title: An analysis of lethal and sublethal interactions among type I and type II pyrethroid pesticide mixtures using standard Hyalella azteca water column toxicity tests.
abstract: A novel 2-tiered analytical approach was used to characterize and quantify interactions between type I and type II pyrethroids in Hyalella azteca using standardized water column toxicity tests. Bifenthrin, permethrin, cyfluthrin, and lambda-cyhalothrin were tested in all possible binary combinations across 6 experiments. All mixtures were analyzed for 4-d lethality, and 2 of the 6 mixtures (permethrin-bifenthrin and permethrin-cyfluthrin) were tested for subchronic 10-d lethality and sublethal effects on swimming motility and growth. Mixtures were initially analyzed for interactions using regression analyses, and subsequently compared with the additive models of concentration addition and independent action to further characterize mixture responses. Negative interactions (antagonistic) were significant in 2 of the 6 mixtures tested, including cyfluthrin-bifenthrin and cyfluthrin-permethrin, but only on the acute 4-d lethality endpoint. In both cases mixture responses fell between the additive models of concentration addition and independent action. All other mixtures were additive across 4-d lethality, and bifenthrin-permethrin and cyfluthrin-permethrin were also additive in terms of subchronic 10-d lethality and sublethal responses. Environ Toxicol Chem 2016;35:2542-2549. © 2016 SETAC.
authors.affiliation: School of Veterinary Medicine, Department of Anatomy, Physiology and Cell Biology, University of California, Davis, California, USA. Krista.Hoffmann@water.ca.gov.
authors.forename: Krista Callinan
authors.initials: KC
authors.lastname: Hoffmann
authors.affiliation: School of Veterinary Medicine, Department of Anatomy, Physiology and Cell Biology, University of California, Davis, California, USA.
authors.forename: Linda
authors.initials: L
authors.lastname: Deanovic
authors.affiliation: Swiss Center for Applied Ecotoxicology Eawag-EPFL, Dübendorf, Switzerland.
authors.forename: Inge
authors.initials: I
authors.lastname: Werner
authors.affiliation: School of Veterinary Medicine, Department of Anatomy, Physiology and Cell Biology, University of California, Davis, California, USA.
authors.forename: Marie
authors.initials: M
authors.lastname: Stillway
authors.affiliation: State and Federal Water Agency, Sacramento, California, USA.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Fong
authors.affiliation: School of Veterinary Medicine, Department of Anatomy, Physiology and Cell Biology, University of California, Davis, California, USA.
authors.forename: Swee
authors.initials: S
authors.lastname: Teh
mesh_terms: D033304:Amphipoda / Q000187:drug effects* / Q000254:growth & development; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D007928:Lethal Dose 50; D008954:Models, Biological; D010575:Pesticides / Q000633:toxicity*; D011722:Pyrethrins / Q000633:toxicity*; D018570:Risk Assessment; D018675:Toxicity Tests; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D010575:Pesticides; D011722:Pyrethrins; D014874:Water Pollutants, Chemical
keywords: Concentration addition; Dose-response modeling; Independent action; Mixture toxicology; Mixtures; Pyrethroids; Risk assessment; Sublethal effects