Environmental impact assessment of dicationic ionic liquids with ammonium-phosphonium cations and amino acid anions.

Progress in the development of biodegradable or biobased ionic liquids (ILs) has led to the design of green compounds for several applications. Herein, four biocompatible dicationic ionic liquids (DILs) with ammonium-phosphonium cations and amino acid anions were synthesized and investigated their environmental impact. The structures of the DILs were confirmed by spectral analyses (1H, 13C and 31P NMR). Furthermore, physicochemical properties such as density, viscosity and refractive index were determined. Water content, bromide content and solubility were thereafter determined as the parameters needed for further studies. Subsequently, their antifeedant activity towards economically important pests of grain in storage warehouses: the granary weevil, the confused flour beetle, and the khapra beetle was examined, showing the dependence on structure. Moreover, selected DILs were investigated for toxicity towards white mustard, Daphnia magna, and Artemia franciscana to specify the environmental impact. These studies were complemented by understand the biodegradation of DILs by bacterial communities derived from soil at the agricultural land. The result was DILs with limited environmental footprints that have great potential for further application studies.

Enhancing cannabidiol bioaccessibility using ionic liquid as emulsifier to produce nanosystems: Characterization of structures, cytotoxicity assessment, and in vitro digestion.

The emulsifying potential of a biocompatible ionic liquid (IL) to produce lipid-based nanosystems developed to enhance the bioaccessibility of cannabidiol (CBD) was investigated. The IL (cholinium oleate) was evaluated at concentrations of 1 % and 2 % to produce nanoemulsions (NE-IL) and nanostructured lipid carriers (NLC-IL) loaded with CBD. The IL concentration of 1 % demonstrated to be sufficient to produce both NE-IL and NLC-IL with excellent stability properties, entrapment efficiency superior to 99 %, and CBD retention rate of 100 % during the storage period evaluated (i.e. 28 days at 25 °C). The in vitro digestion evaluation demonstrated that the NLC-IL provided a higher stability to the CBD, while the NE-IL improved the CBD bioaccessibility, which was mainly related to the composition of the lipid matrices used to obtain each nanosystem. Finally, it was observed that the CBD cytotoxicity was reduced when the compound was entrapped into both nanosystems.

Removal of mercury by silica-supported ionic liquids: Efficiency and ecotoxicological assessment.

Anthropogenic impacts have affected the coastal environment and contributed to its contamination. Mercury (Hg) is widespread in nature and has been shown to be toxic in even the smallest amounts, negatively affecting not only the marine ecosystem but also the entire trophic chain due to its biomagnification. Mercury ranks third on the Agency for Toxic Substances and Diseases Registry (ATSDR) priority list and it is therefore imperative to develop more effective methods than those currently available to avoid the persistence of this contaminant in aquatic ecosystems. The present study aimed to evaluate the effectiveness of six different silica-supported ionic liquids (SIL) in removing Hg from contaminated saline water, under realistic conditions ([Hg] = 50 µg/L), and to ecotoxicologically evaluate the safety of the SIL-remedied water, using as test model the marine macroalga Ulva lactuca. The results revealed that SIL [Si][C3C1im][SCN] (250 mg/L) was the most effective in removing Hg from solution, with a efficiency up to 99 % in just 6 h, that enable to obtain < 1 µg/L Hg (European guideline in drinking water). U. lactuca exposed to either the SIL and/or the remedied water showed no significant changes in relative growth rate and chlorophyll a and b levels, compared to the control condition. Biomarker analysis (LPO, GSH, GSSG, SOD, GPx, CAT and GRed) also showed no significant changes in the biochemical performance of U. lactuca. Therefore, it could be assumed that water treatment with SIL or its presence in an aqueous environment does not pose toxicity levels that could inhibit the metabolism or cause cell damage to U. lactuca.

Cumulative impact assessment of hazardous ionic liquids towards aquatic species using risk assessment methods.

