title: Toxicity of the insecticide terbufos, its oxidation metabolites, and the herbicide atrazine in binary mixtures to Ceriodaphnia cf dubia.
abstract: The acute toxicity of terbufos and its major metabolites, tested alone, in binary mixtures or in combination with atrazine were evaluated using neonates of the cladoceran Ceriodaphnia cf dubia. Terbufos, terbufos sulfoxide, and terbufos sulfone tested individually were highly toxic to C. cf dubia, with mean 96-h EC(50) values of 0.08, 0.36, and 0.19 μg/l, respectively. The addition of atrazine (10 μg/l) significantly increased the toxicity of terbufos. The toxicity of terbufos sulfone was unaffected by atrazine, whereas the results for terbufos sulfoxide were equivocal. Equitoxic mixtures of the metabolites showed additive toxicity to C. cf dubia. The high toxicities of terbufos and its environmentally persistent oxidative metabolites suggest that contamination of aquatic systems with this insecticide mixture and the coapplied herbicide atrazine might pose a greater hazard to some biota than their individual toxicities.
authors.affiliation: Department of Biological Sciences, Macquarie University, Balaclava Road, Macquarie University, NSW 2109, Australia. catherine.choung@environment.nsw.gov.au
authors.forename: Catherine B
authors.initials: CB
authors.lastname: Choung
authors.forename: Ross V
authors.initials: RV
authors.lastname: Hyne
authors.forename: Mark M
authors.initials: MM
authors.lastname: Stevens
authors.forename: Grant C
authors.initials: GC
authors.lastname: Hose
mesh_terms: D000818:Animals; D001280:Atrazine / Q000633:toxicity*; D033361:Cladocera / Q000187:drug effects*; D006540:Herbicides / Q000633:toxicity*; D007306:Insecticides / Q000633:toxicity*; D007928:Lethal Dose 50; D009946:Organothiophosphorus Compounds / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity
chemical_list: D006540:Herbicides; D007306:Insecticides; D009946:Organothiophosphorus Compounds; D014874:Water Pollutants, Chemical; C012568:terbufos; D001280:Atrazine; C036515:terbufos sulfone; C036514:terbufos sulfoxide