Ecological risk prediction

NEW APPROACHES TO PREDICTING ECOLOGICAL RISKS PRESENTED BY CHEMICALS... 

A number of EIA theorists believe in incorporating formal RA methods into EIA as a way to cope with uncertainties, especially in impact prediction where a formal framework for ecological risk assessment (EcoRA) is already developed. It includes three generic phases problem formulation, analysis, and risk characterization followed by risk management. The analysis phase includes an exposure assessment and an ecological effects assessment (see, e.g., US EPA (1998)). 

This would allow a more comprehensive ecological risk assessment, and also predict a perspective of the geoecological situation changes, in particularly, in the Northern Caspian under varying input of different pollutants into the river-sea system. 

Table 2 Observed and predicted concentrations, ecological risk values and observed and predicted ISI levels in different Dutch open waters. ...

Area locations Observed concentration range in sediments and SPM Sn-TBT pg.kg- dw (min - max) Calculated concentration range in water Sn-TBT ng.l-i (5 - 95 %tile) Calculated Ecological Risk as PAF (%) Calculated predicted ISIrange (based on 5 - 95 %tile concentrations) Observed ISI (min - max) ... 

For open waters, only two measured ISl values fell within the predicted ISI ranges (North Sea (C)) and Western Scheldt (G), while the rest of the observations were below the calculated ranges. This is presumably a consequence of the asymptotic minimum of 0.07 in Formula 1. Differences in local values may have caused the predicted ISI levels in open waters to exceed the observed ISI values. In this study the is based on measured concentrations in sediment and water from harbours. This is in line with the fact that the correspondence in harbours is much better. It might be possible to derive a dedicated for open waters from the comparison of water and sediment concentrations in open waters, potentially improving the correspondence between predicted and measured ISI levels for these water systems. However, such data are not available. The possible over-estimation of water concentrations in open waters would also imply that the ecological risk values presented in this study have been over-estimated for open waters. 

There is good correspondence between observed ISl levels and the predicted ISI ranges for each harbour. Since almost all observed ISl levels fell within the ranges of predicted ISI levels in open waters, it can be concluded that the spatial distribution of TBT concentrations is a good basis for determining predicted ISI levels, and therefore ecological risk. 

LOE - Chemistry Predicted risk Predicted ISI LOE - Toxicology Observed ISI LOE - Ecology Presence of gastropods at all locations Likely ecological health status in relation to TBT Action... 

Since QSAR models for narcosis toxicity based on Kn/W are available for many endpoints and species, it has become a popular approach applied for screening the ecological risk posed by substances for which no data are available. ECOSAR itself, with 150 relationships defined for over 50 chemical classes, has been used to predict toxicity and estimate hazards for chemical warfare agents in marine environments [96], pharmaceuticals [102-104], direct and indirect food additives, and industrial chemicals [105]. Although there are several QSAR and other predictive tools currently available, this section focuses on ECOSAR as it is one of the most widely and easily used. 

This chapter proposes the use of SSD and mixture toxicity models in ecological risk assessment of species assemblages by calculating the multisubstance potentially affected fraction of species on the basis of measured or predicted (biologically active) concentrations of toxic compounds in the environment. The msPAF method has been scrutinized for its conceptual basis. To address this scrutiny, we cite the human toxicology work of Ashford (1981) as a cross-link. 

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