title: Reproductive toxicity of binary and ternary mixture combinations of nickel, zinc, and lead to Ceriodaphnia dubia is best predicted with the independent action model.
abstract: Metals occur as mixtures in the environment. Risk assessment procedures for metals currently lack a framework to incorporate chronic metal mixture toxicity. In the present study, the toxicity of binary and ternary mixture combinations of Ni, Zn, and Pb was investigated in 3 large-scale experiments using the standard chronic (7-d) Ceriodaphnia dubia reproductive toxicity test. These metals were selected because of anticipated differences in mode of action. The toxicity of the metals in most mixtures, expressed as either free metal ion activities or as dissolved metal concentrations, were antagonistic relative to the concentration addition model, whereas no significant (p < 0.05) interactive effects were observed relative to the independent action model. The only exception was the binary Pb-Zn mixture, for which mixture effects were noninteractive based on the dissolved concentrations, but antagonistic based on free ion activities all relative to the independent action model. Overall, the independent action model fitted the observed toxicity better than the concentration addition model, which is consistent with the different modes of action of these metals. The concentration addition model mostly overestimated toxicity. Finally, the present study warns against extrapolation of the type of interactive effects between species, even when they are closely related. Environ Toxicol Chem 2016;35:1796-1805. © 2015 SETAC.
authors.affiliation: Faculty of Bioscience Engineering, GhenToxLab, Ghent University, Ghent, Belgium.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Nys
authors.affiliation: Faculty of Bioscience Engineering, GhenToxLab, Ghent University, Ghent, Belgium.
authors.forename: Colin R
authors.initials: CR
authors.lastname: Janssen
authors.affiliation: Laboratory for Ecophysiology, Biochemistry, and Toxicology, University of Antwerp, Antwerp, Belgium.
authors.forename: Ronny
authors.initials: R
authors.lastname: Blust
authors.affiliation: Division Soil and Water Management, KULeuven, Leuven, Belgium.
authors.forename: Erik
authors.initials: E
authors.lastname: Smolders
authors.affiliation: Faculty of Bioscience Engineering, GhenToxLab, Ghent University, Ghent, Belgium.
authors.forename: Karel A C
authors.initials: KA
authors.lastname: De Schamphelaere
mesh_terms: D000818:Animals; D033361:Cladocera / Q000187:drug effects* / Q000254:growth & development; D007854:Lead / Q000032:analysis / Q000633:toxicity*; D008962:Models, Theoretical; D009532:Nickel / Q000032:analysis / Q000633:toxicity*; D012098:Reproduction / Q000187:drug effects; D018570:Risk Assessment; D013054:Spectrophotometry, Atomic; D036401:Toxicity Tests, Chronic; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000633:toxicity*; D015032:Zinc / Q000032:analysis / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D007854:Lead; D009532:Nickel; D015032:Zinc
keywords: Daphnia; Freshwater; Metals; Mixture toxicity; Risk assessment