethoxam, acetamiprid, clothianidin, thiacloprid, and dinotefuran) and one butenolide (flupyradifurone) to the freshwater amphipod Hyalella azteca. Chronic (28-d), water-only, static-renewal tests were conducted. Survival was assessed weekly, and growth was measured at the end of the exposure. Effects of neonicotinoids varied depending on the compound. Acute (7-d) LC50s were 4.0, 4.7, 60, 68, 230, and 290 μg/L for clothianidin, acetamiprid, dinotefuran, thiacloprid, imidacloprid, and thiamethoxam, respectively. Chronic (28-d) survival and growth were reduced at similar concentrations to acute (7-d) survival for thiamethoxam, acetamiprid, clothianidin, and dinotefuran. However, chronic survival and growth of amphipods exposed to imidacloprid and thiacloprid were reduced at lower concentrations than acute survival, with respective 28-d LC50s of 90 and 44 μg/L, and EC50s of 4 and 3 μg/L. Flupyradifurone was intermediate in toxicity compared to the neonicotinoids: 7-d LC50, 28-d LC50, and 28-d EC50 were 26, 20, and 16 μg/L, respectively. The concentrations of imidacloprid and clothianidin reported for North American surface waters fall within the effect ranges observed in this study, indicating the potential for these compounds to cause adverse effects to indigenous populations of H. azteca. Highlights • Toxicity of neonicotinoid and butenolide insecticides was assessed in Hyalella. • Range in toxicity among compounds and endpoints was 100-fold. • Clothianidin and acetamiprid had the lowest 7-d and 28-d LC50s. • Acetamiprid, clothianidin, thiacloprid, and imidacloprid had the lowest 28-d EC50s. • Flupyradifurone was intermediate in toxicity compared to neonicotinoids. [ABSTRACT FROM AUTHOR]

Abstract The toxicities of agrochemicals to non-target aquatic organisms are key items in chemical ecological risk assessment. However, it is still an urgent need to develop new tools to assess the agrochemical aquatic toxicity efficiently and accurately. In this work, QSTR studies were performed on a data set containing 639 diverse pesticides with measured EC 50 toxicity against Daphnia magna , by using five machine learning methods combined with seven fingerprints and a set of molecular descriptors. The imbalance problem of the data set was successfully solved by clustering analysis. The top-10 QSTR models displayed greater predicative abilities than ECOSAR. The optimal model, Ext-SVM, showed the best performance in 10-fold cross validation (Q high =0.807, Q moderate =0.806, Q low =0.755, Q total =0.794), and also in the test set verification (Q high =0.865, Q moderate =0.783, Q low =0.931, Q total =0.848). The relevance of the key physical-chemical properties with the toxicity was also investigated, in which the MW, a_np, logP(o/w), GCUT_SLOGP_1, chilv and SMR_VSA7 values displayed positive correlation with Daphnia magna toxicity, whereas the logS and a_don showed negative correlation. The robust QSTR models provided efficient tools for assessing agrochemical aquatic toxicity, and the revealed different physical-chemical properties between the high and low toxic compounds might be useful in the discovery and design of low aquatic toxic pesticides. Graphical abstract fx1 Highlights • Robust models were developed by machine learning methods with molecular descriptions. • Clustering analysis could handle imbalanced data distribution problem. • The top-10 models were superior to ECOSAR in toxicity evaluation on Daphnia magna. • The relevance of molecule physical-chemical properties to toxicity was revealed. [ABSTRACT FROM AUTHOR]

Abstract In vitro experimental systems based on continuous piscine cell lines can be used as an alternative to animal tests for obtaining qualitative and quantitative information on the possible fate and effect of chemicals in fish. However, their capability to reproduce complex metabolic processes and toxic responses as they occur in vivo is limited due to the lack of organ-specific tissue architecture and functions. Here we introduce a three-dimensional (3D) in vitro experimental system based on spheroidal aggregate cultures (spheroids) of the continuous rainbow trout liver cell line RTL-W1 and provide a first description of their structural and functional properties including growth, viability/longevity, metabolic activity, ultrastructure and cytochrome P450 1A (CYP1A) expression determined by bright-field, multi-photon fluorescence and transmission electron microscopy as well as RT-qPCR analysis. Our results show that RTL-W1 cells in 3D spheroids (ø ~ 150 µm) (including those in the interior) were viable, metabolically active and had higher basal and β-naphthoflavone-induced CYP1A expression levels than conventional 2D cell cultures. Furthermore, they displayed ultrastructural characteristics similar to differentiated hepatocytes. The available evidence suggests that 3D RTL-W1 spheroids may have enhanced hepatotypic functions and be a superior in vitro model to assess hepatic biotransformation, bioaccumulation and chronic toxicity compared to conventional cell monolayer cultures. Graphical abstract fx1 Highlights • 3D spheroids of the continuous fish liver cell line RTL-W1 were developed. • Cells in the interior of 15 day-old, 150 µm-large (ø) spheroids were viable. • Cells in spheroids showed ultrastructural characteristics of differentiated hepatocytes. • CYP1A expression in RTL-W1 spheroids was higher than in monolayer cultures [ABSTRACT FROM AUTHOR]

Abstract Sugarcane vinasse is a residue generated at a rate fifteen times greater than the ethanol production. Because of its high organic and micronutrient content, this residue is used as a fertilizer on sugarcane crops. However, when used in large quantities, vinasse can saturate the soil and contaminate nearby water resources by percolation and leaching. Given the proven toxic potential of in natura vinasse, the present study aimed to evaluate the toxic potential of leached sugarcane vinasse using Nile tilapia (Oreochromis niloticus) as a test organism. A bioassay was performed after vinasse percolation in laboratory soil columns. The bioassay included one control group containing fresh water and two treatment groups, the first exposed to a 2,5% dilution of leached of vinasse and the second to a 2,5% dilution of in natura vinasse. After exposure, histopathological analysis was performed in gills and livers, and the latter were labelled for HSP70 proteins. No significant changes were detected in the gills of the exposed fish. However, in the liver, both in natura and leached vinasse induced statistically significant histopathological changes. These changes include hydropic degeneration, cell boundary losses, pyknotic nuclei and cellular disorganization. HSP70 expression significant increase in liver of both treatment groups were observed, being higher for the in natura vinasse exposed group. Results suggested that both leached vinasse and in natura vinasse were toxic, its still able to provoke histological changes and induce the cytoprotective response in exposed fish liver, evidenced by a immunostaining of cellular stress proteins. Thus, in order to reduce its environmental impact, appropriated effluent disposal is essential. Highlights • Vinasse was percolated in soil columns and the leached of vinasse toxicity was tested on organism of soil and aquatic. • In natura and leached of vinasse presented toxicity and it was capable to promoting significant alterations in the liver. • The use of vinasse requires caution. Its toxic potential needs greater attention in order to reduce its environmental impact. [ABSTRACT FROM AUTHOR]

