title: Rapid toxicity screening of gasification ashes.
abstract: The solid residues including bottom ashes and fly ashes produced by waste gasification technology could be reused as secondary raw materials. However, the applications and utilizations of these ashes are very often restricted by their toxicity. Therefore, toxicity screening of ash is the primary condition for reusing the ash. In this manuscript, we establish a standard for rapid screening of gasification ashes on the basis of in vitro and in vivo testing, and henceforth guide the proper disposal of the ashes. We used three different test models comprising human cell lines (liver and lung cells), Drosophila melanogaster and Daphnia magna to examine the toxicity of six different types of ashes. For each ash, different leachate concentrations were used to examine the toxicity, with C0 being the original extracted leachate concentration, while C/C0 being subsequent diluted concentrations. The IC50 for each leachate was also quantified for use as an index to classify toxicity levels. The results demonstrated that the toxicity evaluation of different types of ashes using different models is consistent with each other. As the different models show consistent qualitative results, we chose one or two of the models (liver cells or lung cells models) as the standard for rapid toxicity screening of gasification ashes. We may classify the gasification ashes into three categories according to the IC50, 24h value on liver cells or lung cells models, namely "toxic level I" (IC50, 24h>C/C0=0.5), "toxic level II" (C/C0=0.05<IC50, 24h<C/C0=0.5) and "toxic level III" (IC50, 24h<C/C0=0.05). Such a simple yet informative approach can help to determine the toxic effects of various types of ashes generated in gasification plants every day. Subsequently, appropriate disposal methods can be recommended for each toxicity category.
authors.affiliation: NUS Environmental Research Institute, National University of Singapore, 1 Create Way, Create Tower #15-02, Singapore 138602, Singapore; Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore.
authors.forename: Xu
authors.initials: X
authors.lastname: Zhen
authors.affiliation: NUS Environmental Research Institute, National University of Singapore, 1 Create Way, Create Tower #15-02, Singapore 138602, Singapore; Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore.
authors.forename: Le
authors.initials: L
authors.lastname: Rong
authors.affiliation: NUS Environmental Research Institute, National University of Singapore, 1 Create Way, Create Tower #15-02, Singapore 138602, Singapore; Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore.
authors.forename: Wei Cheng
authors.initials: WC
authors.lastname: Ng
authors.affiliation: Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, 4 Medical Drive, Singapore 117597, Singapore.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Ong
authors.affiliation: Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, 4 Medical Drive, Singapore 117597, Singapore.
authors.forename: Gyeong Hun
authors.initials: GH
authors.lastname: Baeg
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Wenlin
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Si Ni
authors.initials: SN
authors.lastname: Lee
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Sam Fong Yau
authors.initials: SF
authors.lastname: Li
authors.affiliation: School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai 200240, China.
authors.forename: Yanjun
authors.initials: Y
authors.lastname: Dai
authors.affiliation: NUS Environmental Research Institute, National University of Singapore, 1 Create Way, Create Tower #15-02, Singapore 138602, Singapore; Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore.
authors.forename: Yen Wah
authors.initials: YW
authors.lastname: Tong
authors.affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore.
authors.forename: Koon Gee
authors.initials: KG
authors.lastname: Neoh
authors.affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore. Electronic address: chewch@nus.edu.sg.
authors.forename: Chi-Hwa
authors.initials: CH
authors.lastname: Wang
mesh_terms: D000818:Animals; D002460:Cell Line; D060729:Coal Ash / Q000633:toxicity*; D003621:Daphnia / Q000187:drug effects*; D004331:Drosophila melanogaster / Q000187:drug effects*; D056945:Hep G2 Cells; D006801:Humans; D020128:Inhibitory Concentration 50; D012037:Refuse Disposal; D023382:Toxicity Tests, Acute / Q000379:methods*
chemical_list: D060729:Coal Ash
keywords: Bottom ashes; Fly ashes; Gasification; Toxicity evaluation