The UNEP/SETAC recommended characterisation factors for human health and aquatic ecotoxicity: results and future

Over the last two years, the developers of seven toxicity characterization models collaborated to carry out a comprehensive model comparison as part of the UNEP/SETAC Life Cycle Initiative. The models in this evaluation included CalTOX, IMPACT 2002, USES-LCA, BETR, EDIP, WATSON, and EcoSense. This paper summarizes and draws lessons from this model evaluation process. The main objectives of this effort were to 1) identify specific sources of differences in model results, 2) define common and indispensable model components, and 3) use the selected models to build a “scientific consensus” model, called USEtox, to serve as a repository for recommended practice. USEtox is a parsimonious and transparent tool that currently provides human-health characterisation factors (CFs) for some 1000 chemicals and aquatic ecotoxicity CFs for more than 2000 substances. The accuracy of these factors relative to other models remains within 1-3 orders of magnitude compared to 12 orders of magnitude variation among the chemicals. The main task of model development is complete, but the following future activities are foreseen for the upcoming second phase of the UNEP/SETAC Life Cycle Initiative: 1) increase of substance coverage and quality assurance of substance data; 2) accommodation of metals; 3) inclusion of terrestrial and marine ecotoxicity; 4) incorporation of indoor emissions; 5) including parameter uncertainty in the uncertainty estimates on the CFs; 6) publication of model documentation 7) development and distribution of a user-friendly version of USEtox; 8) industry/stakeholder workshops on comparative assessment of chemicals and training courses in USEtox. The promising scientific results now need to be transferred into daily LCA practice, which is the main goal of these activities, aiming at a broad acceptance and consideration of the toxicity impact categories.