Abstract Creosol and 4-ethylguaiacol are two important methoxyphenols, lignin pyrolysis products, which are discharge into the atmosphere in large quantities. In this work, theoretical calculations of the reaction mechanism towards the two compounds with NO 3 radicals was performed using DFT method. The rate constants and toxicity assessment were also investigated. The atmospheric lifetime for creosol and 4-ethylguaiacol were 0.82 and 0.19 h, respectively. A new reaction pathway was proposed for the transformation of methoxyl into hydroxyl, which has not yet been clarified in previous studies. The toxicity of methoxyphenols and their degradation products is closely related to their hydrophobicity. Although most degradation products are less toxic, they also should be pay more attention, especially for nitro-substituents. A new reaction pathway was proposed for the transformation of methoxyl into hydroxyl. The toxicity is closely related to their hydrophobicity. Graphical abstract Image 1 Highlights • We used quantum chemical methods to discuss the reactions in this work. • A new reaction pathway was proposed for the transformation of methoxyl into hydroxyl. • The NO 3 addition and abstraction reactions are major pathways. • The toxicity of methoxyphenols and their degradation products is closely related to their hydrophobicity. [ABSTRACT FROM AUTHOR]

Abstract Thiamethoxam is a neonicotinoid insecticide used widely in agriculture to control a broad spectrum of insect pests. To assess potential risks from this compound to non-target aquatic organisms, an outdoor mesocosm study was performed. Mesocosms (1300 L) were treated once with a formulated product with the active substance (a.s.) thiamethoxam at nominal concentrations of 1 (n = 3), 3 (n = 3), 10 (n = 4), 30 (n = 4), and 100 (n = 2) μg a.s./L, plus untreated controls (n = 4). Primary producers (phytoplankton), zooplankton, and macroinvertebrates were monitored for up to 93 days following treatment. Thiamethoxam was observed to have a water column dissipation half-life (DT50) of ≤1.6–5.2 days in the mesocosms. Community-based principal response curve analysis detected no treatment effects for phytoplankton, zooplankton, emergent insects, and macroinvertebrates, indicating a lack of direct and indirect effects. A number of statistically significant differences from controls were detected for individual phytoplankton and zooplankton species abundances, but these were not considered to be treatment-related due to their transient nature and lack of concentration-response. After application of 30 μg a.s./L, slight temporary effects on Asellus aquaticus could not be excluded. At 100 μg a.s./L, there was an effect with no clear recovery of Asellus observed, likely due to their inability to recolonize these isolated test systems. A statistically significant but transient reduction in the emergence of chironomids by day 23 at the 100 μg a.s./L treatment was observed and possibly related to direct toxicity from thiamethoxam on larval stages. Therefore, a conservative study specific No Observed Ecological Adverse Effect Concentration (NOEAEC) is proposed to be 30 μg a.s./L. Overall, based on current concentrations of thiamethoxam detected in North American surface waters (typically <0.4 μg/L), there is low likelihood of direct or indirect effects from a pulsed exposure on primary producers, zooplankton, and macroinvertebrates, including insects, as monitored in this study. Graphical abstract Image 1 Highlights • Thiamethoxam is detected in the surface waters of agroecosystems. • A mesocosm study to understand freshwater aquatic organism responses was performed. • No indications of ecologically significant direct or indirect effects at environmental concentrations. Acute exposures to the neonicotinoid insecticide thiamethoxam at environmentally relevant concentrations do not pose a significant risk to freshwater biota. [ABSTRACT FROM AUTHOR]

Neonicotinoid insecticides are environmentally persistent and highly water-soluble, and thus are prone to leaching into surface waters where they may negatively affect non-target aquatic insects. Most of the research to date has focused on imidacloprid, and few data are available regarding the effects of other neonicotinoids or their proposed replacements (butenolide insecticides). The objective of this study was to assess the toxicity of six neonicotinoids (imidacloprid, thiamethoxam, acetamiprid, clothianidin, thiacloprid, and dinotefuran) and one butenolide (flupyradifurone) to Hexagenia spp. (mayfly larvae). Acute (96-h), water-only tests were conducted, and survival and behaviour (number of surviving mayflies inhabiting artificial burrows) were assessed. Acute sublethal tests were also conducted with imidacloprid, acetamiprid, and thiacloprid, and in addition to survival and behaviour, mobility (ability to burrow into sediment) and recovery (survival and growth following 21 d in clean sediment) were measured. Sublethal effects occurred at much lower concentrations than survival: 96-h LC50s ranged from 780 μg/L (acetamiprid) to >10,000 μg/L (dinotefuran), whereas 96-h EC50s ranged from 4.0 μg/L (acetamiprid) to 630 μg/L (thiamethoxam). Flupyradifurone was intermediate in toxicity, with a 96-h LC50 of 2000 μg/L and a 96-h EC50 of 81 μg/L. Behaviour and mobility were impaired significantly and to a similar degree in sublethal exposures to 10 μg/L imidacloprid, acetamiprid, and thiacloprid, and survival and growth following the recovery period were significantly lower in mayflies exposed to 10 μg/L acetamiprid and thiacloprid, respectively. A suite of effects on mayfly swimming behaviour/ability and respiration were also observed, but not quantified, following exposures to imidacloprid, acetamiprid, and thiacloprid at 1 μg/L and higher. Imidacloprid concentrations measured in North American surface waters have been found to meet or exceed those causing toxicity to Hexagenia , indicating that environmental concentrations may adversely affect Hexagenia and similarly sensitive non-target aquatic species. [ABSTRACT FROM AUTHOR]

Saponin-rich extracts from Quillaja saponaria and Chenopodium quinoa have been registered by US EPA as active ingredients in biopesticides, and extract from tea seed powder, Camellia oleifera has been proposed for biocidal use. If saponin-rich biopesticides are efficient against pests, they are most likely also bioactive in the aquatic environment against non-target organisms. The aim of this study was to conduct an effect assessment of saponin-rich plant extracts by using species sensitivity distributions based on acute toxicity tests. The maximal concentrations protecting 95% of the aquatic species (HC 5 ) of saponins extracted from quillaja bark, tea seed coat and quinoa seed coat were 2.91 ± 1.00, 0.22 ± 0.11 and 22.9 ± 5.84 mg/L, respectively. The 100-fold difference in toxicity between the saponin-rich extracts from different plant species, indicate that saponin toxicity depends on the species it origins from, making “read-across” between saponins a dubious exercise. In addition, the predicted environmental concentrations of different saponins are close to or higher than their water quality standard, which means that the extracts might pose a risk to the aquatic environment if not used cautiously. [ABSTRACT FROM AUTHOR]

Biodiesel is considered an important renewable energy source but still there is some controversy about its environmental toxicity, especially to aquatic life. In our study, the toxicity of water soluble fraction of biodiesel was evaluated in relatively low concentrations using a battery of bioassays: Vibrio fischeri bioluminescence inhibition, Sinapis alba root growth inhibition, Daphnia magna immobilization, boar semen live/dead ratio and DNA fragmentation and Unio pictorum micronucleus test. While the S. alba test indicated nutritive (stimulating) effect of the sample, the biodiesel exerted toxic effect in the aquatic tests. D. magna was the most sensitive with EC 50 value of 0.0226%. For genotoxicity assessment, the mussel micronucleus test (MNT) was applied, detecting considerable genotoxic potential of the biodiesel sample: it elucidated micronuclei formation already at low concentration of 3.3%. Although this test has never been employed in biodiesel eco/genotoxicity assessments, it seems a promising tool, based on its appropriate sensitivity, and representativity. [ABSTRACT FROM AUTHOR]

