title: Meta-analysis of ionic liquid literature and toxicology.
abstract: A meta-analysis was conducted to compare the total amount of ionic liquid (IL) literature (n = 39,036) to the body of publications dealing with IL toxicity (n = 213) with the goal of establishing the state of knowledge and existing information gaps. Additionally, patent literature pertaining to issued patents utilizing ILs (n = 3358) or dealing with IL toxicity (n = 112) were analyzed. Total publishing activity and patent count served to gauge research activity, industrial usage and toxicology knowledge of ILs. Five of the most commonly studied IL cations were identified and used to establish a relationship between toxicity data and potential of commercial use: imidazolium, ammonium, phosphonium, pyridinium, and pyrrolidinium. Toxicology publications for all IL cations represented 0.55% ± 0.27% of the total publishing activity; compared with other industrial chemicals, these numbers indicate that there is still a paucity of studies on the adverse effects of this class of chemical. Toxicity studies on ILs were dominated by the use of in vitro models (18%) and marine bacteria (15%) as studied biological systems. Whole animal studies (n = 87) comprised 31% of IL toxicity studies, with a subset of in vivo mammalian models consisting of 8%. Human toxicology data were found to be limited to in vitro analyses, indicating substantial knowledge gaps. Risks from long-term and chronic low-level exposure to ILs have not been established yet for any model organisms, reemphasizing the need to fill crucial knowledge gaps concerning human health effects and the environmental safety of ILs. Adding to the existing knowledge of the molecular toxicity characteristics of ILs can help inform the design of greener, less toxic and more benign IL technologies.
authors.affiliation: Barrett, The Honors College, School of Life Sciences, College of Liberal Arts and Sciences, Arizona State University, Tempe, AZ 85281, USA.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Heckenbach
authors.affiliation: Barrett, The Honors College, Chemical Engineering, School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, AZ 85281, USA.
authors.forename: Felicia N
authors.initials: FN
authors.lastname: Romero
authors.affiliation: Chemical Engineering, School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, AZ 85287-6106, USA.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Green
authors.affiliation: Center for Environmental Security and Global Security Initiative, The Biodesign Institute, Arizona State University, Tempe, AZ 85287-5904, USA. Electronic address: halden@asu.edu.
authors.forename: Rolf U
authors.initials: RU
authors.lastname: Halden
mesh_terms: D000818:Animals; D002412:Cations / Q000737:chemistry / Q000633:toxicity; D004785:Environmental Pollutants / Q000737:chemistry / Q000633:toxicity*; D055772:Green Chemistry Technology; D006801:Humans; D052578:Ionic Liquids / Q000737:chemistry / Q000633:toxicity*; D007928:Lethal Dose 50; D010330:Patents as Topic; D012997:Solvents / Q000737:chemistry / Q000633:toxicity*
chemical_list: D002412:Cations; D004785:Environmental Pollutants; D052578:Ionic Liquids; D012997:Solvents
keywords: Environmental health; Green chemistry; Ionic liquids; Meta-analysis; Sustainability; Toxicity