title: Evaluating the Combined Toxicity of Cu and ZnO Nanoparticles: Utility of the Concept of Additivity and a Nested Experimental Design.
abstract: Little is understood regarding the effects of mixtures of different metal-based nanoparticles (NPs). Using concentration-addition (CA) and independent-action (IA) models, we evaluated the combined toxicity of Cu and ZnO NPs based on five nested combinations, i.e., Cu(NO3)2-CuNPs, Zn(NO3)2-ZnONPs, Cu(NO3)2-ZnONPs, Zn(NO3)2-CuNPs, and CuNPs-ZnONPs on root elongation of Lactuca sativa L. The CA and IA models performed equally well in estimating the toxicity of mixtures of Cu(NO3)2-CuNPs, Zn(NO3)2-ZnONPs, and Zn(NO3)2-CuNPs, whereas the IA model was significantly better for fitting the data of Cu(NO3)2-ZnONPs and CuNPs-ZnONPs mixtures. Dissolved Cu proved to be the most toxic metal species to lettuce roots in the tests, followed by Cu NPs, dissolved Zn, and ZnO NPs, respectively. An antagonistic effect was observed for ZnO NPs on the toxicity of Cu NPs. This antagonistic effect is expected to be the result of interactions between dissolved Cu and dissolved Zn, particulate Zn and dissolved Zn, particulate Cu and dissolved Zn, and between particulate Zn and dissolved Cu. In general terms, assuming additivity gives a first indication of the combined toxicity with soluble and insoluble metal particles, both being important in driving the toxicity of metal-based NPs to higher plants.
authors.affiliation: Faculty of Environmental Science and Engineering, Kunming University of Science and Technology , Kunming, Yunnan Province, 650500 China.|Institute of Environmental Sciences (CML), Leiden University , Leiden, 2300 RA The Netherlands.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Institute of Environmental Sciences (CML), Leiden University , Leiden, 2300 RA The Netherlands.|Centre for Ecology & Hydrology (CEH) , MacLean Building, Benson Lane, Wallingford, Oxfordshire, OX10 8BB United Kingdom.
authors.forename: Jan
authors.initials: J
authors.lastname: Baas
authors.affiliation: Institute of Environmental Sciences (CML), Leiden University , Leiden, 2300 RA The Netherlands.|National Institute of Public Health and the Environment (RIVM), Center for Safety of Substances and Products , Bilthoven, 3720 BA The Netherlands.
authors.forename: Willie J G M
authors.initials: WJ
authors.lastname: Peijnenburg
authors.affiliation: Institute of Environmental Sciences (CML), Leiden University , Leiden, 2300 RA The Netherlands.
authors.forename: Martina G
authors.initials: MG
authors.lastname: Vijver
mesh_terms: D018545:Lactuca / Q000187:drug effects; D053768:Metal Nanoparticles; D019216:Metals, Heavy / Q000494:pharmacology; D012107:Research Design; D015034:Zinc Oxide / Q000494:pharmacology*
chemical_list: D019216:Metals, Heavy; D015034:Zinc Oxide