Ecotoxic compounds, QSAR

Principal component analysis and QSAR were used to analyze various biological test systems for the quantification of ecotoxic compounds [808]. The QSAR of in vitro approaches for developing non-animal methods to substitute the in vivo LDso test has been reviewed [809]. 

The data-quality requirements for QSAR models relate to several aspects of the experimental procedure, data transformation and the selection of the appropriate test compounds. Only if the input data of a QSAR meet the highest quality standards may a sound model be derived. Because the accuracy of predictions can never be better than the variability of the respective measurements (usually 20% and more), validity assessment of the activity and effects data is crucial in QSAR derivations. The data should be generated by tests that are methodologically and mechanistically defined. The latter is not trivial for parameters such as biodegradability, soil sorption and ecotoxicity. With regard to the considerable variability of measurements, inter- and also intra-laboratory, the test results, especially when collected from different literature sources, should be critically evaluated with respect to ... 

The compounds subject to a QSAR analysis must differ sufficiently in activity to provide the basis for a representative model and to avoid the description of local phenomena. If the activity range is too narrow it may over-value the inherent variance in the experimental data, which may significantly exceed 20% for parameters such as soil sorption, bioconcentration and ecotoxicity. The difference in activity between compounds must therefore clearly exceed that among the replicated measurements for each of the test substances. Otherwise, the derived QSAR may show an artificial relationship between the compounds structure and the experimental scatter, but not the effects under investigation. 

The data sets required for the assessment of environmental hazard and risk resulting from the use of chemicals include information on persistence, accumulation, mobility and ecotoxicity. The basic concept of environmental risk assessment is a comparison of the levels of exposure and toxicity (Part 3). An evaluation is made of the probability that the exposure level of potential contaminants may exceed effective, toxic concentrations in the environmental compartment of concern. The severity of the impact is also taken into consideration. The respective exposure and effects concentrations are determined from experimental or, if not available, QSAR data (Nendza, Volmer and Klein, 1990). For that, compound-specific data are required in addition to information on the release rates and the environmental scenario of concern ... 

OpenTox Web resource provides the ecotoxicity data of chemical compounds. It has standardized data exchange, allows to calculate descriptors on-line and to apply of mathematical methods for QSAR modeling http //www.opentox.org... 

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