title: Comparative aquatic toxicity evaluation of 2-(thiocyanomethylthio)benzothiazole and selected degradation products using Ceriodaphnia dubia.
abstract: 2-(Thiocyanomethylthio)benzothiazole (TCMTB) is a biocide used in the leather, pulp and paper, and water-treatment industries. TCMTB may enter aquatic ecosystems during its manufacture and use. TCMTB is environmentally unstable; therefore, it is important to evaluate the toxicity of the more persistent degradation products. This study compared the toxicity of TCMTB with its degradation products 2-mercaptobenzothiazole (2-MBT), 2-(methylthio)benzothiazole (MTBT), benzothiazole (BT), and 2-hydroxybenzothiazole (HOBT). Toxicity was determined using Ceriodaphnia dubia 48-hour acute and 7-day chronic test protocols. TCMTB was the most toxic compound evaluated in both the acute and chronic tests with EC50s of 15.3 and 9.64 microg/L, respectively. 2-MBT, the first degradation product, was the second most toxic compound with acute and chronic EC50s of 4.19 and 1.25 mg/L, respectively. The toxicity of MTBT and HOBT were similar with acute EC50s of 12.7 and 15.1 mg/L and chronic EC50s of 6.36 and 8.31 mg/L, respectively. The least toxic compound was BT with acute and chronic EC50s of 24.6 and 54.9 mg/L, respectively. TCMTB was orders of magnitude more toxic than its degradation products. Toxicity data on these benzothiazole degradation products is important because of concerns regarding their release, degradation, persistence, and non-target organism effects in aquatic ecosystems.
authors.affiliation: Department of Cancer Biology, University of Texas-Houston, M.D. Anderson Cancer Center, Houston, Texas 77001, USA.
authors.forename: S T
authors.initials: ST
authors.lastname: Nawrocki
authors.forename: K D
authors.initials: KD
authors.lastname: Drake
authors.forename: C F
authors.initials: CF
authors.lastname: Watson
authors.forename: G D
authors.initials: GD
authors.lastname: Foster
authors.forename: K J
authors.initials: KJ
authors.lastname: Maier
mesh_terms: D000818:Animals; D052160:Benzothiazoles; D033361:Cladocera / Q000187:drug effects* / Q000502:physiology; D007928:Lethal Dose 50; D019055:No-Observed-Adverse-Effect Level; D013844:Thiazoles / Q000737:chemistry / Q000633:toxicity*; D013861:Thiocyanates / Q000737:chemistry / Q000633:toxicity*; D023382:Toxicity Tests, Acute; D036401:Toxicity Tests, Chronic; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D052160:Benzothiazoles; D013844:Thiazoles; D013861:Thiocyanates; D014874:Water Pollutants, Chemical; C104310:2-(thiocyanomethylthio)benzothiazole