The contamination of uranium in aquatic ecosystems has raised growing global concern. However, the understanding of its chronic effects on aquatic organisms is limited, particularly with regards to transgenerational toxicity. In this study, we evaluated the maternal transfer risk of uranium using zebrafish. Sexually mature female zebrafish were exposed to 2 and 20 ng/g of uranium-spiked food for 28 days. The induced bioconcentration, thyroid disruption, and oxidative stress in both the adults (F0) and their embryos (F1) were further investigated. Element analysis showed that uranium was present in both F0 and F1, with higher concentrations observed in F1, indicating significant maternal offloading to the offspring. Meanwhile, an increased malformation and decreased swim speed were observed in the F1. Thyroid hormone analysis revealed significant decreases in the levels of triiodothyronine (T3) in both the F0 adults and F1 embryos, but thyroxine (T4) was not significantly affected. Additionally, the activities of antioxidant defenses, including catalase (CAT) and superoxide dismutase (SOD), and the expression of glutathione (GSH) and malondialdehyde (MDA) were significantly altered in the F0 and F1 larvae at 120 hpf. The hypothalamic-pituitary-thyroid (HPT) axis, oxidative stress, and apoptosis-related gene transcription expression were also significantly affected in both generations. Taken together, these findings highlight the importance of considering maternal transfer in uranium risk assessments. [Display omitted] • Uranium was enriched in F0 and F1 after maternal exposure. • Uranium showed stronger maternal transfer ability. • Multiple toxic effects occurred in F1 after maternal uranium exposure. • Maternal uranium exposure resulted in thyroid disruption in both F0 and F1. • The reduction of T3 levels in F0 influenced the TH levels in F1. [ABSTRACT FROM AUTHOR]

Styrene oligomers (SOs) are ubiquitous contaminants that appear in the environment, sometimes to significant extent (see section 3.1). Despite the ongoing international debate on the human health risks posed by SOs, to the best of my knowledge, there are no studies on the aquatic toxicity and environmental fates (biodegradation and atmospheric degradation) of SOs in the environment. This study is to predict the aquatic toxicity and environmental fate of SOs by using the US EPA EPI suite program as an in-silico method. For better understanding, the risks and fates of SOs are compared with those of the well-known bisphenol A (BPA) and styrene monomer (SM or styrene). As a result of this study, SOs are predicted to be relatively more toxic than BPA and SM to aquatic and terrestrial organisms in the freshwater, marine, and terrestrial environments. In particular, the biodegradability of SOs is predicted to be relatively very slow in the environment, and most SOs are more likely to be effectively decomposed by hydroxyl radicals than by ozone in the atmosphere. As a result, this study can contribute to motivating understanding of the aquatic toxicity and fate of ubiquitous SOs in the environment. • This study is the first attempt to investigate the ecotoxicity of styrene oligomers (SOs). • This study is the first attempt to investigate the environmental fate of SOs. • SOs are predicted to be relatively more toxic than bisphenol A (BPA). [ABSTRACT FROM AUTHOR]

Chlorpyrifos is a widely used organophosphorus insecticide because of its high efficiency and overall effectiveness, and it is commonly detected in aquatic ecosystems. However, at present, the impact of chlorpyrifos on the aquatic micro-ecological environment is still poorly understood. Here, we established aquatic microcosm systems treated with 0.2 and 2.0 µg/L chlorpyrifos, and employed omics biotechnology, including metagenomics and 16S rRNA gene sequencing, to investigate the effect of chlorpyrifos on the composition and functional potential of the aquatic and zebrafish intestinal microbiomes after 7 d and 14 d chlorpyrifos treatment. After 14 d chlorpyrifos treatment, the aquatic microbial community was adversely affected in terms of its composition, structure, and stability, while its diversity showed only a slight impact. Most functions, especially capacities for environmental information processing and metabolism, were destroyed by chlorpyrifos treatment for 14 d. We observed that chlorpyrifos increased the number of risky antibiotic resistance genes and aggravated the growth of human pathogens. Although no clear effects on the structure of the zebrafish intestinal microbial community were observed, chlorpyrifos treatment did alter the metabolic capacity of the zebrafish. Our study highlights the ecological risk of chlorpyrifos to the aquatic environment and provides a theoretical basis for the rational use of pesticides in agricultural production. [Display omitted] • Chlorpyrifos disrupted aquatic microbial composition, structure, and stability. • Chlorpyrifos destroyed aquatic microbial functions. • Chlorpyrifos increeased risky ARGs and promoted human pathogens grow. • Chlorpyrifos altered the metabolic capacity of the zebrafish. [ABSTRACT FROM AUTHOR]

Chemical analyses and toxicity testing using six marine species were used to characterize the hazard of produced waters (PW) to marine life from twelve Australian offshore platforms. Hazard data were used in conjunction with platform-specific plume discharge dilution and species sensitivity distribution modeling to estimate cumulative risks by calculating the multiple substance potentially affected fraction of species in the local marine environment. Results provided two independent lines of evidence demonstrating that cumulative risks to marine life from these discharges meet intended 95% species protection goals at the edge of the mixing zone. A limited number of PW constituents (hydrocarbons, sulphide and ammonia) appeared to dictate risk thereby informing management and providing a rationale for more targeted analyses in future monitoring studies. Based on these findings a tiered framework is proposed to foster consistent screening and potential refinement of cumulative risk evaluations for PW discharges. [ABSTRACT FROM AUTHOR]

Ketamine has been increasingly used in medicine and has the potential for abuse or illicit use around the world. Ketamine cannot be removed by conventional wastewater treatment plants. Although ketamine and its metabolite norketamine have been detected to a significant degree in effluents and aquatic environments, their ecotoxicity effects in aquatic organisms remain undefined. In this study, we investigated the acute toxicity of ketamine and its metabolite, along with the chronic reproductive toxicity of ketamine (5–100 μg/L) to Daphnia magna . Multiple environmental scenarios were also evaluated, including drug mixtures and sunlight irradiation toxicity. Ketamine and norketamine caused acute toxicity to D. magna , with half lethal concentration (LC 50 ) values of 30.93 and 25.35 mg/L, respectively, after 48 h of exposure. Irradiated solutions of ketamine (20 mg/L) significantly increased the mortality of D. magna ; pre-irradiation durations up to 2 h rapidly increased the death rate to 100%. A new photolysis byproduct (M.W. 241) of norketamine that accumulates during irradiation was identified for the first time. The relevant environmental concentration of ketamine produced significant reproductive toxicity effects in D. magna , as revealed by the reduction of the number of total live offspring by 33.6–49.8% (p < 0.05). The toxicity results indicate that the environmental hazardous risks of the relevant ketamine concentration cannot be ignored and warrant further examination. [ABSTRACT FROM AUTHOR]