In the present research work, a comprehensive tool for cumulative ecotoxicological impact assessment of ionic liquids (ILs) to aquatic life has been constructed. Using the probabilistic tool, impact of individual ILs to a group of aquatic species is assessed by chemical toxicity distributions (CTDs). The impact of group of ILs to individual aquatic species is assessed by species sensitivity distributions (SSDs). Acute toxicity data of imidazolium ILs with chloride (Cl-), bromide (Br-), tetrafluoroborate (BF4-), and hexafluorophosphate (PF6-) anions are used in CTD and SSD. Allowable concentrations for a group of Imidazolium ILs with the same mode of action (SMOA) to five aquatic species; Daphnia magna, Vibrio fischeri, Algae, Zebrafish, and Escherichia coli are estimated by CTDs. It has been concluded that 1-Butyl-3-methylimidazolium chloride (BMIMCl) possess the lowest risk at an acceptable risk value of 750 × 10-5 mmol/L which is 12% less than that of OMIMCl. Furthermore, the sensitivities towards the aquatic species reveal that from the studied ILs, BMIMBF4 with an acceptable risk value of 3200 × 10-5 mmol/L is the most suitable IL towards the selected aquatic species. Hence, current work provides cumulative allowable concentrations and acceptable risk values for ILs which release to aquatic compartment of ecosystem.

Subacute toxicity assessment of biobased ionic liquids in rats.

Ionic liquids (ILs) derived from compounds obtained from natural sources, such as fatty acids (FAs) have attracted the interest of the scientific and industrial communities because of their sustainable appeal and possible low toxic effects or nontoxicity. These aspects open new perspective of applications in other fields, which demands a better comprehension of their toxicity. This work evaluated the subacute toxicity of bis(2-hydroxyethyl)ammonium carboxylates in Wistar rats, considering the alkyl chain length of FAs (capric and oleic acids), and the concentration (0.16%, 1.6% or 3.2%, wIL/wOil) of ILs added in diets. The blood serum of the rats was evaluated in relation to total cholesterol, triglycerides, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and γ-glutamyl transferase. Lipid peroxidation was determined in plasma, liver and kidney tissues by determining the level of thiobarbituric acid reactive substances. Histological analyses of the liver and kidney tissues were performed in order to evaluate morphological changes. No signal of toxicity was observed according to lipid peroxidation. Triglycerides increased with the increasing of the concentration and alkyl chain length of the IL, but no difference in serum level of lipid peroxidation was observed. This behavior may be attributed to the amphiphilic nature of FAs based ILs, which might facilitate lipid digestion. However, more studies are necessary in order to understand such behavior. Therefore, the synthesis of ILs from FAs, has been evaluated as a strategy to produce compounds with low or without toxicity for the agro-food, pharmaceutical or cosmetic industries.

Toxicity and inhibition assessment of ionic liquids by activated sludge.

Toxicity of 13 ionic liquids (ILs) corresponding to different families were studied by inhibition respiration assays (15 min) using activated sludge. Toxicity increased as increasing the number of carbons in the alkyl-chain of imidazolium-based ILs, with EC50 values from 4.19 to 0.17 for 1-ethyl-3-methylimidazolium chloride ([Emim][Cl]) and 1-octyl-3-methylimidazolium chloride ([Omim][Cl]), respectively. An increase in toxicity was observed for aromatic-based ILs (pyridinium- and imidazolium-based ILs) due to the hydrophobic character of the head groups in comparison with linear structures as phosphonium and ammonium cations. Among to the anions studied fixing [Emim]+ as cation, [HSO4]- and [NTf2]- presented low EC50 values (0.34 mM and 1.69 mM, respectively) while [Cl]- and [EtSO4]- were considered harmless anions due to the hydrophilic character of chloride and the organic nature of [EtSO4]-. ILs toxicity/inhibition was determined by adding a biodegradable compound and measuring the sludge response after being in contact with the ILs for at least 15 h. The exposure of sewage sludge to ILs for more than 15 min used in short inhibition assays caused more toxic effect on microorganisms, even for [Choline][NTf2], previously defined as practically harmless (EC50 = 2.79 mM). Biodegradability assays confirmed the biodegradable nature of choline cation, related with TOC conversion of 40%, only due to cation consumption. No oxygen consumption or even lysis of microbial cells was observed for Tetrabutylammonium bis(trifluoromethylsulfonyl)imide and for 1-Ethyl-3-methylimidazolium hydrogensulphate due to the presence of anions previously defined as hazardous ([NTf2]- and [HSO4]-), maintaining their recalcitrant character to sewage systems.

In vitro cytotoxicity assessment of monocationic and dicationic pyridinium-based ionic liquids on HeLa, MCF-7, BGM and EA.hy926 cell lines.

