## 2 Topical Research Areas Related to Ionic Liquids and the Contribution of Spiroammonium Compounds
### Green Chemistry and the IL Concepts
#### 2.2.3 The Toxic Properties of ILs; Their Screening with Organisms of Different Trophic Levels
The subjects of the research were chosen primarily on the basis of human exposure, level of commercial production, and chemical structure. Three exposure concentrations per IL were used to compare the relative toxicities of the four ILs when administered via drinking water: 1-ethyl-3-methylimidazolium chloride (Emim-Cl), 1-butyl-3-methylimidazolium chloride (Bmim-Cl), 1-butyl-1-methylpyrrolidinium chloride (Bmpy-Cl), and n-butylpyridinium chloride (NBuPy-Cl). The three-month toxicity studies of the ILs in male and female Sprague Dawley (Hsd: Sprague Dawley(r) SD(r)) rats and B6C3F1/N mice (n = 10/sex/exposure group) were performed as preclinical studies in accordance with Good Laboratory Practice Regulations. Overall, the results from this comparative study suggest that Emim-Cl, Bmim-Cl, Bmpy-Cl, and NBuPy-Cl in drinking water have minimal effects on rats and mice at low exposure concentrations (<3 mg/mL). Exposure to higher IL concentrations (\(\geq\)3 mg/mL) results in lower body weights. The lowest observed effect levels (LOELs) on the exposed male mice were assigned as 10 mg/mL for Emim-Cl, 3 mg/mL for Bmim-Cl, 10 mg/mL for Bmpy-Cl, and 6 mg/mL for NBuPy-Cl. The LOELs for female mice differed slightly. These studies indicate that IL-induced toxicity may be attributable to alkyl chain length and cation type. ILs with longer alkyl chains typically exhibit increased toxicity compared to ILs with shorter alkyl chains. However, the difference in toxicity among cations (imidazolium vs. pyrrolinium vs. pyridinium) is less clear and is both sex and endpoint-dependent. A multidisciplinary study on ILs is emerging, including chemistry, materials science, chemical engineering, and environmental science. More specifically, some important fundamental viewpoints are now different from the original concepts, as insights into the nature of ILs become deeper. For example, the physicochemical properties of ILs are now recognized as ranging broadly from the oft quoted \"nonvolatile, non-flammable, and air and water stable\" to those that are distinctly volatile, flammable, and unstable [72]. The issue of stability of ILs in any of their uses from laboratory studies to large-scale industrial applications becomes a priority in terms of toxicity both under standard conditions at atmospheric pressure and r.t., without exposure to aggressive factors, and in specific conditions for the using of ILs at high temperatures, aggressive environments, and pressure differences. Researching the thermal decomposition features of ILs holds paramount importance for the application in battery electrolyte. Imidazole ILs based on nitrates have become the subject of study in terms of their fire and explosion hazards and toxicity of released substances [73,74]. The thermal decomposition peculiarities of 1-allyl-3-methylimidazole nitrate IL were systematically analyzed by means of thermogravimetric analyzer, differential scanning calorimetry, and accelerating rate calorimeter techniques, and the relevant thermodynamic parameters and thermal decomposition models were derived [73]. The results showed that flammable gas, toxic gas, and asphyxiating gas are formed during the pyrolysis of 1-allyl-3-methylimidazole nitrate IL. Besides, [Amim][NO\({}_{3}\)] showed strong potential thermal hazard in non-isothermal adiabatic environment. The heat \(\Delta\)H generated by adiabatic decomposition was as high as 2330.13 J/g, which presents a high explosive risk. Risk assessments indicate that once thermal runaway occurs, the substance can lead to catastrophic consequences. The 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)limide [EMIM][Tf\({}_{2}\)N] has an autoignition temperature of 478 \({}^{\circ}\)C. It was observed with the TGA/DSC system that the decomposition of [EMIM][Tf\({}_{2}\)N] was endothermic in a nitrogen atmosphere but exothermic in an air atmosphere [74].