An index of effluent aquatic toxicity designed by partial least squares regression, using acute and chronic tests and expert judgements

The evaluation of the ecotoxicity of effluents requires a battery of biolog ical tests on several species. In order to derive a summary parameter from such a battery, a single endpoint was calculated for all the tests: the EC1 0, obtained by nonlinear regression, with bootstrap evaluation of the confi dence intervals. Principal component analysis was used to characterize and visualize the correlation between the tests. The table of the toxicity of t he effluents was then submitted to a panel of experts, who classified the e ffluents according to the test results. Partial least squares (PLS) regress ion was used to fit the average value of the experts' judgements to the tox icity data, using a simple equation. Furthermore, PLS regression on partial data sets and other considerations resulted in an optimum battery, with tw o chronic tests and one acute test. The index is intended to be used for th e classification of effluents based on their toxicity to aquatic species.