Predicting Ecotoxicological Effects

Aquatic chemical exposure prediction tool Ecotoxicological effects Not considered... 

The ecotoxicology of pharmaceuticals is of critical concern to the issue of PIE. The all important question is not whether pharmaceuticals are present in the environment-there is ample evidence that they are-but, at the concentrations at which they are found, whether they do any harm The almost universally used paradigm for attempting to answer this question is the comparison of the Predicted Environmental Concentration (PEC) with the Predicted No Effect Concentration (PNEC)-the so called PEC/PNEC ratio. 

Structure-activity relationships (SARs) and quantitative structure-activity relationships (QSARs), referred to collectively as QSARs, can be used for the prediction of physicochemical properties, environmental fate parameters (e.g., accumulation and biodegradation), human health effects, and ecotoxicological effects. A SAR is a (qualitative) association between a chemical substructure and the potential of a chemical containing the substructure to exhibit a certain physical or biological effect. A QS AR is a mathematical model that relates a quantitative measure of chemical structure (e.g., a physicochemical property) to a physical property or to a biological effect (e.g., a toxicological endpoint). 

Prediction of ecotoxicological effects for other types of chemical classes as well as for foodchain transfer is less founded, and should be studied further to extend our knowledge and the applicability in using the internal effect concentrations. 

In addition to gaps in knowledge for currently existing classes of chemicals and ecotoxicological effects, other mechanisms of actions that are currently not yet studied, or other processes, may require further studies. For example, recently it has become clear that phototoxic effects may be a realistic problem for polycylic aromatic hydrocarbons (PAHs) in aquatic and benthic organisms. The amount of UV-light which is required for phototoxicity, is thus an example of a parameter which was not introduced earlier as an important environmental parameter to describe or predict toxicity [148]. Other examples are if the internal effect concept can be used for metals and organometals in risk assessment [149,150]. 

Model for Predicting the Ecotoxicological Effects of Transformation Products... 

The model for predicting the ecotoxicological effects of mixtures of metabolites and their parent compounds assumes concentration addition of the effects of metabolites and their parent compound. If concentration addition holds and additionally all assumptions pertinent to the toxic equivalency concept apply [14], the toxic potential of the mixture of a parent compound and its metabolites, TPmixture. is defined as the sum of the fraction of parent after metabolism, /parent, and the product of the fraction of each metabohte i, fi, scaled by the potency of the given metabolite RPi, in relation to 100% potency of the parent compound (Eq. 1). 

Ecotoxicity of Transformation Products (Sinclair and Boxall) and Predicting the Ecotoxicological Effects of Transformation Products (Escher et al.) describe the ecotoxicological effects of transformation products and discuss approaches that could be employed for estimating ecotoxicity based on transformation product structure and information on the associated parent chemicals. Finally, in Treatment of Transformation Products, Adams et al. discuss how transformation products can be removed in treatment processes but also discuss how treatment processes can act as routes of transformation product formation. 

T. C. M. Brock, The Value of the Species Sensitivity Distribution Concept for Predicting Field Effects (Non-) Confirmation of the Concept Using Semi-Field Experiments. In Use of Species Sensitivity Distributions in Ecotoxicology, L. Posthuma, T. P. Traas, G. W. Suter (Eds.), Lewis Publishers, Boca Ration, Fla., USA, 2001,... 

Zinc carbonate (0.6 to 5ppb seawater 5 to lOppb river water) has moderate solubility as a carbonate (21 mg/100 mL) (73). Zinc compounds are not particularly hazardous above certain limits they may be toxic and irritating. The maximum level allowed in sludge from wastewater is 3 g/kg. The predicted no effect concentration (PNEC) for ecotoxicological effects was 50 p g/L (5 pg/lOOmL) dissolved zinc (73). Current values are not a very serious risk. High zinc levels protect against cadmium intoxication and reduce lead absorption. Pockets of historical contamination exist (73). 

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