Abstract
Ionic liquids are salts used in a variety of industrial processes, and being relatively non-volatile, are proposed as environmentally-friendly replacements for existing volatile liquids. Methylimidazolium ionic liquids resist complete degradation in the environment, likely because the imidazolium moiety does not exist naturally in biological systems. However, there is limited data available regarding their mammalian effects in vivo.This study aimed to examine the effects of exposing mice separately to 2 different methylimidazolium ionic liquids (BMI and M8OI) through their addition to drinking water. Potential effects on key target organs–the liver and kidney–were examined, as well as the gut microbiome.Adult male mice were exposed to drinking water containing ionic liquids at a concentration of 440 mg/L for 18 weeks prior to examination of tissues, serum, urine and the gut microbiome. Histopathology was performed on tissues and clinical chemistry on serum for biomarkers of hepatic and renal injury. Bacterial DNA was isolated from the gut contents and subjected to targeted 16S rRNA sequencing.Mild hepatic and renal effects were limited to glycogen depletion and mild degenerative changes respectively. No hepatic or renal adverse effects were observed. In contrast, ionic liquid exposure altered gut microbial composition but not overall alpha diversity. Proportional abundance of Lachnospiraceae, Clostridia and Coriobacteriaceae spp. were significantly greater in ionic liquid-exposed mice, as were predicted KEGG functional pathways associated with xenobiotic and amino acid metabolism.Exposure to ionic liquids via drinking water therefore resulted in marked changes in the gut microbiome in mice prior to any overt pathological effects in target organs. Ionic liquids may be an emerging risk to health through their potential effects on the gut microbiome, which is implicated in the causes and/or severity of an array of chronic disease in humans.
Highlights
Ionic liquids are salts that are normally liquid at ambient temperature and in some cases, are liquids at room temperature
Widely-available methylimidazolium ionic liquids are a class of ionic liquids composed of a cationic methylimidazolium moiety with an alkyl chain increasing in length by 2 carbons and a variety of different anions (e.g. Cl, Br, tetrafluoroborate etc)
Based on registrations submitted to the European Chemicals Agency (ECHA), the total number of methylimidazolium ionic liquids used in the EU at present, is likely to be in the order of up to 60–70 [3]
Summary
Ionic liquids are salts that are normally liquid at ambient temperature (typically below 100 ̊C) and in some cases, are liquids at room temperature. Methylimidazolium-based ILs are most often proposed as solvents in a variety of industrial applications such as separations, catalysis and dissolution, with 1-ethyl-3-methylimidazolium acetate (likely used at high levels since the ECHA database indicates several variants manufactured at up to 100 tonnes/annum or manufacture levels are reported as confidential [3]). This methylimidazolium ionic liquid has shown outstanding performance in the fields of biomass dissolution and biopolymer processing [4]
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