title: Incorporating bioavailability into toxicity assessment of Cu-Ni, Cu-Cd, and Ni-Cd mixtures with the extended biotic ligand model and the WHAM-F(tox) approach.
abstract: There are only a limited number of studies that have developed appropriate models which incorporate bioavailability to estimate mixture toxicity. Here, we explored the applicability of the extended biotic ligand model (BLM) and the WHAM-F(tox) approach for predicting and interpreting mixture toxicity, with the assumption that interactions between metal ions obey the BLM theory. Seedlings of lettuce Lactuca sativa were exposed to metal mixtures (Cu-Ni, Cu-Cd, and Ni-Cd) contained in hydroponic solutions for 4 days. Inhibition to root elongation was the endpoint used to quantify the toxic response. Assuming that metal ions compete with each other for binding at a single biotic ligand, the extended BLM succeeded in predicting toxicity of three mixtures to lettuce, with more than 82% of toxicity variation explained. There were no significant differences in the values of f(mix50) (i.e., the overall amounts of metal ions bound to the biotic ligand inducing 50% effect) for the three mixture combinations, showing the possibility of extrapolating these values to other binary metal combinations. The WHAM-F(tox) approach showed a similar level of precision in estimating mixture toxicity while requiring fewer parameters than the BLM-f(mix) model. External validation of the WHAM-F(tox) approach using literature data showed its applicability for other species and other mixtures. The WHAM-F(tox) model is suitable for delineating mixture effects where the extended BLM also applies. Therefore, in case of lower data availability, we recommend the lower parameterized WHAM-F(tox) as an effective approach to incorporate bioavailability in quantifying mixture toxicity.
authors.affiliation: Institute of Environmental Sciences, Leiden University, Leiden, The Netherlands.|Division Soil and Water Management, KU Leuven, Heverlee, Belgium.
authors.forename: Hao
authors.initials: H
authors.lastname: Qiu
authors.affiliation: Institute of Environmental Sciences, Leiden University, Leiden, The Netherlands.
authors.forename: Martina G
authors.initials: MG
authors.lastname: Vijver
authors.affiliation: Division Soil and Water Management, KU Leuven, Heverlee, Belgium. e2.he@vu.nl.|Department of Ecological Science, VU University, Amsterdam, The Netherlands. e2.he@vu.nl.
authors.forename: Erkai
authors.initials: E
authors.lastname: He
authors.affiliation: Institute of Environmental Sciences, Leiden University, Leiden, The Netherlands.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.affiliation: Department of Hydrology, University of Bayreuth, Bayreuth, Germany.
authors.forename: Bing
authors.initials: B
authors.lastname: Xia
authors.affiliation: Division Soil and Water Management, KU Leuven, Heverlee, Belgium.
authors.forename: Erik
authors.initials: E
authors.lastname: Smolders
authors.affiliation: Division Soil and Water Management, KU Leuven, Heverlee, Belgium.
authors.forename: Liske
authors.initials: L
authors.lastname: Versieren
authors.affiliation: Institute of Environmental Sciences, Leiden University, Leiden, The Netherlands.|National Institute of Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Willie J G M
authors.initials: WJ
authors.lastname: Peijnenburg
mesh_terms: D002104:Cadmium / Q000633:toxicity*; D045424:Complex Mixtures / Q000633:toxicity; D003300:Copper / Q000633:toxicity*; D018527:Hydroponics; D018545:Lactuca / Q000187:drug effects / Q000254:growth & development; D008024:Ligands; D008956:Models, Chemical; D009532:Nickel / Q000633:toxicity*; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development; D012996:Solutions; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D045424:Complex Mixtures; D008024:Ligands; D012996:Solutions; D014874:Water Pollutants, Chemical; D002104:Cadmium; D003300:Copper; D009532:Nickel
keywords: Bioavailability; Biotic ligand model; Metals; Mixture interactions; Toxicity; WHAM-F tox