Dicationic ionic liquids (ILs) generally possess higher thermal and electrochemical stability than the analogous monocationic ILs, which makes them more suitable for high-temperature applications as solvents for organic reactions, lubricants or stationary phase in gas chromatography. However, knowledge on dicationic IL cytotoxicity is still scarce. Here we explore the cytotoxicity of twelve mono- and dicationic pyridinium-based ILs on HeLa, MCF-7, BGM and EA.hy926 cells. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, cell cycle arrest assays, apoptosis experiments and orange staining were carried out. The results showed that dicationic ILs are generally less cytotoxic than their monocationic counterparts. In monocationic ILs, cytotoxicity was stronger when they contain long alkyl chains, because of their higher lipophilicity. However, the full effect of the length of the linkage alkyl chain of dicationic ILs on cytotoxicity is not clear probably because the chain is "trapped" between both cationic moieties. IL cytotoxicity is highly dependent on the cell type, and HeLa cells exposed to [C12Pyr]Br die via apoptosis. The present study increases our knowledge of IL cytotoxicity on human and monkey cells and clarifies the cell death mechanism. The results suggest that dicationic ILs offer the potential to replace some monocationic ILs because of their lower cytotoxicity.

Integrative Assessment of Mixture Toxicity of Three Ionic Liquids on Acetylcholinesterase Using a Progressive Approach from 1D Point, 2D Curve, to 3D Surface.

The joint toxicities of [BMIM]BF4, [BMIM]PF6, and [HMIM]BF4 on acetylcholinesterase (AChE) were systematically investigated by using a progressive approach from 1D single effect point, 2D concentration-response curve (CRC), to 3D equivalent-surface (ES) level. The equipartition equivalent-surface design (EESD) method was used to design 10 ternary mixtures, and the direct equipartition ray (EquRay) design was used to design 15 binary mixtures. The toxicities of ionic liquids (ILs) and their mixtures were determined using the microplate toxicity analysis (MTA) method. The concentration addition (CA), independent action (IA), and co-toxicity coefficient (CTC) were used as the additive reference model to analyze the toxic interaction of these mixtures. The results showed that the Weibull function fitted well the CRCs of the three ILs and their mixtures with the coefficient of determination (R2) greater than 0.99 and root-mean-square error (RMSE) less than 0.04. According to the CTC integrated with confidence interval (CI) method (CTCICI) developed in this study, the 25 mixtures were almost all additive action at 20% and 80% effect point levels. At 50% effect, at least half of the 25 mixtures were slightly synergistic action, and the remaining mixtures were additive action. Furthermore, the ESs and CRCs predicted by CA and IA were all within the CIs of mixture observed ESs and CRCs, respectively. Therefore, the toxic interactions of these 25 mixtures were actually additive action. The joint toxicity of the three ILs can be effectively evaluated by the ES method. We also studied the relationship between the mixture toxicities and component concentration proportions. This study can provide reference data for IL risk assessment of combined pollution.

How green are ionic liquids? - A multicriteria decision analysis approach.

Due to various desirable physicochemical properties, ionic liquids (ILs) are still gaining in popularity. ILs have been recurrently considered green solvents. However, environmental, health and safety assessments of ILs have raised certain doubts about their benignness, and their greenness status is currently unclear. To clarify the situation on their greenness, we perform a comprehensive assessment of more than 300 commercially available ILs. We apply multicriteria decision analysis, the tool that allows ranking many alternatives according to relevant criteria. They are toxicity towards various organisms, biodegradability, hazard statements and precautionary measures during their handling. We incorporated organic solvents to rankings, as their greenness is better described, so they serve as greenness reference points. The ranking results obtained considering the whole set of criteria show that ILs are placed between recommended polar solvents and problematic/undesirable non polar organic solvents in terms of greenness. However, the exclusion of toxicity data due to unavailability of endpoints results in assessment of ILs as greener than most of organic solvents.

Assessment the ecotoxicity and inhibition of imidazolium ionic liquids by respiration inhibition assays.

