Accounting of media conditions in the Life Cycle Impact Assessment of Metals on Aquatic Ecosystems

Impact from metals play a major role in all Life Cycle Impact Assessment (LCIA) studies. Nevertheless, LCIA methods are typically not adapted for such compounds ignoring problems of speciation and bioavailability. Current uncertainty on metal toxicity estimates are on average twice as high as for other chemical compounds (Figure1). Perspectives for the reduction of uncertainty on metals toxicity are presented below. Focusing on the example of chromium (VI), the main factors influencing the toxic response from Daphnia (hardness and pH) are identified. Analysis is based on ecotoxicological data (US. EPA, 2002). 80 Acute Daphnia magna EC50 on 4 different chromium compounds, all with the same oxidation state (VI), were retrieved: chromic acid diNa salt (N=14), potassium dichromate (N=40), potassium chromate (N=14) and sodium chromate (N=12). Two statistical methods are used for the assessment of the influence of media condition on the toxicity : Partial Least Square projection to latent Structure Regression (PLSR) was carried out to estimate the relative variable importance and linear regression was used to, identify the relation between media parameters the response of Daphnia magna.