Systematic Evaluation of Chronic Metal-Mixture Toxicity to Three Species and Implications for Risk Assessment.
Metal contamination generally occurs as mixtures. However, it is yet unresolved how to address metal mixtures in risk assessment. Therefore, using consistent methodologies, we have set up experiments to identify which mixture model applies best at low-level effects, i.e., the independent action (IA) or concentration addition (CA) reference model. The toxicity of metal mixtures (Ni, Zn, Cu, Cd, and Pb) to Daphnia magna, Ceriodaphnia dubia, and Hordeum vulgare was investigated in different waters or soils, totaling 30 different experiments. Some mixtures of different metals, each individually causing <10% inhibition, yielded much larger inhibition (up to 66%) when dosed in combination. In general, IA was most accurate in predicting mixture toxicity, while CA was the most conservative. At low-effect levels important in risk assessments, CA overestimated mixture toxicity to daphnids and H. vulgare, on average, with a factor 1.4 to 3.6. Observed mixture interactions could be related to bioavailability or by competition interactions, either for binding sites of dissolved organic carbon or for biotic ligand sites. Our study suggests that the current metal-by-metal approach in risk evaluations may not be conservative enough for metal mixtures.
Laboratory of Environmental Toxicology and Aquatic Ecology, UGent Campus Coupure , Coupure Links 653, B-9000 Gent, Belgium.
Charlotte
0000-0001-9646-3744
C
Nys
Division Soil and Water Management, KU Leuven , Kasteelpark Arenberg 20 bus 2459, B-3001 Leuven, Belgium.
Liske
L
Versieren
Department of Biology (SPHERE Group), University of Antwerp Campus Groenenborger , Groenerborgerlaan 171, GU761, B-2020 Antwerpen, Belgium.
Katherine I
KI
Cordery
Department of Biology (SPHERE Group), University of Antwerp Campus Groenenborger , Groenerborgerlaan 171, GU761, B-2020 Antwerpen, Belgium.
Ronny
R
Blust
Division Soil and Water Management, KU Leuven , Kasteelpark Arenberg 20 bus 2459, B-3001 Leuven, Belgium.
Erik
0000-0003-3054-2444
E
Smolders
Laboratory of Environmental Toxicology and Aquatic Ecology, UGent Campus Coupure , Coupure Links 653, B-9000 Gent, Belgium.
Karel A C
KAC
De Schamphelaere
D000818:Animals; D033361:Cladocera / Q000187:drug effects; D003621:Daphnia / Q000187:drug effects*; D019216:Metals, Heavy / Q000633:toxicity*; D008962:Models, Theoretical; D018570:Risk Assessment; D014874:Water Pollutants, Chemical / Q000633:toxicity
D019216:Metals, Heavy; D014874:Water Pollutants, Chemical