The ecotoxicity and inhibition of 12 imidazolium ionic liquids (ILs) with alkyl chain from C4 to C10 and chloride (Cl-), tetrafluoroborate (BF4-) and bis(trifluoromethanesulfonyl)imide (NTf2-) anions have been studied by means of respiration inhibition assays using activated sludge collected from a wastewater treatment plant. This test represents an alternative easy, economic and quick way to evaluate the true impact of ILs on activated sludge-based wastewater treatment. For comparison purposes, the EC50 values were also determined by the Microtox test (Vibrio fischeri). It was observed that this widely used microbial test overestimates the effect of the ILs on biological wastewater treatment facilities, especially in the case of ILs with lower ecotoxicity. The results of the biological tests showed that the alkyl chain length plays a crucial role in the ecotoxicity of ILs. A significant increase of the toxicity with the length of the n-alkyl chain was found. Regarding to the impact of the anion, the ecotoxicity measured by respiration inhibition assays follows the order NTf2- > Cl- > BF4-, being the anion effect higher as decreasing the length of cation alkyl chain. According to the hazard substances ranking for aquatic organisms (Passino and Smith, 1987), imidazolium ILs with C4 alkyl chain can be classified as "practically harmless" compounds whereas those with alkyl chains C8 or C10 correspond to "highly toxic" species.

Assessment of the cytotoxicity of ionic liquids on Spodoptera frugiperda 9 (Sf-9) cell lines via in vitro assays.

Cytotoxicity studies are important tools for the assessment of the toxicity of ionic liquids (ILs). In the present study, the cytotoxicity of eleven ILs against Spodoptera frugiperda 9 (Sf-9) cell lines were evaluated via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. The effect on cellular morphology, ultrastructural morphology, and nuclear morphology induced by 1-ethyl-3-methylimidazolium bromide ([C2mim][Br]) was studied via inverted light microscopy observation, acridine orange staining, and transmission electron microscope (TEM) analysis, respectively. The effect on cell DNA fragmentation, cell apoptosis and cell cycle induced by [C2mim][Br] was also investigated via DNA agarose gel electrophoresis and flow cytometry analysis, respectively. The results showed that the cytotoxic effect of ILs on Sf-9 cells was related to the IL structures, concentrations, and length of exposure. The morphological features of apoptosis induced by [C2mim][Br] such as cell shrinkage and convolution, apoptotic bodies, pyknosis, and karyorrhesis were observed. All these phenomena confirmed that Sf-9 cells exposed to [C2mim][Br] died via apoptosis. This study complements the current knowledge about the cytotoxic properties of ILs on insect cells and highlights the mechanism by which ILs kill these cells. Furthermore, it provides a basis for further studies on the future applications of ILs as insecticides.

Ecotoxicity assessment of dicationic versus monocationic ionic liquids as a more environmentally friendly alternative.

One of the reasons why ionic liquids have received growing interest from researchers is their environmentally interesting characteristics, such as their negligible vapour pressure and their good chemical and thermal properties. In particular, dicationic ionic liquids whose thermal and electrochemical stability is higher than that of monocationic ionic liquids have begun to gain attention during recent years. In this work, monocationic and dicationic ionic liquids were synthesized, characterized and tested for their toxicity, which was assessed using the luminescent bacterium Vibrio fischeri. The results revealed that the toxicity of the ionic liquids mainly depends on the head groups and linkage chain length of their cationic structure. Introduction of a new cationic head decreased the EC50 (concentration which leads to 50% reduction in bioluminescence of the bacteria) of the ionic liquids. The results present a promising picture of dicationic ionic liquids as alternatives with lower environmental impact than their monocationic counterparts and underline the significance of designing particular structures for ionic liquids.

Evaluation of risk assessment of new industrial pollutant, ionic liquids on environmental living systems.

Ionic liquids (ILs) are much known for their promising alternative for volatile solvents in industries and gained popularity as a greener solvent, however industrial effluent discharge containing ILs are also increasing. There is a scarcity of information on the toxicity of ILs; the present study will explore different facts about their harmfulness. The toxic effects of five different ILs: [C4MIM]Br, [Hx3PC14]N(CN)2, [C10MIM]BF4, [BTDA]Cl and [C4MPY]Cl were analysed on bacteria, fungi, plant and animal cells. Both Gram positive and negative bacteria were found to be more susceptible to [C10MIM]BF4 and [BTDA]Cl than [C4MIM]Br, [Hx3PC14]N(CN)2 and [C4MPY]Cl, whereas fungi revealed quite a resistance to all ILs. All ILs were toxic towards Triticum aestivum affecting their roots and shoots, however [C10MIM]BF4 and [BTDA]Cl were more toxic amongst them. Studies on Allium cepa described their toxic behaviour at the genetic level by altering cell division and nuclear material. Furthermore, studies on human red blood cells described by % haemolysis in which [Hx3PC14]N(CN)2 and [BTDA]Cl exhibited higher toxicity at very lower concentrations. While the genotoxic effect on blood lymphocytes exerted by [Hx3PC14]N(CN)2, [C10MIM]BF4 and [BTDA]Cl confirmed their toxic effects on human cells.