Tire particles (TPs) generated on roads are a main contributor to microplastic environmental pollution. In this study, TP leachates from three vehicle types (bicycle, car, and electric scooter) were prepared. TP leachate toxicity impacts on three organisms (Vigna radiata , Daphnia magna , and Danio rerio) were analyzed, in addition to their chemical compositions. Zinc and benzothiazole were the most commonly detected compounds in all three leachate types. Growth inhibition of V. radiata , mortality of D. magna , and abnormality in D. rerio were observed as toxicological impacts. Overall, the lethal effects of TP leachates showed a significant, positive relationship with zinc and benzothiazole concentration. The results confirmed that TPs are complex contaminants, which release chemicals into the environment that affect both soil and aquatic organisms. These findings highlight the need for stricter control measures and environmental regulations to mitigate the ecotoxic effects of TPs and related contaminants across ecosystems and trophic levels. • The effects of tire particle (TP) leachates on living organisms were assessed. • TPs released zinc and benzothiazole as the main chemicals. • Plants, water fleas, and fish embryos were exposed to three TP leachate types. • TP leachate-exposed organisms showed growth inhibition, mortality, and abnormality. [ABSTRACT FROM AUTHOR]

Pesticides could induce long-term impacts on aquatic ecosystem via transgenerational toxicity. However, for many chiral pesticides, the potential enantioselectivity of transgenerational toxicity has yet to be fully understood. In this study, we used zebrafish as models to evaluate the maternal transfer risk of tebuconazole (TEB), which is a chiral triazole fungicide currently used worldwide and has been frequently detected in surface waters. After 28-day food exposure (20 and 400 ng/g) to the two enantiomers of TEB (S - and R -TEB) in adult female zebrafish (F0), increased malformation rate and decreased swimming speed were found in F1 larvae, with R -TEB showing higher impacts than S -enantiomer. Additionally, enantioselective effects on the secretion of thyroid hormones (THs) and expression of TH-related key genes along the hypothalamic-pituitary-thyroid (HPT) axis were found in both F0 and F1 after maternal exposure. Both the two enantiomers significantly disrupted the triiodothyronine (T3) and thyroxine (T4) contents in F0 with different degrees, whereas in F1, significant effects were only found in R -TEB groups with decreasing of both T3 and T4 contents. Most of the HPT axis related genes in F0 were upregulated by TEB and more sensitive to R -TEB than to S -TEB. In contrast, most of the genes in F1 were downregulated by both R - and S -TEB, especially the genes that are primarily responsible for thyroid development and growth (Nkx2–1), TH synthesis (NIS and TSHꞵ) and metabolism (Deio1). Findings from this study highlight the key role of enantioselectivity in the ecological risk assessment of chiral pesticides through maternal transfer. • Maternal TEB exposure resulted in enantioselective toxicity in both F0 and F1. • R -TEB showed stronger thyroid disruptive effects than S -TEB in F0. • Changes of TH levels in parents modulated the THs in offspring. • R -TEB caused stronger developmental and behavior toxicity than S -TEB in F1. • The expression of TH-related key genes showed different patterns between F1 and F0. [ABSTRACT FROM AUTHOR]

Residues in surface water of ribavirin, which used extensively during the COVID-19 pandemic, have become an emerging issue due to its adverse impact on the environment and human health. UV/H 2 O 2 and UV/peroxydisulfate (PDS) have different degradation effects on ribavirin, and the same operational parameter have different effects on the two processes. In this study, the reaction mechanism and degradation efficiency for ribavirin were studied to compare the differences under UV/H 2 O 2 and UV/PDS processes. We calculated the total rate constants of ribavirin with HO• and SO 4 •- in the liquid phase as 2.73 × 108 and 9.39 × 105 M−1s−1. The density functional theory (DFT) calculation results showed that HO• and SO 4 •- react more readily with ribavirin via H-abstraction (HAA). The nitrogen-containing heterocyclic ring is difficult to undergo ring-opening degradation. The UV/PDS process was more stable and performed better than the UV/H 2 O 2 for the ribavirin degradation when the same molar oxidant dosage was applied. HO• plays an extremely important role in the degradation of ribavirin by UV/PDS. The reason for this phenomenon is the combination of the higher yield of HO• produced in the UV/PDS process and the faster reaction rate of ribavirin with HO•. The UV/H 2 O 2 process is more sensitive to pH than UV/PDS. Alkaline condition can significantly inhibit the ribavirin degradation. The effects of natural organic matter (NOM) and ribavirin concentration were also compared. Eventually, the toxicity prediction of the product showed that the opening-ring products were more toxic than the parent compound. [Display omitted] • HAA is easier to occur than RAF and SET. • The nitrogen-containing heterocyclic ring is difficult to undergo ring-opening. • The UV/PDS process is more stable and performed better than the UV/H 2 O 2. • Kinetics modeling was performed to study the effect of parameters on efficiency. • Toxicity evaluation of ribavirin and products was investigated. [ABSTRACT FROM AUTHOR]

Sugarcane vinasse is one of the main residues generated by the transformation of cane into ethanol. Because of the high organic content (COD), high biochemical oxygen demand (BOD), low pH, the large amount that this residue is generated (15 l for every liter of ethanol produced) and their use as fertilizer on the sugarcane crop, this residue is potentially polluting to the soil ecossystem and by percolation to water ecossystem too. Thus, this study aimed to assess the toxicity of vinasse by analyzing Oreochromis niloticus gills exposed to different dilutions (1%, 2.5%, 5% and 10%) in two bioassays. The gills were collected, fixed and analyzed using ultra morphological, histological, and histochemical techniques. After exposure to the vinasse, a statistically significant reduction of the ridges present on the surface of pavimentous cells was observed in one of the bioassays; such structures are responsible for mucus retention, which helps to protect the tissue. In addition, an intumescence of the cells was observed in the treatments with vinasse as well as an increase in the amount of chloridric cells. Some striking tissue changes detected in the treatments were epithelial detachment and loss of integrity of secondary lamellae, causing their rupture and consequent hemorrhage. In the first bioassay, the amount of these changes was statistically significant at the 5% dilution, and the focus of hemorrhage was significant at all dilution ratios. In the second bioassay, the epithelial disorganization was statistically significant only at the 2.5% dilution of vinasse. Moreover, for both bioassays performed, a significant increase in mucous cells was observed when compared with the control. Our results demonstrate the toxic action of sugarcane vinasse, which caused histopathological changes in the exposed animals at all four dilution tested. This highlights the need for caution in the disposal of sugarcane vinasse on the soil, especially due to its capacity for being leached or percolated into water resources, which could seriously damage aquatic fauna. [ABSTRACT FROM AUTHOR]

