Ecotoxicity data sets

To undertake an assessment of the different approaches an experimental ecotoxicity data set was generated by randomly selecting fifty transformation products from the daphnid data set described previously. An assessment of the predictive performance of five techniques was undertaken by comparing predictions from each approach to the experimentally determined data. The data set included transformation product ecotoxicity data from a range of pesticide classes, i.e. insecticides, herbicides and fungicides and chemical classes, e.g. organophosphorus insecticides, sulfonylureas and azoles. 

ECOSAR is a freely available software system which matches the structure of a query molecule to one (or more) of its defined chemical class(es). For most classes, aquatic ecotoxicity values are then predicted using available hn-ear correlations between toxicity and hydrophobicity. Row is estimated for the query molecule using KOWWIN (discussed in the chapter by Howard). The most recent version of ECOSAR (used in this study) contains over 150 relationships for approximately 50 chemical classes. For the purposes of assessing ECOSAR for predicting, transformation product toxicity, the structures of each of the chemicals in the data set were entered into the software system and in instances where the query compound was matched to one or more chemical classes, the most potent ecotoxicity estimate for daphnids was selected for comparative purposes. 

For new substances not in EINECS, a standardised set of toxicity and ecotoxicity data (known as the base set ) will be available, on which assessment can be based. The detailed guidance [8] includes tables of values for specific release scenarios, organised by product type and use, which are an attempt to refine the risk assessment. 

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 ... 

The information necessary for the assessment of environmental hazard and risk, resulting from the use of chemicals, is preferably obtained from field monitoring and laboratory studies, but often it has to be supplemented by estimates based on various modelling techniques. The input data set required for risk assessments comprises data on the persistence, accumulation, mobility and ecotoxicity of chemicals as well as detailed information on the particular environment, to estimate in stepwise fashion the exposure concentration and the toxic levels for a regional scenario (Figure 9.1). 

The data sets inform about the chemical and physical properties of the microbicides, their toxicity (including their ecotoxicity), their antimicrobial effectiveness and applicability. Sources for toxicity data are, if not otherwise indicated ... 

As of 1981, when theEuropeanchemicalspolicy was implemented, theEuropean Union required the submission of base set test data for physiochemical, environmental fate, toxicological properties and health effects, and ecotoxicity parameters for new... 

Besides meeting its assumptions, other problems in the application of SSD in risk assessment to extrapolate from the population level to the community level also exist. First, when use is made of databases (such as ECOTOX USEPA 2001) from which it is difficult to check the validity of the data, one does not know what is modeled. In practice, a combination of differences between laboratories, between endpoints, between test durations, between test conditions, between genotypes, between phenotypes, and eventually between species is modeled. Another issue is the ambiguous integration of SSD with exposure distribution to calculate risk (Verdonck et al. 2003). They showed that, in order to be able to set threshold levels using probabilistic risk assessment and interpret the risk associated with a given exposure concentration distribution and SSD, the spatial and temporal interpretations of the exposure concentration distribution must be known. 

Limited Set of Hazards Approach. A third approach would be to benchmark chemicals based on a few hazards for which experimental and QSAR data are readily available. For example, persistence, bioaccumulation potential, and ecotoxicity are three hazards for which experimental and QSAR data, as well as a QSAR tool (the PBT profiler) are readily available for many chemicals. This type of... 

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