Assessment and prediction of joint algal toxicity of binary mixtures of graphene and ionic liquids.

Graphene and ionic liquids (ILs) released into the environment will interact with each other. So far however, the risks associated with the concurrent exposure of biota to graphene and ILs in the environment have received little attention. The research reported here focused on observing and predicting the joint toxicity effects in the green alga Scenedesmus obliquus exposed to binary mixtures of intrinsic graphene (iG)/graphene oxide (GO) and five ILs of varying anionic and cationic types. The isolated ILs in the binary mixtures were the main contributors to toxicity. The binary GO-IL mixtures resulted in more severe joint toxicity than the binary iG-IL mixtures, irrespective of mixture ratios. The mechanism of the joint toxicity may be associated with the adsorption capability of the graphenes for the ILs, the dispersion stability of the graphenes in aquatic media, and modulation of the binary mixtures-induced oxidative stress. A toxic unit assessment showed that the graphene and IL toxicities were additive at low concentration of the mixtures but antagonistic at high concentration of the mixtures. Predictions made using the concentration addition and independent action models were close to the observed joint toxicities regardless of mixture types and mixture ratios. These findings provide new insights that are of use in the risk assessment of mixtures of engineered nanoparticles and other environmentally relevant contaminants.

Assessment of ionic liquids' toxicity through the inhibition of acylase I activity on a microflow system.

Acylase I (ACY I) plays a role in the detoxication and bioactivation of xenobiotics as well in other physiological functions. In this context, an automated ACY I assay for the evaluation of ionic liquids' (ILs) toxicity was developed. The assay was implemented in a sequential injection analysis (SIA) system and was applied to eight commercially available ILs. The SIA methodology was based on the deacetylation of N-acetyl-l-methionine with production of l-methionine, which was determined using fluorescamine. ACY I inhibition in the presence of ILs was monitored by the decrease of fluorescence intensity. The obtained results confirmed the influence of ILs' structural elements on its toxicity and revealed that pyridinium and phosphonium cations, longer alkyl side chains and tetrafluoroborate anion displayed higher toxic effect on enzyme activity. The developed methodology proved to be robust and exhibited good repeatability (RSD < 1.3%, n = 10), leading also to a reduction of reagents consumption and effluents production. Thus, it is expected that the proposed assay can be used as a novel tool for ILs' toxicity screening.

Automated cytochrome c oxidase bioassay developed for ionic liquids' toxicity assessment.

A fully automated cytochrome c oxidase assay resorting to sequential injection analysis (SIA) was developed for the first time and implemented to evaluate potential toxic compounds. The bioassay was validated by evaluation of 15 ionic liquids (ILs) with distinct cationic head groups, alkyl side chains and anions. The assay was based on cytochrome c oxidase activity reduction in presence of tested compounds and quantification of inhibitor concentration required to cause 50% of enzyme activity inhibition (EC50). The obtained results demonstrated that enzyme activity was considerably inhibited by BF4 anion and ILs incorporating non-aromatic pyrrolidinium and tetrabutylphosphonium cation cores. Emim [Ac] and chol [Ac], on contrary, presented the higher EC50 values among the ILs tested. The developed automated SIA methodology is a simple and robust high-throughput screening bioassay and exhibited good repeatability in all the tested conditions (rsd<3.7%, n=10). Therefore, it is expected that due to its simplicity and low cost, the developed approach can be used as alternative to traditional screening assays for evaluation of ILs toxicity and identification of possible toxicophore structures. Additionally, the results presented in this study provide further information about ILs toxicity.

Imidazolium-Based Ionic Liquids in Water: Assessment of Photocatalytic and Photochemical Transformation.