Pesticide pollution from agricultural field run-off or spray drift has been documented to impact river ecosystems worldwide. However, there is limited data on short- and long-term effects of repeated pulses of pesticide mixtures on biotic assemblages in natural systems. We used reported pesticide application data as input to a hydrological fate and transport model (Soil and Water Assessment Tool) to simulate spatiotemporal dynamics of pesticides mixtures in streams on a daily time-step. We then applied regression models to explore the relationship between macroinvertebrate communities and pesticide dynamics in the Sacramento River watershed of California during 2002–2013. We found that both maximum and average pesticide toxic units were important in determining impacts on macroinvertebrates, and that the compositions of macroinvertebrates trended toward taxa having higher resilience and resistance to pesticide exposure, based on the Species at Risk pesticide (SPEAR pesticides ) index. Results indicate that risk-assessment efforts can be improved by considering both short- and long-term effects of pesticide mixtures on macroinvertebrate community composition. [ABSTRACT FROM AUTHOR]

Nanoparticle contamination in freshwater habitat leads to the drastic reduction in the population of freshwater micro crustaceans. Both Ceriodaphnia cornuta and Moina micrura were considered as the potential biological bio-tracers of freshwater ecosystem. This study describes the chemical synthesis of zinc oxide nanoparticles (ZnO NPs) using zinc nitrate as the starting material. The physico-chemical characterization of ZnO NPs was made by UV–Vis spectroscopy, X-Ray Diffraction (XRD), Fourier Transform Infra Red (FTIR) and Transmission Electron Microscopy (TEM). ZnO NPs elicited 100% and 76% mortality of freshwater crustaceans, Ceriodaphnia cornuta and Moina micrura at 160 μg L −1 respectively. The accumulation of ZnO NPs in the intestine and loss of antennae and carapace were clearly visualized through light microscopy. The exposure of C. cornuta and M. micrura neonates at 160 μg L −1 of ZnO NPs showed abnormal swimming behaviour after 12 h. However, chitosan significantly reduced the mortality and enhanced the survival of C. cornuta and M. micrura at 100 μg ml −1 . This study concludes the protective effect of chitosan against the hazardous effect of ZnO NPs in C. cornuta and M. micrura . [ABSTRACT FROM AUTHOR]

Organisms in the aquatic environment are exposed to a variety of substances of numerous chemical classes. The unintentional co-occurrence of pharmaceuticals and other contaminants of emerging concern may pose risk to non-target organisms. In this study, individual and binary mixture toxicity experiments of selected pharmaceuticals (ibuprofen and ciprofloxacin) and chlorophenols (2.4-dichlorophenol (2,4-DCP) and 3-chlorophenol (3-CP)) have been performed with freshwater algae Chlorella vulgaris . All experiments have been carried out according to the 96-h algal growth inhibition test OECD No. 201. Binary mixture tests were conducted using proportions of the respective IC 50 s in terms of toxic unit (TU). The mixture concentration-response curve was compared to predicted effects based on both the concentration addition (CA) and the independent action (IA) model. Additionally, the Combination Index (CI)-isobologram equation method was used to assess toxicological interactions of the binary mixtures. All substances individually tested had a significant effect on C. vulgaris population density and revealed IC 50 values <100 mg L −1 after exposure period of 96-h. The toxic ranking of these four compounds to C. vulgaris was 2,4-DCP>ciprofloxacin>3-CP>ibuprofen. Generally, it can be concluded from this study that toxic mixture effects of all tested chemicals to C. vulgaris are higher than the individual effect of each mixture component. It could be demonstrated that IC 50 values of the tested mixtures predominately lead to additive effects. The CA model is appropriate to estimate mixture toxicity, while the IA model tends to underestimate the joint effect. The CI-isobologram equation method predicted the mixtures accurately and elicited synergism at low effect levels for the majority of tested combinations. [ABSTRACT FROM AUTHOR]

Tricyclazole is used as a common fungicide to control rice blast. However, studies on the toxicity of tricyclazole to crabs in the rice-crab co-culture system are still extremely rare. Here, the environmental dissipation of tricyclazole was monitored in this model, and the potential toxicity of tricyclazole to E. sinensis at environmental concentrations as well as the dietary risk was evaluated. The results showed that tricyclazole had no significant acute toxicity to E. sinensis (LC 50 > 100 mg/L), while it promoted body weight gain. Tricyclazole in the hepatopancreas had a higher persistent bioaccumulation risk than in the muscle. Tricyclazole suppressed the immune response of E. sinensis under prolonged exposure and there should be gender differences, with females being more sensitive. Lipid metabolism enzymes were also significantly inhibited. While tricyclazole stimulated males molting but prolonged molting duration, both molting and duration of females were also disturbed. The dietary risk assessment indicated that tricyclazole intake from current crab consumption was low risk. This evidence demonstrated that tricyclazole may have potential risks to individual development, nutritional quality, and economic value on E. sinensis and should be used with caution in rice-crab co-culture system whenever possible. [Display omitted] • Effects of tricyclazole on E. sinensis were researched. • Tricyclazole continuously bioaccumulate in the hepatopancreas of E. sinensis. • Tricyclazole inhibited lipid metabolism and immune response in E. sinensis. • Tricyclazole inhibited the normal molting system of E. sinensis. [ABSTRACT FROM AUTHOR]

Transformation products (TPs) of emerging organic contaminates (EOCs) in water are still rarely considered in environmental risk assessment, although some have been found to be concern. OH is believed as an important reactive species both in indirect phototransformation and advanced oxidation technology. Thus, eco-toxicity and human estrogenic exposure risks of four phthalates and TPs during the OH-initiated photochemical process were investigated using computational approach. Four phthalates can be degraded through OH-addition and H-transfer pathways. The OH-addition TPs were predominant for dimethyl phthalates, while H-transfer TPs were predominant for other three phthalates. Compared with phthalates, OH-addition TPs ( o -OH-phthalates) were one level more toxic to aquatic organisms, and m -OH-phthalates exhibit higher estrogenic activity. Although H-transfer TPs were less harmful than OH-addition TPs, some of them still have aquatic toxicity and estrogenic activity. Therefore, more attentions should be paid to photochemical TPs and original EOCs, particularly those exhibiting high estrogenic activity to humans. [ABSTRACT FROM AUTHOR]

A significant number of studies have centred on the single actions of heavy metals against test animals in predicting aquatic toxicity. However, practical existence of environmental toxicants is in multiple mixtures and variable undefined ratio combinatorial concentrations. Pollution abatement approaches in setting representative safe boundaries for metal contaminants is crucial with factual data on predictively modelled exposures of organisms to multiple mixtures. In continuance of our approach to toxicity of individual heavy metals, we determined the toxicity of binary mixtures of copper and zinc at predetermined ratios against tilapia species and also evaluated the coergisms based on synergistic ratio model for effective formulations of safe limits. Orecohromis niloticus species were exposed to copper and zinc (Cu:Zn) at ratios of 1:1 and 1:2 on 96hLC 50 index and mortality response analysed following the probit-log-dose regression with metal–metal interactions effectively modelled. The 96hLC 50 values for Cu:Zn were calculated to be 68.898 and 51.197 mg/l for ratios 1:1 and 1:2, respectively. The joint action toxicity of the metal mixtures was observed to differ from the metals acting singly against the same animal species. Synergistic coergisms were realized in most of the ratio mixtures except the antagonistic effect displayed by the combination of Cu:Zn in the ratio 1:1 when compared to the single action of copper. Biological toxicity of heavy metals however still appears uncertain, and consideration of multiple mixtures and interactions of toxicants in natural milieu is very crucial in environmental management of the existing and emerging contaminating metals. [ABSTRACT FROM AUTHOR]

