title: Estimating the combined toxicity by two-step prediction model on the complicated chemical mixtures from wastewater treatment plant effluents.
abstract: The toxicities of chemical mixtures containing 10 compounds, detected in wastewater treatment plant (WWTP) effluents, were investigated using Daphnia magna in a two-step prediction (TSP) model. The 10 chemicals determined by gas chromatography/ mass spectrometry in WWTP effluents included three groups: Three acetylcholinesterase inhibitors, six narcosis inhibitors, and one seedling root inhibitor. In the first step, a concentration addition (CA) model was used to predict the mixture toxicities for the three component groups with similar modes of action; in the second step, an independent action (IA) model was used for the newly developed concentration-response curves from the three CA predictions. The CA predictions did not show a statistically significant difference from the observed results with respect to the three groups of chemicals, whereas the IA model did not conform to the experimental results. Therefore, the concentration-response curves obtained from the mixture toxicity tests in each group was considered as a single curve and applied in the next step of the mixture toxicity prediction. However, the observed toxicity of the 10-chemical mixture showed large differences from the results of the IA and CA model predictions, whereas the TSP model predicted the toxicity well and with statistical significance (p = 0.0501, n = 17). This suggests that the TSP model would provide a valid prediction for a randomly selected chemical mixture having various modes of action if the concentration-response function for an individual component is obtained.
authors.affiliation: Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju 500-712, Korea.
authors.forename: Jin Sung
authors.initials: JS
authors.lastname: Ra
authors.forename: Byoung Cheun
authors.initials: BC
authors.lastname: Lee
authors.forename: Nam Ik
authors.initials: NI
authors.lastname: Chang
authors.forename: Sang Don
authors.initials: SD
authors.lastname: Kim
mesh_terms: D000818:Animals; D003621:Daphnia / Q000187:drug effects; D007220:Industrial Waste; D008962:Models, Theoretical; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D007220:Industrial Waste; D014874:Water Pollutants, Chemical