title: Benefits from hazards: mixture hormesis induced by [emim]Cl despite its individual inhibitions.
abstract: The threshold model based on monotonic concentration-response curves (CRCs) is unsuitable to assess the risk of chemicals with non-monotonic CRCs. The non-monotonic CRCs of mixtures may relate to the characteristics of some individual component. To reveal the cause of the mixtures resulting in the non-monotonic CRCs, we used the microplate toxicity analysis to determine the toxicity effects of six 1-alkyl-3-methyl-imidazolium ([amim]X) salts and their mixtures on Vibrio qinghaiensis sp.-Q67 (Q67). It was shown that the CRCs of six [amim]X salts are monotonic S-shaped while those of the senary mixtures designed by the uniform design ray (UD-ray) are all non-monotonic. The mixtures were further split into two ternary mixtures, one containing 1-ethyl-3-methyl-imidazolium ([emim]X) salts (noted as UTE) and the other one containing 1-butyl-3-methyl-imidazolium ([bmim]X) salts (noted as UTB). It was found that the CRCs of UTE mixtures are all non-monotonically J-shaped, while only one (UTB-R3) among UTB mixtures has a little stimulating effect and the CRCs of the other three mixtures (UTB-R1, UTB-R2 and UTB-R4) are monotonic. The CRCs of the binary mixtures designed by the direct equipartition ray design (EquRay) procedure were further examined. The CRCs of the mixtures containing [emim]Cl are non-monotonic J-shaped while those of the mixtures without [emim]Cl are still monotonic. Thus, it can conclude that it is [emim]Cl that causes the non-monotonic CRCs in [amim]X mixtures, even though the CRC of individual [emim]Cl is monotonic.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China; College of Biological, Chemical Sciences and Engineering, Jiaxing University, Jiaxing, Zhejiang 314001, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China. Electronic address: ssliuhl@263.net.
authors.forename: Shu-Shen
authors.initials: SS
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China; College of Resources and Environment, Qingdao Agricultural University, Qingdao, Shandong 266109, PR China.
authors.forename: Xiang-Wei
authors.initials: XW
authors.lastname: Zhu
mesh_terms: D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004787:Environmental Pollution; D059165:Hormesis / Q000187:drug effects*; D007093:Imidazoles / Q000633:toxicity*; D018570:Risk Assessment; D018675:Toxicity Tests; D014733:Vibrio / Q000187:drug effects*
chemical_list: D007093:Imidazoles; C518739:1-ethyl-3-methylimidazolium
keywords: 1-Ethyl-3-methyl-imidazolium chloride; Concentration-response curve; Direct equipartition ray design; Mixture hormesis; Uniform design ray