Thallium has been shown to significantly increase in both water and aquatic biota after exposure to metal mine effluent, however, there is a lack of knowledge as to its fate and effect in the aquatic environment. The objectives of this project were to assess (1) fate of thallium by conducting speciation analysis and determining the influence of water quality on toxicity and (2) effects of thallium (I) and (III) on three aquatic species; the algae, Pseudokirchneriella subcapitata , the invertebrate Ceriodaphnia dubia and the vertebrate Pimephales promelas. Speciation analysis proved challenging with poor recovery of thallium (I), however analysis with solutions >125 μg/L revealed that over a 7-d period, recovery of thallium (III) was less than 15%, suggesting that the majority of thallium (III) was converted to Thallium (I). It was only in fresh solutions where recovery of Thallium (III) was greater than 80%. The lowest IC25s generated during our effects assessment for both Thallium (I) and (III) were more than 10-fold greater than the highest concentration recorded in receiving environments (8 μg/L) and more than 100-fold greater than the current guideline (0.8 μg/L). To assess the influence of water quality on thallium toxicity, the concentrations of both potassium and calcium were reduced in dilution water. When potassium was reduced for both C. dubia and P. subcapitata tests, the lowest IC25 generated was 5-fold higher than the current guideline, but within the range of concentrations reported in receiving environments for both Thallium (I) and (III). When calcium was reduced in dilution water, toxicity only increased in the Tl (III) tests with C. dubia ; the IC25 for Tl(III), similar to the exposures conducted with reduced potassium, was within the range of total thallium concentrations reported in the receiving environment. Without an accurate, repeatable method to assess thallium speciation at low concentrations it is not possible to draw any firm conclusions as to whether the IC25s for Tl (III) are relevant to concentrations present in receiving environments. Based on the results of our study we recommend that any test, to determine Thallium (III) toxicity, use fresh solutions, made daily, to get good recovery and accurate toxicity results. The results generated in our effects and exposure assessment would indicate that the current guideline of 0.8 μg/L is protective. Special attention should be placed on the concentration of potassium in receiving environments when estimating thallium toxicity. [ABSTRACT FROM AUTHOR]

A risk-based screening exercise was carried out to evaluate the significance of chemicals of emerging concern measured in water and sediment of the Great Lakes Basin. Chemical classes included pesticides, pharmaceuticals, organic wastewater constituents, nonylphenol ethoxylates, perfluorinated surfactants, chlorinated paraffins, synthetic musks and flame retardants. Maximum measured concentrations were compared to benchmarks selected or developed to reflect a conservative no-effect level and/or the lowest-effect level. These benchmarks reflected traditional effect information such as survival, growth and reproduction. From this analysis, several pesticides, pharmaceuticals, polycyclic aromatic hydrocarbons and nonylphenol ethoxylates were identified as potential concerns and needs for further work were identified. Five of these chemicals (all pesticides) were identified in waters of both the US and Canada (azinphos-methyl, chlorpyrifos, diazinon, malathion and metolachlor). Chlopyrifos, malathion and metolachlor are still registered for use in both jurisdictions; diazinon is registered for use only in the US and azinphos-methyl is not registered for use in either jurisdiction, reflecting the persistence of these chemicals. The results of this screening exercise also were compared to those of several other studies, revealing some common chemicals. Although there are several uncertainties and data gaps in the benchmarks and monitoring data used in the current screening exercise, the results of this risk-based screening can be used by agencies for priority setting, program development, and to support ongoing collaborative research and monitoring programs. [ABSTRACT FROM AUTHOR]

Stabilization of bottom ash generated from hazardous waste incineration by the means of solidification was assessed by applying three different amounts of cement admixture (10%, 20% and 30%) and four distinct solidification periods (1 day, 4 days, 7 days and 28 days) in order to decrease the amount of harmful elements or compounds in the waste. Complex assessment of all the observed parameters was performed both according to the EU standard 2003/33/EC for waste acceptable at landfills for hazardous waste and by using ecotoxicological test on the freshwater algae Desmodesmus subspicatus . Whilst unmodified bottom ash exceeded the permit limit concentrations, after the solidification, most of the elements was immobilized in the admixture. The growth inhibition of D. subspicatus was, however, found out to be increasing during the process, possibly because the increase of molybdenum in the leachate with the increased cement addition and prolonged solidification period. From all the combinations tested, 30% cement addition and the standard 28 days solidification period appears to be the ideal one. [ABSTRACT FROM AUTHOR]

The present study aimed to evaluate biochemical and cellular responses of the freshwater mussel, Hyriopsis bialata , to the herbicide atrazine (ATZ). The mussels were exposed to environmentally-relevant concentrations of ATZ (0, 0.02 and 0.2 mg/L) and a high concentration (2 mg/L) for 0, 7, 14, 21 and 28 days. Tissues comprising male and female gonads, digestive glands and gills were collected and assessed for ethoxyresorufin-O-deethylase (EROD) activity, glutathione S-transferase (GST) activity, multixenobiotic resistance mechanism (MXR), histopathological responses, DNA fragmentation and bioaccumulation of ATZ and its transformation derivatives, desethylatrazine (DEA) and desisopropylatrazine (DIA). Additionally, circulating estradiol levels were determined. It appeared that ATZ did not cause significant changes in activities of EROD, GST and MXR. There were no apparent ATZ-mediated histopathological effects in the tissues, with the exception of the male gonads exhibiting aberrant aggregation of germ cells in the ATZ-treated mussels. Contrarily, ATZ caused significant DNA fragmentation in all tissues of the treated animals in dose- and time-dependent manners. In general, the circulating estradiol levels were higher in the females than in the males. However, ATZ-treated animals did not show significant alterations in the hormonal levels, as compared with those of the untreated animals. Herein, we showed for the first time differentially spatiotemporal distribution patterns of bioaccumulation of ATZ, DEA and DIA, with ATZ and DEA detectable in the gonads of both sexes, DEA and DIA in the digestive glands and only DEA in the gills. The differential distribution patterns of bioaccumulation of ATZ and its derivatives among the tissues point to different pathways and tissue capacity in transforming ATZ into its transformation products. Taken together, the freshwater mussel H. bialata was resistant to ATZ likely due to their effective detoxification. However, using DNA damage as a potential biomarker, H. bialata is a promising candidate for biomonitoring aquatic toxicity. [Display omitted] • Atrazine (ATZ) did not alter phase I and II biotransformation. • ATZ had no effects on multixenobiotic resistance mechanism and estradiol levels. • ATZ caused male germ cell aggregation. • ATZ and its derivatives revealed specific bioaccumulation in different tissues. • ATZ was associated with tissue DNA fragmentation. [ABSTRACT FROM AUTHOR]

