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(P352) The Ohio data 2: the spatial variability of mixture risk estimates.
De Zwart, Dick*,1, Mulder, Christian1, Posthuma, Leo1, Hawkins, Chuck3, Dyer, Scott2, 1 RIVM, P.O. Box 1, Bilthoven, The Netherlands3 Utah State University, Logan, UT, USA2 The Procter & Gamble Co, Cincinnati, OH
ABSTRACT- A dataset consisting of nearly 1400 sampling sites with fish, invertebrate, habitat and chemistry data has been compiled for Ohio, USA, using state and federal agency data sources. The objective was to produce a comprehensive, eco-epidemiological description of this dataset in terms of habitat degradation and the role of chemical mixtures. The combined risk of chemical mixtures (ms-PAF, the Potentially Affected Fraction of species in a hypothetical species assemblage) for all local sites is calculated by means of the appropriate Species Sensitivity Distributions, constructed of laboratory toxicity data on NOECs and on EC50s, respectively. In the calculus, attention is given to take site conditions into account in view of an appropriate assessment of organism exposures. Further, attention focused specifically on aquatic macrofauna and fishes as different types of ecological receptors. Analyses of the concentration data showed that the ms-PAFs ranged from 3 to 51% for fishes and from 12 to 87% for macrofauna when judged by NOECs. Further, when judged by EC50s, these values were 1 to 13% and 2 to 39% respectively. The latter indicates substantial, likely easy to observe field effects. Both the NOEC and the EC50-based risk estimates suggest significant differences in risks between all sampling sites, which can be used as a basis for an integrated analysis of statistical cause- and effect patterns. Although the ms-PAF values are sometimes used as an endpoint of the assessment, suggesting an absolute meaning of them, in this case the relative range of value is considered to be of importance for the further eco-epidemiological analyses of the dataset.
Key words: Predictive modeling, SSD, Eco-epidemiology
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