The photoinduced transformation of two ionic liquids, 1-methylimidazolium hydrogensulfate (HMIM) and 1-ethyl-3-methylimidazolium hydrogensulfate (EMIM), was investigated under photocatalytic conditions in the presence of irradiated TiO2. We monitored substrate disappearance, transformation products (TPs), degree of mineralization, and toxicity of the irradiated systems. Acute toxicity measures suggested in both cases the occurrence of more toxic TPs than the parent molecules. A total of five TPs were detected by HPLC-HRMS from HMIM and nine from EMIM. Complete mineralization and stoichiometric release of nitrogen was achieved for both compounds within 4 h of irradiation. The photochemical transformation kinetics and pathways in surface waters (direct photolysis and indirect photoreactions) were studied for EMIM, to assess its persistence in sunlit water bodies such as rivers or lakes. Environmental phototransformation would be dominated by direct photolysis, with half-life times of up to one month under fine-weather conditions.

Exploring simple, transparent, interpretable and predictive QSAR models for classification and quantitative prediction of rat toxicity of ionic liquids using OECD recommended guidelines.

The present study explores the chemical attributes of diverse ionic liquids responsible for their cytotoxicity in a rat leukemia cell line (IPC-81) by developing predictive classification as well as regression-based mathematical models. Simple and interpretable descriptors derived from a two-dimensional representation of the chemical structures along with quantum topological molecular similarity indices have been used for model development, employing unambiguous modeling strategies that strictly obey the guidelines of the Organization for Economic Co-operation and Development (OECD) for quantitative structure-activity relationship (QSAR) analysis. The structure-toxicity relationships that emerged from both classification and regression-based models were in accordance with the findings of some previous studies. The models suggested that the cytotoxicity of ionic liquids is dependent on the cationic surfactant action, long alkyl side chains, cationic lipophilicity as well as aromaticity, the presence of a dialkylamino substituent at the 4-position of the pyridinium nucleus and a bulky anionic moiety. The models have been transparently presented in the form of equations, thus allowing their easy transferability in accordance with the OECD guidelines. The models have also been subjected to rigorous validation tests proving their predictive potential and can hence be used for designing novel and "greener" ionic liquids. The major strength of the present study lies in the use of a diverse and large dataset, use of simple reproducible descriptors and compliance with the OECD norms.

Galleria mellonella as a novel in vivo model for assessment of the toxicity of 1-alkyl-3-methylimidazolium chloride ionic liquids.

The larval form of the Greater Wax Moth (Galleria mellonella) was evaluated as a model system for the study of the acute in vivo toxicity of 1-alkyl-3-methylimidazolium chloride ionic liquids. 24-h median lethal dose (LD50) values for nine of these ionic liquids bearing alkyl chain substituents ranging from 2 to 18 carbon atoms were determined. The in vivo toxicity of the ionic liquids was found to correlate directly with the length of the alkyl chain substituent, and the pattern of toxicity observed was in accordance with previous studies of ionic liquid toxicity in other living systems, including a characteristic toxicity 'cut-off' effect. However, G. mellonella appeared to be more susceptible to the toxic effects of the ionic liquids tested, possibly as a result of their high body fat content. The results obtained in this study indicate that G. mellonella represents a sensitive, reliable and robust in vivo model organism for the evaluation of ionic liquid toxicity.

Assessment of bromide-based ionic liquid toxicity toward aquatic organisms and QSAR analysis.

The toxicities of 24 bromide-based ionic liquids (Br-ILs) towards Vibrio fischeri (V. fischeri) and Daphnia magna (D. magna) were determined. These Br-ILs are composed of a bromide ion and a generic cation (i.e., pyrrolidinium, piperidinium, pyridinium or imidazolium) with different alkyl side chains. QSAR models with relatively high correlation coefficients, R(2), of 0.954 and 0.895 were developed for V. fischeri and D. magna. The model for V. fischeri indicated that the Br-IL toxicity towards V. fischeri was negatively correlated with the energy of the lowest unoccupied molecular orbitals (ELUMO) which reflects the electron affinities (EAs) and positively correlated with the volumes of Br-IL cations. For the D. magna model, the Br-IL toxicity was positively correlated with the dipole moment (µ) and negatively correlated with the total energy (TE) that is highly correlated with the molecular volume (V). For Br-ILs with the same cation ring, the toxicity increased as the length of the alkyl chains increased. For the same alkyl chain length, the toxicity order for V. fischeri was pyridinium>imidazolium>piperidinium>pyrrolidinium, except for those containing octyl side chains, while the toxicity ranking for D. magna was imidazolium~pyridinium>piperidinium>pyrrolidinium.