Bakelite, the first synthetic plastic, is a rather unexplored material in the field of ecotoxicology, despite its long production and use. The aim of this study was to investigate the ecotoxicity of Bakelite microplastics (before and after leaching) and its leachates on four aquatic organisms: the crustacean Daphnia magna , the plant Lemna minor , the bacterium Allivibrio fischeri and the alga Pseudokirchneriella subcapitata. Bakelite microplastics before and after leaching and leachates affected all organisms, but to varying degrees. Leachates showed increased ecotoxicity to Daphnia magna , while Pseudokirchneriella subcapitata was more affected by particles. For Lemna minor and Allivibrio fischeri , the effects of particles before leaching and leachate were comparable, while the negative effect of particles after leaching was minimal or not present. All leachates were analysed, and phenol and phenol-like compounds were the predominant organics found. In addition, bioadhesion of Bakelite microplastics to the surface of Daphnia magna and Lemna minor was confirmed, but the particles were mainly weakly adhered. Results of this study suggest that, in addition to the recently studied microplastics from consumer products (e.g. from polyethylene and polystyrene), microplastics from industrial plastics such as Bakelite may be of increasing concern, primarily due to leaching of toxic chemicals. [Display omitted] • Bakelite microplastics and its leachates affected aquatic organisms. • Bakelite microplastics exhibit a lower ecotoxicological profile after leaching. • They adhere to surface of Lemna minor and Daphnia magna. • Phenol and phenol-like compounds were predominant organics in leachates. [ABSTRACT FROM AUTHOR]

The widespread application of the hydrocarbons benzene, toluene, ethylbenzene and xylene (BTEX) has led to their consideration as major aquatic environmental pollutants, and exposure to these hydrocarbons has become a serious concern given their detrimental health effects on aquatic species. We investigated in the present study the impact of chronic exposure to BTEX on the testis of the freshwater leech Erpobdella johanssoni. The results revealed that BTEX induced severe histological alterations revealed by vacuolar degeneration in the spermatogenic cysts, and a complete loss of normal cysts was observed. The cytophore was grossly destroyed, and extensive necrosis and detached germ cells from cytophore were observed. Interestingly, BTEX exposure induced a significant increase in malondialdehyde (MDA) levels by 85.71% in the testicular tissue of treated leeches compared to the control (P < 0.00005), whereas the activity levels of SOD, GPx and CAT antioxidant biomarkers were significantly decreased by 60%, 81.81% and 47.5%, respectively. Additionally, using the alkaline comet assay, we observed that BTEX exposure induced significant DNA fragmentation in the testis cells of treated leeches compared to controls (P < 0.00005). Overall, this study unravels the histopathologic, oxidative stress and DNA damage induced by BTEX on the testis of the freshwater leech E. johanssoni. [ABSTRACT FROM AUTHOR]

Summary: Disinfectants for foot-and-mouth disease were sprayed on livestock barns and roads from early February to May 2011. Although 90% of the disinfectant was concentrated on the roads, 10% was sprayed on cattle sheds and other sites where foot-and-mouth disease occurred. Since the outbreak of foot-and-mouth disease in November 2010, there has been a steady increase in disinfectant use. Consequently, its adverse environmental effects have prompted government officials to take preventive measures. The major chemical components of the disinfectants are citric acid, potassium sulfate base complex, quaternary ammonium compound, malic acid, and glutaraldehyde, ranging in amounts from tons to hundreds of tons. The exact amount of each component of the disinfectants could not be identified because the types of components used in the different commercial formulations overlapped. In this review, we obtained information on disinfectants that are widely used nationwide, including the types of major chemical components and their respective toxicities (both human and ecological). [Copyright &y& Elsevier]

Predicting responses of organisms exposed to toxic materials in the field from results produced in laboratory studies and confirming those predictions has been a central question in aquatic toxicology since its inception. A field treatment of a cyanobacterium and laboratory measurements of responses to algaecide exposures provided an opportunity to address that question. This research involved predicting the response of Lyngbya magnifica to an algaecide exposure (Phycomycin® SCP) in the laboratory and evaluating that prediction with a comparable exposure in the field. Based on the results from initial laboratory experiments, an effective algaecide and concentration (i.e. 92mg Phycomycin® SCP/g algae) were selected for field application in a farm pond. L. magnifica chlorophyll a and biomass were measured initially and 1, 4, 7, 10, and 21 days after treatment (DAT) for both laboratory and field exposures. Measurements of chlorophyll a decreases in the field treatment at 7, 10, and 21 days after treatment were significantly greater than responses obtained in similar laboratory exposures of Phycomycin® SCP. Biomass was significantly decreased in the field at 21 DAT compared to laboratory measurements. This approach can be effective for site specific predictions and can provide valuable information for informed decisions regarding water resource management and should be included in a management plan for increased product efficiency and ecological safety. [Copyright &y& Elsevier]

The purpose of this work is to develop robust and interpretable quantitative structure"activity relationship (QSAR) models for assessing the aquatic toxicity of phenols using a combined set of descriptors encompassing the logP and recently developed variables (Monconn-Z variables). The used dataset consists of 250 chemicals with toxicity data to the ciliate Tetrahymena pyriformis. For each compound, a total of 197 physico-chemical descriptors including logP and Molconn-Z descriptors were calculated. Multiple linear regression (MLR) and Partial least squares (PLS) were used to obtain QSARs and the predictive performance of the proposed models were verified using external statistical validations. The results of stepwise-MLR analysis reveal that the AlogP, MlogP and ClogP models were not successful for the prediction of aquatic toxicity for all the compounds. And by using the logP (AlogP and MlogP) with Molconn-Z descriptors, the obtained QSARs were not successful enough nutill removal of some outliers. Two optimal QSARs were built with R2 of 0.71 and 0.70 for the training sets and the external validation Q2 of 0.69 and 0.68 respectively. All these selected descriptors in the best models account for the hydrophobic (AlogP, MlogP) and other electrotopological properties like SHCsatu, Scarboxylicacid, SHBa, gmax and nelem. PLS produces a good model using all the calculated descriptors with R2 of 0.78 and Q2 of 0.64, and hydrophobic and electrotopological descriptors show importance for the prediction of phenolic toxicity. [ABSTRACT FROM AUTHOR]

