title: Toxicity of tetramethylammonium hydroxide to aquatic organisms and its synergistic action with potassium iodide.
abstract: The aquatic ecotoxicity of chemicals involved in the manufacturing process of thin film transistor liquid crystal displays was assessed with a battery of four selected acute toxicity bioassays. We focused on tetramethylammonium hydroxide (TMAH, CAS No. 75-59-2), a widely utilized etchant. The toxicity of TMAH was low when tested in the 72 h-algal growth inhibition test (Pseudokirchneriellia subcapitata, EC50=360 mg L(-1)) and the Microtox® test (Vibrio fischeri, IC50=6.4 g L(-1)). In contrast, the 24h-microcrustacean immobilization and the 96 h-fish mortality tests showed relatively higher toxicity (Daphnia magna, EC50=32 mg L(-1) and Oryzias latipes, LC50=154 mg L(-1)). Isobologram and mixture toxicity index analyses revealed apparent synergism of the mixture of TMAH and potassium iodide when examined with the D. magna immobilization test. The synergistic action was unique to iodide over other halide salts i.e. fluoride, chloride and bromide. Quaternary ammonium ions with longer alkyl chains such as tetraethylammonium and tetrabutylammonium were more toxic than TMAH in the D. magna immobilization test.
authors.affiliation: Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan. Electronic address: imori@okayama-u.ac.jp.
authors.forename: Izumi C
authors.initials: IC
authors.lastname: Mori
authors.affiliation: Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan.
authors.forename: Carlos R
authors.initials: CR
authors.lastname: Arias-Barreiro
authors.affiliation: Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan.
authors.forename: Apostolos
authors.initials: A
authors.lastname: Koutsaftis
authors.affiliation: Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Ogo
authors.affiliation: School of International Environmental Science, The University of Kitakyushu, Kitakyushu 808-0135, Japan.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Kawano
authors.affiliation: School of International Environmental Science, The University of Kitakyushu, Kitakyushu 808-0135, Japan.
authors.forename: Kazuharu
authors.initials: K
authors.lastname: Yoshizuka
authors.affiliation: Faculty of Health Sciences, Univerisiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia.
authors.forename: Salmaan H
authors.initials: SH
authors.lastname: Inayat-Hussain
authors.affiliation: Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan.
authors.forename: Isao
authors.initials: I
authors.lastname: Aoyama
mesh_terms: D048908:Aliivibrio fischeri / Q000187:drug effects; D000818:Animals; D059001:Aquatic Organisms / Q000187:drug effects*; D000460:Chlorophyta / Q000187:drug effects; D003621:Daphnia / Q000187:drug effects; D004357:Drug Synergism; D009990:Oryzias / Q000378:metabolism; D011193:Potassium Iodide / Q000633:toxicity*; D000644:Quaternary Ammonium Compounds / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D000644:Quaternary Ammonium Compounds; D014874:Water Pollutants, Chemical; D011193:Potassium Iodide; C027917:tetramethylammonium
keywords: Aquatic toxicity; D. magna; Potassium iodide; Semiconductor wastewater; Synergism; Tetramethylammonium hydroxide