This paper summarizes the environmental hazard assessment of physicochemical properties, environmental fate and behavior and the ecotoxicity of a category of 61 anionic surfactants (ANS), comprised of alkyl sulfates (AS), primary alkane sulfonates (PAS) and alpha-olefin sulfonates (AOS) under the High Production Volume Chemicals Program of the Organisation for Economic Co-operation and Development (OECD). The most important common structural feature of the category members examined here is the presence of a predominantly linear aliphatic hydrocarbon chain with a polar sulfate or sulfonate group, neutralized with a counter-ion. The hydrophobic hydrocarbon chain (with a length between C8 and C18) and the polar sulfate or sulfonate groups confer surfactant properties and enable the commercial use of these substances as anionic surfactants. The close structural similarities lead to physico-chemical properties and environmental fate characteristics which follow a regular pattern and justify the applied read-across within a category approach. Common physical and/or biological properties result in structurally similar breakdown products and are, together with the surfactant properties, responsible for similar environmental behavior. The structural similarities result in the same mode of ecotoxic action. Within each of the three sub-categories of ANS the most important parameter influencing ecotoxicity is the varying length of the alkyl chain. Although the counter-ion may also influence the physico-chemical properties, there is no indication that it significantly affects chemical reactivity, environmental fate and behavior or ecotoxicity of these chemicals. Deduced from physico-chemical and surfactancy properties, the main target compartment for the substances of the ANS category is the hydrosphere. They are quantitatively removed in waste water treatment plants, mainly by biodegradation. Quantitative removal in biological treatment plants is reflected by low AS concentrations measured in effluents of waste water treatment plants (mostly below 10μg/L). In addition, bioaccumulation of ANS does not exceed regulatory triggers based upon experimental data. A considerable number of reliable aquatic toxicity data for the whole ANS category are available, including chronic and subchronic data for species of all trophic levels. Based upon the highest quality data in hand, there appears to be no singularly most sensitive trophic level in tests on the toxicity of alkyl sulfates, with a large degree of overlap among algae, invertebrates and fish. Algae proved to be more variable in sensitivity to alkyl sulfate exposure compared to fish and daphnia. The key study for the aquatic hazard assessment is a chronic test on Ceriodaphnia dubia, which covers a range of the alkyl chain length from C12 to C18. A parabolic response was observed, with the C14 chain length being the most toxic (7d-NOEC=0.045mg/L). Responses of aquatic communities to C12 AS and C14–15 AS have been studied in high quality stream mesocosm studies containing a broad range of species and ecological interactions. These studies are regarded as a better approximation to reality when extrapolating to the environment. The 56-d chronic NOEC for C12 AS and C14–15 AS were 0.224 and 0.106mg/L, respectively, based on integrated assessments of periphyton (algal, bacterial and protozoan) and invertebrate communities. Taking into account the rapid biodegradation of the ANS compounds as well as the low concentrations measured in different environmental compartments, this category of surfactants is of low concern for the environment. [Copyright &y& Elsevier]

A feed-forward artificial neural network (ANN) with an improved group contribution method has been developed to predict the aquatic toxicity (IGC50) of organic compounds to Tetrahymena pyriformis. In addition to the chemical groups, several molecular descriptors were applied to the ANN model to improve the predictive capability. The parameters of ANN models were divided into two parts (groups and properties) as the descriptors. A data set of 660 out of 824 organic compounds was used to train the ANN, while another data set of 82 organic compounds was used as a test set to validate the ANN model. The remaining 82 chemicals were used as the predicting set to prove that the ANN model can effectively predict the value of the toxicity. The network based on chemical groups had an accuracy of R²=0.912 and MSE=0.090 while the improved group contribution method had an accuracy of R²=0.948 and MSE=0.059. [ABSTRACT FROM AUTHOR]

Fifteeen pesticides (eight herbicides and seven insecticides) commonly used in Thailand were assessed with the LuminoTox bioassay, a recently-commercialized rapid toxicity testing procedure employing photosynthetic enzyme complexes (PECs) that measure photosynthetic efficiency. LuminoTox responses were then compared with those of the most sensitive species reported in the literature for acute! chronic toxicity tests conducted at diverse taxonomic levels (e.g., bacteria, algae, invertebrates, fish) on the same pesticides. In general, the LuminoTox test displayed more sensitive responses towards herbicides than insecticides thereby indicating its potential usefulness as a top candidate toxicity screening test particularly for the former group of chemicals. When pesticide hazard potential was estimated based on a classification scheme proposed by EU-Directive 93/67/EEC after comparing LuminoTox and literature bioassay measurement endpoint data, responses displayed a wide spectrum of effects ranging from non toxic (e.g., toxic effect> 100 mg/L after paraquat exposure to bacteria) to extremely toxic (e.g., toxic effect < 0.1 mg/L after methyl-parathion exposure to micro-invertebrates). The observed differences in magnitude of effects confirmed that toxic responses to the pesticides were clearly biological level-, test procedure- and endpoint-specific and justify the use of representative species within test batteries to properly appraise the toxic potential of such pesticides. From this comparative bioana- lytical investigation, we propose that a test battery made up of the LuminoTox assay, a micro-algal assay conducted with a chlorophyte species (Scenedesmus supspicatus or Pseudokirchneriella subcapitata), a micro-invertebrate assay conducted with daphnids (Daphnia magna) and a fish test conducted with a salmonid species (Salino trutta or On-corhinchus mykiss) would prove efficient for detecting the presence of pesticides such as those investigated in our study in water samples collected from aquatic environments influenced by agricultural activities. [ABSTRACT FROM AUTHOR]

Municipal wastewater effluents are one of the largest single effluent discharges in Canada. Chlorination of wastewater effluents is a widespread practice throughout Canada (excluding Quebec), the United States and parts of Europe. As chlorine in wastewater effluents is toxic to aquatic biota, dechlorination chemicals may be used to reduce residual chlorine concentrations to below 0.02 mg/L (as Cl2) as mandated by Canadian law. However, the potential aquatic health impacts of residual dechlorination chemicals must also be determined. Seven dechlorination agents (ascorbic acid, hydrogen peroxide, calcium thiosulfate, sodium sulfite, sodium thiosulfate, sodium metabisulfite, sodium bisulfite) were evaluated with regards to their 48 hour acute toxicity. Tests were conducted using Daphnia magna to identify the acute (48 h) toxicity affects of the dechlorination chemicals over a range of concentrations (0-200 mg/L). Sodium sulfite and thiosulfate were found to have the least aquatic mortality effects while hydrogen peroxide and calcium thiosulfate had the most deleterious effects. [ABSTRACT FROM AUTHOR]

Haloacetic acids (HAA), such as trichloroacetic acid (TCA), are commonly occurring by-products from disinfection and bleaching processes using sodium hypochlorite. Currently, the lowest no observed effect concentration (NOEC) for TCA is reported to be 8.7μgL−1, which was derived from a toxicity study conducted in 1981 on Chlorella pyrenoidosa. The purity of the test material was not documented and it is unknown if other halogenated impurities or co-formulants were present. However, this NOEC is used to derive a predicted no effect concentration, which is used in various regulatory risk assessments. We present a range of algal toxicity studies conducted on five different algal species and two HAAs and observed no toxicity of TCA to C. pyrenoidosa at 115mgL−1. The most sensitive species to TCA (NOEC, 3mgL−1) were Pseudokirchneriella subcapitata and Scenedesmus subspicatus, demonstrating that the toxicity of TCA to algae is over two orders of magnitude less sensitive than previously reported. [Copyright &y& Elsevier]